Test Methods for Textile Composites - NASA · Test Methods for Textile Composites Pierre J....
Transcript of Test Methods for Textile Composites - NASA · Test Methods for Textile Composites Pierre J....
NASA Contractor Report 4609
Test Methods for Textile Composites
Pierre J. Minguet, Mark J. Fedro, and Christian K. Gunther
Boeing Defense & Space Group • Philadelphia, Pennsylvania
National Aeronautics and Space AdministrationLangley Research Center • Hampton, Virginia 23681-0001
Prepared for Langley Research Centerunder Contract NAS1-19247
July 1994
https://ntrs.nasa.gov/search.jsp?R=19950006380 2020-03-05T08:16:51+00:00Z
Abstract
Various test methods commonly used for measuring properties of tape laminate
composites were evaluated to determine their suitability for the testing of textile
composites. Three different types of textile composites were utilized in this
investigation: 2-Dimensional triaxial braids, stitched uniweave fabric and 3-
Dimensional interlock woven fabric. Ten categories of material properties were
investigated: Tension, Open-Hole Tension, Compression, Open-Hole Compression, In-
Plane Shear, Filled-Hole Tension , Bolt Bearing, Interlaminar Tension, Interlaminar
Shear and Interlaminar Fracture Toughness.
The main issue in the tension test program was the effect on strength of the
specimen size compared to the material unit cell dimensions. Little or no effect on
strength was observed for the 2-D braids which have the largest unit cell size of all
material tested. The effect of specimen width to hole diameter ratio (W/D) was
investigated in the open-hole tension. Results showed that the standard W/D=6 was
adequate. A comparison of the Boeing Open Hole Compression, Zabora Fixture, NASA
Short Block, NASA 1142, Modified IITRI, sandwich column, Boeing Compression After
Impact and NASA ST-4 specimens was conducted in the compression test program. The
Boeing Open Hole Compression, sandwich column, Boeing Compression After Impact
and NASA ST-4 specimens were found to be inadequate for strength testing. Among the
remaining methods, the NASA Short Block specimen consistently produced the highest
mean strength. In the open hole compression tests, a comparison of the Boeing Open
Hole Compression, Zabora Fixture, NASA Short Block, NASA 1142 and Modified IITRI
was conducted for hole diameters up to 0.375". Results show that the Modified IITRI
produced the highest mean strength, while the Boeing OHC produced the lowest. Both
the Boeing Compression After Impact and NASA ST-4 gave good results for larger hole
from 0.5" to 1.25". For the in-plane shear testing, a comparison of tube torsion, rail shear
and compact shear specimens was conducted. Significant differences in both strength
and modulus were obtained between these test methods. Testing was conducted only
with the 2-D braided material for filled-hole tension strength and confirmed that, as for
tape laminates, filled hole tension is the critical case when developing material design
allowables for the Room Temperature/Dry environment. Testing for bolt bearing
strength was conducted only with the 2-D braided material. As for tape laminates, the
stabilized single shear bearing test is recommended. Testing for interlaminar tension
was conducted with the 2-D braided material and 3-D woven materials using a C-shape
and a L-shape specimens. Strength values from the L-shape configuration were slightly
higher. Testing for interlaminar shear was conducted with the 2-D braided material and
3-D woven materials using the Short Beam Shear (SBS) and Compression Interlaminar
Shear (CIS) specimens. Strength values obtained from the SBS specimen were
consistantly higher than those from the CIS specimen. Testing for interlaminar fracture
toughness was conducted only with the 2-D braided material using the Double
Cantilever Beam and End Notched Flexure specimens. Results showed much higher
toughness in this type material than in conventional laminated composites.
_:'.:_6GIIOW_ PAGE IILANK NOT IFII.MEID
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Table of Contents
Abstract ................................................................................................................. I I I
Table of Contents ................................................................................................. Iv
List of Figures ....................................................................................................... v I I
List of Tables ........................................................................................................ x I
1. Introduction ..................................................................................................... 1
2. Material Systems ............................................................................................. 2
2.1 2-D Braided Composites ......................................................................... 2
2.2 Stitched Uniweave Composites ............................................................. 3
2.3 3-D Interlock Woven Materials ............................................................ 4
3. Data Reduction Techniques ........................................................................... 5
3.1 Fiber Volume Measurements ................................................................. 5
3.2 Thickness Normalization ....................................................................... 5
3.3 Stress, Modulus and Poisson's Coefficient Calculation ..................... 7
3.4 Open-Hole Data ....................................................................................... 7
4. Strain Gage Size Sensitivity Study ................................................................ 9
4.1 Test Specimens and Procedures ............................................................ 9
4.2 Strain Gages Investigated ....................................................................... 9
4.3 Experimental Results .............................................................................. 10
4.4 2-D Braided Materials ............................................................................. 11
4.5 3-D Woven Materials .............................................................................. 12
5. In-Plane Tension Test Program ..................................................................... 15
5.1 Test Configuration .................................................................................. 15
5.2 2-D Braid Materials ................................................................................. 16
5.2.1 Test Section Width, Length and Thickness Effects ................. 16
5.2.2 Longitudinal Tension Test Summary ....................................... 185.2.3 Transverse Tension ..................................................................... 20
5.3 Stitched Uniweave Materials ................................................................. 21
5.4 3-D Woven Materials .............................................................................. 22
5.5 Test Recommendations ........................................................................... 22
6. Open-Hole Tension Test Program ................................................................ 24
6.1 Test Configuration .................................................................................. 24
6.2 2-D Braid Materials ................................................................................. 25
6.2.1 Width to Diameter Ratio Effect ................................................. 25
6.2.2 Thickness Effect ........................................................................... 26
6.2.3 Hole Size Effect ............................................................................ 26
6.2.4 Summary ...................................................................................... 29
6.3 Stitched Uniweave Materials ................................................................. 30
6.4 3-D Woven Materials .............................................................................. 31
6.5 Test Recommendations ........................................................................... 33
IV
7. In-Plane Compression Test Program ............................................................ 34
7.1 Test Configurations ................................................................................. 34
7.2 2-D Braid Materials ................................................................................. 37
7.2.1 Test Section Length and Thickness Effects .............................. 37
7.2.2 Longitudinal Compression ........................................................ 387.2.3 Sandwich Column ....................................................................... 41
7.2.4 Boeing Open Hole Compression Fixture ................................. 42
7.2.5 Transverse Compression ............................................................ 42
7.3 Stitched Uniweaves Materials ............................................................... 43
7.3.1 Longitudinal Compression ........................................................ 43
7.3.2 Transverse Compression ............................................................ 43
7.4 3-D Woven Materials .............................................................................. 44
7.4. 1 Longitudinal Compression ....................................................... 44
7.4.2 Transverse Compression ............................................................ 44
7.5 Test Recommendations ........................................................................... 45
8. Open Hole Compression Test Program ....................................................... 48
8.1 Test Configurations ................................................................................. 48
8.2 2-D Braid Materials ................................................................................. 49
8.2.1 Test Method Comparison ........................................................... 498.2.2 Hole Size Effect ............................................................................ 53
8.3 Stitched Uniweave Materials ................................................................. 56
8.4 3-D Woven Materials .............................................................................. 58
8.5 Test Recommendations ........................................................................... 59
9. In-Plane Shear Test Program ......................................................................... 62
9.1 Test Configurations ................................................................................. 62
9.2 2-D Braid Materials ................................................................................. 63
9.3 Stitched Uniweave Materials ................................................................. 65
9.4 3-D Woven Materials .............................................................................. 66
9.5 Test Recommendations .......................................................................... 67
10. Filled-Hole Test Program ............................................................................. 69
10.1 Test Configuration ................................................................................ 69
10.2 2-D Braids ............................................................................................... 69
11. Bolt-Bearing Test Program ........................................................................... 71
11.1 Test Configuration ................................................................................ 71
11.2 2-D Braids ............................................................................................... 73
12. Interlaminar Tension ..................................................................................... 78
12.1 Specimen Configurations ..................................................................... 78
12.2 2-D Braids Materials ............................................................................. 79
12.3 3-D Woven Materials ............................................................................ 81
13. Interlaminar Shear ......................................................................................... 82
13.1 Test Configurations ............................................................................... 82
v
13.3 2-D Braided Materials ........................................................................... 83
13.3 3-D Woven Materials ............................................................................ 84
14. Interlaminar Fracture Toughness ................................................................ 85
14.1 Test Configurations ............................................................................... 85
14.2 2-D Braided Materials ........................................................................... 86
15. Conclusions .................................................................................................... 88
References ............................................................................................................. 90
Appendix A Test Data ........................................................................................ A.1
Appendix B Typical Stress-Strain Curves ........................................................ B. 1
Appendix C Boeing Specifications ................................................................... C.1
VI
Figure 2.1
Figure 2.2
Figure 3.1
Figure 5.1.a
Figure 5.1.b
Figure 5.2.a
Figure 5.2.b
Figure 5.2.c
Figure 5.2.d
Figure 5.3
Figure 5.4
Figure 5.5
Figure 5.6
Figure 5.7
Figure 6.1
Figure 6.2
Figure 6.3
Figure 6.4.a
Figure 6.4.b
Figure 6.4.c
Figure 6.4.d
Figure 6.5
Figure 6.6
Figure 6.7.a
Figure 6.7.b
Figure 6.7.c
Figure 7.1 .a
Figure 7.1.b
List of Figures
Illustration of 2-D Triaxial Braid Configuration ....................................... 3
Depiction of 3-D Interlock Woven Materials ............................................ 4
Example of Relationship between Fiber Volume Fraction and
Thickness for SLL, LSS and SU-1 Specimens ............................................ 6
Typical Tension Specimen Configuration ................................................. 15
Dogbone Tension Specimen Configuration .............................................. 16
Effect of Specimen Width on Tensile Strength of 2-D Braid SLL ........... 17
Effect of Specimen Width on Tensile Strength of 2-D Braid LLS ........... 17
Effect of Specimen Width on Tensile Strength of 2-D Braid LLL ........... 18
Effect of Specimen Width on Tensile Strength of 2-D Braid LSS ........... 18
Effect of Specimen Length on Tensile Strength of 2-D Braids ................ 18
Tensile Strength of Baseline, Dogbone and Net-Shape 2-D
Braided Specimens ........................................................................................ 20
Transverse Tension Strength and Nominal Strain for 2-DBraided Materials .......................................................................................... 20
Summary of Longitudinal Tension Strengths and NominalStrains of Stitched Uniweave Materials ..................................................... 21
Comparison of Longitudinal Tension Strengths and NominalStrains of 3-D Woven Materials ................................................................ 22
Open Hole Specimen Configuration .......................................................... 24
Comparison of Gross, Net and Corrected Stress in SLL and LLS
1/8" Thick Specimens with a 3/8" Diameter Hole .................................. 26
Comparison of Open Hole Tensile Strength in SLL and LLS 1/8"
and 1/4" Thick Specimens with a 3/8" Diameter Hole .......................... 26
Effect of Hole Diameter on
Effect of Hole Diameter on
Effect of Hole Diameter on
Tension Strength of SLL Specimens ........... 27
Tension Strength of LLS Specimens ........... 28
Tension Strength of LLL Specimens ........... 28
Effect of Hole Diameter on Tension Strength of LSS Specimens ........... 29
Effect of Hole Diameter on Open Hole Tension Strength ofStitched-Uniweave Materials ....................................................................... 30
Open Hole Tension Strength Data for 3-D Woven Materials ................. 31
Effect of Hole Diameter on Open Hole Tension Strength of 3-DWoven Materials OS-1 and OS-2 ................................................................. 32
Effect of Hole Diameter on Open Hole Tension Strength of 3-DWoven Materials LS-1 and LS-2 .................................................................. 32
Effect of Hole Diameter on Open Hole Tension Strength of 3-DWoven Materials TS-1 and TS-2 .................................................................. 33
Modified IITRI Specimen and NASA Short Block Specimen ................. 35
Sandwich Column Specimen, Zabora Fixture and Boeing OHCFixture ............................................................................................................ 36
vii
Figure 7.1.c
Figure 7.2
Figure 7.3
Figure 7.4
Figure 7.5
Figure 7.6.a
Figure 7.6.b
Figure 7.6.c
Figure 7.6.d
Figure 7.7
Figure 7.8
Figure 7.9
Figure 7.10
Figure 8.1
Figure 8.2.a
Figure 8.2.b
Figure 8.2.c
Figure 8.2.d
Figure 8.3.a
Figure 8.3.b
Figure 8.3.c
Figure 8.3.d
Figure 8.4.a
Figure 8.4.b
NASA ST-4 or Boeing CAI Specimen and Boeing OHC or
Zabora Fixture Specimen ............................................................................. 36
Test Section Length Effect on Compression Strength in NASA
Short Block Test Configuration ................................................................... 37
Test Section Length Effect on Compression Strength in modified
IITRI Test Configuration .............................................................................. 38
Test Section Length Effect on Compression Modulus in NASA
Short Block and modified IITRI Test Configurations .............................. 38
Compression Modulus of 2-D Braided Materials ..................................... 39
Compression Strength and Nominal Strain of SLL Braid ....................... 40
Compression Strength and Nominal Strain of LLS Braid ....................... 40
Compression Strength and Nominal Strain of LLL Braid ...................... 40
Compression Strength and Nominal Strain of LSS Braid ........................ 41
Deviation from Mean Strength for Unnotched Compression TestMethods .......................................................................................................... 46
Mean Strength CoVs for Unnotched Compression TestMethods .......................................................................................................... 47
Deviation from Mean Modulus for Unnotched CompressionTest Methods .................................................................................................. 47
Mean Modulus CoVs for Unnotched Compression TestMethods .......................................................................................................... 47
NASA 1142 Specimen Configuration ......................................................... 49
Comparison of Open Hole Compression Strength for VariousTest Methods of SLL Materials ................................................................... 50
Comparison of Open Hole Compression Strength for VariousTest Methods of LLS Materials ................................................................... 50
Comparison of Open Hole Compression Strength for VariousTest Methods of LLL Materials .................................................................. 50
Comparison of Open Hole Compression Strength for VariousTest Methods of LSS Materials ................................................................... 51
Comparison of Coefficient of Variations for Open Hole
Compression Test Methods of SLL Materials .......................................... 51
Comparison of Coefficient of Variations for Open Hole
Compression Test Methods of LLS Materials ........................................... 51
Comparison of Coefficient of Variations for Open Hole
Compression Test Methods of LLL Materials .......................................... 52
Comparison of Coefficient of Variations for Open Hole
Compression Test Methods of LSS Materials ........................................... 52
Effect of Hole Diameter on Open Hole Compression Strength of2-D Braided Materials SLL ........................................................................... 54
Effect of Hole Diameter on Open Hole Compression Strength of2-D Braided Materials LLS ........................................................................... 55
VIII
Figure 8.4.c
Figure 8.4.d
Figure 8.5
Figure 8.6
Figure 8.7
Figure 8.8
Figure 8.9
Figure 8.10
Figure 9.1
Figure 9.2
Figure 9.3
Figure 9.4
Figure 9.5
Figure 9.6
Figure 9.7
Figure 10.1
Figure 10.2
Figure 11.1a
Figure 11. lb
Figure 11. lc
Figure 11.2
Figure 11.3
Figure 11.4.a
Figure 11.4.b
Figure 11.5
Effect of Hole Diameter on Open Hole Compression Strength of2-D Braided Material LLL ............................................................................ 55
Effect of Hole Diameter on Open Hole Compression Strength of2-D Braided Material LSS ............................................................................. 56
Comparison of Mean Coefficient of Variation for all Stitched
Uniweave Open Hole Compression Tests ................................................. 57
Comparison of 1/4" Open Hole Compression Strength andNominal Strains for Stitched Uniweave Materials ................................... 57
Effect of Hole Diameter on Open Hole Compression Strength ofStitched Uniweave Materials ....................................................................... 58
Comparison of 1/4" Open Hole Compression Strength for 3-DWoven Materials ............................................................................................ 59
Normalized Mean Deviations for Open Hole Compression TestMethods in 2-D Braided Materials .............................................................. 60
CoVs for Open Hole Compression Test Methods in 2-D BraidedMaterials ......................................................................................................... 61
Rail Shear Specimen and Compact Shear Specimen ................................ 63
Comparison of Shear Modulus by Various Test Methods for 2-DBraided Materials .......................................................................................... 64
Comparison of Shear Strength Various Test Methods for 2-DBraided Materials .......................................................................................... 65
Shear Modulus of Stitched Uniweave Materials ...................................... 66
Shear Modulus of 3-D Woven Materials with Rail Shear and
Compact Shear Specimen Methods ............................................................ 67
Mean Deviations for In-plane Shear Test Methods .................................. 68
CoVs for In-plane Shear Test Methods ...................................................... 68
Comparison of Net, Gross and Corrected Stress for Filled HoleTension Test of SLL Braid ............................................................................ 70
Comparison of Open and Filled Hole Tension Strength Data for2-D Braided Material ..................................................................................... 70
Baseline Dimensions for Stabilized Single-Shear Specimen ................... 72
Baseline Dimensions for Unstabilized Single-Shear Specimen .............. 72
Baseline Dimensions for Double-Shear Specimen .................................... 73
Effect of W/D and e/D on Stabilized Single Shear Bearing
Ultimate Strength of 2-D Braided Materials SLL and LLS ...................... 74
Effect of e/D on Unstabilized Single Shear Bearing Ultimate
Strength of 2-D Braided Materials SLL and LLS ...................................... 75
Effect of W/D and e/D on Double Shear Bearing Ultimate
Strength of 2-D Braided Materials SLL ...................................................... 75
Effect of W/D and e/D on Double Shear Bearing Ultimate
Strength of 2-D Braided Materials LLS ...................................................... 76
Comparison of all Bearing Tests with W/D=6 and e/D=3 for 2-
Ix
Figure 12.1
Figure 12.2
Figure 12.3
Figure 12.4
Figure 13.1
Figure 13.2
D Braided Materials ...................................................................................... 76
Interlaminar Tension C-Shape Specimen .................................................. 79
Interlaminar Tension L-Shape Specimen ................................................... 79
Interlaminar Tension Strength Measured with C-Shape
Specimen ......................................................................................................... 80
Interlaminar Tension Strength Measured with L-Shape
Specimen ......................................................................................................... 81
Short Beam Shear and Compression Interlaminar Shear
Specimens ....................................................................................................... 82
Interlaminar Shear Strength Measured with Short Beam Shear
and Compression Interlaminar Shear Test Methods ............................... 83
X
Table 2.1
Table 2.2
Table 2.3
Table 3.1
Table 4.1
Table 4.2
Table 4.3
Table 4.4
Table 4.5
Table 5.1
Table 5.2
Table 5.3
Table 5.4
Table 5.5
Table 6.1
Table 6.2
Table 6.3
Table 6.4
Table 7.1
Table 7.2
Table 7.3
Table 7.4
Table 7.5
Table 7.6
List of Tables
Description of 2-D braided Co .mposites Architectures .................................. 2
Description of Stitched Uniweave Materials ................................................... 3
Description of 3-D Interlock Woven Materials ............................................... 4
Summary of Normalized Thicknesses ............................................................. 7
Strain Gage Description ...................................................................................... 10
2-D Braid Longitudinal Modulus Measurements .......................................... 12
2-D Braid Transverse Modulus Measurements .............................................. 13
3-D Weave Longitudinal Modulus Measurements ........................................ 13
3-D Weave - Transverse Modulus Measurements ......................................... 14
Test Matrix for Tension Test Program .............................................................. 16
Summary of Tension Properties of 2-D Braided Materials ........................... 19
Summary of Transverse Tension Properties of 2-D Braided
Materials ............................................................................................................... 20
Summary of Longitudinal Tension Properties of Stitched Uniweave
Materials ............................................................................................................... 21
Summary of Longitudinal Tension Properties of 3-D Woven
Materials ...................................... :........................................................................ 22
Test Matrix for Open Hole Tension Test Program ......................................... 25
Mean Stress and CoV for Open Hole Tension Tests of 2-D Braided
Materials ............................................................................................................... 29
Mean Strength and CoV for Open Hole Tests of Stitched-Uniweave
Materials ............................................................................................................... 30
Mean Strength and CoV for Open Hole Tests "of 3-D Woven
Materials ............................................................................................................... 31
Test Matrix for Compression Test Program .................................................... 35
Summary of Longitudinal Compression Properties for 2-D Braid
Materials ............................................................................................................... 41
Sandwich Column Compression Properties for 2-D Braid
Materials ............................................................................................................... 42
Summary of Transverse Compression Properties for 2-D Braid
Materials Using Modified IITRI Test Method ................................................. 42
Summary
Uniweave
Summary
Uniweave
of Transverse Compression Properties for Stitched
Materials ............................................................................................ 43
of Transverse Compression Properties for Stitched
Materials Using the Modified IITRI Test Method ....................... 44
xI
Table 7.7
Table 7.8
Table 7.9
Table 8.1
Table 8.2
Table 8.3
Table 8.4
Table 8.5
Table 9.1
Table 9.2
Table 9.3
Table 9.4
Table 9.5
Table 9.6
Table 10.1
Table 10.2
Table 11.1
Table 11.2
Table 11.3
Table 11.4
Table 12.1
Table 12.2
Table 12.3
Table 13.1
Table 13.2
Table 13.3
Table 14.1
Table 14.2
Summary of Longitudinal Compression Properties for 3-D Woven
Materials ............................................................................................................... 44
Summary of Longitudinal Compression Properties for 3-D Woven
Materials the Using Modified IITRI Test ......................................................... 45
Mean Deviations A---xnand CoVs for Unnotched Compression Test
Methods ................................................................................................................ 46
Test Matrix for Open Hole Compression Test Program ................................ 48
Summary of Open Hole Compression Test Results for 2-D Braided
Materials ............................................................................................................... 53
Summary of Open Hole Compression Test Results for Stitched
Uniweave Materials ........................................................................................... 57
Summary of Open Hole Compression Test Results for 3-D Woven
Materials ............................................................................................................... 58
Mean deviations AXknand Axn for Open-Hole Compression Test
Methods ................................................................................................................ 60
Test Matrix for Shear Properties ....................................................................... 62
Summary of Tube Torsion Test Results for 2-D Braids ................................. 64
Summary of Rail Shear and Ifju Fixture Test Results for 2-D Braids ........... 64
Shear Properties of Stitched Uniweave Materials .......................................... 65
Shear Properties of 3-D Woven Materials ........................................................ 66
Normalized Mean Deviations AXn for Shear Test Methods ......................... 68
Filled Hole Tension Test Program .................................................................... 69
Filled Hole Tension Test Program .................................................................... 70
Bolt-Bearing Test Matrix .................................................................................... 71
Stabilized Single Shear Bearing Ultimate Strength Results for 2-D
Braids .................................................................................................................. 77
Unstabilized Single Shear Bearing Ultimate Strength Results for 2-D
Braids .................................................................................................................. 77
Double Shear Bearing Ultimate Strength Results for 2-D Braids ................. 77
Interlaminar Tension Test Matrix ..................................................................... 78
Interlaminar
Interlaminar
Interlaminar
Interlaminar
Interlaminar
Interlaminar
Interlaminar
Tension Strength Measured with C-Shape Specimen ............. 80
Tension Strength Measured with L-Shape Specimen ............. 81
Shear Test Matrix ......................................................................... 83
Shear Strength in 2-D Braided Materials .................................. 84
Shear Strength in 3-D Woven Materials ................................... 84
Toughness Test Matrix ................................................................ 86
Toughness Test Results ............................................................... 87
XII
1. Introduction
Carbon/Epoxy composites made from textile fiber preforms manufactured with a
Resin-Transfer-Molding (RTM) process have potential for reducing costs and increasing
damage tolerance of aerospace structures. While many standardized test methods are
available for conventional tape laminates, these may not be directly applicable to textile
composites. The main concern is that textile composites tend to be less homogeneous
than conventional tape laminates. Thus, it was anticipated that some scaling effects may
be observed and that larger size specimens may be required. The objective of the task
described in this report was to evaluate existing test methods for measuring stiffness
and strength properties of specimens loaded in tension, with and without holes,
compression, with and without holes, shear and bolt bearing, and to make
recommendations for changes in the test configuration. A secondary objective of this
task was to increase the database of mechanical properties of textile composites in order
to assist in the development of analytical models and the assessment of the benefits of
textile composites for future applications.
As a result of a NASA Advanced Composite Technology (ACT) Program Steering
Committee recommendation, this program was initiated out of the Mechanics of
Materials Branch at the NASA Langley Research Center. This program was assembled
to address critical technology needs for the ACT Program and other NASA funded
programs.
This report describes work accomplished under Contract NAS1-19247 from the
National Aeronautics and Space Administration, Langley Research Center, Hampton
VA. Mr Clarence C. Poe Jr., NASA LaRC, was the NASA Technical Monitor. Bill Fedor
of Boeing Aerospace Operations was the program manager. The Structures Technology
organization of the Boeing Defense & Space Group, Helicopters Division was
responsible for completing this task. Most of the specimen manufacturing was
performed by Boeing Defense and Space Group Research and Engineering (Seattle,
WA), while all the material testing was conducted at Integrated Technologies, Inc.
(Intec, Bothell, WA.) Dr John Masters of Lockheed Engineering & Science contributed
Section 4 of this report.
The objectives of this report are to summarize all the strength and stiffness
properties measured for the various textile composites investigated, to assess the
performance of various test methods and, where possible, to provide recommendations
on preferred test configurations for textile composites.
2. Material Systems
Three different types of textile composites were utilized in this investigation: 2-
Dimensional triaxial braids, stitched uniweave fabric and 3-Dimensional interlock
woven fabric. Textile preforms were procured from their respective vendors mentioned
below. All preforms were Resin Transfer Molded (RTM) and cured at Boeing Defense
and Space Group, Seattle, WA. Hercules AS4 fibers is used for all fabrics. The resin
system used for all materials is Shell RSL-1895, a two-par_ epoxy system with Shell
Epon Curing Agent W formulated for RTM to have comparable properties to Hercules
3501-6 resin system. All details of the manufacturing process can be found in NASA CR
191505, "Resin Transfer Molding of Textile Composites ," (Ref. 1).
2.1 2-D Braided Composites
The 2-D braided fabric contains two types of tows, the longitudinal (axial, or 0 °) tow
and the braided (or bias) tows oriented at angle 0 to the axial tow as illustrated in Figure
2.1. The braid pattern used is a 2X2 pattern, meaning that each braided tow goes over
and under two tows at a time. All preforms were manufactured by Fiber Innovations
Inc., Norwood, MA.
Three important braid parameters are braid angle, yarn size (measured in K, where
1K equals 1000 filaments), and proportion of fixed (0 °) yarns. The four braids in Table
2.1 were designed to give three combinations of these parameters so that changes to
mechanical properties due to changes in these parameters can be determined. The tow
sizes were different for the first and third braids (SLL and LLL), the braid angles were
different for the second and third braids (LLS and LLL), and the percentage of fixed
yarns were different for the second and fourth braids (LLS and LSS). The 46% of axial
tows for the first three braids is typical of a braid optimized for predominantly
longitudinal loading. The 12% of axial tows for the fourth braid (LSS) is typical of a
braid optimized for predominantly shear loading. The braids marked "-2" and "-3" are
variations of the basic architectures used only in the interlaminar properties tests.
Name
Table 2.1 Description of 2-D braided Composites Architectures
LSS
LongitudinalTow Size
Braided Tow
Size% Longitudinal
Tow
SLL 30 K 6 K 46
LLS 36 K 15 K 46
LLL 75 K 15 K 46
12
SLL-2
6K
15K
30K
15 K
LLS-2
15K
3K
12K
6KLLS-3
46
47
47
Braid
Angle [°]I
7O
Unit Cell
Width [in]
0.458
45 0.415
70 0.829
45
7O
45
45
0.415
0.349
0.349
0.262
Unit Cell
Length [in]
0.083
0.207
0.151
0.207
0.063
0.175
0.131
2
The unit cell dimensions vary considerably and are typically quite large. The unit
cell width is defined as twice the spacing of the axial tows, while the unit cell length is
twice the distance, along an axial tow, between the intersections of an axial tow and a
+0 tow (these factors of 2 are due to the fact that this is a 2X2 pattern).
Braider Yarn
Unit Cell IHeight
Figure 2.1
Axial Yarn
Unit Cell Width
Braid Angle
Illustration of 2-D Triaxial Braid Configuration.
2.2 Stitched Uniweave Composites
Stitched uniweave fabric consists of several plies of unidirectional graphite fibers
woven with a light E-Glass tow (8 picks per inch). This fabric was produced by Textile
Technologies Inc. (Style 4003-PW). Several of these layers were then stitched together
through the thickness by Cooper Composites. All the materials used here have a quasi-
isotropic [+45/0/-45/9016s layup. As shown in Table 2.2, the variables examined relate
to the stitching process itself. The effects of stitch material, pitch, spacing (between rows
of stitches) and size are investigated with the five different configurations shown in
Table 2.2.
Table 2.2 Descri _tion of Stitched Uniweave Materials
Name Stitch Material Stitches per inch Stitch Spacing [in] Stitch Tow Size
SU-1 $2 Glass 8 0.125 3 K
SU-2 $2 Glass 8 0.125 6 K
SU-3 Kevlar 29 8 0.125 6 K
SU4 Kevlar 29 4 0.250 6 K
SU-5 Kevlar 29 8 0.125 12 K
3
2.3 3-D Interlock Woven Materials
Interlock woven fabric is a three-dimensional fabric in which yarns are interlaced
through the thickness to improve interlaminar properties over conventional laminates.
The warp tows run parallel to the weaving machine direction, with the weft tows
running perpendicular to these. The interlock tows wrap around the weft tows in
parallel to "the warp tows. Three interlock configurations with different tow sizes were
used as described in Table 2.3 and illustrated in Figure 2.2. All preforms were produced
by Textile Technologies Inc. (TTI).
Table 2.3 Description of 3-D Interlock Woven Materials
Name
OS-1
OS-2
TS-1
TS-2
LS-1
LS-2
Description
Through -the-thickness
orthogonai interlock
Through-the-thickness
angle interlock
Layer-to-layer interlock
Warp Tow
24 K (59%)
12 K (58%)
24 K (57%)
12 K (56%)
24 K (58%)
12 K (57%)
Weft Tow
12 K (33%)
6 K (37%)
12 K (33%)
6 K (38%)
12 K (34%)
6 K (36%)
Weaver Tow
6 K (7.4%)
3 K (6.1%)
6 K (9.8%)
3 K (5.8%)
6 K (6.8%)
3 K (5.9%)
Figure 2.2
Weft (90 °) Warp (0 °)
T-t-t Orthogonal T-t-t Angle Layer-to layer
Depiction of 3-D Interlock Woven Materials.
4
3. Data Reduction Techniques
The different techniques used to analyze the experimental data described in the
following chapters are documented here. These include specimen fiber volume
measurement and thickness normalization, strength and stiffness properties calculation,
and open hole strength analysis.
3.1 Fiber Volume Measurements
Resin digestion tests were performed on all panels used in this investigation to
determine fiber volume fraction and void content. All resin digestion procedures are
carried out using a microwave technique. The method consists of obtaining both the dry
and submerged weight of a 0.5 inch by 0.5 inch composite specimen to determine its
specific gravity. The specimen is placed in a reaction pressure vessel to which 25 to 30
ml of nitric acid is added. The reaction vessel is sealed and placed in a microwave oven
for heating. The digestion is run in four stages, with each consecutive stage ramping to
a higher pressure. Running the experiment at higher pressure enables the temperature
to increase without boiling the acid. Upon complete digestion of the resin, the fibers are
filtered from the acid and rinsed with water and acetone. After drying, the carbon fibers
are weighted and their volume fraction determined. The fiber and resin densities used
in the calculation were 1.80 g/cm 3 and 1.18 g/cm3 respectively.
3.2 Thickness Normalization
One of the first difficulties encountered when examining the experimental data was
the fact that there is some scatter in fiber volume fraction from plate to plate. This is
especially true of the 2-D braided materials. In order to calculate stress and modulus
from the data, a method to normalize these results had to be chosen. Typically, when
dealing with tape or fabric laminates, a normalized thickness corresponding to a given
fiber volume is determined and kept constant for all calculations. A similar approach is
used in the present investigation. As illustrated in Figure 3.1, volume fraction and
thickness data was obtained for each material system. The mean thickness and fiber
volume was determined across all panels of a given material and nominal thickness. In
general, the scatter was always much higher for the 2-D braided materials than for the
other material systems. The thickness corresponding to a 60% volume fraction was
then calculated and used to calculate all stresses and moduli for that material form.
The resulting thicknesses are listed in Table 3.1. Note that for the 2-D braided
material, two thicknesses were used to look at the influence of this parameter. When
referring to these materials in the text of this report, their nominal values of 1/8" and
1/4" will often be used for simplicity, alfl_ough the actual value is somewhat different.
5
Figure 3.1
CO
O
u-
E
O
U_
0.700 SLL 2-D Braid ArchitectureT
0.600 _ [] 13 []
0.500
O.4O0
0.300
0.200
0.100
0.000
0.102
, ! , I , I , I , I
0.104 0.106 0.108 0.110 0.112
Thickness [in]
O
I.J-
E._=O>$
..13
U-
0.700
0.600
0.500
0.400
0.300
0.200
0.100
LLS 2-D Braid Architecture
_ __"_____ £_J1_m-J'l [] n
0.000 .... I .... ! .... I , ,, , , I
0.100 0.105 0.110 0.115 0.120
Thickness [in]
t.-.9
IJ_
E
iT
0.700
0.600
0.500
0.400
0.300
0.200
0.100
0.000
0.220
SU-1 Stiched Uniweave CompositeIN Ilmu_lmlmll_n "- l,
, I , I , I
0.221 0.222 0.223
Rmg
, I
0.224
Thickness [in]
Example of Relationship between Fiber Volume Fraction and Thickness
for SLL, LSS and SU-1 Specimens.
6
Table 3.1 Summary of Normalized Thicknesses
Name Thickness Name
linl
SLL 0.110 or 0.215
LLL 0.114 or 0.229
LLS 0.112 or 0.220
LSS 0.111 or 0.215
LS-1 0.226
LS-2 0.230
OS-1 0.234
OS-2 0.226
TS-1 0.237
TS-2 0.228
Thickness
[inl
SU-1 0.247
SU-2 0.265
SU-3 0.261
SU-4 0.241
SU-5 0.274
3.3 Stress. Modulus and Poisson's Coefficient Calculation
The first issue that arises when reducing material testing data from load to stress is
the question of how to define thickness. One observation made when analyzing the data
generated in this test program was the higher than usual scatter in some of the results.
Although this is somewhat inherent to the materials tested here, it was found that part
of that scatter was due to the use of actual measured specimen thickness because of the
variability in thickness and fiber volume fraction from panel to panel. Therefore, in this
report, ultimate stress is defined as the specimen ultimate load divided by the specimen
actual width and nominal thickness calculated in the previous section:
P(l -
W t_om
where P is the load, w the specimen width and tnom the nominal thickness
The specimen modulus was calculated by performing a linear regression of load
versus axial strain The axial strain range used in the calculation is 1000 to 3000
microstrains. The specimen actual width and nominal thickness are used in the
calculation. Similarly, the Poisson's coefficient was calculated by performing a linear
regression of transverse versus axial strain over the same range of axial strain.
3.4 Open-Hole Data
When analyzing data from an open hole test, there are several ways to calculate and
report stress at failure. The first approach is to use the gross stress defined as load
divided by the cross-section area of the specimen away from the hole.
7
P(_gross -
w tno m
The second way is to use net stress by using the section area through the hole.
P(_net = where d is the hole diameter
(W - d) tno m
Another way to reduce the data is to correct the gross stress with the width correction
factor described in Ref. 2. This factor is defined as the ratio of stress concentration factor
in the finite width coupon to stress concentration factor for a hole in an infinitely wide
plate. Although this factor should vary with the elastic constants of the material, that
correction factor is fairly small for the type of specimens typically used. Thus, it is
customary to use the correction factor developed for a quasi-isotropic laminate for all
laminates.
(loo _ W
O0ro,,For example, in the following chapters, testing of specimens with w/d = 4, 6 and 8 will
be performed. Thus, for these specimens, the correction factor is equal to 1.076 for
w/d=4, 1.031 for w/d=6 and 1.017 for w/d=8.
In order to analyze the data for the effect of hole size, a procedure similar to the Mar-
Lin fitting technique is used (Ref. 3). After obtaining the mean strength for each hole
diameter, a best fit curve was calculated by performing a linear regression of the
logarithm of strength versus the logarithm of diameter:
Iog(_ = a Iogd + b or (5 = s d a with s = 10 b
The parameter a can be roughly interpreted as the material sensitivity to hole diameter.
4. Strain Gage Size Sensitivity Study
Significant variations in displacement field homogeneity have been identified in
textile composite specimens through the use of Moir6 interferometry. Uniaxial tension
test results indicate, for example, that local strains may vary by as much as a factor of
two within the unit cells of laminates formed from 2-D triaxially braided preforms (Ref.
4). Test specimens must, therefore, be designed to encompass representative volumes of
material within their test sections to obtain characteristic measures of mechanical
response. The size and type of instrumentation used plays a similarly critical role in
obtaining accurate measurements.
A series of tensile tests were conducted to determine the sensitivity of strain
measurements to the size of the strain gage. The objective of this study was to establish
a database which will be used to develop guidelines for the instrumentation of textile
composites. Descriptions of the test specimens and test procedures employed in the
study and the strain gages investigated are presented in the following sections. They are
followed by a review of the test results.
4.1 Test Specimens and Procedure,#.
Samples of the four 2-D triaxial b_'aids and the six 3-D weaves described earlier in
this report were loaded in uniaxial tension. Strains in both the longitudinal direction
(parallel to the 0 ° yarns) and the transverse direction (perpendicular to the 0 ° yarns)was measured.
Forty specimens were tested in the program. Because of limited quantities of
material, only four specimens, 2 axial and 2 transverse, were used for each material
type. The longitudinal or axial tension specimens were 1.5 in. wide and 10.0 in. long.
The transverse tension specimens were 1.5 in. wide and 7.0 in. long. All specimens
tested in this study were nominally 0.250 inches thick. Strain measurements were made
over a 3 inch long section centered along the length of the specimen.
All tests were conducted on a 50 Kip servo-hydraulic test machine. It was
programmed to run in displacement control at a ramp rate of 0.01 in/min. Strain was
monitored throughout the test. Loading was halted at 3250 microstrain and the
specimen was unloaded. Each specimen was loaded three times in this manner. Load,
displacement, and strain were continuously recorded via a data acquisition system
which monitored each channel once a second.
4.2 Strain Gaoes Investioated.
Six gage types were investigated in this study. They were chosen to provide a range
of gage lengths from 0.125 inch to 0.500 inch, and widths ranging from 0.062 inches to
0.500 inches. Three of the gages featured square grids; three had rectangular grids. The
9
length-to-width ratio of the rectangular gageswas approximately 2 to 1. A total of ninestrain gages (three of each type) were mounted on each specimen; six on one side andthree on the other. Table 4.1 lists all gages used and their dimensions, resistance andcost per package of five gages.
Table 4.1Strain GageDescription
Strain Gage Type Gage Dimensions Resistance Price
[in] [Ohmsl {S/Pkg.]i
EA-06-125BZ-350 0,125 x 0.062 350 17
EA-06-125AD-120 0.125 x 0.125 120 17
CEA-06-250UN-350 0.250 x 0.120 350 30
EA-06-250AE-350 0.250 x 0.250 350 32
CEA-O6-500UW-350 0.500 x 0.180 350 48
EA-O6-500AE-350 0.500 x 0.500 350 80
4.3 Experimental Results.
The strains recorded by each gage mounted on the specimen were used to compute
modulus. The resulting moduli were then averaged together. Standard deviations and
coefficients of variation were also computed to measure the scatter in the data.
The longitudinal and transverse tension tests results obtained for the 2-D braid
materials are given in Tables 4.2 and 4.3, respectively. Test results obtained for the 3-D
weave materials are listed in Tables 4.4 and 4.5. The tables list the average moduli
measured for each gage type, i.e. the average of three gages per gage type, and the
standard deviations of these measurements. The coefficients of variation of these
measurements are given in parenthesis in the tables. These data have not been
normalized to a common fiber volume or thickness. The thicknesses of the individual
specimens are listed in Tables 4.2-4.5.
In most cases, the materials' moduli were computed over the 1000 to 3000
microstrain region of the stress-strain curves. The slopes of the curves were established
through linear regression of the data. The two exceptions were the 2-D braid laminate
LLL and the 3-D weave laminate LS1. They both apparently developed damage at
approximately 2500 microstrain. The moduli in these cases were computed over
narrower ranges since the gages reflected the damage development.
A review of these test results is necessarily restricted to qualitative assessments due
to the limited amount of data available. Only three replicate gages could be mounted on
the specimens and only two specimens were available for each material type.
Qualitative assessments are, however, possible and general trends in the data are
apparent.
10
4.4 2-D Braided Materials
A review of the data obtained for the four braided laminates indicates that the
reproducibility of the measurements is greatly increased as the gage length increases.
This is illustrated in Figure 4.1 which plots the coefficient of variation of the moduli
measurements obtained for each gage type versus the gage length. Both the longitudinal
and transverse test results are displayed in the figure. The gage length in this case has
been normalized by dividing the strain gage's length by the material's unit cell length.
A vertical line marks the point at which the strain gage length is equal to the unit cell
length. As the figure demonstrates, the data's coefficient of variation greatly decreases
when the strain gage length exceeds the length of material's unit cell. In fact, the
coefficient of variation exceeded 5% (as indicated by the horizontal Line in the figure) in
only two of the twenty-four cases in which the gage was longer than the unit cell.
25.00
Figure 4.1
A
20.00¢-om
i..15.00
>
c_ 10.oo
0(3 5.O0
; .... .I .... I .... I . . •
Gage Length =
Unit Cell Height
[]
oH•
Arn
• Gage: 125 BZ (.125 x .062)
[] Gage: 125 AD (,125 x ,125)
• Gage: 2S0 UN (.250 x .120)
z_ Gage: 250 AE (.250 x .250)
• Gage: 500 UW (.SO0 x .180)
O Gage: SO0 AE (.SO0 x .500
[]
z_Coefficient of Variation = 5 %
m o i0
A0.00 .... ...... Y--n .... = .... m .... m ....
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Normalized Gage Length (Gage Length/Unit Cell Length)
Coefficient of Variation of Moduli for each Gage Type.
While the coefficient of variation of the moduli measurements decreased with
increasing gage length, there was no clear pattern to changes in mean moduli as strain
gage length increased. Although there were several cases in which the moduli were
lower as gage length increased, the change in moduli that accompanied an increase in
strain gage length was within the scatter of the data in a majority of cases. It was
apparent, however, that changes in modulus were small (i.e. less than 5%) when the
gage length was increased beyond the unit cell length.
The data also permitted a comparison of the effect of strain gage width on the
measurements. As in strain gage length sensitivity comparison discussed above, in a
11
majority of cases the change in moduli that accompanied an increase in strain gage
width was within the scatter of the data. However, when comparisons were possible,
i.e. when changes in modulus exceeded the coefficients of variation of the moduli, the
data indicated that increasing gage width decreased modulus. These changes exceeded
5% in several cases. No relationship between gage dimensions and unit cell dimensions
was discerned, however.
4.5 3-D Woven Materials
Many of the trends noted for the braided laminates were also apparent when the
woven laminate data listed in Tables 4.4 and 4.5 were examined. Scatter in the data, as
monitored by the coefficient of variation, again decreased as gage length increased.
Almost half of the modulus measurements made using the shortest, 0.125 in., gages had
coefficients of variation in excess of 5%. The number of instances in which the
coefficients of variation exceeded this value decreased markedly as gage length
increased to 0.250 in. and 0.500 in.
Instances in which the measured modulus decreased as gage length increased were
also evident in the woven laminate test results. However, as noted above for the braided
laminates, the change in moduli that accompanied an increase in strain gage length was
within the scatter of the data in a majority of cases. Increasing strain gage width had a
similar effect on the measured moduli.
Table 4.2 2-D Braid Longitudinal Modulus Measurements
Material Thick Modulus |Msi]
125 BZ 125 AD 250 UN 250 AE 500 UW 500 AE
8.78 + 0.83 9.25 + 0.28 8.74 + 0.34
(9.5%) (3.0%) (3.9%)
8.75 + 0.40 8.86 + 0.30 8.58 + 0.18
(4.6%) (3.4%) (2.0%), ii
8.61 __+0.88 9.14 __+0.67 9.06 + 0.22
(10.2%) (7.3%) (2.4%)
9.47 +__0.64 8.50 + 0.22 8.67 + 0.15
(6.8%) (2.6%) (1.7%)
•222 10.06 + 0.82 9.81 + 0.45 - 9.52 +-0.34(8.2%) (4.6%) (3.6%)
SLL
[in]
.219
SLL
LLL
LLL
LLS
LLS
LSS
LSS
.220
.218
.230
.252
.221
.223
8.85 + 0.96 8.87 + 0.25 8.96 + 0.08
(10.8%) (2.8%) (1.0%)
4.79+0.14 4.77+0.15 4.92+0.07
(2.9%) (3.1%) (1.4%)
4.52 + 0.36 4.50 + 0.08 - 4.34 + 0.02
(8.0%) (1.7%) (0.5%)
12
Table 4.3 2-D Braid Transverse Modulus Measurements
Material
SLL
SLL
LLL
LLL
LLS
LLS
LSS
LSS
Thick
[in]
.223
.223
.221
.223
.222
.250
.223
.222
Modulus [Msil
125 BZ 125 AD 250 UN 250 AE 500 UW
7.63 + 0.80 6.41 _+0.81 - 6.89 + 0.10
(10.5%) (12.6%) (1.5%)
5O0 AE
6.84 + 1.0 6.32 _+0.28 6.29 _+0.(_5
(14.6%) (4.4%) (1.0%)
8.06 + 0.65 7.82 - 6.98 ± 0.90
(8.0%) (12.9%)
7.03 ± 3.51 - - 6.41 ± 0.21
(50.0%) (3.3%)
3.22 + 0.20 - 2.94 ± 0.28
(6.2%) (10.0%)
- 2.68 +_0.53 2.51 ± 0.15 -
(19.8%) (6.0%)
6.64 ± 0.69
(10.4%)
2.80 + 0.12
(4.0%)
2.98 +_0.03
(1.0%)
3.12 __+0.17 - 3.33 -+0.02
(5.4%) (0.6%)
2.79 ± 0.11
(3.9%)
3.07 ± 0.22 3.22 + 0.12 - 3.21 + 0.04
(7.2%) (3.7%) (1.2%)
Table 4.4 3-D Weave Longitudinal Modulus Measurements
Material Thick Modulus [Ms±]
TS1
TS1
TS2
TS2
LS1
LS1
LS2
LS2
OS1
OSI
OS2
OS2
[in]
.230
.230
.226
.227
125 BZ 125 AD 250 UN 250 AE
11.59 ± .41 12.04 _+.84
(3.5%) (7.0%)
12.36 ± .51 12.27 + .09
(4.0%) (0.7%)
11.42 ± .43 - 10.49 __+.78
(3.8%) (7.4%)
11.82 + .55 11.35 + .04
(4.7%) (0.4%)
500 UW 500 AE
11.62 + .25
(2.0%)
11.93 + .19
(1.5%)
10.94 + .18
(1.6%)
11.03 ± .10
(0.9%)
.222
.227
.231
.228
.228
.226
.230
.230
13.06 ± .42 13.32 ± .63
(3.2%) (4.7%)
13.89 ± 3.54 - 13.03 -+ .40
(25.0%) (3.1%)
- 12.14 +__.27 12.26 +__.06
(2.2%) (0.5%)
12.10 + .62 - 11.83 + .43
(5.1%) (3.6%)
11.28 __+.59 12.71 __+.34
(5.2%) (2.7%)
11.73 __+.60 - 11.56 -+ .75
(5.1%) (6.5%)
10.69 ± .23 11.07 + .42
(2.2%) (3.8%)
10.62 __+.25 - 10.03 __+.40
(2.4%) (4.(/%)
12.65 ± .32
(2.5%)
12.34 + .26
(2.1%)
11.72 ± .17
(1.5%)
11.28 + 06
(0.5%)
11.41 ± .20
(1.8%)
10.45 + .32
(3.1%)
11.26± .21
(1.9%)°
11.29 + 1.0
(8.9%)
13
Table 4.5 3-D Weave - Transverse Modulus Measurements
Material Th ick Modulus [Msi]
TS1
[in]
.229
125 BZ
6.43 ± .48
(7.5%)
125 AD 250 UN 250 AE
6.53 _+.19
(2.9%)
500 UW 500 AE
6.35 + .06
(1.0%)
TS1 .229
TS2 .224
TS2 .231
LS1 .228
LS1 .223
LS2 .233
LS2 .231
OS1 .229
OS1 .225
OS2 .232
0S2 .232
6.44 + .20
(3.1%)
7.25 + .33
(4.6%)
7.32 + .61
(8.3%)
6.18 _+.29
(4.7%)
6.15 + .42
(6.8%)
6.58 + .61
(9.3%)
6.70 _+.89
(13.3%)
6.91 + .43
(6.2%)
7.17 +_.67
(9.3%)
6.35 + .14
(2.2%)
6.76 _+.15
(2.2%)
7.25 _+.36
(5.0%)
6.41 _+.59
(9.2%)
6.98 + .41
(5.9%)
7.00 + .16
(2.3%)
6.49 + .03
(0.5%)
6.70 + .07
(1.0%)
6.83 + .17
(2.5%)
6.78 + .06
(0.9%)
6.27 + .02
(0.3%)
6.03 + .26
(4.3%)
6.35 + .50
(7.9%)
6.53 + .05
(O.8%)
6.89 + .50
(7.3%)
6.58+ 11
(1.7%)
6.78 + .06
(0.9%)
6.91 + .28
(4.1%)
6.75 _+.08
(1.2%)
6.22 + .07
(1.1%)
6.01 + .09
(1.5%)
6.20 _+.14
(2.3%)
6.21 + .07
(1.1%)
6.14+ .12
(2.0%)
14
5. In-Plane Tension Test Program
The behavior of textile composites under unidirectional tensile loading is examined
in this chapter. Strength, stiffness and Poisson's coefficient are measured. The effect of
specimen width and length is the main focus of the test method evaluation.
5.1 Test Confiouration
The test matrix used for this program is shown in Table 5.1. A total of 156 2-D
braided specimens, 15 stitched uniweave specimens and 18 3-D woven specimens were
used. Specimen configuration effects were studied with the 2-D braided specimens,
while the stitched uniweave and 3-D woven specimens used a single size, 2 inch wide
by 7 inch long.
The basic specimen for this test program is the straight sided coupon described in
ASTM D3039 and illustrated in Figure 5.1. This specimen was used to measure tension
strength, modulus and Poisson's ratio. A dogbone specimen configuration in Figure
5.1b was also used for some of the tests. Beveled fiberglass tabs, with 5 ° taper angle and
0.050 inch thick, were bonded to the straight-sided specimens. The dogbone and
transverse tension specimens were not tabbed since initial tests of such specimens
resulted in failures within the test section. During testing, the specimen ends were
gripped with hydraulic grips and the coupon loaded to failure at a stroke rate of 0.05
inches per minute.
An extensometer with a one inch gage length was used in all tests. The extensometer
was attached at the center of the gage length with rubber bands and hot glue or M-Bond
200. A few specimens experienced extensometer slippage prior to failure, generally
because of local fiber or matrix failure prior to final failure. Most specimens were also
instrumented with longitudinal and transverse 1/2 inch square strain gages
(Measurements Group Inc. EA-06-500AE-350).
F 0.050" Fiberglass Tab, 5° TaperI
Figure 5.1.a
back longitudinal and transverse gages
2.25" _--i_ Length vI_1
Typical Tension Specimen Configuration.
15
Figure 5.1.b
_31" Radius
01
J_7.0"11.5"
Dogbone Tension Specimen Configuration.
Table 5.1 Test Matrix for Tension Test Program.
r .............. III
Gage Section Material Systems I
I Dimensions
Width Length Note SLL SLL LLS LLS LLL LLL LSS LSS Others
[in] [in] 1/8" 1/4" 1/8" 1/4" 1/8" 1/4" 1/8" 1/4" (1)
1.00 3.50 3 3 3 3 3 3 3 3
1.50 5.25 3 3 3 3 3 3 3 3 I
I 2.00 5.50 3 3 3 3
2.00 7.00 3 3 3 3 3 3 3 3 3
2.00 8.50 3 3 3 3
-----2.50 8.75 ..... 3 3-- - 3 3 - 3 - -3 ..... 3 .... 3 ........ I
. 1.60 7.00 Dog-Bone 3 3 3 3
1.50 [ ZOO Net-Shape 3 3 3 3i
-2-_--- ZOO Transverse 3 3 3 3
27 18 27 18 21 12 21 12 33
(1) Five Stitched Uniweave and Six 3-D Woven Materials.
5.2 2-D Braid Materials
5.2.1 Test Section Width, Length and Thickness Effectsv
One issue of interest in the tensile testing was the effect of the specimen width
compared to the unit cell size of the materials. A certain minimum number of unit cells
should be present across the test section to insure a representative failure mode. The
baseline test section used here is 2 inches wide and 7 inches long. Specimens with a
width ranging from 1 to 2.50 inches were tested to detect any sensitivity to width.
Results for the four braid types are shown in Figure 5.2, where strength and
coefficient of variations (CoV) are reported. No clear trend can be identified, either by
looking at the mean values or the CoV. It is interesting to note that the largest unit cell
width is that of the LLL braid at about 0.83 inch and that a one inch wide coupon
16
contains just over one cell. Yet, no difference was observed in strength.
Similarly, no trend can be identified between thin and thick specimen in terms of
scatter. The difference in mean result between thin and thick specimens with a width
greater or equal to 1.5 inch was +2.9% for SLL, +4.4% for LLS, +0.2% for LLL and 0% for
LSS. Since these values are within the results scatter, there appears to be no significant
difference between 1/8" and 1/4" thick specimens.
Finally, results for the SLL and LLS specimens are plotted in Figure 5.3 as a function
of the specimen test section length. No trend in tension strength can be observed in
changing the length from 5.5 to 8.75 inches.
2-D Braid, SLL Architecture 2-D Braid, SLL Architecture140 o_" 1012o 9
..1: .9 8100 ._ 7
L-.
680 _ 560 _
g 40 E 4
i_ 20 ,.-:-_ 2o 1
0.50 1.00 1.50 2.00 2.50 3.00 0 01 1.5 2 2.5
Specimen Width [in]
Figure 5.2.a
Specimen Width [in]
Effect of Specimen Width on Tensile Strength of 2-D Braid SLL.
140
_ 12o
100
_ 80
r-.o
¢-.
I--
2-D Braid, LLS Architecture
6O°
40!
20 i
0"
0.50.... I .... I .... I .... I .... I
1.00 1.50 2.00 2.50 3.00
Specimen Width [in]
Figure 5.2.b
o_ 109
t--o 8,B
76
> 54
¢..
3"° 2
1oo 0
2-D Braid, LLS Architecture
.... I .... I .... I1.5 2 2.5
Specimen Width [in]
Effect of Specimen Width on Tensile Strength of 2-D Braid LLS.
17
140" 120
100
8o60
g 4o_ 20
_ o
2-D Braid, LLL Architecture
0.50 1.00 1.50 2.00 2.50 3.00
2-D Braid, LLL Architecture
._ 108
6i,2
8 o1 1.5 2 2.5
Specimen Width [in] Specimen Width [in]
Figure 5.2.c Effect of Specimen Width on Tensile Strength of 2-D Braid LLL.
..=.r,-
09t-._oct_
140
120
100
8O
60
4O
2O
0
0.50
2-D Braid, LSS Architecture o_ 1
t-O
>"5t"
(1)0o
1.00 1.50 2.00 2.50 3.00
Specimen Width [in] Specimen Width [in]
Figure 5.2.d Effect of Specimen Width on Tensile Strength of 2-D Braid LSS.
140 2-D Braid, SLL Architecture _ 140 2-D Braid, LLS Architecture
100 _ 100
80 _ 80
60 60
40 .o 40
20 #. 200 0 , , I , , I ,, I
2-D Braid, LSS Architecture09876543210
1 1.5 2 2.5
4. 6. 8. 10. 4. 6. 8. 10.
Figure 5.3
Gage Section Length [in] Gage Section Length [in]
Effect of Specimen Length on Tensile Strength of 2-D Braids.
5.2.2 Longitudinal Tension Test Summary
The results from all the tension tests are summarized in Table 5.2. Since it was seen
in the previous section that gage length and width had a minimal influence on the
results, data from all specimen configurations were averaged together for each type of
material. In this table, maximum strain refers to the last strain gage reading prior to
18
failure, while nominal strain is simply the ultimate stress divided by modulus. Because
of the possibility of local damage developing under the strain gage prior to failure, the
maximum strain reading is not always very reliable and shows quite a bit of scatter.
Therefore, it is listed here mostly for reference purpose. In design practice, the value
used is always the nominal strain since materials are assumed to behave linearly to
failure. Results for both thin and thick specimens are listed although there does not
appear to be any significant difference between the two. Poisson's coefficient
measurements were not very reliable in general and showed a very high scatter.
A particularly interesting comparison can be made between the SLL and LLL
specimens where only the longitudinal and bias tow sizes have been changed by a
factor of 2.5. This results in a 20% strength reduction and 5% modulus reduction.
As mentioned above, a dogbone shape coupon was considered as an alternative test
configuration. A strength comparison with the baseline specimens is shown in Figure
5.4. A slightly higher strength is obtained in half the cases, and a slightly lower strength
in the other two. Thus, there does not appear to be a strong reason to prefer the
dogbone specimen which, in addition, is more expensive to prepare.
In all the previous tests, the specimens were cut from large panels. However,. in
certain structural elements, the material does not need to be cut and can be molded to
net shape by folding the dry preform along the edge of the part. This fold results in a
slightly different fiber orientation along the edge of the specimens. A series of tests was
conducted to investigate this effect using a coupon with a 1.5 inch wide by 7 inches long
test section. A strength comparison with the baseline is also shown in Figure 5.4. All
net-shape specimens exhibited a higher strength. Two of the likely reasons for this are
that the fiber architecture is different near the edge with more fibers oriented
longitudinally, and possibly that free-edge stresses are reduced.
Table 5.2 Summary of Tension Properties of 2-D Braided Materials
Property
Strength [ksi]
Nominal Strain [_ts]
CoV [%]
Modulus [msi]
CoV [%]
Max. Strain [Its]
CoV [%l
Poisson's Coefficient
CoV [%]
SLL
1/8"
109.9
11,272
5.2
9.75
3.9
12,437
18.4
0.155
17.0
SLL
1/4"
107.9
10,943
7.1
9.86
4.2
11,760
13.3
0.171
19.9
LLS
1/8"
90.9
8,724
8.7
10.42
4.3
9,103
11.0
0.613
11.2
LLS
114"
92.9
9,063
7.7
10.25
3.7
9,047
7.8
0.616
7.3
LLL
1/8"
88.3
9,536
6.9
9.26
3.4
9,754
12.0
0.152
18.8
LLL
1/4-
87.1
9,416
7.5
9.25
5.5
11,309
5.6
0.130
26.0
LSS
1/8"
52.3
10,608
5.5
4.93
4.3
12,165
4.6
0.709
12.6
LSS
1/4"
53.0
10,600
4.5
5.00
5.6
12,154
3.3
0.787
11.2
19
140t'_' 1204
_'100
" 80
60¢-
O
•_ 40r.
b- 20
SLL
..........
_!:!:!:!:!,...,.,...
................-.-.
.....,..........,,.,. ........_:_:_:_:_:
iii=_iii'=i_=
LLS LLL
D Baseline
[] Dogbone[] Net-Shape
LSS
Figure 5.4 Tensile Strength of Baseline, Dogbone and Net-Shape 2-D Braided Specimens.
5.2.3 Transverse Tension
A series of tests was also conducted along the material transverse direction using
specimens with a 2 inches wide by 7 inches long gage section. In this test, no fiber is
running along the test direction and all the load is carried by the bias yarns. Thus, this
test is very well suited to assess the strength penalty due to the crimp in these tows. As
shown in Figure 5.5 and Table 5.3, surprisingly low strength and strain were obtained.
Once again, the comparison of SLL and LLL shows that the increased tow size leads to a
strength and modulus reduction of 12% and 6% respectively.
40 .........................
35 F-
'- 30 ........ !_ ........ o_
25 ......... o_
lil= iiiiiiiiiil =o 20 ........ ! i o
'iiiiiiiii!!
ii °10 -i >
0 i_!_!!i_!ii!:I ..............II-
SLL LLS LLL LSS
Figure 5.5
LSS
Transverse Tension Strength and Nominal Strain for 2-D Braided Materials.
Table 5.3 Summary of Transverse Tension Properties of 2-D Braided Materials
Property SLL LLS LLL LSS l!
Strength [ksi] 35.2 15.2 30.9 24.7
Nominal Strain [#s] 4810 5840 4490 8440
CoV [%] 7.0 5.5 7.4 4.7
Modulus [msi] 7.32 2.60 6.87 2.92 I
ICoV [%] 5.8 6.0 1.7 1.5L : ' . : - u
2O
5.3 Stitched Uniweave M_terials
All stitched uniweave materials were tested using the baseline specimen and a test
section of 2 by 7 inches. Strength and stiffness properties are summarized in Table 5.4
and Figure 5.6 for all five materials. Overall, the scatter in the results was much less
than for the 2-D braids. The failure strains were also higher, indicating that the stitching
and weaving process introduces less of a strain concentration than the braiding process.
Material SU-1 with the smaller fiberglass stitches performed best, while material SU-5
with the large Kevlar stitches performed worst. Unfortunately, most failures occurred
near or under the fiberglass tabs due in part to the fact that these were fairly thick
specimens for which a load introduction through shear will introduce some stress
concentration in the outer plies.
Table 5.4 Summary of Longitudinal Tension Properties of Stitched Uniweave Materials
Property
Strength iksi]
Nominal Strain Ipsi
CoV [%]
Modulus [msi]
CoV !%1
SU-1
85.8
12,410
3.0
6.92
0.8
SU-2
75.9
11,700
2.1
6.49
1.5
SU-3
_.0
11,430
1.6
6.91
2.0
SU-4
82.2
11,630
2.8
7.06
0.3
SU-5
70.3
10,460
9.0
6.72
0.8
Poisson's Coefficient 0.306 0.293 0.341 0.303 0.304
100
90
80
,_ 70
_ 60_ 50
_- 400
'_ 30r--
_ 20
10
0
iiiiiiiiiiii............""""...........!.iiiiii'-!i !
_ itli!iiiiiiiii!iiiiiiiiii"iiiiiiiiiiiiiiiiiil""iiili!iiiiiiiiiiiiii"i_i!_i iiii _iiiiiiiiiiiiiiiiii- _iiiiiiiii!iiiiiiiiSU-1 SU-2 SU-3 SU-4 SU-5
¢..
C=
.o_r--
t--
¢.-
E0
z
14000
12000
10000
8000
6000
4000
2000
0
iii!iiiiiiiiii!iii.:.:.:,:.:.:,:.:.:
:!!!!!:!!!!!!!:_:!.:..::.:.:.:-:-:,:,..-......: ........,.,...,......
::!!!::!!!!!!!::i!::!!::::::::::::::::::
[!i!iiii!!i!_iii_!
i!!i!i!i!i!ii!!!i!
:-:.:-:-:-:.:-:-:................:.:-:-:-:.:-:-:-:
i!i::!::ili::i_i_!_;i:::::::::::::::::::
::::::::::::::::::::.:.:.:.:,:.:.u,:
SU-1
i!ililiiiiiiiiiii_ili_i_iiiii_i_iii_iiiiiiii_iiiii_i_i_
-i iii- iiii-iii::::::::: :::::::::............... .................. .................
:+:,:.:.:.:.:.:. :.:+:.:.:.:.:.:. .....:........ :.:.:.:.:.:.:.:.:.
............ .. :::::::::::::::::::.:.:.;.:.:.:.:.: :,:.:4+:.:.:+
:............ .........:::::::::::::::::::::::::::...................................-l_i_i_i_i_i_i_i_i_i" ,,;_i_,i_i_i_,i_i_i_,i-.........!iiiiiii_,iiiii'_iii_- ',ii',.iiiiiiiiiiiiii
I ......... I ':'!'!'!'!'!'!_!I ......... I .........SU-2 SU-3 SU-4 SU-5
Figure 5.6 Summary of Longitudinal Tension Strengths and Nominal Strains of
Stitched Uniweave Materials.
21
5.4 3-D Woven Materials
The 3-D woven materials were tested using the baseline specimen with a test section
of 2 by 7 inches. Strength and stiffness properties are summarized in Table 5.5 and
Figure 5.7 for all six materials. In two of three cases, the -2 material with the larger tow
size performed rather poorly. The Poisson's coefficient for this type of material is
always very low and for that reason, measurements exhibited a lot of scatter.
Table 5.5 Summary of Longitudinal Tension Properties of 3-D Woven Materials
Property
Strength [ksi]
Nominal Strain [psi
CoV [%l
OS-1
137.4
11,900
2.9
OS-2
92.9
7,890
2.6
TS-1
137.6
10,950
1.8
TS-2
131.8
11,350
1.5
LS-1
138.9
11,300
7.3
LS-2
96.1
7,870
5.1
Modulus [msiJ 11.55 11.78 12.57 11.61 12.29 12.22
CoV [%] 1.8 0.4 0.6 0.1 2.0 0.4
Poisson's Coefficient 0.034 0.046 0.060 0.040 0.060 0.040
CoV [%] 14.9 9.8 7.2 19.0 7.2 19.0
140
120
_10o
'_ 80e--
P60
N 40
.£_ 20
I--0
............. _ ...._--
, _
0S-1 0S-2 TS-1 IS-2
'i iiiiI
kS-1
!!!!!!!!!!!!i
:.:.:,:.x,:
i!!!i!!!!!!!_
ii!iiii_iiiiLS-2
12000
::!!i!i!!i_i!!!!i
,ooooi?Iiii.=_m_o 8000
o= lili"_ 6000 ........_!_i-:.:_Q) ::::::::
4000 iiiiiiiiiiii!ii"_ iiiii_iiiiiiill
....-.......-...
o 2000 !;!i!i!i!;!;!i!;...............,:.:,:.:.:.:.:.:2ZIZI
_.
OS-1
F iiiiiii iiiiiii!iiiiiiiii
-
i iiili,lliii-i , ii,0S-2 TS-1 TS-2 LS-1 LS-2
Figure 5.7 Comparison of Longitudinal Tension Strengths and Nominal Strains of
3-D Woven Materials.
5.5 Test Recommendations
The main concern in this test program was whether there are any scaling effects due
to the unit cell size compared to the specimen size. Based on the data shown here, very
little, if any, effects were observed from varying the specimen width and length.
Specimens as narrow as about 2 unit cells were tested with little difference from larger
one. Thus, for the materials evaluated here, the standard specimen width of 1.5 inch
22
would be considered adequate compared to unit cell sizes of 0.4 inch to 0.5 inch.
Another concern in unnotched tension tests is to obtain a good failure mode inside
the test section and away from the tab region. Most laminated materials tend to fail
close to the tabs where small stress concentrations cannot be avoided. However, for the
2-D braided materials, failure was obtained within the test section, mostly due to the
fact that the material itself contains stress concentrations due to tow waviness and
crimp more severe than at the edge of the tabs so as to induce failure in the gage section.
The use of a dogbone specimen produced strength results which are not significantly
different from the straight sided specimen. Therefore, the use of a dogbone specimen is
probably not worth the extra cost of specimen machining. Conversely, for the stitched
uniweave material, since the material appears to contain less severe stress
concentrations, failure usually occurred in the tab regions. The use of thinner specimens
is recommended for this type of material.
Scatter in the results for the 2-D braided materials was slightly higher than for other
materials and Poisson's coefficient measurements were particularly poor. This suggests
the use of a somewhat larger number of specimens in order to obtain statistically
adequate test data and to avoid taking a penalty when calculating B-basis allowables.
23
6. Open-Hole Tension Test Program
The strength of textile composites with open holes under unidirectional tensile
loading is examined in this chapter. The effect of specimen width and hole diameter is
the main focus of the test method evaluation.
6.1 Test Confiouration
A straight-sided coupon with no tabs was used in this test program, as shown in
Figure 6.1. The length was kept constant and the width varied as indicated below in the
test matrix. All holes were drilled with ST carbide drill bits. Specimens were gripped in
hydraulic grips and loaded to failure at a rate of 0.05 in/min. No strain measurements
were taken and only load and machine stroke were recorded during these tests.
Figure 6.1
_ +.003"
CL F D..000-
l : .............. W/2 + 0 005"
I
[-_ 11,5"
Open Hole Specimen Configuration.
The test matrix used for the Open Hole Tension test program is shown in Table 6.1.
Because the objective is the evaluation of the test method, the first parameter of interest
is the specimen width to hole diameter ratio. A ratio of W/D equal to 6 is typically used
in testing composite materials. However, since material availability can be sometimes
limited, it is of interest to find out how small a specimen can be used while still
obtaining adequate data. Conversely, as in the tension test program, one needs to verify
whether the large unit cell size has any influence and whether larger specimens than
usual need to be used. Two material systems, SLL and LLS, were tested more
extensively to investigate this effect on both thin and thick specimens. A second effect,
more important from a mechanics of material point of view is the hole diameter since it
is well known that strength is strongly dependent on the notch size for composite
materials. Fewer tests were conducted on the other two 2-D braid architectures, LLL
and LSS. Only 1.50 inch wide specimens were tested in this case. For all other material
systems, i.e., stitched uniweave and 3-D woven angle interlock, 1.50 inch wide
specimens were also used.
24
Table 6.1 Test Matrix for Open Hole Tension Test Program
Dimensions
Width Diameter W/D SLL SLL LLS
[in] iinl 1/8" 1/4" 1/8"
1.50 .375 4 3 3 3
1.50 .250 6 3 3 3
1.50 .188 8 3 3 3
2.25 .562 4 3 3 3
2.25 .375 6 3 3 3
2.25 .281 8 3 3 3
3.00 .750 4 3 3 3
3.00 .500 6 3 3 3
3.00 .375 8 3 3 3
27 27 27
Material Systems
LLS LLL LLL LSS LSS Others
1/4" 1/8" 1/4" 1/8" 1/4" (1)
3 3
3 3
3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3
3
3
27 9 9 9 9 99
(1) Five Stitched Uniweave and Six 3-D Woven Materials.
6.2 2-D Braid Materiai#
6.2.1 Width to Diameter Ratio Effect
When analyzing data from an open hole test, there are several ways to calculate and
report stress at failure. As described in Section 3.4, the options are gross stress, net stress
and stress corrected to infinite plate width. As an example, these three stresses are
shown in Figure 6.2 for two braid architectures, SLL and LLS. This data was obtained
for 1/8" specimens with a 3/8" hole using three test configurations with w/d=4, 6 and
8. If there is no material or specimen sensitivity to w/d and if the finite width correction
factor is accurate, the corrected stress should be the same for all test configurations. The
data shown in Figure 6.2 indicates that this is roughly the case and that the corrected
stress remains constant within the data scatter. On the other hand, net stress clearly
varies with w/d and is not the best way to report the data. Since the values obtained are
always higher, it is also a less conservative approach when using the data for design
purpose. Therefore, stress calculated with the infinite width plate correction factor will
be used in this report for all open hole tests. Other stresses can always be calculated if
necessary from the raw data presented in Appendix A. Further more, this method is
customarily used when determining composite material allowables. Also, several series
of specimens were tested with both a varying hole diameter and w/d. Without a way of
correcting the effect of w/d, it would not be possible to determine the influence of the
hole diameter.
25
_120_
c-o 60
oae-
_ 40
-6 20:"r
¢- 0
O 4
Figure 6.2
2-D Braid, SLL Architecture
-"'°"--Gross INet
Corrected
I I I
.--_.120"
.E
1ooi-_ _ 80!
r--O_ 60(/)
_ 40:o--c 20e-
I "_ 08 0
2-D Braid, LLS Architecture
•-_o---Gros s
---o-.--Ne t-----a,-_ Corrected
5 6 7 4 5 6 7Width to Diameter Ratio Width to Diameter Ratio
13
Comparison of Gross, Net and Corrected Stress in SLL and LLS 1/8"
Thick Specimens with a 3/8" Diameter Hole.
6.2.2 Thickness Effect
Testing was conducted with two different thicknesses for all architectures, but data
is available at a common hole diameter only for the SLL and LLS with a 3/8" hole
diameter. This data, shown in Figure 6.3, reveals a certain sensitivity to thickness when
a specimen with a low w/d is used. For instance, at w/d=4, the mean strength of the
1/4" specimens is 17% below that of the 1/8" ones. At w/d=8, the difference is reduced
to 5%. For the LLS architecture, the difference is 16% at w/d=4, and 8% at w/d=8.
_ 2-D Braid, SLL Architecture '_
_--_100"T !1 _'90
90 1 m
•80 • B i __" 8070 o o o _ 70
o ¢n 6060 o =•- o 50
" 50 1 m ,/o in,oK c
_ 40I-- 40 ....,, .,.,_:_,. I--(D"6 30 _ 30 --r- 20 o 1/4"Thick T° 20-¢.-
_. lo g 10-O 0 = = = _0
2 4 6 8 2
Width to Diameter Ratio
Figure 6.3
2-D Braid, LLS Architecture
ii
I
0
1/8" Thick
1/4" Thick
I I
4 6
Width to Diameter Ratio
I
8
Comparison of Open Hole Tensile Strength in SLL and LLS 1/8" and 1/4"
Thick Specimens with a 3/8" Diameter Hole.
I_,2.3 Hole Size Effect
The parameter with the strongest influence is the hole diameter and it is well known
that the strength of notched composite materials is sensitive to the notch size itself.
Results for the four braid architectures are shown in Figure 6.4.a to 6.4.d. Because of the
26
thickness sensitivity mentioned in the previous section, data from 1/8" and 1/4"
specimens were separated. Unnotched strength (i.e., d = 0) is also indicated in each plot
for reference.
The curve fitting technique described in Section 3.4 was used to help interpret the
data and establish a relationship between strength and hole diameter. Note that
unnotched strength is not used in this fitting process. Because of the scatter in data and
the variability from panel to panel, this technique is very helpful in identifying series of
data points for a given material which differ from the overall trend in behavior.
However, it is also possible that fitting the whole range of hole diameters with a single
curve is not completely accurate. For instance, at small hole diameters, i.e., hole sizes
less than the unit cell width, one could expect a slightly different behavior and notch
sensitivity than in specimens with a hole much larger than a unit cell. The results for the
SLL architecture are fairly typical of the data obtained. For instance, for the 1/8"
specimens, note that two points fall below the trend, for d=0.28" and d=0.56". Similarly,
for the 1/8" LLS architecture, the data for d--0.25" and d=0.50" do not follow the
general trend.
In general, the data for the thick specimens is always lower than for the thin
specimens and appears to be slightly more consistent for the various hole diameters.
However, the low values are partially due to the fact that the data was obtained in
several cases from specimen with a low w/d. Also, there appears to be more difference
between the two thicknesses at small diameters than at large diameters.
Figure 6.4.a
100
U3
80¢-
(3)C
60CO
c.9m 40C
I---
20
..............
[] 1/8" Specimens
S=72 17*d^-O. 165
0 1/4" Specimens
- S=7250"d^-0.129
0 .... t .... ! .... I .... I
0.00 0.20 0.40 0.60 0.80
Hole Diameter [in]
Effect of Hole Diameter on Tension Strength of SLL Specimens.
27
00 ........... _ .......... .-.. ............ . ........
_ 80 ........... "_ ........... "ID.................
6o ...................... .2_":.._.-. - .._..___'_'_'___O9
¢-o
"P= 4O
2O
0
0.00
Q 1/8" Specimens
S=61.27"d^-0.208
Q 114" Specimens
-S=54.19"d^-0254
.... I .... I .... I .... I
0.20 0.40 0.60 0.80
Hole Diameter [in]
Figure 6.4.b Effect of Hole Diameter on Tension Strength of LLS Specimens.
20 ............. _ ....... - ..................... ---
_-,001 .....
0t)
¢-
.940r-
I--
2O
0
0.00
E:! 1/8" Specimens
,--.. .................. ..o
S=5299"d^-0315
• 1/4" Specimens
S=53.51°d^-0.244
.... I .... I,,.,,I .... I .... I .... I
0.10 0.20 0.30 0.40 0.50 0.60
Hole Diameter [in]
Figure 6.4.c Effect of Hole Diameter on Tension Strength of LLL Specimens.
28
0.00 0.10 0.20 0.30 0.40 0.50 0.60
Hole Diameter [in]
Figure 6.4.d Effect of Hole Diameter on Tension Strength of LSS Specimens.
6.2.4 Summary
Mean stresses corrected to infinite plate width and coefficients of variation are
shown for each configuration in Table 6.2. Most coefficients of variation are below 7%.
Once again, the comparison of SLL and LLL allows to assess the strength penalty due to
the use of larger tow sizes.
Table 6.2 Mean Stress and CoV for Open Hole Tension Tests of 2-D Braided Materials
Hole Diameter
[in]
0.188
W/D=8
Property
Strength Iksi]
Coy I%1
0.250 Strength [ksi]
W/D =6 CoV I%1
0.281 Strength [ksi]
W/D = 8 CoY 1%]
0.375 Strength [ksi]
W/D = 4,6, 8(1) CoV [%]
0.500 Strength [ksi]
W/D = 6 CoV [%]
0.562 Strength [ksi]
W/D = 4 CoY [%1
0.750
W/D =4
Strength [ksi]
Coy [%1
SLL SLL LLS LLS LLL LLL LSS LSS
1/8- 1/4- 1/8- 1/4- 1/8- 1/4- 1/8- 1/4-
99.1 91.8 89.5 86.2
3.5 9.o 4.6 2.1
91.4 82.2 74.3 75.6
6.7 18.5 6.6 2.2
82.4 91.7 81.5 72.7 77.5 72.7 40.3 40.8
3.5 1.5 0.9 3.0 9.2 3.0 7.9 3.7
87.6 76.9 76.3 68.4 74.8 68.4 37.3 40.1
5.4 11.4 6.4 4.9 2.5 4.9 5.9 5.0
81.0 81.9 78.0 65.8
6.7 4.4 4.8 4.2
75.5 77.0 66.7 61.6 62.8 61.6 33.6 34.7
4.0 4.5 3.9 5.0 4.8 5.0 6.7 4.6
79.2 76.2 62.9 59.7
2.3 8.0 3.8 5.2
(1) Average Result for W/D = 4, 6 and 8
29
6.3 _titched Uniweave Materials
A more limited series of open-hole tension tests was conducted with stitched
uniweave materials and mean stresses corrected to infinite plate width are shown in
Figure 6.5 and Table 6.3. The results for all five materials were quite similar, indicating
that the type of stitching used appears to have little influence on the strength. Therefore,
a single curve appears to be sufficient to fit all the data. Once again, very little scatter in
the data was observed for this type of material.
100.0 .............................................
Figure 6.5
0.0 'lllll'llllllZllllllllllllllllllllllllllll'l_
60,0 ..........................................
u)SU-2
SU-3
SU-4
SU-5
S_35.30"d ^-0 30':3
40.0 O
A
O20.O
O
l | m I
t-.(2_rY)t-OI--
0.0 ' i ,' , , , I .... I d , , , I
0.00 0.10 0.20 0.30 0.40
Hole Diameter [in]
Effect of Hole Diameter on Open Hole Tension
Uniweave Materials.
Strength of Stitched-
Table 6.3 Mean Strength and CoV for Open Hole Tests of Stitched-Uniweave Materials
Hole Diameter iin]
0.188
W/D=4
Property
Strength [ksi]
CoY 1%1
0.250 Strength [ksi]
W/D=6 CoVl%}
0.375
W/D = 8
Strength [ksi]
CoY 1%]
SU-1 SU-2
59.2 58.0
0.9 1.8
54.1 52.4
2.8 0.8
47.8 47.0
5.1 0.9
SU-3
58.0
4.6
53.0
7.1
48.5
3.0
SU-4 SU-5
61.3 56.6
0.9 2.8
55.9 51.4
2.0 2.7
52.6 46.8
3.1 4.2
30
6.4 3-D Woven Materi_l$
A limited series of open-hole tension tests was conducted with 3-D woven materials
and results are shown in Figure 6.6 and Table 6.4. The lack of a clear trend and the
limited data made it difficult to use the log-log fitting technique here for three of the
materials, OS-2, LS-2 and LS-1. Based on the best fit curves obtained for the other three
materials, an exponent of -0.25 was chosen for these three materials and the value of the
constant was chosen to fit two of the three data points. The results of this operation are
shown in Figure 6.7.a to 6.7.c. Since the exponents are approximately the same in all the
curve fits, a comparison of the constants can be used to compare the notch sensitivity of
the different configurations. This comparison indicates that the -2 configurations (with
the smaller tow sizes) suffer a strength penalty of 21% for OS, 15% for LS and 15% for
TS. Among the -1 configurations, LS-1 is the strongest by about 15% compared to TS-1.
140.0 =............................................
0120.0 ................... .._ ..... "0" ................
0
_" 100.0 ........................... "6 ............ "1_'"
r-- rl 0S-1 IP'_ 80.0 ............ -m---C " ............... --AL
II OS-2 j"
c 60.0 --- OLS-1 ..................................o
c • LS-2® 40.0 ......................................
I.-OTS-1
20.0 .... OTS-2 ..................................
0.0 .... I .... I .... I .... I
0.00 0.10 0.20 0.30 0.40
Figure 6.6
Hole Diameter [in]
Open Hole Tension Strength Data for 3-D Woven Materials.
Table 6.4 Mean Strength and CoV for Open Hole Tests of 3-D Woven Materials
Hole Diameter [in]
0.188
W/D =4
Property
Strength [ksi]
CoY 1%1
0.250 Strength [ksi]
W/D = 6 CoY I%1
0.375
W/D=8
Strength [ksi]
CoY i%1
OS-1 OS-2 LS-1 LS-2 TS-1 TS-2
117.5 80.0 126.5 80.9 109.3 92.6
0.9 12.1 0.3 17.1 2.7 5.0
101.2 87.9 119.2 99.3 100.4 87.9
12.8 1.6 6.8 0.8 3.5 4.8
97.7 72.9 87.1 90,3 92.2 78.2
12.2 17.8 5.1 5.0 0.3 3.6
31
140
120
-_,100
¢-
c 80
C/),- 60.o= 40(D
20
0
[] 0S-1
s = 74.7"d^_ 254
0 0S-2
........ s = 58.9"d^-0.25
[]
O _''" q=
.... I .... I .... ! .... I
0 0.1 0.2 0.3 0.4
Hole Diameter [in]
Figure 6.7.a Effect of Hole Diameter on Open Hole Tension Strength of 3-D Woven
Materials OS-1 and OS-2.
140
120
-=- 100e-
_- 80
09¢ 60._o¢/)
_- 40a)
F--
20
[] LS-1
s = 83.2"d^-0.25
O LS-2
........ s = 70.8"d^-0.25
o
0 .... I .... I .... I .... I
0 0.1 0.2 0.3 0.4
Hole Diameter [in]
Figure 6.7.b Effect of Hole Diameter on Open Hole Tension Strength of 3-D Woven
Materials LS-1 and LS-2.
32
140
Figure 6.7.c
120
100.E:
,'- 80
CO_- 60o
,'- 40I.-
20
0
[] TS-1 I
s = 72.4"dA-0248
O TS-2
........ s = 61.6"dA-0.248
i w i w I i i w
0 0.1
I .... I .... I
0.2 0.3 0.4
Hole Diameter [in]
Effect of Hole Diameter on Open Hole Tension Strength of 3-D Woven
Materials TS-1 and TS-2.
6.5 Test Recommendations
The standard straight-sided untabbed specimen configuration performed well in all
the testing done here. The two parameters that were seen to influence the test are the
specimen thickness and width to diameter ratio (W/D). For all 2-D braided materials,
thicker specimens exhibited a lower strength, but this is not necessarily a consequence
of the test method. When using the correction factor for infinite plate width, little effect
of W/D was observed for the thin (1/8") specimens. For the thick specimens (1/4"), a
lower strength was obtained for W/D=4. Therefore, a ratio of W/D=6 is recommended
as a minimum. Also, the use of multiple hole sizes and the log-log fit of strength versus
diameter was particularly useful in detecting anomalies.
33
7. In-Plane Compression Test Program
The strength of textile composites under unidirectional compressive loading is
examined in this chapter. In contrast to tension testing, a large number of test fixtures
and specimen configurations are available for compression testing. Thus, the main focus
of this investigation is a comparison of the different methods.
7.1 Test Confiourations
Seven different techniques, described below, were evaluated in this investigation
using the test matrix shown in Table 7.1. Sketches of the different configurations are
shown in Figures 7.1.a to 7.1.c.
Sandwich column compression specimens were tested in the Zabora Sandwich
Compression fixture. The specimen ends are machined with a shallow 10 ° "V" in order
to match the specimen ends to the fixture.
The NASA short block fixture is the smallest specimen of all used. The loaded edges
are clamped over 0.3" and no side support is provided. Load is introduced by contact
across the specimen cross-section and thus specimen machining and alignment in the
fixture is extremely important. Because the specimen is very short, a slower loading rate
of 0.025" per minute is recommended.
The modified IITRI is a straight specimen with unbevelled fiberglass tabs. Instead of
using the special IITRI loading fixture, the specimen is gripped in the test machine with
hydraulic grips. Special attention to machining the specimen tabs is taken to insure that
the tab surfaces are parallel. Care is also taken in aligning the specimen so that no initial
bending is induced in the specimen.
The Boeing Compression After Impact (CAI) fixture utilizes a rectangular 4" by 6"
specimen. The loaded edges are clamped in the fixture over 0.3", while the sides are
simply supported between rails which are snug but not tight so that the specimen can
slide between them. Load is introduced by contact against the specimen ends, and thus,
parallelism of the ends is important. The standard loading rate of 0.05" per minute is
used.
The NASA ST-4 specimen is very similar to the Boeing CAI specimen and is
described in the NASA 1092 ST-4 specification (Ref. 5). The only difference is that a
larger 5" by 10" specimen is used.
The Boeing Open Hole Compression and Zabora fixtures were used also to test
unnotched specimens. The specimen is a straight untabbed 1.5" by 12" coupon.
34
Table 7.1 Test Matrix for Compression Test Program.
Dimensions Material Systems
Width Length Note SLL SLL LLS LLS LLL LLL LSS LSS[in] [in] 1/8" 1/4" 1/8" 1/4" 1/8" 1/4" 1/8" 1/4"
Sandwich (2olurnn
3.00 6.00 3 3 3 3
1.50 6.00 3 3
2.25 6.00 3 3
3.00 2.00 3 3
3.00 8.00 3 3
3.00 6.00 Core Effect 3 3
NASA Short Block
1.50 1.50 3 3 3 3
1.50 1.00 3 3
1.50 2.00 3 3
NASA ST-4
5.00 10.0 3 3 3 3
Boeing CAI
4.00 6.00 3 3 3 3
Modified I|TR1
1.50 1.00 3 3 3 3 3 3
1.50 1.50 3 3 3 3
1.50 2.00 3 3
1.50 1.50 Transverse 3 3 3 3
Boeing OHC
1.50 12.00
1.50 12.00 Net-Shape 3 3 3 3
Zabora Fixture
1.50 I 11.50 [ 3 3 3 3
27 27 27 27 12 15 12 15
Others(1)
3
3
3
99
(1) Five Stitched Uniweave and Six 3-D Woven Materials.
Figure 7.1.a
Le th
O"
Modified IITRI Specimen and NASA Short Block Specimen.
35
l"Z
Nomex Honeycomb Core
Composite Facesheet
1/16" Fiberglass Tabs
Aluminum Honeycomb Core
1.52"
7.s.,o I i:o
I I I
I I I
O i i iO
.07"
3.0"
e'-
.E
J
12."
Figure 7.1.b Sandwich Column Specimen, Zabora Fixture and Boeing OHC Fixture.
5" NASA ST-4,r
4" Boeing CAI
_N__ Clarr
I:
I
(i
I'
,/ .Simply
)ed
-- Clamp_
• /d
10" NAS, ST-4,
6" Boeil g CAI 12"
ppo_ed
I t
Figure 7.1.c NASA ST-4 or Boeing CAI Specimen and Boeing OHC or Zabora Fixture
Specimen.
36
7.2 2-D Braid Materials
7.2.1 Test Section Length and Thickness Effects
The main concern in compression testing is whether the test fixture provides
adequate support to prevent failure by global specimen instability. Thus, specimen gage
length and thickness are of prime interest. On the other hand, just as in tensile testing, a
certain minimum number of unit cells should be present across the test section to insure
a representative failure mode. This effect was investigated with the SLL and LLS braid
for the NASA Short Block and modified IITRI methods. The baseline test section used
here is 1/4 inch thick, 1.5 inches wide and 1.5 inches long. Specimens were also tested
with a length of I and 2 inches to detect any sensitivity to length, and with a thickness
of 1/8 inch to detect sensitivity to thickness.
Results for the two braid types are shown in Figure 7.2 and 7.3, where strength is
reported. In general, there does not appear to be a very strong trend for the range of
values tested, although the 2 inch gage length seemed to lead to more scatter and
slightly lower values. Note that one set of data, the 1 inch long LLS NASA Short Block
test, is much above the other results and appears to be an anomaly for which no cause
could be identified. Moduli measured with these configurations are shown in Figure 7.4
where no effect from gage length can be observed.
Also, at a gage length of 1 inch, little difference was found between 1/8" and 1/4"
thick specimen. For instance, for the SLL specimens the strength of the 1/8" is 4% below
that of the 1/4" specimen when both are tested with the modified IITRI method.
However, when examining strain data obtained using back-to-back gages, the 1/8"
specimen does exhibit some non-linearity in behavior which indicates some stability
problem.
100
80t-
c-
.¢ 60u)
cL 40Eo 200
o
.0
Figure 7.2
2-D Braid, SLL Architecture
°
I I
1.5 2.0
Test Section Length [in]
100
80t-
t-
_ 60if)
d. 40Eo
0
2-D Braid, LLS Architecture
El
20
0 I I
1.0 1.5 2.0
Test Section Length [in]
Test Section Length Effect on Compression Strength in NASA Short Block
Test Configuration.
37
100Or)
80r"
60
d. 40Eo 20
0
1.0
Figure 7.3
10
8¢,D
"5 6"OO
4d.E 2O
0
.0
Figure 7.4
2-D Braid, SLL Architecture
[] [][]
[]
I (
1.5 2.0
100
80J_
_" 60
o9
0
o
40
20
0
1.(
2-D Braid, LLS Architecture
B
! I
1.5 2.0
Test Section Length [in] Test Section Length [in]
Test Section Length Effect on Compression Strength in modified IITRI Test
Configuration.
2-D Braid, SLL Architecture
[] IITRI
• NASA SB
' l10
E 8
5 6O
d.EOo
2-D Braid, LLS Architecture[]
| i
[] IITRI I• NASA SB
4
2
0
1.0
I I I
1.5 2.0 1.5 2.0
Gage Length [in] Gage Length [in]
Test Section Length Effect on Compression Modulus in NASA Short Block
and modified IITRI Test Configurations.
7.2.2 Longitudinal Compression
The compression stiffness modulus and ultimate strength were determined for all
four braids using the NASA Short Block, modified IITRI, NASA ST-4, Boeing CAI and
Zabora test methods. The moduli are reported in Figure 7.5. The NASA Short Block test
method always resulted in lower moduli, while the Zabora fixture usually produced
slightly higher values.
The strength and nominal strain (defined as the stress divided by nominal modulus)
of all five test methods are summarized in Figure 7.6.a to 7.6.b for all four materials. The
NASA Short Block and Zabora test methods gave the highest results each in two of the
four cases. The modified IITRI and Boeing CAI test method consistently gave lower
results than the NASA Short Block by I0 to 15%. Results from the NASA ST-4 were
always much below the others, indicating that this method is not suitable for this type
of testing. This is in part due to the large test section, which does not provide adequate
stability to test unnotched or unflawed specimens to failure. A summary of the
38
compression properties is provided in Table 7.2. The strength value from the NASA
Short Block, modified IITRI and Zabora fixture tests are reported, while the moduli are
the averages of the NASA Short Block, modified IITRI and Zabora tests. In terms of
scatter, the Short Block test method produced the lowest coefficients of variation. One
possible explanation for the higher strength of the Short Block specimen than the
modified IITRI specimen is the difference in load introduction and the fact that both
these specimens are fairly thick: in the Short Block test, load is introduced by contact
over the whole specimen cross-section, resulting in a uniform loading through-the-
thickness, while in the modified IITRI specimen, load is introduced in shear in the outer
plies of the specimen, thus resulting in slightly higher stress levels in these plies nearthe tabs.
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90.0
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70.0¢--
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30.0
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:::::::::::::i;:: : :.: :.:.:.:: : ::::::::::::::::21
!_i!iii_:i_::_il-!!i!!:/iiii!iii_:-........- _- _000i:i:i:!:!:_:i:i:!: __ E
,_i!iiil;iii:_!!i!_!!ii_i;ii;-iiiiiiii!i!iiiiioo............... i'ii _ .......... I 0! !
NASA Boeing ZaboraST-4 CAI
i:ilili_!i!_!i_
'[[::. _ !!iii!_iiiiiiiiiii•,.....,.,,...., .:.:.:.:,:,:.:.:.:
- -iiiiiii_ii!iii!iiiii-
........ :::..::. .........._i_:i_i_!ii!ii_ :!:!:!:!:i:i:i:!:i !iii!_ili!i!!i!iii
•:,:.:+:.:+: ::::::::::::::;:::_::!_iiiiiiiii::iiii::iii!i:::iij:_:i,i,i:!:i:
:_:::::_-ililili_ili_i_i_i!........._:!:!:!:i:i:!:i: ',','..'.'.'.,,"
::_:::::i, !iiiiiiiii!iii_i!!i !_!_i_!_i_i::i_INASA IITRI NASA
SB ST-4
Compression Strength and Nominal Strain of LSS Braid
iiii!!iiiiiiiiii_
......... _!!!!_!!
:::::::::::::::::: ...............+x+>x+: +x+:x.:
......... +x+x+:
..................!i!i_i_!!!i!!!!!
iiiiiiiiiiiiiiii!i:.:.:.:.:.:.:.:iiiiiiii!i!i!i!i......................... .:.:.:.:.:.:.:.:
: | _i!i!_!i:i_i_:!IBoeing Zabora
CAI
Table 7.2 Summary of Longitudinal Compression Properties for 2-D Braid Materials
Property
NASA SB Strength lksil
CoY I%1
Nominal Strain [ITS/
Mod. IITRi Strength Iksil
CoV [%1
Nominal Strain [I.tsl
Zabora Strength [ksil
CoY [%1
Nomina] Strain [/as]
SLL
78.8
3.7
9140
70.6
6.4
7860
84.4
14.2
9328
LLS
62.8
2.7
7211
59.2
5.3
6743
58.0
4.2
6405
LLL
58.6
7.7
6995
48.7
10.8
5699
66.6
5.4
7467
LSS
46.2
1.7
11391
45.5
5.9
1O378
44.9
3.9
9511
Modulus [msil 8.92 8.82 8.37 4.38
CoV [%1 2.9 5.4 8.5 7.3
7.2.3 Sandwich Column
The results of the sandwich column specimens were not included in the previous
discussion since they were not satisfactory for two reasons. The first problem with the
sandwich specimens is that no fiber volume fraction measurements were obtained on
the facesheet materials because the specimens were delivered as a complete sandwich.
Thus a normalized thickness corresponding to a 60% fiber volume fraction could not be
established as for the other tests. Instead, a nominal 0.0625" thickness was used for all
specimens. The second problem is that no material strength data could be generated
with this specimen configuration. The failure mode of this specimen is always a
structural failure mode rather than a material failure mode. In all tests, failure occurred
41
when one of the facesheets separated from the core due to either core or bond failure.
Results from these tests are summarized in Table 7.3. Moduli measured with this
method were usually lower than when measured with the other test methods, possibly
due to the use of nominal thickness. In one case (LLS), the modulus was much higher
and in another (LLL) much lower, with no available explanation for this.
Table 7.3 Sandwich Column Compression Properties for 2-D Braid Materials.
Property
Strength [ksi]
Coy I%1
Nominal Strain [las]
Modulus [msi]
CoY I%1
SLL
28.2
8.3
365O
7.74
3.8
LLS
_.3
6.1
3020
11.34
2.5
LLL
16.3
6.5
2990
5.46
3.2
LSS
16.7
1.2
4870
3.43
1.2
7.2.4 Boeing Open Hole Compression Fixture
The results of the Boeing Open Hole Compression fixture were also not included in
the previous discussion since they were not satisfactory. Abnormally high strength
results were obtained in several cases probably due to friction or interference between
the fixture and specimen.
7.2.5 Transverse Compression
Specimens of each material were tested in the transverse direction with the modified
IITRI method. This is particularly interesting for this type of material since there are no
fibers running directly along the loading direction and all the load is carried by the
braided tows. As seen in Table 7.4, the transverse strength of the SLL, LLS and LLL
architecture is relatively poor. The change in tow size between the SLL and LLL has a
particularly drastic effect and leads to a 25% strength reduction, but practically no
change in modulus.
Table 7.4 Summary of Transverse Compression Properties for 2-D Braid Materials UsingModified IITRI Test Method
Property
Strength [ksil
CoV [% ]
Nominal Strain [Its]
SLL
42.1
3.4
5805
LLS
25.3
10.1
8377
LLL
31.6
4.8
4252
LSS
43.1
2.1
14224
Modulus ]msi] 7.25 3.03 7.42 3.03
CoY [%! 2.2 1.8 1.3 4.7
42
7.3 Stitched Uniweaves Material_
7.3.1 Longitudinal Compression
The testing of the stitched uniweave material was conducted with the NASA Short
Block and modified IITRI specimens only. Results are shown in Table 7.5. The
conclusions from these tests are very similar to the ones found in the previous section.
The Short Block test gave higher strength values by 9 to 14 %, but a slightly lower
modulus by 4 to 8 % compared to the modified IITRI. The best strength was achieved by
the SU-lmaterial with the 3K S2-Glass stitch. For the Kevlar stitches, increasing the
stitch spacing or yarn size actually gave slightly higher results, but in general, the
influence of the stitching type is small. Also, as for other properties, the coefficients of
variation for this type of material were less than for the 2-D braid.
Table 75 Summary of Trartwerse Compression Prow_rties for Stitched Uniweave Materials
Property
Mod. IITRI Strength [ksi]
Coy I%1
Nominal Strain [Its]
NASA SB Strength [ksi]
CoY I%1
Nominal Strain I_s]
SU-1
52.3
1.0
8235
57.0
3.3
9783
SU-2
44.9
1.8
7414
51.1
3.3
8759
SU-3
45.5
3.5
7477
52.0
2.5
8875
SU-4
49.7
0.8
7470
54.9
1.8
8559
SU-5
46.8
0.7
7519
53.8
5.1
9061
Mod. IITRI Modulus [msi] 6.35 6.06 6.09 6.65 6.22
CoY [% ] 0.9 0.8 1.3 0.4 0.5
NASA SB Modulus [msi] 5.83 5.84 5.86 6.41 5.93
CoV [% ] 2.6 0.9 0.8 0.2 0.8
7.3.2 Transverse Compression
Compression testing was also conducted in the transverse direction using the
modified IITRI method. As shown in Table 7.6, although the layup is quasi-isotropic,
the strength results are surprisingly higher than in the longitudinal direction, ranging
from 4.5% for the SU-1 to 21.8% for the SU-5 (when comparing the modified IITRI
method in both cases). Modulus showed much less difference between the two
directions, except for SU-5 (9.4% difference). One possible explanation is that the
stitching runs parallel to the 0 ° direction and induced more fiber distortion in the 0 ° ply
than in the 90 ° ply.
43
Table 7.6 Summary of Transverse Compression Properties for Stitched Uniweave
Materials Using the Modified IITRI Test Method
Property
Strength [ksil
CoY [%i
Nominal Strain [its]
Modulus Imsil
CoY l%1
SU-1
54.7
3.9
8623
6.34
2.6
SU-2
51.1
1.8
8343
6.12
.9
SU-3
52.1
3.3
8336
6.25
0.8
SU-4
53.5
3.7
7881
6.79
(1.2
SU-5
57.0
1.6
8365
6.81
0.8
7.4 3-D Woven Materials
7.4. 1 Longitudinal Compression
Testing of the 3-D woven materials leads to the same conclusion as before, with the
Short Block Method yielding the highest strength in all but one case as shown in Table
7.7. Unlike in the previous case, the difference in moduli between the two test method
was smaller. In terms of tow size influence (the difference between the -1 and -2
material), the smaller tow size (-1) usually produced a slightly higher strength and
modulus. The orthogonal interlock (OS architecture) produced better strength results,
possibly because of the lesser distortion induced in the 0 ° fibers. Coefficients of
variations were in general low.
Table 7.7 Summary of Longitudinal Compression Pro :_erties for 3-D Woven Materials.
Property
Mod. IITRI Strength [ksil
CoY 1%1
Nominal Strain [itsl
OS-1
84.0
5.0
7661
OS-2
77.8
7.3
7615
TS-1
76.2
5.0
6990
TS-2
63.8
3.4
6167
LS-I
76.7
3.4
6713
LS-2
62.2
2.4
5649
NASA SB Strength [ksi] 87.0 90.6 75.4 70.2 81.7 79.9
CoV [%] 3.3 6.0 1.5 6.0 4.8 8.4
Nominal Strain [its] 7895 8714 7198 6952 7282 7315
Mod. I1TRI Modulus 10.96 10.21 10.9 10.35 11.43 11.01
[msi] 0.9 1.1 1.2 1.0 1.0 0.6
CoY [%1
NASA SB Modulus [msi] 11.03 10.40 10.48 10.09 11.23 10.92
CoV [%] 1.6 6.5 2.9 2.6 1.3 1.5
7.4.2 Transverse Compression
As for the previous materials, testing was also conducted in the transverse direction
with the modified IITRI method. Assuming that the nominal strains at failure are equal
for loading in the longitudinal and transverse directions, the strengths and moduli for
44
the transverse direction should be about 60% of those in the longitudinal direction
based on the 0 ° and 90 ° fiber percentages. As seen in Table 7.8, except for the LS-1 and
LS-2 weaves, the nominal strains at failure were similar and those for the weaves with
the largest yarns (-1) were somewhat less than those with the smallest yarns(-2). The
nominal strains at failure for the LS-1 and LS-2 weaves were significantly less than the
others, and that for LS-1 somewhat greater than for LS-2. The transverse strength
deviated from 60% of the longitudinal strengths accordingly. The median value for the
transverse moduli was 57%.
Table 7.8 Summary of Longitudinal Compression Properties for 3-D Woven Materials
the Using Modified IITRI Test
Property
Strength [ksi]
CoV [%1
Nominal Strain [Ds]
Modulus [msi]
CoV I%]
O.%1
41.3
2.3
6729
6.14
2.7
OS-2
52.2
1.4
8875
5.88
1.0
TS-1
37.2
7.1
6410
5.80
0.8
TS-2
52.7
3.8
7197
7.32
2.3
L.%2
32.4
14.4
5264
6.15
1.4
LS-2
27.8
20.2
4371
6.35
0.2
7.5 Test RecommendatiQn_
An A or B basis allowable increases with increasing mean value and decreases with
increasing coefficient of variation (CoV). Thus, the test method that would produce the
maximum allowable would maximize the mean and minimize the CoV. Test data for
the different materials were pooled, and means and CoVs were calculated for the NASA
short block, modified IITRI and Zabora methods. The CoVs for the various materials
can be pooled together directly since they are non-dimensional quantities, but the
means cannot. Thus, a normalized metric for the mean was calculated as follows:
1) Means for each material were calculated with:
1 N_
Xm N _ xmnn=1
where m is the material number, n the test method number, N the number of test
methods and Xmnthe mean value for a given test method and material combination.
2) A mean deviation from _mWaS calculated for each test method with:
I _. Xrnn - Xm_-Xn = M -- Xrnm=l
where M is the number of materials for a given test method.
Values of Axn and CoV for the strengths and moduli are given in Table 7.9 and plotted
in Figures 7.7 to 7.10.
45
The results indicate that the modified IITRI test method gave the largest allowable
for compression moduli, but the NASA Short Block and Zabora methods gave the
largest allowable for strength. Note however that the number of data points for this
method was much smaller. Also, because of the side supports on the specimen, there is
a possibility of some load being lost through friction in the fixture. In terms of mean
strength, the NASA Short Block test method gave consistently higher results than the
modified IITRI method by about 9% to 12 %.
In terms of stability, a length to thickness ratio (L/t) of less than 10 is recommended
for the modified IITRI and NASA Short Block method. A ratio of 6 appears to be a good
compromise in terms of having a sufficiently large test section and good stability. Both
the NASA ST-4 and Boeing CAI specimens are inadequate for compression testing of
unnotched specimens because of their lack of stability.
Table 7.9 Mean Deviations AXn and CoVs for Unnotched Compression Test Methods
Test Method
Material Property Modified I1TRI NASA Short Block Zabora
A---xn CoY A---xn CoV A---xn CoY
2-D Modulus 2.1% 6.4 % -7.7 % 4.0 % 5.6 % 3.3 %
Braids Strength -6.7 % 8.5 % 2.1% 3.9 % 4.6 % 6.9 %
Stitched Modulus 2.5 % 0.9 % -2.5 % 2.1% n/a n/a
Uniweave Strength -5.9 % 1.5 % 5.9 % 3.2 % n/a n/a
3-D Modulus 0.2 % 1.5 % -0.2 % 2.8 % n/a n/a
Woven Strength -4.9 % 4.4 % 4.9 % 5.0 % n/a n/a
Figure 7.7
6.0
,_, 4.0
¢" 2.0
E 0.0_or" -2.0.9
"_ -4,0a_o
-6.0
-8.0
I!_i!i!i!i!i!i!i!i!iiiiiiiiiiiiiiiiiiiii
!iiiill:.:.:.:.:-:.:.:.:.:
i!iiiiiiiiiiiiiiiii!!!!!!!!!!!!!::!!!!_!
IITR_ NASA SB Zabora
[] 2-D Braid
[] Stitched Uniweaw
[] 3-D Woven
Deviation from Mean Strength for Unnotched Compression Test Methods.
46
Figure 7.8
Figure 7.9
Figure 7.10
9.0
8.0 4-,
7.0_
o_ 6.0 -.-,
>o 5.00
c 4.0
3.0
2.0
1.0
0.0
,...........
:.:.:.:.:+:.:.
............. .......,..•.
.............
!iii!iii!,........Ji:i:i:i:
-- I I:i:!:i:!.:.:.:.:,'k,,r,,
i!ililiiiii!i!iill
!!!!!!!!iiii!iii!!
iiiiiiiiiiiiiiii!'.:.:<.:.:+:.:
.:.:+:.:.:+:
................
!!!!!!!!!!_!!!i!:.:.:.:+:+:.
!:!:!:!:!:!:_:i:...............•.....•..._..,.
..............................
NASA SBI ITRI Zabora
I_ 2-D Braid
Stitched Uniweave
3-D Woven
Mean Strength CoVs for Unnotched Compression Test Methods.6.0
4.0
c 2.0
E 0.0oc -2.0 -
._o
"._ -4.0 --
t_-6.0 --
-8.0 --
Deviation
Methods.
i!!!i!i!i!i!i!!!
IITRI
from
l!i!iiiiiiiiiiiiiiiii_iJF::::.-.-.......:
,ll
ilili,iiii, ID!!!ii!_!!i!ii!ii!!!ii!i;iii [] Stitched Uniweave
i!i'::!i!i!i!i!i':i! m3-DWoven1:1:1:1:1:1:191:• • : : :
NASA SB Zabora
Mean Modulus for Unnotched Compression
7.0
6.0
5.0
> 4.0OOt-in 3.0
2.0
1.0
0.0
iiiiii_
!i!!
:::;::
iill
_!!! - 1
i!iiiiiiiii!iiiiiiii!iil
_i!i!i!i!i!i!i!iii!_!
:+:+:.:.:.:.:.:.
::::::::::::::::::::::::::::::
iii!iiiiiiiiiiii!i!:
I :::::::::::::::::::::
IITRI NASA SB Zabora
l i 2-D Braid
Stitched Uniweave
3-D Woven
Mean Modulus CoVs for Unnotched Compression Test Methods.
Test
47
8. Open Hole Compression Test Program
The strength of textile composites with open holes under unidirectional compression
loading is examined in this chapter. The test methods and the effect of hole diameter are
the main focus of this test program.
8.1 Test Confiaurations
Six of the seven test methods discussed in Chapter 7 were used as shown in Table
Table 8.1 Test Matrix for Open Hole Compression Test Program.
Dimensions [in]
Width Diameter W/D
Boein[_ IOpen Hole Comp.
1.50 .375 4
1..50 .250 6
1.50 .188 8
NASA Short Block
1.50 .375 4
1.50 .250 6
1.50 .188 8
NASA 1142
1.50 .375 4
1.50 .250 6
1.50 .188 8
Modified IITRI
1.50 .375 4
1.50 .250 6
1.50 .188 8
Zabora Fixture
1.50 .375 4
1.50 .250 6
1.50 .188 8
Boein[_ CAI Fixture
4.00 0.500 4
4.O0 0.8OO 5
4.00 1.000 8
NASA ST-4
5.00 I 1.250 I 4
Material Systems
SLL SLL LLS LLS LLL LLL LSS LSS Others
1/8" 1/4" 1/8" 1/4" 1/8" 1/4" 1/8" 1/4" (1)
3 3
3 3
3 3
3 3 3
3 3
3 3 3
3 3
3 3
3 3 3
3 3
3
3 3 3 3
3 3 3 3
3 3 3 3
3 3 3 3
3 3 3 3
3 3 3 3
3 3
3 3 3
3 3
12
3 3
18 39 18 39 12 18
3
18 132
(1) Five Stitched Uniweave and Six 3-D Woven Materials
48
8.1. The sandwich column was dropped becauseof its complexity to manufacture andits poor performance in the previous testprogram. In addition to these, the NASA 1142method, shown in Figure 8.1, was also considered (Ref. 6). Because both the holediameter and the width to diameter ratio are varied simultaneously, the correctionfactor for infinite width was used again to calculate the strength and make it possible tostudy the influence of hole diameter. However, no direct comparison of the influence ofW/D canbe made. No strain gageswere used on thesespecimens.
10"
iiiiiiiiiiiiiiiiiiiiiiiiii C,amped Clampe d iiiiii;iiiiiiiii!i!;i;!i!
.............lug. \iiiii::iii::?:?:i::ili!i::ii?:i::ii::i_iiiiii_7......
1.5o" _!i !!V iiiiiiiiii!iiiii!iiiiii i!i
Figure 8.1 NASA 1142 Specimen Configuration.
8.2 2-D Braid Materials
8.2.1 Test Method Comparison
Five of the seven test methods were compared directly: the Boeing Open Hole
Compression (OHC) fixture, the NASA Short Block specimen, the NASA 1142
specimen, the modified IITRI specimen and the Zabora Test Fixture. Two of the 2-D
braided materials, the SLL architecture and the LLS architecture were used for this
comparison. Some sets of data seem to show a high scatter, while others do not. Possible
explanations are variability in material quality or a material sensitivity to hole position
with respect to architecture due to the non-uniform nature of the material.
Mean values and CoVs for all test methods are shown in Figures 8.2 and 8.3,
respectively, and Table 8.2. As in previous sections, the column marked "Strain" is the
nominal strain obtained by dividing ultimate stress by the average compression
modulus measured in the previous section.
No single method produced the highest strengths for all materials. On the other
hand, the Boeing OHC and Zabora test methods typically produced the highest CoVs.
The thinnest materials (1/8") were tested with these two methods; perhaps local
instabilities caused the large CoVs. The CoVs for the LSS material were the lowest, even
for the 1/8" thick material. This is possibly due to the fact that this is a rather soft layup
which is not as notch sensitive as the other two.
49
7O
--'=" 6O(/)
40o_t-
.o_ 30_0
2oEoo 10
Figure
6O
_ 50
4O-
30-t-O
¢O
_ 20-
Eo 10-
O
0
Figure
r-
¢-
¢-
.o
Eo
O
Figure
2-D Braid, SLL Architecture
lili i_ii
0. 188" Hole
8.2.a Comparison
Methods of
0.250" Hole
of Open Hole Compression
SLL Materials.
2-D Braid, LLS Architecture
] :i
_iill
0.375" Hole
Strength for
iili_l_i ?iiiii!iii!iiiiiiii_
0.1 88" Hole
8.2.b Comparison
Methods
60
50
40
30
20
10-
00.188"
iiii_iiIti iiiiiiiiiiii]i
lliiili!iiiiiiiiiiiiiiiiillI
0.250" Hole 0.375" Hole
of Open Hole Compression
of LLS Materials.
2-D Braid, LLL Architecture:::.:::.:.::::::./: : ::_!i!ii_:ili!i!:
:.:,x,:,x.:,
:iiiii_ii_ii!ii_! :::::::::::::::_
......H.,., .::+::.:+:!
iiiiiii!ili!!!!! i !i_ii!i!_:_:!-_
:.:,;:,:,::,. .:.:.::+::.l:i:!:i:i:_:i:i:i i:_:i:i:i:i:_:_|
i:i:_:i:i:i:i:i: .:,:,:.:.:.:.:+ : .....,...,_:J:i:i:i:J:;:J:_ 2::::2:-
!i_i_iii_i_i!i:i_ _:_;i_i!'_--.........,,......... .........=i?iiiii!i!:!i!i!::..... r_:?_i:i:i_ii_!!.......:+:+:.:.:. :.:.:.:,::.:.:,a
........ iiiiiiiiii!iiii|::: ::.:: ::::: .........::::.:::::::::: ::::::::::::::::!
::.:+:x: I I :.:.x.:.+:,..
Hole 0.250" Hole
Compression8.2.c Comparison of Open Hole
Methods of LLL Materials.
Strength for
: i_
I
0.375" Hole
Strength for
• Boeing OHC
• NASA SB
[] NASA 1142
[] Mod. IITRI
[] Zabora
Various Test
• Boeing OHC
• NASA SB
E3 NASA 1142
[] Mod IITRI
[] Zabora
Various Test
• Boeing OHC
• NASA SB
[] NASA 1142
r_ Mod. IITRI
[] Zabora
Various Test
5O
t-
t-
O3
¢-O
Or)
Q..Eo
¢,.)
Figure
40.
35.
30.
25
20
15
10
5
0
_HHH
HH_H
H.H
.... H'
2-D Braid, LSS Architecture
I
H
_-HHHH
Xq:::+.::
H •
::X:::
IO. 188" Hole 0.250" Hole 0.375" Hole
8.2.dComparison of Open Hole Compression Strength
Methods of LSS Materials.
• Boeing OH(
• NASA SB
t_ NASA 114_
D Mod. IITRI
1:3Zabora
I
for Various Test
25
,'- 20o
"C
m 15>
o
o 50
Figure 8.3.a
2-D Braid, SLL Architecture
-1J
O. 188" Hole O.250" Hole
II
I0.375" Hole
• Boeing OHC
II NASA SB
I_ NASA 1142
[] Mod IITRI
[3 Zabora
Comparison of Coefficient of Variations for Open Hole Compression Test
Methods of SLL Materials.
Figure 8.3.b
2-D Braid, LLS Architecture
• Boeing OHC
[] NASA SB
E_ NASA 1142
1:3M0d. IITRI
O Zabora
,0.188" Hole 0.250" Hole 0.375" Hole
Comparison of Coefficient of Variations for Open Hole Compression Test
Methods of LLS Materials.
51
35
3O
25
_' 20._o
"t- 15>
o
10
o 5-
0
Figure 8.3.c
0.188" Hole
2-D Braid, LLL Architecture
u
• Boeing OHC
J NASA SB
El NASA 1142
rl Mod IITRI
13 Zabora
0.250" Hole 0.375" Hole
Comparison of Coefficient of Variations for Open Hole Compression Test
Methods of LLL Materials.
,.- 4o.D
.¢,-
3>
"6
o 1L)
Figure 8.3.d
2-D Braid, LSS Architecture
O. 188" Hole 0.250" Hole
• Boeing OHC
B NASA SB
E] NASA 1142
13Mod IITRI
FI Zabora
0.375" Hole
Comparison of Coefficient of Variations for Open Hole Compression Test
Methods of LSS Materials.
52
Table 8.2 Summary of Open Hole Compression Test Results for 2-D Braided Materials
SLL
D Stress Strain CoV
[inl lksil I%1
Boeing Open Hole Compression
0.188 56.0 6281 25.9
0.250 59.1 6630 23.9
0.375 54.8 6139 6.4
NASA Short Block
0.188 68.5 7684 3.3
0.250 58.7 6585 11.9
0.375 50.9 5707 3.5
NASA 1142 Fixture
0.188 62.7 7034 3.9
0.250 55.8 6252 14.2
0.375 54.6 6116 0.9
Modified IITRI Specimen
0.188 64.(I 7172 3.7
0.250 64.6 7247 15.5
0.375 48.1 5392 0.8
Zabora Fixture
0.188 64.2 7201 5.4
0.250 63.6 7135 7.9
0.375 56.9 6379 6.6
Boeing CAI Fixture
0.500 54.5 6107 12.7
0.800 41.6 4667 3.6
1.000 41.6 4667 4.1
NASA ST-4 Fixture
1.250 I 36.8 I 4122 I 14.6
LLS
Stress Strain CoV
[ksil [%1
47.4 538(/ 5.8
46.4 5259
43.4 4924 4.6
50.0 5669 2.3
47.0 5333 6.3
41.1 4661 5.9
48.9 5542 3.9
49.5 5610 3.6
45.2 5121 7.1
LLL LSS
Stress Strain CoV Stress Strain CoV
[ksil [%1 [ksil [%1
39.1 4669 26.2
j .............
34.4 I 7848 3.3
....
43.1 5155 2.(1 32.8 7489 2.9
51.8 6185 11.0 36.8 8405 3.0
52.6 5958 1.2 58.7 7018 3.5
49.4 5601 6.4 53.9 6438 5.7
45.3 5138 8.7 51.1 6102 5.9
54.7 62(/2 5.1 47.5 5677 26.(I
47.5 5380 9.8 44.4 5310 17.9
44.7 5(}66 2.2 42.5 5079 32.3
40.7 4617 3.1
35.9 4073 5.7
32.3 3658 4.3
37.0 8447 2.0
36.6 8352 1.9
33.8 7734 (1.5
38.7 4623 2.0 31.4 7164 0.6
1306I 65I 60I I I I 18.2.2 Hole Size Effect
In addition to the test methods compared in the previous section, the NASA ST-4
and Boeing CAI specimens were used to examine the open hole compression strength in
the presence of larger holes than the ones used in the other specimens. As for the open
hole tension tests, the log-log fitting technique of strength versus hole diameter was
used to analyze the results. For each hole diameter, the results from different test
methods were averaged together when available. Some series of results with a high CoV
53
or a low mean due to a premature failure in one of the specimen, were eliminated in
certain cases from this average whenever it was possible to reduce the overall scatter for
a given diameter. Results for all four 2-D braids are shown in Figure 8.4 and a rather
good fit is obtained in all cases. For reference purpose, the mean compression strength
is also indicated in each plot. For the hole diameters of 0.188", 0.250" and 0.375", the
specimens were only 1.50" wide; thus, for the 0.375" diameter hole, the ligaments on
either side of the hole are only 0.563" wide. The unit cell widths, which ranged from
0.415" to 0.829" for the braids were essentially as wide or wider than the ligaments. On
the other hand, the CAI and ST-4 specimen have a good amount of material in the net
section. When looking at the data point corresponding to the 0.375" hole in Figure 8.4,
one can see that it lies within the normal scatter of the curve fit across all hole sizes.
Thus, this would indicate that the small number of material unit cells in the net section
did not significantly influence the results.
Once again, an interesting observation of the tow size effect can be made by
comparing SLL and LLL. For a hole diameters of 0.188", SLL is about 26% stronger than
LLL. However, for a larger hole diameter.of 0.800", the difference is only 7%. This is
possibly due to the fact that for large hole diameters, materials appear to be more
homogenous compared to the hole size and thus, the coarse architecture of LLL makes
less of a difference. The effect of changing the braid angle from 70 ° to 45 ° is seen in
comparing the results of LLL and LLS. Interestingly, in term of stress, there is not much
difference between the two. Finally, the LSS material with its high percentage of 45 °
appears to have little sensitivity to the notch size.
7O
40
{/3
Or) 30 ................................................
Eo 20 [] SLL Tesl lil .........................
O
10 s = 40.5"d^- 304
0 ,, , I,,, I,,,I, ,,I,, ,I,,,I ,,,I
0.00 0.20 0.40 0.60 0.80 1.00 120 1.40
Hole Diameter [in]
Figure 8.4.a Effect of Hole Diameter on Open Hole Compression Strength of 2-D
Braided Materials SLL.
54
0 ......................................... -------
-_ 6o ................................................
5O
40g"_ 30
E 20o
10
0
0.00
[] LLS Test ..........................
S = 330"d^-278
,, ,I,,, I,,,I, ,,I,, ,I,,,I ,,,I
0.20 0.40 0.60 0.80 1.00 1.20 1.40
Hole Diameter [in]
Figure 8.4.b Effect of Hole Diameter on Open Hole Compression Strength of 2-D
Braided Materials LLS.
0 ................................................
0 ................................................
60 ...............................................
5O
o
30
O..
E 2OoO
10 i1 [] LLL TestS -- 365"d^-.187
0
0.00
,, ,I,,, I,,,I, ,,I,, ,I,,,I ,,,I
0.20 0.40 0.60 0.80 1.00 1.20 1.40
Hole Diameter [in]
Figure 8.4.c Effect of Hole Diameter on Open Hole Compression Strength of 2-D
Braided Material LLL.
55
5O
t-O
r_Eo0
3O
2O
I0
L
D LSS Test
S = 30.5*dA-.106 ..........................
0 ,, ,I,,, I,,,I, ,,I,, , I,,,I ,,,I
0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40
Hole Diameter [in]
Figure 8.4.d Effect of Hole Diameter on Open Hole Compression Strength of 2-D
Braided Material LSS.
8.3 Stitched Uniweave Materials
Stitched uniweave materials were tested only with the Boeing OHC specimen and
modified IITRI methods. Results from this testing are summarized in Table 8.3. A
comparison of the two methods for the 1/4" hole shows that the average difference is
only 2.1% , with, unlike for the 2-D braided materials, the modified IITRI being the
lower. A comparison of the mean CoV for each method is shown in Figure 8.5 and
reveals that both method are fairly similar. Note that in general, the scatter is much
lower than for the 2-D braids.
A comparison of the five materials is shown in Figure 8.6, where nominal strains are
calculated with the compression modulus; not much difference is observed between the
different types of stitching: SU-1 fared best, with SU-3 12% lower. Using the same log-
log fit of strength versus hole diameter as in the open-hole tension test program, a
comparison of SU-1 and SU-3 is shown in Figure 8.7, where SU-3 appears to be
somewhat more notch sensitive than SU-1.
56
Table83 Summary of Opm Hole Corn
Boeing OHC
0.250" Hole
SU-1
Strength [ksi]
CoY l%l
47.3
4.2
_ression Test Results for Stitched _ve Materiak
SU -3
40.1
4.1
SU4
40.6
1.8
SU-2
42.1
1.8
SU-5
45.8
1.2
Mod. IITRI Strength 47.9 42.4 45.0 46.3 46.8
0.188" Hole CoV 2.2 2.1 1.0 3.4 0.8
Mod. IITRI Strength 44.5 39.5 40.7 43.0 43.0
0.250" Hole CoV 3.4 7.2 4.7 2.1 3.5
Mod. IITRI Strength 42.9 37.3 37.8 39.0 39.0
0.375" Hole CoV 3.3 3.5 1.2 0.9 1.2
Figure 8.5
>O
oC
:s
4.50
4.00 I
3.50 ",-
3.00 .*-
2.50 JF { ;:I.:.I.I:;.I:I:;:;:::;:I:I:I:I:i oo, i!...........!....1.5o..,- I ......................
" iC::_:;i_::_:;_::;::_i_:::::!i;!_::_1.00 -.- i_iiii;_iiiii_;_iiiii_::i::!iiii::i::iiiii::i
o.5of II ! ,i!iii' il0.00 , iii_iiiii:,iii;_!i;_;_i':': ii;ii_il
Boeing OHC0.250"
!i!ii!i!iiiiJiiiiiiiiiii [_iiiiiiiiiiiii!iiiiiii::!:!:!:!:!:!:!:!:!S_
i:i:i:i:i:i:i:i:i:i:i:
:?iiiiiii!?i?!i_?!_!i .:.:.:,:.:.:.:.:,:.:
iiiiiiiiiiiiiiiiiiii ....................... ':i:::,::!::i::iii?iii?iiiiiii!i?ii::
!!!iii!!!iiiiiiiiiii is::s::iii:=:iiis:=siiiiii!ii::i::iiii...................._!!!!!!!!_!!!:!!!!! :::::::::::::::::::::::::::::::::iiiiiii!}i::::::::::::::::::::::::::::::::
.......... •..................... :.i!i!i:.;il.............................. ,. ,.,., ..,.....,....,....
j m::: :::: j _ii!_iiiiiiiiiii!ii!i! j i:!:_:i:i: i:i'!:!:!:!:!:i:?i: I
Mod. IITRI Mod. IITRI Mod. IITRI
0.188" 0.250" 0.375"
Comparison of Mean Coefficient of Variation for all Stitched Uniweave
Open Hole Compression Tests.
(,0
r"
C
.o_¢/;
8_EO
o
O
"1-
c
8.O
50.0
40.0
30.0
20.0
10.0
0.0
..................:!:_;!:!:!:!:!:!:!:!.........................,.....................:...
i!ili!i!iiiiiiiiiiii..,....,...............,.....,..........,..,..,:,..,....., ,...,...,...,,,.,...............,.,,..,....,........,...., ....,......:::::5:::::::::::::
i:ii:i:ii:i;;:i:iil;ii;iiiiiil;iiill::::::::::::::::::::.,..............:.:.:.:.:.:.:.:.:.:._ii!iiiiiiii!i!iii_i
iiii!iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!i!i!i!i!i!i!i!i!ij!;!;!::::::;:::::i:::
SU-1
Figure 8.6
_Z?: Z'!??I
...,.:...,..,,,,,.,......, ..,....:....................._.,.......
..........,....
...............................!iii!i!i!i!i_i!i!!!i
!i!i!i!i!iiiiiiiiiii•........,,........:+:.:.::.:.:.:.:.::::::::::::::::::::.,.............
::::::::::.........................,._.,..::::::::::::::::::::
:::::::::::::::::::::::::::::::::::::+:.:.:.:.:.:.:.:.
iiiiiiiiiiiii!iiiiii
SU-2
iiiiiiii!iiiiiiiiiii;::;::::::::::::::::
iiiiii!iiiiiii!iiii!_iiiCiCiCili_i_:::::::::::::::::;::i!!i!i_!!_i!iii!i!_i,.,.,,.,,,,,. ,..
!iiiiiiiiiiiiiiii!ill
!i!i!i!i!i!i!i!!iii_i)il))i)il;);i))i)il:.:.:.:.:.:,:.:,:+:
,........ ,...,.::2:::::::::::::::..,.,,...........
i!ii_iiiiiiiiii_iiill
:iiiCiiiCi_i_iii_I "
SU-3
iiiiiiiiiiiii_ii_iii!i I
iffjiiiiii i,:.:+:.:.:.:.:.:..
!iiii!iii!!ii!ii!!!_iiili!iiiiiiiiiiiiiiiii_: :i:!::::i:i:::!::i
iii!iiiiiiiiiii!iiiii!
:.::.;.:.: ;.:; : :.
;::::::::::
ii::i:.!:_i::;:.!ii::iiiiiii!:!:i:!:!:i:i:i:!:]:?.:i:i:i:i:i:i:iSi:i:!::i:i:i:!:i:i:: :!:!::.:.:.:.:+:.:.:.:,::+:.:.:.:.:,:,:.:,:,................,:.:.:.:.;,:.:.::,:.:..,.., ,..,.,,.,::::::::::::::::::::::
! ISU-4
Comparison of 1/4"
iii_ii%!iii!:i:!:!:i:i:!:!:!:!:!
iiiiiiii!!ii!iiii!!ii!iiii[ii_i_iiiiiiii
iiii!ii!ii!ii!i!!iil!iiiii!iii!i!ii!ii!!. .... -.......
.:,:.:+:.:.:.:,:.:., _................,. ,..
::::::::::::::::::::::+:.:.:,:.;.:.:.:,::::::::::::5::::::....,.,. ,.....:!:_:!¢!:!;i:i:i:i:.:+:.:,:,:,:,:,:.:i:i:iSi:i:_:i:i:i:
i!!ii!i_ii_!!!!:i!!!..........
SU-5
Open
8000c
7000
._ 6000
5000
E4000
3000
2000
1000
o
Hole Compression
::::::::::::::::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::,.,, .,., ....., :::::::::::::::::::iiiii::iii=:iiiii::iiii21::::::::::::::::::::!:!:!:_:!:i:_q:!:_:[ ii!iiiii_i!i[iiiiiii
iiii::iiiii::iiiii::ii_il:i_iC::ii_is::_i:i:!:,:,:.:+:.:.:.:.:+ :.:.:.:.:.:.::.:.:
ii::!::!ii::!ii::i::iiil;ilj!_:i:::!_!::!_:::_:!!_!_!ii_i_T!!_i_i_ ..........
iiiiiiiiiiiiiii i i .............iiiiiiiiii!iii' iiiii""'""-'"'""" :::::2::::::::':::
iiiiiiiiii
!!ii!iiiiiiiiiii;ii!ii!iiiiiiiiiiiiiii!i!
','.',V.'.V..'.'.
i1-1 '1-,i .... _
SU-1 SU-2
Strength
":':T:':':':':'f:
:E:_:_:i:i:i:!:i:!:i......,.....,...,......,•....,...
iiiiiiiiiiiiii iiiii......,..........
iiiiii!!iiiiiiiiiiii ili i!!i! !!iiiiii...y,..,..,,.....
!iii!ii!i!i!i!i!iii
:.:,:,:,:.:+:.:.:
j .
SU-3
Strains for Stitched Uniweave Materials.
iiiiiiii!iiiiiiiiiii ::::::::::::::::::::
::::::::::::::::::::
. ,..,..,...,, ... ..........T!!!iii!!ii!!i!!!i!i!i I ii_iiii!_i_i_i_i_i_:
iiii!iii ,ili ,ii i;iii........... !i!:!i!i',ili!ii iil::::::::::::::::::::: ..,.. ,.........
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::i:i:i:i:i:i:i:i:i:i:i: , : :':':':':':':':':'........... ,.......,......,
;!_!iiiiiiiiil;iiiiii!....................ii!:::i!iii!ii==!::!::iii!:_:::::_:_:_:_:_:_:_
::iii==ili!i!iii:=i!i!i!iI=_:_:_:::_:_:_:_:_:_.....................iil;ii!iii::C::i!_ii::i.:i:i:i:i:i:i:i:_:i:i
I I ISU-4 SU-5
and Nominal
57
0 "mml_mlmmllmlmmlmmlmmmmNmmlmmmmmmmmmmmmmllmlmmml
Figure 8.7
0 ......................... _ ..... _ ...............
'3
r-.ou}
EOo
30
20
10
0
!_ su-t
S = 36.3 • d_-.168
0 su-3
s = 290 *d_-257
; ,' , , I , , , , ! = ,'
0.00 0.10 0.20
, , I .... I .... I
0.30 0.40 0.50
Hole Diameter [in]
Effect of Hole Diameter on Open Hole Compression Strength of Stitched
Uniweave Materials.
8.4 3-D Woven Materials
The results of the open hole compression testing of the 3-D woven materials are
summarized in Table 8.4. The average difference between Boeing OHC and modified
IITRI is only about 2.4% and the average CoV is about 6%. A comparison of the six
materials is shown in Figure 8.8. The OS-1 configuration yielded the highest strength,
while OS-2 produced the lowest. Other configurations exhibited fairly similar strengths.
Table 8.4 Summary of Open Hole Compression Test Results for 3-D Woven Materials
Boeing OHC
0.250" Hole
Strength [ksi]
CoV 1%1
OS-1
66.2
2.3
OS-2
n/a
LS-1
63.3
9.7
LS-2
58.3
5.1
TS-1
55.8
2.2
TS-2
55.8
6.2
Mod. IITRI Strength [ksi] 70.3 71.3 62.9 58.5 63.2 59.3
0.188" Hole CoV [%] 4.4 4.3 7.7 5.5 3.8 3.2
Mod. IITRI Strength [ksi] 68.7 46.8 61.8 60.2 56.3 59.2
0.250" Hole CoV [%] 6.1 8.2 4.1 7.5 3.7 6.3
Mod. IITRI
0.375" Hole
56.6
14.4
61.5
2.3
51.6
9.4
Strength lksil
Coy I%1
51.3
2.1
53.6
4.4
49.2
5.4
58
Figure 8.8
70.0
¢--- 60.0C
50.0[,.-
O
40.0
t'_
Eo 30.0(,.)
o 20.0T¢-,
O 10.0
"-- 0.0
Y//y_/d:iii_i
ii!iii iiiiiiiiiiiiiiiii iiiii !
_:.: x.:,:+:.:+:+x+J_ii:iiiiii!ii!i!!!i:ii!i!ii!iii!
,i::: ::::_::_::;::i::;i:_::;i::l
ii:iii_ii_ii_i.liiii_iiiiiiI_iiiiiii_iiiiiiiiiiiiiiiiiiiiiiiiiiiii_ii_ii_ili!!_!!!!i! i!i:i!i_:i!_iiii_ii!i!!!!i!!!
ii!!!!!ii!iii!i!i_iiiiii_iiii;i!iiii:iiiii!ii!iii:iii_iii:::::::::::::::::::::::::: ============================
i:i:!:i:i:i:i:i_:i:i:_:i'!: :::::::::::::::::::::::::
!ii!iii_ili:i_iii:ii!ili!il!i_i!iiiiiiiiiiiiiiiiii!iii!iiiiii_iiiii:ii:iii!i!i!i.i!: :::::::::::::::::::::::::::::
_i_i_i_i_i_i:i:ii:i!i:i!i_i _!i:;_:i_i:ii!:i:i:!!_!ii!!i
:::::::::::::::::::::: :::::::::::::::::::::::::::::
======================::::::::::::::::::::::::::::
iiiiiiiii!iiiiiiiiiiiii_iilli_i_!ii_iiiii_ili_ii!i!i!i!il
i!_ii_ii:!i_ii!iii:_ili!i!ii i_i!i!ili!ii:ii:ii_iiiiii!!ii
............. ii i iiiiiiiiiiiii !i! i{ii!:....... | ........
iii_i!i_i_i!iiiiiiiiiiiiiiiii!i!
0S-2
i i:_:i_i:i:i:i:!!.!:]:!!:i:
_,+:_x.:+_:,, :-xii!!i!iii!!i!iii!iiiii_iiiii!i:iil}:::::i_ii!_:!ii!!i:ii:i:!i!
iiiiiiili!iiiii!iiiiiiiiiiiiiiiiiiiiiii!iliiiiiiiiiiiiii!iiiii!iii!iiiiiii!ii!i:iiiii!i!ill
iii!i!_ii_iiiiiiii!!i!!!!i!ill
:2:::::::::::::.,.<::;::::_
::::::::::::::::::::::::::::::
iiiiiiiiiii!iii/ /7.1Xi 2
:::::::;:i:i:::::
gi:.iii:,::!!i:.i::i!i:=Y:ii:=i
t ::.:.:::.::+:.::::
LS-1
i:ii::Ti:ii_i!!-ii:!iiiiii:
,i_:i::i_ii_iiiiiiii_iiiiiiiiiiiii
iiiiiiiiiiiii!iiiiiiiiiiiiiiii iiiiii_iiiii_iiiiiii!!iii!!ili_iiiiii!iiiiiiiiiiiiiiiiiiiiii
::::::::::::::::::::::::::::::
iiiiiiiiiiiiiiii!iiiiiiiiiiiii!iii!i!!!ili!iiii!ii_!iiiii!i!
:::::::::::::::::::::::::::::::i:?!?!ii?!:ii!!!?!}!?!!:?i?!)
:::::::::::::::::::::::::::::
iii!iiiiii!iiii!!i!!ii!ii!iiii iiiiiiiiii_ii!ii_2_iiii!iii!
I ...........
kS-20S-1 TS-1 TS-2
Comparison of 1/4" Open Hole Compression Strength for 3-D Woven
Materials.
8.5 Test Recommendation,#
The open-hole compression test methods were analyzed to determine which method
would give the maximum allowable in a manner similar to that which was used to
compare the unnotched compression test methods. For these tests, only material varied,
but here, both material and hole diameter vary. Thus, the normalized mean of strengths
was calculated as follows:
1) Means for each material and hole diameter were calculated with:
1 N
_km = _ Y, Xkmnn=l
where n is the test method number, m the material number, k is the hole size number, N
is the number of test methods and YkmniS the mean for a given hole diameter, material
and test method.
2) A mean deviation from Xkm was calculated for each test method with:
K-- 1 Z aXk.AXn = ._- k = 1
where K is the number of hole diameters and
1 _ Xkmn- XkmA--"_knM m=lz" Xkm
where M is the number of materials for a given test method and hole diameter.
59
Five methods are retained for this comparison: the Boeing Open Hole Compression
fixture, the NASA Short Block, the NASA 1142 specimen, the modified IITRI and the
Zabora fixture. Values of AXkn and AXn are given in Table 8.5 and values of AXn and
mean COV are plotted in Figures 8.9 and 8.10.
The modified IITRI method gave the highest mean strengths (+3%) followed by the
NASA 1142 method (+1%); CoVs were small (<6%) and essentially equal. The CoV for
the NASA Short Block was less than 5%, but the strengths were typically 2% below the
mean. The strengths for the Zabora method were only slightly below the mean, but the
CoV was the highest. The strengths for the Boeing OHC method were the lowest, and
the CoV was next to the highest. As noted previously, the CoVs for the Zabora and
Boeing OHC test methods were very high for the 1/8" thick 2-D braids. All of the other
methods were only used for 1/4" thick materials.
Table 8.5 Mean deviations AXkn and AXn for Open-Hole Compression Test Methods.
Hole Diameter
[inl
0.188
0.250
0.375
AXn
Boeing OHC
-9.1%
-1.7 %
1.0 %
NASA SB
3.4 %
-4.7 %
-5.3 %
-3.2 5
Test Method
-2.2 %
Zabora
-0.4 %
-0.1%
-0.1%
-0.2 %
NASA 1142
-2.3 %
2.9 %
2.9 %
1.2 %
Mod. IITRI
7.0 %
2.2 %
1.0 %
3.4 %
Figure 8.9
¢,-
Eo,.,._
t'-
.o_
111o
4
3
2
1
0
-1
-2
-3
-4
Boeing NASA Zabora NASA Mod.
OHC SB 1142 IITRI
Normalized Mean Deviations for Open Hole Compression Test Methods
in 2-D Braided Materials.
60
Figure 8.10
14
12
10
;iiiiliiiiiiiiilililililili_i_i;i_i_i:::::::::::::::::::::::::::::::::::::
O 6 :::::::::::::::::::::::::::::::::::::
(...) :::::::::::::::::::::::::::::::::::::
..........,..............,...., ,....,...., H, .
2 _!i!i!i!i!i!i!i!i!i!i!i!i!i!i!i!i!i!i!i=====================================
........-.,...., ........-:.:.:.:.:.:.:.:.:.:.:.:.:.:.:,:-:,:,:
0 :!:i:i:i:i:i:i:i:i:i:i:i:i:i:i:_:_:i:i
Boeing
OHC
CoVs for Open
NASA NASA Mod.
SB 1142 IITRI
:.:-:.:-:-::-:-:-:-..--.-.--.--.
:::::::::::::::::::
::::::::::::::::::::::::::::::::::::::::..,..,.,................................,...............-.......:::::::::::::::::::::::::::::::::::.:.::::::::::::::::::::::::::::::::::::::
::::::::::::::::::::::::::::::::::::::
....., .........., ..................,.,,.,..,...,..........=..............
i::!!!::!::!!!::!=:!!_::i=:i::_!i::i!i!!!!!!!!!
i ....,.., ,... ,....,... ,......,
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::::::::::
x+x+x+x+:+x.:+:,
:::::::::::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::::::::::
Zabora
Hole Compression Test Methods in 2-D Braided Materials.
61
9. In-Plane Shear Test Program
9.1 Test Confiaurations
Three test methods were considered for shear testing as shown in Table 9.1: tube
torsion, a modified rail shear and a compact shear specimen. Tube torsion tests were
conducted at The Pennsylvania State University and all details of the testing can be
found in Reference 7. Special end fixtures were designed for the tube torsion test. These
consisted of an inner metal plug, pressure fitted inside the tube by cooling in liquid
nitrogen, and an outer two part collar clamped around the composite tube. A single
tension bolt is fitted in the center of the end fitting to allow for biaxial tension-torsion
loading, although this feature was not used here. Eight 1/4" by 1/8" strain gage
rosettes were used on the first few test specimens, with that number reduced to four on
later specimens. As indicated in Table 9.1, tubes of two different diameters were tested,
1.25" and 2.33".
The modified rail shear method uses a specimen, shown in Figure 9.1, similar in
shape to the standard rail shear test but in a different fixture. The main difference is that
the fixture consists of two vertical rails clamped to a rigid base instead of being hinged.
Serrated rails and three attachment bolts per side are used for load introduction. All 2-D
braided specimens were 1/8" thick, while all other specimens were 1/4" thick. All
specimens were tabbed with fiberglass tabs.
The third test method uses a compact shear specimen configuration developed by
Ifju. Although similar in concept to the rail shear specimen, the coupon geometry is
somewhat different. A specially developed shear strain gage is used to measure the
average shear strain over the entire test section. The test results presented in this section
can also be found with more details in Reference 8.
Table 9.1 Test Matrix for Shear Properties
SLL LLS LLL LSS Others (1)
Small Tube, 1.25" 8 8 4 4
Large Tube, 2.33" 8 8 4 4
Rail Shear 3 3 3 3 3
Compact Shear 6 6 6 6 4 (2)
(1) Five Stitched Uniweave and Six 3-D Woven
(2) Five 3-D Woven only
62
.L. 4.50 _I
o.a75 iiiii',i)iiiii)i_i_iiiii'_iiii'_iii_iiiiiiiiiiiiiii:.__iiiiii_ii',i:.ii)J)))i)t)))))))j))))i)))lm_ I ..... i........_z
_3.00 t J_L'-- 0 25 DIA ! o o
• • k Strain Gages, 0 ,+45 ,-45°,90 °
Figure 9.1 Rail Shear Specimen and Compact Shear Specimen•
/--- Shear Gage
,/J i I
Niiii iiiiil
::[iiiiii::i::i_ii;ii;iii!iiiii
.25"
9.2 2-D Braid Materials
Results from the tube torsion tests are summarized in Table 9.2. Because these
specimens were produced differently from all the other specimens used so far, the
normalized thickness could not be used. Instead, an estimated fiber volume fraction was
calculated based on the braiding machine setup, tow sizes and tube thickness. The
measured results were then normalized to the nominal 60% fiber volume used in this
report. The results from the Rail Shear and Compact Shear specimens are shown in
Table 9.3. All these results are compared graphically in Figures 9.2 and 9.3. For [0i/+0j]tape laminates, the shear modulus is a maximum for 0 = 45 ° and increases with
increasing percentage of 0 plies. One would expect the 2-D braids to behave similarly.
Indeed, the shear modulus for LLS (45 ° and 54% braid) is greater than those for SLL (70 °
and 54% braid) and LLL (70 ° and 54%) braid, which are about equal, and the shear
modulus for LSS (45 ° and 88% braid) is greater than that for LLS.
The results contain much scatter. For the shear modulus, the difference between
highest and lowest data is about 45% for SLL, 28% for LLS, 32% for LLL and 36% for
LSS. Similarly for strengths, the differences are 70% for SLL, 73% for LLS, 71% for LLL,
and 77% for LSS. Small tubes and compact shear specimens made of LSS tended to fail
outside the test section and were not included in the calculation of 77%. The LSS braid
was the strongest Of the 2-D braids•
63
Table 9.2 Summary of Tube Torsion Test Results for 2-D Braids
Property SLL SLL LLS LLS LLL LLL
Estimated Fiber
Volume Fraction [%]
Large
51
Small
53
Large
5O
Small
55
Large
46
Small
45
Norm. Strength [ksi] 11.9 11.0 16.5 11.8 11.5 15.3
CoV [%] 8.9 2.4 6.5 4.5 1.6 4.7
Norm. Modulus [msi] 2.18
7.7CoV[%i
1.87
10.0
1.14
7.9
1.35
22.1
1.33
9.7
1.59
6.7
(1) No specimen was failed during test
Table 9.3 Summary of Rail Shear and If
Property
Strength [ksi]
CoY 1%1
Modulus [msi]
CoY [%1
SLL SLL LLS
Rail Compact
18.7 17.6
8.8 3.5
1.51 1.65
4.6 3.7
Rail
18.2
13.9
2.39
5.0
LSS LSS
Large Small
50 56
>25 (1) 18.1
n/a 3.6
3.57 2.90
4.7 28.0
U Fixture Test Results for 2-D Braids
LLS
Compact
19.5
3.0
LLL
Rail
17.3
4.0
1.78
10.4
LLL
Compact
18.9
3.5
1.35
3.1
LSS
Rail
32.0
25.2
3.93
8.0
1.94
3.7
LSS
Compact
18.9
3.9
3.18
3.3
4.0
3.5
3.0'5E
2.5(,O
"o 2.0O
1.5Or-
091.0
0.5
0.0
Figure 9.2
[] Large Tube
[] Small Tube
[] Rail Shear
[] Compact Shear
SLL LLS
_1 I
LLL LSS
Comparison of Shear Modulus by Various Test Methods for 2-D Braided
Materials.
64
35
3O
25
t-
2OC
_ 15
e-
co 10
5
0
Figure 9.3
[] Large Tube
[] Small Tube
[] Rail Shear
[] Compact Shear
SLL LLS LLL LSS
Comparison of Shear Strength Various Test Methods for 2-D Braided
Materials.
9.3 Stitched Uniweave Materials
Only the modified rail shear method was used for the stitched uniweave materials.
Bearing and shear-out failures at the attachment holes were obtained for all specimens.
Shear modulus was measured and is reported in Table 9.4 and illustrated in Figure 9.4.
Strength is also indicated for reference in this Table in order to provide a lower bound
to the actual shear strength of the material. The use of thinner specimen with a larger
number of attachment holes and with a larger distance between holes and specimen
edge is therefore recommended.
Table 9.4 Shear Properties of Stitched Uniweave Materials
Property
Strength [ksil (1)
CoY I%1
Modulus [msil
CoV [%1
SU-1
21.6
12.7
2.41
0.6
SU-2
20.6
6.5
2.30
7.1
SU-3
21.0
3.7
2.32
3.6
SU-4
22.6
8.1
2.62
1.5
SU-5
20.5
4.7
2.35
1.2
(1) All specimens failed in bearing
65
Figure 9.4
_' 2.5E
¢_ 2"t
"5"o 1,5o
'-_ 0.5
0
:_:_$1:'=i:i:_:!:i:_:!:i.,,,,,.,_...""'"'"""
_'_'..I..........................-------------............,............,.............
ii;...........:i_.:E¢i:i:i¢i:_:_:!:.,,.,.,,...................:..-.x.:._.:.x.:.x.,
_:.::i&'.'.::i:.::;_:_::::.,.,,.........................,......-'"""'"'"-' " '-"'""-""" "
SU-1 SU-2 SU-3 SU-4 SU-5
Shear Modulus of Stitched Uniweave Materials.
9.4 _-D WQv_,n M_terial_
Both the modified rail shear method and the compact shear specimen method were
used for the 3-D woven materials. Bearing failures at the attachment holes were
obtained for many specimens with the rail shear method. Strength and shear modulus
were measured and reported in Table 9.5. Moduli measured by the two methods are
compared in Figure 9.5. A slightly higher value was consistently obtained with the
compact shear specimen. The many bearing failures confirmed that the present rail
shear configuration is not adequate, especially for thick specimens. As in the previous
section, the use of thinner specimen with a larger number of attachment holes and with
a larger distance between holes and specimen edge is recommended for the rail shear
method.
Table 9.5 Shear Properties of 3-D Woven Materials
Test
Rail
Shear
Compact
Shear
Property
Strength [ksi]
Coy l%l
Modulus [msil
CoV 1%1
Strength lksi]
CoY I%l
Modulus lmsil
CoY I%1
OS-1
13.8 (1)
37.6
0.57
2.7
10.1
2.6
0.72
3.9
0S-2
20.4 (2)
5.5
0.54
1.7
n/a
n/a
TS-1
12.7(1)
0.7
0.62
7.9
11.2
2.7
0.77
2.3
TS-2
11.3 (2)
22.2
0.71
2.7
11.3
0.8
0.83
6.9
LS-I
8.0
3.8
0.73
5.2
9.7
2.6
0.85
6.4=
(1) One of three specimens failed in beanng
(2) MI specimens failed in bearing
LS-2
9.1
2.1
0.70
4.1
10.2
1.5
0.81
4.7
66
0.9
0.8
._- 0.7E 0.6
0.5O
0.4
0.3e-
0.2
0'110
Figure 9.5
iiiiMi! _ ..............---....... .:.:.:.:.:.:.:
_l "-- :_:_:_:_:_:_:_iiiiiiiiiiiiii !iiii_ili_iii_ iiiiiiiiiiiiii':':':':':':': : ':+:':':':': : : : _:_:i:_:_:_:;
•"'"'"" ::::::: i:i:i:i:i:i:i: ::.::: i!i_ililiiiiii -- :E:i:i:i:i:i:i ::::: i!ii?ii
i i i i' i iii iiii!!',ii!ii',i ................[]i: :!:: !!_!!i_!_i_!i : !!!!!!!!![_!_! : ::::::::::::::-- ::::::::::::::: :: i:i:i:i:i:i:i: ::::::::::::::.... :.............. .....: _:i:i:i;i;i:i:i...........................:............. Rail
: :i:i:i:i:i:i:i ...........:,:,:.:.:.:.: : :::::::.. :+:.:,:,:.:,::::5::::::::::::::::: ::::::::::::::................ ::: ::::::::2:::!i!iiii!!iiii! !!i!!!i!i!iiii ::.:! :::;::::::::::: : !:!:!:_:!:!:!: : : :':':':':':':"
:::::' _i!!ii_ii_ii_.... :i::;: i_i[iii_iiiii_!:;;;;i;iiiiiiiiiiii!:_: _!_i_i_i_i_i_i:::: iliiiiiili!ii{ [] Compact....... : :i:i:!:!:i:i:i : : ..............:::: ', ::i::iii::::iil;:_ :: ........................................
:_::::_ ..............: ;; ..............: :. ii::il;:iiiil;:il:: iiiiililililil
•...... .:.:.:.:.:.:.: ..............
iiii',iiii!',iii, iiiiiiiiiiiill:::: :: iiiiiiiiiiiiii!iii!!iiiiiii!.............',',',','.','1 ....
OS-1 OS-2 LS-1 LS-2 TS-1 TS-2
Shear Modulus of 3-D Woven Materials with Rail Shear and Compact
Shear Specimen Methods.
9.5 Test Recommendations
The in-plane shear test methods were analyzed to determine which method would
give the maximum allowable in the same manner as the unnotched compression test
methods in Section 7.5. All the rail shear specimens for stitched uniweave and some 3-D
woven materials failed at the attachment holes and those strengths could not be
included in this analysis. Values of Axn for strength and modulus are given in Table 9.6
and values of AXn and CoV are plotted in Figures 9.6 and 9.7. In general, the rail shear
and compact shear tests gave the largest mean values of modulus and strength and the
smallest CoVs for modulus and the largest CoVs for strength. The modulus CoV was
smallest for the compact shear specimen. A special strain gage was used for the compact
shear specimen that extended across the entire 0.75" test section. Likewise, the modulus
CoVs for the tubes and rail shear specimens would probably have been smaller had
larger strain gages been used. It was not expected that the tube specimens would give
the lowest values of strength because tubes have no free edges and are believed to have
the most uniform state of shear stress. However, the difference between manufacturing
methods for the tubes and flat plates could have caused the strengths for tubes to be less
than those for rail and compact shear specimens. Therefore, it would probably be best to
use a tube torsion test for braids that will be used for closed section structures and rail
shear or compact shear specimens for braids that will be used for open sectionstructures.
67
i
Table 9.6 Normalized Mean Deviations AXn for Shear Test Methods
Property
Large Tube
Strength -16.3 %
Modulus -1.8 %
Test Method
Small Tube Rail Compact
-21.7 % 17.8 % 22.5 %
-9.9 % 13.6 % -1.9 %
t-o
,m
a_ar-ca
15
10
5
W-5
-10
Large SmallTube Tube
Figure 9.6
Modulus ..............
I!!!i!!!!!!!!!!!!!!!!!!!!!ii]_iEili_!i!i!!!i!!i!.............
L .............
!_!i!E!_!_!!!!!!!!!!!!!i!!:i:i:i:i:i:i:i:i:i:i:i;i:i C:;ilililililil;iiiilili;iii .9,.....,...,.,.....,......,
!_i_i_i_i_i_iiiiiii!i_ii!_i _::::::::::::::::::::::::::
?]:_:E:!:_:_:i:[:i:i:i:i q_'I a, vvv];;i ,
i:i:]:!:i:i: I i . t-
::::::::::;: 1 ca
:!!!!!!ii!i!i
,...,.,,.,,,
i:!:!:!?!:i
Rail CompactShear Shear
3O
10
0
-10
-20
-30
LargeTube
I
Strength
!::i}!!i!::!::!i!i!::!!!!!::::
_i!!!!!!!!!!!!!i]!_!!i_!!!
|!:!:!:!:!:!:!:?:!:i:i:i:
I " .......... I I
Small Rail CompactTube Shear Shear
Mean Deviations for In-plane Shear Test Methods.
>oo
14
12
10
8
6
4
=. -...-.......
.!!!!!!!!."-'!!!!!!i
• l!i!i_i}]ii]ii_::|!!i!i:-!!!!!i!]f
"!i}!i!i#!!
2 i_iI_i_i_i::oLargeTube
Figure 9.7 CoVs for
Modulus:!!!i!i!i!i!i...........
..................... •
i!!!!!!!!!i!]...........:.:.:.:.:.:
...........
...,..,.,,.
............
............
............
,.........,. -.-...-.-.....- -.-.-.-.-....... •., ...., ........,...,.,,
!:i:!:E:i:i: 2222ZZ2ZZCIZI
""'"' """"""""" I
............ ...z.-...................•....z..... ....,.............,............,..,... .............
............ !iii!ili!i!i}!i!i!!!i!illiiii!i}i!.......................................,..............................,...........z.-.....
.,..... ,.,. .............:.:,:.:,:,:,
:i:i:i:i:!:iI l lllll
I
Small Rail
Tube Shear
>oo
I I
CompactShear
14
12
10
8
6
4
2
0
In-plane Shear Test Methods.
LargeTube
Strength
I
Small
Tube
...z..,..............-..,
:.:.:.:.:.:.:-:.:.:.:.:.:.
-:':':':-:':':':':-:':':':......-...................
i!!!!!!!!!!!!!!!!!!!!}!!!!
-:-:-:-:-:-:-:-:-:-:-:-:-:
_i_!!i_!_!!]!!!!!!!!!!!!!!!_i!![!_!_!_!!!!!!i][!!iii_i}!i!i!i!i!i_i!i!i!i!}ili!iii!!i!i!i!i!i!i!iii!iii!i!_!_!?!!!!!!!!]!!!!!!!!!!!
III
Rail
Shear
I I
CompactShear
68
10. Filled-Hole Test Program
Past experience with composite laminates has shown that installing a fully torqued
fastener in an open-hole specimen often reduces the notch tension strength and thus
makes this condition critical for design considerations. The likely cause of that effect is
that the clamping force of the fastener induces through-the-thickness compressive
stresses around the edge of the hole which delay the onset of delamination. Since
delamination tends to reduce the stress concentration in the longitudinal fibers adjacent
to the hole, reducing delamination decreases strength. Therefore, a limited test program
was conducted to verify if this was also the case with the materials considered in this
investigation.
10.1 Test Confiaura(ion
Because of limited material availability, only three of the 2-D braids were used as
indicated in Table 10.1. The same specimen configuration as in the open hole test was
used with a 1/4" titanium Hilok fastener installed in specimen identical to the open-
hole tension specimen. Once again, the influence of the width to diameter ratio (W/D)
was considered.
Table 10.1 Filled Hole Tension Test Program
Width [inl W/D
1.00 4
1.50 6
2.00 8
SLL LLS
3
3 3
3
LLL
10.2
Results of the test program are shown in Table 10.2. As for the open hole tests, the
simple correction factor for infinite plate width was applied to the strength data. A
comparison of net stress, gross stress and corrected stress is shown in Figure 10.1 for the
SLL material. Results show that the corrected stress is the least sensitive to W/D. Little
difference is seen between W/D=6 and W/D=8, but the result for W/D=4 is slightly
lower (by 4%) than the other two results, thus indicating that a specimen with W/D=6
is sufficiently wide. Filled and open hole strength results are compared in Figure 10.2.
As expected, a small strength reduction is observed with the installation of a fastener,
on the order of 9% for SLL, 14% for LLS and 12% for LLL. This confirms that, as for tape
laminates, filled hole tension is the critical case when developing material design
allowables for the Room Temperature/Dry environment. As in previous tests,
increasing the tow size (going from SLL to LLL) leads to a reduction in strength on the
order of 15%.
69
W/D4
Table 10.2
Property
Stress [ksi]
CoV [%]
Filled Hole Tension Test Program
LLLSLL LLS
81.2
4.6
84.2 71.5
8.7 7.9
84.7
1.7
6 Stress [ksi] 72.0
CoY [%1 2.7
8 Stress Iksil
CoY [%]
Figure 10.1
120
100
80
t::
6O
t-
O 40t-O
_- 20
A t"
Corrected
G ross
Net
I i I
4 6 8
W/D
Comparison of Net, Gross and Corrected Stress for Filled Hole Tension
Test of SLL Braid.
¢1)
t-O
¢-
Figure 10.2
100 -
90--
80-
70--¢-.
60--t-
50-
40--
30--
20--
10--
0 • I
SLL
....,..........,...,.,........-...
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!i!!!!!!!!
:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:-:.:.:::::::::::::::::::::::::::::::::::::
,:.:.:.:.:.:,:.:.:.:.:.:,:.:.:.:.:.:.:
...., ,.....,...... ,.,.,.
iliiiiiiiiiiiiiiiiliiiiii:,:.:.:.:.:. x,:+:.:.:.::::::::::::::::::::::::::
i!i!i!i!i!_:!iii!ii::!::!i!::!::::::::::::::::::::::::::::::::::::::::::::::::::::
.........,...............
_i_i_i_ii_ili_i_i_i_!_i__,
-.-.- -.-..-.-.-.-.- -.
:+x+x+>x+:.:::::::::::::::::::::::::
::::::::::::::::::::::::::+x+x<+:+x.:..................
::::::::::::::::::::::::::
::::::::::::::::::::::::::
x+x+:<+x+:.
LLS LLL
[] Open Hole
[] Filled Hole
Comparison of Open and Filled Hole Tension Strength Data for 2-D
Braided Material.
70
11. Bolt-Bearing Test Program
The last in-plane property examined in this investigation is the testing of textile
composites for bolt bearing strength. Although not strictly a material property in itself,
bearing strength is a key parameter for the design of composite structures. Different test
specimens representing various types of joint configurations are typically used for this
purpose.
11.1 Test Confiauratiorl
Three basic specimens, shown in Figure 11.1, were selected for this investigation: the
unstabilized single shear specimen, the stabilized single shear specimen and the double
shear specimen. Because of limited material availability, only the 2-D braided materials
are considered here as shown in the test matrix in Table 11.1. For each test
configuration, the influence of two geometric parameters is examined: the distance of
the hole center to the edge of the specimen and the width of the specimen. Several edge
to diameter ratios (e/D) and width to diameter ratios (W/D) are included. Note that
when testing laminated composites, ratios of W/D = 6 and e/D = 3 are typical. A 1/4"
titanium Hilok fastener is used for all tests. The influence of fastener torque is also
considered in the double shear bearing test: in one series of tests, a fastener with no nut
is inserted in the hole as a simple pin (no clamp-up) and in the other, the installation
torque is doubled to increase clamp-up and possibly induce some damage.
Table 11.1 Bolt-Bearing Test Matrix
W/D e/D SLL LLS LLL
Stabilized Single Shear Bearing
SLL LLS
Double Shear Bearing
4 2 3 3 3 3
4 3 3 3 3 3
4 4 3 3 3 3
6 2 3 3 3 3
3 3 3 3
8 3 3 3 3 3
8 4 3 3 3 3
6 2
6 3
6 4
6 3
Unstabilized Single Shear Bearing
3 3
3 3 3
3 3
Double Shear, Over-torqued Fastener
3 3
Double Shear, Pinned Fastener
3 36 3
LLL
71
o
9 9
o_m-
o_ 8° o_o _i 0
- 44-
/
_o+4
,.a
OulN
Figure 11.1a Baseline Dimensions for Stabilized Single-Shear Specimen.
z
Iite
.o
_i° _0
o_
-¢
N
1,,.
Figure 11.1b Baseline Dimensions for Unstabilized Single-Shear Specimen.
72
Figure 11. lc
|
/o-ac_-auaual-
_ ca o,.
_o_ _
>z
_z_
i
Baseline Dimensions for Double-Shear Specimen.
Ou_
I,-
¢¢
",r
W
m
11.2 2-D Br_id$
When examining load versus stroke test results, non-linearity due to damage
developing around the hole is usually seen prior to final failure. Two load levels are
therefore identified: limit load, which is defined as the load corresponding to a
permanent hole elongation equal to 2% of the hole diameter, and ultimate load which is
simply the maximum load reached during the test. However, for most bearing tests, the
ratio of ultimate to limit load is typically less than the safety factor used for design
(typically 1.5), thus making the ultimate condition more critical. Therefore, in most of
this discussion, ultimate strength will be considered.
Tables 11.2 to 11.4 summarize the ultimate strength and coefficient of variation
results of the various configurations. Strength was calculated as the ratio of load
divided by nominal thickness and hole diameter. In general, all the data exhibited
moderate scatter, with an average CoV of 5.2% for LLS, 2.6% for SLL in the single shear
tests, and an average CoV of 4.9% for LLS and 3.1% for SLL in the double shear tests.
The influence of the specimen dimensions is examined first by looking at the results
for the SLL and LLS materials. The first test considered involves the stabilized single
shear specimen. As shown in Figure 11.2, W/D appears to have little or no effect on
strength. On the other hand, the edge distance (e/D) has a definite effect on the results.
73
In all cases, a ratio of e/D=2 leads to much lower strength. For the SLL architecture,
little or no difference is seen between e/D=3 and e/D=4. For the LLS architecture, a
slight increase is seen when going from e/D=3 to e/D--4, possibly due to the fact that
the unit cell size of this material is about 2.5 times larger than for SLL. The very same
conclusion is drawn for the unstabilized single shear test shown in Figure 11.3.
A different behavior is seen for the double shear bearing test as shown in Figure
11.4. For both SLL and LLS, ultimate strength continually increases with increasing e/D.
Limit strength is seen to be much less dependent on e/D. This is due to the fact that
local bearing failure occurs first, followed by a progressive shearing out of the fastener.
In specimens with larger edge distance, failed material tends to accumulate between the
loading plates, delaying the final shear-out failure and increasing strength.
Finally, the results of all test configurations with W/D=6 and e/D=3 are compared
in Figure 11.5. The lowest bearing strength is obtained for the pinned double shear
specimen for which no load is transferred through friction. At the opposite end, the
double shear bearing strength is the highest. However, this type of bolted joint
configuration is not the most likely in typical structures. The stabilized single shear
specimen is usually considered to be more representative and gives slightly higher
results than the unstabilized configuration. Using the stabilized single shear as a
baseline, the pinned double shear is 18% lower for SLL and 2% lower for LLS; the
unstabilized single shear is 10% lower for SLL and 7% lower for LLS; and the double
shear is 42% higher for SLL and 48% higher for LLS. The difference between SLL and
LLL is about 9% for stabilized single shear due to the increased tow size.
120 SLL 120 LLS
W/D=4
---"_ID_ W/D=6
-----"0"_ W/D=B
0 0
2 3 4 2 3 4
Figure 11.2
e/D e/D
Effect of W/D and e/D on Stabilized Single Shear Bearing Ultimate
Strength of 2-D Braided Materials SLL and LLS.
74
120
•"_' 100
8009
60
.-= 40f=..
m 20
0
2
Figure 11.3
SLL 120 LLS
•"_' 100
80t.t)
60O)
._- 40t,_
rn 20
0
,,,,_
I I I I
3 4 2 3 4
e/D e/D
Effect of e/D on Unstabilized Single Shear Bearing Ultimate Strength of 2-D Braided Materials SLL and LLS.
160
14oI _" 120 :- -- "--2-'__"-: _'-- 2_'7'7""8
,_ _oo
r_ 80O')"- 60t_
'_ 40£D
20
0 t I
3 4
W/D=4 Ultimale
W/D=6 Ultimate
W/D=8 UIl:t mate
----.O--- W/D=4, Dmll
---.._--- W/D=6, Limil
----_--- W/D=8, Limrt
Figure 11.4.a
e/D
Effect of W/D and e/D on Double Shear Bearing Ultimate Strength of 2-D Braided Materials SLL.
75
160
140
120
100
8O
60
4O
20
0
'5
_=.__ ¢¢.-_-.--.-;- - v -
I I
2 3 4
e/D
,._--,--O-_-- W/D=4, Ultimate
._---,-O---_. W/D=6, Ultimate
.-_W/D=8, Ultimate
- - - -0 - - - W/D=4, Limit
- - - "a - - - W/D=6, Limit
- - - .._- - - W/D=8, Limit
Figure 11.4.b Effect of W/D and e/D on Double Shear Bearing Ultimate Strength of 2-
D Braided Materials LLS.
00.a¢
¢-
O')c-
coo_c-
-t-
in
Figure 11.5
160
140
120
100
8O
60
40
20
0
I
Double
Pinned
Unstabilized Stabilized Double
Single Single
Comparison of all Bearing Tests with W/D=6 and e/D=3 for 2-D Braided
Materials.
76
Table 11.2 Stabilized Single Shear Bearing Ultimate Strength Results for 2-D Braids
SLL LLS LLL
W/D e/D Strength [ksi] CoV [%] Strength [ksi] CoV [%] Strength [ksi] CoV [%]
4 2 87.5 0.5 61.7 10.6
4 3 98.3 3.8 88.8 3.2
4 4 102.4 1.1 94.7 1.8
6 2 90.6 4.6 70.9 5.4
6 3 103.1 1.0 83.6 13.0 91.0 2.4
6 4 103.4 3.1 89.0 2.9
8 2 80.2 5.6 65.8 6.4
8 3 98.0 1.7 87.5 0.3
8 4 100.2 2.2 93.6 3.3
Table 11.3 Unstabilized Single Shear Bearing Ultimate Strength Results for 2-D Braids
SLL
W/D e/D Strength [ksi] CoV [%]
6 2 80.0 2.9
6 3 91.7 5.6
6 4 90.6 3.7
LLS
Strength [ksi] Coy [%1
3.2
LLL
Strength [ksi] Coy I%1
64.6
80.8 3.1 87.3 12.1
84.7 5.8
Table 11.4 Double Shear Bearing Ultimate Strength Results for 2-D Braids
W/D e/D
4 2
4 3
4 4
6 2
6 3
6 4
8 2
8 3
8 4
Pinned Fastener
6 I 3 I
SLL LLS
Strength [ksi] CoV [%]
119.7
Strength [ksi]
101.43.1
136.5 5.6 129.1 2.8
156.9 3.3 143.5 3.3
111.5 3.9 98.4 4.1
136.5 2.6 124.4 11.7
148.6 4.1 154.8 2.3
110.2 1.2 101,7 9.8
134.9 1.8 124.0 1.1
148.1 2.7 137.0 6.8
83.2 11.2 87.4 7.5
Over-torqued Fastener
6 [ 3 I 142.5 7.6
CoV[%l
2.1
77
12. Interlaminar Tension
The interlaminar tension strength of 2-D braided and 3-D woven specimens was
determined using two specimen configuration, a C-shaped specimen and a L-shaped
specimen.
12.1 Specimen Confiourations
Both configurations rely on the same mechanism, the application of a bending
moment around a curved geometry, to generate an out-of-plane tension loading in the
specimen. The first configuration is a C-shaped specimen illustrated in Figure 12.11' As
shown in the test matrix in Table 12.1, four combinations of width and midplane radius
are used. The braids marked "-2" and "-3" are variations of the basic architectures used
in the previous test programs. The characteristics of these architectures are shown in
Table 2.1. The second configuration is a more common L-shaped flange bending
specimen, shown in Figure 12.2. Only one size specimen was used to test both 2-D
braided and 3-D woven materials. For both specimens, the attachment to the test
machine included hinged joints arranged such that the bending moment in the
specimen radius can be easily determined by multiplying the load by the offset from the
load application line to the radius.
For both test results, moments were converted to interlaminar stress with the
simplified formula based on beam theory (see for instance Reference 9):
3.M
Ozz - 2 • R. t
where M is the bending moment per unit width, R is the midplane radius and t the
thickness.
A more exact solution for an homogeneous orthotropic solution is give in Reference
10. Using that analysis, the calculated value for the peak interlaminar stress would be
3.3% higher for the C1 configuration, 7.8% for the C2 one and 8.1% higher for the L
specimen. However, given the highly inhomogeneous nature of the material tested, it is
not very clear whether the more exact solution is actually more accurate.
Config
C1-1
C1-2
C2-1
C2 -2
L
Table 12.1 Interlaminar Tension Test Matrix
Thick. Width Midplane SLL
[inl [inl Radius [inl
0.13 1 0.255 3
0.13 2 0.255 3
0.17 1 0.305 3
0.17 2 0.305 3
0.25 2 0.315 3
LLS LLL LLS-2 LLS-3 SLL-2 3-D
Weaves
3 3 3
3 3 3
3 3 3
3 3 3
6 3 3 3 3 3
78
Figure 12.1
I/4-28 _ _'_--_ _
HYME JOINT_"_r
L___.
Interlaminar Tension C-Shape Specimen.
E}.250 (4 Places)
f SPECIMEN
]-4-----.25
L
0.19R
i Ii1 J
Interlaminar Tension L-Shape Specimen.
_ 2.0
Figure 12.2
12.2 2-D Braids Materials
A summary of the average ultimate out-of- plane tension stress from the C-section
out-of-plane tension test is shown in Figure 12.3 and Table 12.2. Coefficients of
variation were large, up to 24%, although not uncommon for this type of testing.
Failures were visible as interlaminar cracks in the radius, sometimes along many layer
interfaces, although there was no consistent location of the failures through the
thickness: some were nearer the inner radius, others nearer the outer radius. The
waviness of the layer interfaces caused by the textile architectures was clearly visible
along the crack length. Considering the scatter, there appears to be little influence on the
results from the width of the specimens. The results from the 90 ° flange bend out-of-
79
plane tension testsare shown in Figure 12.4and Table 12.3. The 2-D braided specimens
all failed as intended by out-of-plane tension in the radius, which was visible by
interlaminar cracks in the radius, often along many layer interfaces.
"The strength values obtained with theC-shape specimens ranged from 2.5 ksi to 4.3
ksi, while these obtained with the L-shape were higher, ranging from 3.6 ksi to 4.8 ksi.
These values are similar to those measured in laminated specimens. As reported in
Reference 9, where an AS4/3501-6 all unidirectional L-shape specimen was used, a
definite relation was observed between interlaminar tension strength and specimen
thickness, with the strength decreasing for increasing thicknesses. Reported values
ranged from 11.8 ksi for a .077" thick specimen, to 2.5 ksi for 0.26" thick specimen. The
main cause for that effect was attributed to the fact that the laminate quality in the
radius area tends to degrade with increasing thickness due to the manufacturing
process.
Table 12.2 Interlaminar Tension Strength Measured with C-Shape Specimen
SLL LLS-2 LLS-3 SLL-2Config.
C1-1 Strength lksi]
CoV [%]
3.0
17
3.2 2.9
15 11
2.5 2.7
5 10
3.4 4.0
18 7
3.1 3.7
1 24
3.2
16
C1-2 Strength [ksi] 3.0 2.8
CoV I%] 9 11
C2-1 Strength [ksi] 2.5 4.3
CoV [%] 6 13
C2-2 Strength [ksi] 2.7 3.8
CoV [%] 8 8
s "_ 1 [
Figure 12.3
4
cD¢-.o 3¢-
c 2D..
9
0 1
iJl Config. 1, 1" WideConfig. 1,2" Wide I
[] Conlig. 2, 1"Wide I
[3 Config. 2, __Wide F-_ J------..... i
_ .1___ _1__ __-L
IJIT
| 11I-!EIliF II',1
II
SLL LLS-2 LLS-3 SLL-2
Interlaminar Tension Strength Measured with C-Shape Specimen.
80
Table 12.3Interlaminar Tension Strength Measured with L-ShapeSpecimen
Config.
L Strength [ksi]
Coy [%J
SLL LLS LLL TS-1 TS-2 OS-1 OS-2 LS-1 LS-2
4.8 4.2 3.6 2.2 3.0 3.5 2.9 2.7 2.2
17 12 5 5 9 5 6 16 4
Figure 12.4
5
4
•a 3
2
O 1
0
SLL LLS LLL TS-1 TS-2 08-1 0S-2 LS-1 LS-2
Interlaminar Tension Strength Measured with L-Shape Specimen.
12.3 3-D Woven Materials
The 3D angle interlock specimens failed by in-plane tension at the inner radius, with
some evidence of out-of-plane tension or interlaminar shear failures as well. Some of
these specimens also had compressive in-plane failures on the outer radius. Therefore,
all the values shown in Figure 12.4 and Table 12.3 should be considered lower bounds
to the actual strength.
81
13. Interlaminar Shear
The interlaminar shear strength of the 2-D braided material and 3-D woven material
was determined using two specimen configurations, the Compression Interlaminar
Shear (CIS) specimen and Short Beam Shear (SBS) specimen.
13.1 Test Confiourations
Both specimen configurations are illustrated in Figure 13.1. Three specimens of each
material system were tested as indicated in Table 13.1. All Compression Interlaminar
Shear specimens were tested in a modified D695 compression fixture shown in Boeing
specification BSS 7260 (see Appendix C). The load rate was 0.05 inch per minute. The
shear stress was calculated assuming a uniform shear stress distribution:
P_xz --
d-w
where P is the ultimate load
w is the specimen widthd is the distance between notches
All Short Beam Shear testing was performed according to ASTM D2344. A small
flexure fixture with 1/8" diameter support rods, 1/4" diameter loading rod and a 1.0:
span was used. The load rate was also 0.05 inch per minute. The shear stress was
calculated assuming a parabolic stress distribution through-the-thickness:
0.75. P'_xz --
w.t
where P is the ultimate load
w is the specimen widtht is the thickness
T- I-. 1.5"
TI II.5" i i
_K__ iI
m ' U _I_ 3.2"x ,,\\l,\\\\lx\\\xr,, \\\ Y
1.o"--"1 xFigure 13.1 Short Beam Shear and Compression Interlaminar Shear Specimens.
82
Table 13.1Interlaminar Shear Test Matrix
Config. Width
[in]
CIS 0.5
SBS O.5
Length Thickness SLL
[in] [in]
3.2 0.25 3
1.5 0.25 3
LLS LLL LSS 3-D
Woven(l
3 3 3
3 3 3
(1) Six configurations, OS-1, OS-2, LS-1, LS-2, TS-1, TS-2.
13.3 2-D Braided Materi_ls
A summary of the average interlaminar shear stresses from the Short Beam Shear
and Compression Interlaminar Shear tests is shown in Figure 13.2 and Table 13.2. The
failures for the short beam shear specimens occured in the y-z plane at either the left or
right support rod. The failures for the compression interlaminar shear specimens
occured in the x-y plane between the notches. The shear failures were generally along a
layer of fixed yarns (braid) or along a layer of warp yarns (weave), although
occasionally the crack jumped between interfaces. Some specimens broke into two
pieces showing the wavy failure surface due to the textile architecture.
The main conclusion from this set of tests is that the short beam shear test gave
consistently higher interlaminar shear strengths than the compression interlaminar
shear tests by about 20% on average. Coefficients of variation were lower as well. These
values are somewhat low when compared to comparable laminated material systems
where interlaminar shear strengths in the range of 12 ksi to 17 ksi are typical.
12
_" 10
8
6r-
42
0
I I ' -I I I I
@ Short Beam ShearCompression Interlaminar Shear
Im I I I 1 I
IIWLJ illl Iml I
I I I I
I I I
1 I_t_N,N."]I I_Wx\NI I_N. x] I_\x,_[ I mmlN.N.NII_ml_ x,"
I
P
i
SLL LLS LLL LSS TS-1 TS-2 OS-1 OS-2 LS-1 LS-2
Malerial
Figure 13.2 Interlaminar Shear Strength Measured with Short Beam Shear and
Compression Interlaminar Shear Test Methods
83
Table 13.2 Interlaminar Shear Strength in 2-D Braided Materials
SLL LLS LLL LSSConfig.
CIS
SBS
Strength [ksi]
CoY [%]
Strength [ksil
CoV [%l
5.2
12
7.4
5.5
7.2
10
9.0
1.9
6.0
5.3
6.2
11
6.9
10
7.3
6.7
13.3 _-D Woven Materials
A summary of the average interlaminar shear stresses from the Short Beam Shear
and Compression Interlaminar Shear tests is shown in Figure 13.2 and Table 13.3. The
failures for the short beam shear specimens were like those of the braided materials
except for the three OS-2 specimens, which failed in tension on the lower surface.
Significant permanent deformation was visible after the loads were removed only for
the OS-1 and OS-2 specimens. The failures for the compression interlaminar shear
specimens were also like those of the braided materials between the notches except for
one OS-2 specimen, which failed in compression at the two notched sections. A
replacement from this group was tested which failed in shear.
Much as for the braided materials, the short beam shear test gave consistently higher
interlaminar shear strengths than the compression interlaminar shear tests by about
27% on average. Also the OS-2 material appears to have a higher interlaminar shear
strength than the other materials and different failure modes.
Table 13.3 Interlaminar Shear Strength in 3-D Woven Materials
Config. TS-1 TS-2 O,%1 0`%2 LS-1 LS-2
CIS Strength [ksi] 5.3 6.3 4.5 9.5 6.6 6.2
CoV [%] 9.4 6.6 15 22 7.2 11
SBS Strength [ksi] 8.2 8.1 7.0 9.7 6.6 7.5
CoV [%] 5.0 1.8 1.2 4.9 9.2 8.4
84
14. Interlaminar Fracture Toughness
The mode I and mode II interlaminar fracture toughness of the braided materials are
examined in this chapter. These were determined using the Double Cantilever Beam
(DCB) and End Notch Flexure (ENF) test configurations.
14.1 Test Confiourations
Four 2-D braided architectures were used in this test program. Three specimens of
each kind were used as indicated in Table 14.1. The braids marked "-2" and "-3" are
variations of the basic architectures used in the previous test programs. The
characteristics of these architectures are shown in Table 2.1. All specimens were 0.5"
wide and 0.25" thick. In all cases, the delamination was propagated along the 0 °direction.
All Double Cantilever Beam specimens were tested according to Boeing specification
BSS 7273 (see Appendix C). A bonded block hinge was used to load the specimen
instead of the triangular grips specified in BSS 7273. The edge of the specimen was
painted white to illustrate the progression of the crack more clearly. The crack was
initially extended by 0.5 inch to move the crack tip away from the effects of the Kapton
tape used to form the initial crack. A crack approximately one inch long was extended
three times for each specimen. The load rate was 1 in per minute. The actual crack
length was measured with calipers and the area under the load-displacement curve was
calculated by the test software. Both the area and initiation methods were used to
calculate the mode I fracture toughness GIc:
Area Method:
GI c _ E (in. lb / in 2)A.W
Initiation Method:
GI c = 3-P- Y (in. lb / in 2)2.W.a
where E is the area under the load-deflection curve
A is the increase in crack length
W is the specimen width
P is the peak load prior to crack extension
a is the crack length
Y is the deflection corresponding to P
All End Notch Flexure specimens were tested in a small test fixture with 1/4"
diameter loading rods and 4" span. The load rate was 0.1 in per minute. The crack was
initially extended in flexure by 0.5 inch to move the crack tip away from the Kapton
tape used to form the initial crack. The crack was extended three times for each
specimen. The compliance was calculated from the actual slope of the load-deflection
O___.-(>Q,.
85
curve between 33%and 66%of the ultimate load for eachcrack growth. The actual cracklength was recorded for eachcrack but a nominal crack length of 1 inch was used in thecalculation as specified. The values for GIIc were calculated with the equation given inthe specification:
GIIc
where
= 9.a 2.P2-C (in.lb/in 2)
2.W-(2.L 3 + 3.a 3)
C is the compliance
L is half the length of the loading span
W is the specimen width
P is the peak load prior to crack extension
a is the crack length
Table 14.1 Interlaminar Toughness Test Matrix
SLL LLS-2 LLS-3 SLL-2
DCB 3 3 3 3
ENF 3 3 3 3,.
Note: Each specimen tested for 3 crack extensions
14.2 2-D Braided Materials
Results for the mode I fracture toughness tests are shown in Table 14.2 and Figure
14.1. The scatter in the results is extremely large, especially considering the fact that 15
repeats of each test were conducted. The average values themselves are extremely high
compared to the typical values measured in laminated composite materials (by a factor
of 3 to 5). The results from both the area and initiation method gave comparable results
considering the scatter in the results. There appears to be some correlation between the
bias fiber angle and the toughness: the two architectures with 70 ° bias angle gave much
higher results than the ones with a 45 ° angle.
The probable cause for these high values is that the crack did not propagate in a
resin-rich layer between plies as in a laminate. Although the 2-D braids are still formed
by putting down successive layers of material, nesting of the different plies does occur.
When looking at the edge of the specimen, the crack path was not straight but rather
followed a "scalloped" pattern going around the tows. Also, when examining the
surface of the delamination, it appears that failure did not progress between layers of
material but inside a braided layer. Parts of the same bias tow were observed on both
sides of the fracture surface, with a thin layer of the tow on one side and the majority of
the tow on the other side. This also implies that some fiber breakage must occur where a
bias tow on the surface of a braided ply enters the ply to pass underneath the other
tows. That could significantly increase the energy necessary to separate the material,
much as fiber bridging in tape laminates.
86
Results for the mode II fracture toughness tests are shown in Table 14.2 and Figure
14.2. As above, the scatter in the results is extremely large, especially considering the
fact that 15 repeats of each test were conducted. The energy release rate values are also
two or three times higher than for tape laminates with similar resin systems, much forthe same reason as for the mode I results..
Table 14.2 Interlaminar Toughness Test Results
Area Method
Gic [in-lb/in 21
CoY I%1
Initiation Method
Gic [in-lb/in2]
Coy !%1
GIlc [in-lb/in 21
CoY [%1
SLL
7.03
33.2
7.89
40.5
13.1
21
LLS-2
4.72
38.1
4.72
20.8
13.4
17
Note: Each specimen tested for 3 crack extensions
LLS-3
4.49
17.7
5.19
20.8
11.6
19
SLL-2
7.43
33.7
7.18
13.2
14.4
20
Figure 14.1
8 • Area7
6 • Init.
5
4o 3(.9
2
1
0
SLL LLS-2 LLS-3 SLL-2
Mode I Fracture Toughness in 2-D Braided Materials.
Figure 14.2
¢M
¢.-
0t-
O
16
14
12
10
8
6
4
2
0 I I
SLL LLS-2 LLS-3 SLL-2
Mode II Fracture Toughness in 2-D Braided Materials.
87
15. Conclusions
Only the main conclusion from each test program is briefly summarized here.
Because of the large variety of tests conducted, the reader should refer to each sub-
section for the conclusions relating to a specific material or test type.
Tension
The main issue in the tension test program was the effect on strength of the specimen
size compared to the material unit cell dimensions. Little or no effect on strength was
observed for the 2-D braids which have the largest unit cells of all material tested.
Therefore, the standard specimen width of 1.5" is recommended.
Open Hole Tension
The effect of specimen width to hole diameter ratio (W/D) was investigated. Results
showed that the standard W/D=6 was adequate.
Compression
A comparison of the Boeing Open Hole Compression, Zabora Fixture, NASA Short
Block, NASA 1142, Modified IITRI, sandwich column, Boeing Compression After
Impact and NASA ST-4 specimens was conducted. The NASA Short Block specimen
and Zabora fixture consistently produced the highest mean strength, but the Zabora
fixture was evaluated only for a limited number of 2-D braids.
Open Hole Compression
A comparison of the Boeing Open Hole Compression, Zabora Fixture, NASA Short
Block, NASA 1142 and Modified IITRI was conducted for hole diameters up to 0.375".
Results show that the Modified IITRI produced the highest mean strength, while the
Boeing OHC produced the lowest. Both the Boeing Compression After Impact and
NASA ST-4 gave good results for larger hole from 0.5" to 1.25".
In-plane Shear
A comparison of tube torsion, rail shear and compact shear specimens was conducted.
Significant differences in both strength and modulus were obtained between these test
methods. The compact shear specimen produced on average strength data 30% to 40%
greater than the tube torsion, while the rail shear method experienced numerous
bearing failures at the attachment holes.
Filled-Hole Tension
Testing was conducted only with the 2-D braided material and confirmed that, as for
tape laminates, filled hole tension is the critical case when developing material design
allowables for the Room Temperature/Dry environment. The standard W/D=6
specimen configuration appeared to be adequate for this type of testing.
Bolt Bearing
Testing was conducted only with the 2-D braided material. As for tape laminates, the
stabilized single shear bearing test with W/D=6 and e/D=3 is recommended.
88
Interlaminar Tension
Testing for interlaminar tension was conducted with the 2-D braided material and 3-D
woven materials using a C-shape and a L-shape specimens. Strength values from the L-
Shape configuration were slightly higher than those with the C-shape specimens,
possibly due to the lesser fiber distortion in the L-shape specimen. The 3-D weaves did
not fail actually in interlaminar tension but showed transverse cracks indicative of in-
plane failure.
Interlaminar Shear
Testing for interlaminar shear was conducted with the 2-D braided material and 3-D
woven materials using the Short Beam Shear (SBS) and Compression Interlaminar Shear
(CIS) specimens. Strength values obtained from the SBS specimen were consistently
higher than those from the CIS specimen.
lnterlaminar Fracture Toughness
Testing for interlaminar fracture toughness was conducted only with the 2-D braided
material using the Double Cantilever Beam and End Notched Flexure specimens.
Results showed much higher toughness in this type material than in conventional
laminated composites.
Observations on 2-D Braided Material
Unnotched tension and compression strength appear to be lower than expected in a
conventional tape laminate. However, in the presence of holes, the 2-D braids appear to
be less notch sensitive in tension. As seen from the comparison of the SLL and LLL
architectures, the larger tow size reduces strength and stiffness, but on the other hand,
the larger tow size can reduce the cost of manufacturing the preform. The transverse
strength in 2-D braids seems to be relatively low in tension, compression and shear.
Since only a limited amount of testing was conducted in that direction, this should be an
area of further investigation.
89
References
1 Falcone, A., Dursch, H., Nelson, K., Avery, W., "Resin Transfer Molding of Textile
Composites," NASA CR 191505, March 1993.
2 Peterson, R.E., "Stress Concentration Factors," Second ed. John Wiley & Sons, Inc.,
Publishers, New York, 1974.
3 Lin, K.Y., "Fracture of Filamentary Composite Materials," Ph.D. Thesis, M.I.T., 1977.
4
5
Masters, J. E., Fedro, M. J., Ifju, P. G., "Experimental and Analytical Characterization
of Triaxially Braided Textile Composites", NASA Conference Publication 3178,
Proceedings Third NASA Advanced Composites Technology Conference, 8 - 11 June
1992, pp. 263 - 287.
NASA Reference Publication 1092, " Standard Tests for Toughened Resin
Composite ," May 1982.
6 NASA Reference Publication 1142, "NASA/Aircraft Industry Standard Specification
for Graphite Fiber/Toughened Thermoset Resin Composite Material," June 1985.
7 McCarty, C.M., "Shear Evaluation of Braided Composite Cylinders,", M.S. Thesis,
Penn State University, August 1993.
8 Ifju, P. G., "Shear Testing of Textile Composite Materials," SEM Spring Conference,
Baltimore, MD, June 1994. Also to appear in ASTM Journal of Composite
• Technology & Research.
9 Seely, F.B., Smith, J.O., "Advanced Mechanics of Materials," Second ed. John Wiley
& Sons, Inc., Publishers, New York, 1952.
10 Jackson, W.C., Martin, R.H., "An Interlaminar Tensile Strength Specimen", ASTM
Standard Technical Publication 1206,1993, pp. 333-354.
90
Appendix A Test Data
All the individual test data are included in this appendix as reported by Intec. Note
that stresses in these spreadsheets are normalized by the actual specimen thickness.
Most specimens are labeled using the following convention: BH2-A-BC-X, where:
A = Material Form 01 = 2-D Braid SLL
B = Task Number
02=
03=
04=
05=
06=
07=
08=
09=
10=
11 =
12=
13=
14=
15=
1 =
2 =
3 =
4 =
5 =
6 =
7 =
2-D Braid LSS
2-D Braid LLL
2-D Braid LSS
3-D Weave TS-1
3-D Weave TS-2
3-D Weave OS-1
3-D Weave OS-2
3-D Weave LS-1
3-D Weave LS-2
Stitched Uniweave SU-1
Stitched Uniweave SU-2
Stitched Uniweave SU-3
Stitched Uniweave SU-4
Stitched Uniweave SU-5
Unidirectional Properties
Strain Gage Study
Tension Test Program
Open Hole Tension Test Program
Compression Test Program
Open Hole Compression Test Program
In-Plane Shear Test Program
C = Test Type and Configuration (A-Z)
X = Repetition Number
A.1
Tension Test Program
A.2
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A.30
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A.45
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A.62
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_ _---,_
_,__
_1 _O0oOCOooO_
_ _ "_
0 0 0 0 0 _ 0
0 _- _ o_ ¢_ o_
'_:'-- 0 0 ¢:)
if)
o4 _4 ¢'41
i, u.
o o o
U3 U3 tt_
_0 _5 _0
0 0 0
999-7-£ _:en en rn I
9-
o_E
"5
to
A.79
_n
:: 6"6
&o
.., -r
-=5_
IS o __
o
,< c
.=-i o. -
&O3
o; _ ¢0'0;(o r,,. u-) tD i
¢o
Iogg_e
'iN
NNN_ e
9o, 9
"7"7"7
o
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o o o
m
cn _n cn
o
CO --
o
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Z
A.80
o
rm
-6
D
i
- 1_ Imm m
, o o o °_ 00 o °_ 0 o 00_ o o o _ o o o,_ _ 0 o o o_ 0 o o _ _
r_ _ 0 o o o _0 o o 0 00 o o dm _ ooo m, O0_ _ OOo_ OOOo_ 0o0
o_ o_ ¢D o _,
z:_: oo o_ ooo 00o Oo o_ 00o_ oO o_ 0oo ,o oo_
_a ooo ggg ggo ggg ooo ooo ooo oo
E _
_D
Z
A.81
• rInterlamma Shear Test Program
A.82
t/I
e
o=u_
&E8
"6
o
r_
Z_
ms
g
_v
_s
O3
,oE-
- _c
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03"- E
E
g_
o7
A.83
m
C/)
E
t-o
.0o.Eo0
"6
o
Oo
"o
E. u-' =
oJ
6,
w
o
o_
.cz _" _ ,_
....... _,_._EEE EEE
A.84
(/I
m,-
E
I,..-
I--me
r,,
oe,i
em
-- ..,m
.o
-._oZ" E
®®® _®® ®®® ®®® ®®® ®®®
A.85
._® ®,,® _=_ =....s-- _,
_._ _-_ ooo _!® Q _ ¢" e" ¢" Q 0
" '- -': ®®® _ _0,(,0 (,0 g') F-- t,- I--
_o_° ! _ ;_ _._ o _i,,_ _t:, _
_® _ .........
0o0 000 000
A.86
Fracture Toughness Test Program
A.87
A.88
W
re
z
E.__
i
A.89
Appendix B Typical Stress-Strain Curves
Typical stress-strain data are shown in this Appendix for the 2-D Braided, 3-D
Woven and Stitched-Uniweave materials for a variety of test conditions.
B.1
(/)CO
Figure B.1
120 r .......I
I
!
!
100 ' _ll_"!
'(i!
80 .....I
II
I
60 _ ....
' t!
!!
!
40 _ .... J -I
I
I
I
I
20 _- .....I
I
I
!
0 i , , ,
BH2-01-3A -1
-2000
....... ,....... r ...... 1 ....... ,....... r ...... 1 ....... ,I I I I I I I
I I I I I I I
I I I I II |
iI I I I I
I I I I III I
I I I _lf I I I
I I i I _/ I I I
I I I I I I
I I I I I I I
I I I I I I I
....... I ....... I-------------4 -I- ..... -4 ---------I
' ' i ' "I I I I I I
I I I I I
' ! ' ' ', ....., , , , .---4 ....... I ....... P. .... ----....... I----- ......... --. ----.4 --II
............ I. ...... -4....... I Axial ,_,_I ! I
- i" - Transverse Gage, , , I , , , I , , , I ......... I , , , I
0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Typical 0 ° Tension Test Strain Data for 2-D Braided Material SLL.
Figure B.2
100
9O
8O
7O
6O
5O
4O
3O
2O
10
BH2-02-3A-3
0
-6000
r ...... 1 ....... ..................... ....... r ...... 1 .......I ! I I I # I
I _ I I I , I I
L -. _ - - - J ....... I .................... a ....... L ...... J ....... II % ! J I I I ;
I i, I _ I I dl_ _ _ "1"_I I _ I
I I I '
I |_ , I _m I I
......._-......,............. I....... _.......--"..... I.......r i
, I '__ , , , .--.41/L/-I,- .... I _
i
I I I I I I _ I
L ...... d _ ._ .... , ............. j ....... i ..... J ....... I
% I I I _ II I I I _
I I I
------_.t-_-----I- -----,------,-------,
I I _ I I I I
I I I II I I
_ I _ I I I I _ I
I I I I I I _
I I ,_ I I I _ I
L ..... .J ....... I. 4 ........... J ..... I _ _ I
_ I I I I Insometer ,_ I I
I I , -- I _
i_ ...... 'I " " ..... I Ilr...... 11 ....... ' ...... 7_ ....... i ..... Ax_Cage
'I '_ I' _t "" ''--/-- -- i ....... !' ........ Tra P-=_'r ...... i ....... =.... -_ • nsverse _e
,' ,' ,' '"'_ '/'l. i : 'i,,.,,,,i,,,_ ' , . . ,, , , I , , , I , , , i , , , ! , , , i
4000 2000 0 2000 4000 6000 8000 10000
Strain [microstrain]
Typical 0 ° Tension Test Strain Data for 2-D Braided Material LLL.
B.2
.¢-,
09
Figure B.3
120
100
"ii60 ....
"i!2O
=
0 , ,
BH2_3-3A-3
.............. I....... r ...... 1 ....... I....... r ...... "1....... oI I I I I I I
I I I I I I I
I I I I I I I
I I I I I I I
I I I I I I I
, , , _/ , , I I
....... l....... I- ...... 4_I_-_P lw .... ,....... I- ...... =I ....... ,
I I I I I I I
I I I I I I
I I I I I I I
I I I I i I I
I I I I I I I
....... I............ 4 ....... l....... I- ...... 4 ....... I
I I I I
I I I I I
I I I I I
I I I I I
I I I I I
I I I I
I I I I I
I I I I I
I I I l I
I
• I I I I I, , , I , , , I , , , I , , , I , , , I , , . I , , , I
-2000 0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Typical 0° Tension Test Strain Data for 2-D Braided Material LLS.
(/]
(fJ
Figure B.4
60
5O
4O
3O
2O
10
BH2_4-3A-2
r .... 3 ..... ,..... T ....I I I I
I I I I
I I I I
I I I I
I I I I
I" " * ''_I I ..... I ..... T ....
I _14 I I
I I
I
I
i" .....
I
I
I
I
I
I*----
I
I
I
I
I
I. ....
I
I
I
I
I
I. ....
I
I
I
I
I
=11-
I
I
I
I
I
"1"-
I
I
I I
' ,I I
.... _I_ .... TI .... "I==I
I • I I
i % , i
I • I I
..... ,'.... \," .... I""! I
I I IIi
- - - - -=Ik- -..... I- - I, -,l-
I I • I
, , _! !
I I I l
I I I 11,iii
I I I
I I I
I I I
r ....
i
i
i
i
l
.... T ....
!
I
!
I
I
.... T ....
I
I
I
I
I
.... I ....
I
I
I
I
I
"i ..... i" .... T ..... i ..... i
I I I l I
l l I l I
I l I I I
I I I I I
I I I I I
"1 ..... IP .... T ..... l" "
I I I I I
I I I I I
I I I I
I O I I
I I I I
=I ..... I-- .... • ------I
l I I I
I I I I
I I I I
I I I I I
I I I I I
•=I .... ,I, ..... I ..... I
I I I I
I I I I
I I I I I
I I I I i
I I I I I
=Ii i . * = ,I_ i * = = if= = = . . I
Extensome_er
Axial Gage
........ Transverse Gage
-10000 -8000 -6000 -4000 -2000 0 2000 4000 6000 8000 10000 12000
Strain [microstrain]
Typical 0 ° Tension Test Strain Data for 2-D Braided Material LSS.
B.3
35
3O
25
(_ 20
(Jl
•-, 15_0
10
0
BH2_1-3Q-1
............ I" ........... i ............ i ........... "1 ........... '1
! I I ! I
I i I l I
I I , | I ,, i
I I / I I |
............ I-- ........... _iiiiJ .......... ! ........... -=ll ........... '4
I ! l ! I
| I I I I
I I I l
I I I I I
............ I=, .......... I ............ I ........... ..I ........... J
I I I I I
! I ! l I
l I ! l I
! I I I I
............ [_ ...... i........... J ........... J
! ! l l I
I I I I I
................... "--'I" ........... $'--" ........ '=I .......... ""
I I I
I | I I
I I I I
I I I I
/i i.........I I I I
I I I I
........... I- ........... I............ I........... =4 ...........
I I I I
I I I I
I I I I
, , , I , , , I , , , I , , , t , , , I
0 2000 4000 6000 8000 10000
Strain [microstrain]
Figure B.5 Typical 90 ° Tension Test Strain Data for 2-D Braided Material SLL.
callfall
16
14
12
10
8
6
4
2
0
BH2-O2-3Q- 1
............ I" ........... I ............ I ........... -I ........... "11
I I I I I
I I I I I
I I I I I
........... Ii ........... I ............ I ........... J ........... J
I I I I
I I I I
I I I I
I I I I
i I I i
_I _'-: --/_--------" , , ,I I I I
............ L .............. i ........... j ........... j
i i I I
I I I I I
I I I I I
I I I I I
....... ----------I------ ........ I ....... ------I ..... - ..... -4- .......... 4
I I I I I
I I I I I
I I I I I
I I I I I
............ ,': .......... ,............ ,............ i ........... ;I I I I
I I I I I
I I I I I
.......... k .... = ...... I ....... -- .... I..... -- ..... .=4-- ......... --4
I I I I I
I I I I I
I I I I I
I I I I I
...... I........... --I ........... '1
•'/ i .i .' .' .'I I l I I
I I I I I
, , , I , , , I , , , I , , , I , , , I
0 2000 4000 6000 8000 10000
Strain [microstrain]
Figure B.6 Typical 90 ° Tension Test Strain Data for 2-D Braided Material LLL.
B.4
3O
25
2O
lO
5
0
BH2-O3-3Q-1
I
I
I!
I
!
!
!
I
!!
I
I
I
!
I
I
!
I
!
!
!
I
!
I
I
!!
!
I
........................................................ I
!
!
!
I=
, . , i , , , I , , , i
0 2000 4000 6000
Strain [microstrain]
Figure B.7 Typical 90 ° Tension Test Strain Data for 2-D Braided Material LLS.
25
2O
.-'=" 15_9
C/)
co 1o
BH2-O4-3Q-1
I I, , I
• iI I
I II I
I I
I I
- -J ......... ! .... L..-
,l
2000 4000 6000 8000 10000 12000 14000 16000
Strain [microstrain]
Figure B.8 Typical 90 ° Tension Test Strain Data for 2-D Braided Material LSS.
B.5
(/)L_.U)(/)
8O
70
60
5O
40
3O
2O
10
0
-2000
r ...... _ ...... rI
I
I
L f
t
| I
i J
I t
_---_--I I
i !
I !
L .... J-t !
m !
: iD- ..... I"| t"
n u:
_. ...... L
I
I
i I I !
BH2-O1-5L-2
...... T ....... , ....... r ...... _ ....... r ...... "_I I , , I ' '
, , I I I I '
I ' I , I
L I ....... o....... L ...... _ ...... L ...... J
, , , .- , _,_ , ,I I ' J J_ " ' ' '
I I I I I I ', , _/, / : ', , ,I. J. .... L. _I._. ..... L ...... J ....... L ...... J
....... , ...... , I I , I, , /f, : ', , ,I I , I I ' I, ,// ', ,, : , ,
....... '- ...... _ -I .... '...... I. ..... -, ....... _- ...... -,, , ' I ' I '
, / Lf ', °' " ' '
, "_rl I ,I I , ..... / , ....... I ...... I....... ,--- _'/__- r --, r -,I ' I ' ' ' ',// ', : 1, ' ,,'// ' ! ! I .... AxialGage1 I"_/-'--': ....... ',....... rl I,, , I ' " I._, : : ',1........ Ax_Ga_2 I,
-,-f- { I'...................... - ....... Transverse Gage
I ' , I,r : : ,, ',1 I,, , , I , , , I , , , I , , , ! , , , I , , , I , , , I
2000 4000 6000 8000 10000 12000 14000
Figure B.9.a
Strain [microstrain]
Typical IITRI Compression Test Strain Data for 2-D Braided Material SLL,
(1/8" Thick, 1." Long).
U:l
(D
8O
70
60
5O
40
30
20
10
0
BH2_l-5M-2
-I" ...... T ....... , ....... r ...... -* ....... r ...... -i
I
I
I
I
I
I
Axial Gage 1
,A}_I Gage 2
Transverse Gage
-2000 0 2000 4000 6000 8000 10000 12000 14000
Figure B.9.b
Strain [microstrain]
Typical IITRI Compression Test Strain Data for 2-D Braided Material SLL,
(1/4" Thick, 1.5" Long).
B.6
BH2_1-5G-3
90 rI
I
I I
80 r-_--l 1I, _
......60 ,.-L .......
I I
* t! I
50 [--_.......I t
I !
40 _--. _ -I I
I
,30 _ ......' |!
, LA_
ZO _ .... _ .....
' tI
!
lO ,_.....I
I
0
r .......................................- , r -, r
i i i
i i
i
IJ')* II I
I I
I
! I
! !
iI I
I
I
I
J.
I I !
! ! I
! ! I
I I i
I I I I
I I I I
I I I I I
I I I I I
I I I I
I I I I
I I I I
I I J
I I I
I I I
I I I
I I I
I I I
I I I
I I I
I I I
.... li
.... Ii=!
-2000 0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Figure B.9.c Typical Short Block Compression Test Strain Data for 2-D Braided
Material SLL, (1/4" Thick, 1.5" Long).
in
.x.C/)
O9
6O
BH2_2-5L-2
I" .... " .... r
i I
! - iti !
i
50 , ...... _--,I I&t II I
I • I
|
_^ , P4U : ......... ,'k ......................
I
I I % I
I I % I
I I % I
I I t30 .......... " ........ ........ 'I I I
%I I I i
I I% II
I I
I I l%
20 _ ......... _ ..... ,--I I •
I I
t t! !
I I III I
10 *- ......... L .......I I I
I I I
I I
! I
I I
I I I I
I I I I
I I I I
I I I I
, , _ _"| !
I !
m !
l
I I
I I
I I
I I
I I
........ I......... -I
I I
I I
I I
I I
I I
---I .......... I......... -4
I I I
I I I
I I I
I I I
. I I I................ I .......... I ......... -I
' r I'/ : Axial Gage 1 :I I
. __' ....... -AxialGage 2 J
,; ........ Transverse Gage ::
I I
-4000 -2000 0 2000 4000 6000 8000
Figure B.10.a
Strain [microstrain]
Typical IITRI Compression Test Strain Data for 2-D Braided Material
LLS, (1/8" Thick, 1." Long).
B.7
U)U)
O3
BH2_2-5M-2
45 tI
I
!,t0 r
! t I
I35 _ ....... _-_ ........
! I
30 _ .........| I t
J j_
| | •
I I t
I I I
| | t
| ! I
i I t
I ! t.&...lb ="......... _ ....
I I •
| | t!! I
10 ,- ......... _ ...... •I I t
I I
_) I,. ......... I. ......
i II I
I I
t I I I
ql I I I
i
I
I
I
II
I
I
I
I
J
I
II
I
I
I
I
:] [i ,AxiN Gage 1 ',I
L .... .. -J
= ,Axial Gage 2 ;I
' i...... _ ........ Transverse GageI
I ,L I
I
I
I
t
I I
I I
-I-
I I
J !
I I
I I
t I
I I
I
I
I
-4000 -2000 0 2000 4000 6000 8000
Figure B.10.b
Strain [microstrain]
Typical IITRI Compression Test Strain Data for 2-D Braided Material
LLS, (1/4" Thick, 1.5" Long).
O_
7O
6O
5O
BH2-02-5G- 1
I I I I I I I
I I I I I I I
t I I I I I I
! ' , , ,................. ,4 ........ I- ....... '4 .......... •
t I I I I
I_ I I I I I I
I l I I I I I II I I I I I I
=__,,..... ; .................................., , ,,-....... ,I t I I I
I
I
II • I
4rl L. .... • . -J .......I L I
I • I
I L I
I I I
_ , ,,r ....... t'l .......
I •
I I t
20 ' '2r ....... -i I," .....
I I %I I
Io ' \....... ,4 ......l I
l I
I I
| I
I I I
I I I I
J ........ I- .... J ........ I_ .......I I I I
I I I I
I I I
I I I
I I I
1 .... "1 ("
! D ! !
r # t t
I I I I
, 'i.... r'------
I
I
!
I !
I ........ ,""-I !
I I
I !
Axial Gage 1
Axial Gage 2
........ Transverse Gage
-4000 -2000 0 2000 4000 6000 8000 10000
Figure B.10.c
Strain [microstrain]
Typical Short Block Compre'ssion Test Strain Data for 2-D Braided
Material LLS, (1/4" Thick, 1.5" Long).
B.8
60
50
"_ 40
_ 3o
20
10
Figure B.11.a
BH24)3-SL-2
7O........... mr ........... I- ........... j- ........... i- ........... i
I I I I
I I I I
I I I I
• I I I I
........ _ ............. I-- ........... I-- .......... --_ I-- ....... i_ _- --I
I ' I I _ I d I
• ' I I i I, . , , / ,/ ,........ t .............. L_........... L. - - _ ...... _ ........... ,
• _ , , , I"I _, ,I . , ' / /" ' ', • , ,/ J , ,I • ' jr. f ' ,
........ _ .............. L ......... J.I__. _......... I_........... J" . l I _ I I,. , f 11" ,' . , _ _ , ,
, _ I, , ,.......... '-"......... ' ..,_----_-_L ......... 'J 1 " I I I _ i 1 1 J l i_ -- i -- _ ........... F ...........
I I . | I l
l I I,/ / II l
' ' i 'I = I I
r .......... _ ............... I ..... Axial Gage 1, _ / .,,,r ; I" : / ,'" '! ', I ....... _,_e2
........... ,- _---_ .... '- ........... '--I' 'f z : .' I .......: .",/ ,-" i i I ........ Traosve,_eGage
0 I ...... I , , , I , , , I , , , I
-2000 0 2000 4000 6000 8000
Strain [microstrain]
Typical IITRI Compression Test Strain Data for 2-12) Braided Material
LLL, (1/8" Thick, 1." Long).
50
45
4O
35
.-'=" 30
_ 25
_ 20
15
10
5
0
Figure B.11.b
BH2-O3-5M-2
[.................,._I......................E......................iI • ........... I ........... I ....... I ........... I_ I _' , :I ' , _/ ; ,I- .................... _.. ........... I- ......... I- ........... I, r --I , ,7"/ ........ : ,' _ :I , ,_" , ,
, ....... -_----1-........... ,-......... -/#'-.......... ;-........... ',I I I I I I, , _1 , I/: ', ,
' _1. 'I I I I I I
t I I I I I
k" ........ -_ ............ I- ............................ I
' '} Z- i '1 I I I I I
/ ......... __ --- I l I I
i i ........ ": .......... '- ........... ," ........... ,I _ I I I
I I I I I
I. ......... I ..................... l: ',_ -7"-F........... ,"-I Axial Gage 1 r:.... -/ ....- ......... "-I ..... _ F'I" .......... I............ p ........... r- - I
, ,: xlal Gage 2 ,
' "-/ ' '1 tI I" " ....... I ........... I - I
........... _. "- II l_ ........ Transverse Gage :
! ...... I , , , I , , , I , , , I
-2000 0 2000 4000 6000 8000
Strain [microstrain]
Typical IITRI Compression Test Strain Data for 2-D Braided Material
LLL, (1/4" Thick, 1.5" Long).
B.9
01(f)
.i.-,o')
45
40
35
30
25
2O
15
10
5
BH2_3-5G-3
I I I III | ! !|
B...--.m--...,.l_ ,. D. i......, n. _p.......---- ..- -_---- _--- -_m-_-- II I I I
I h ! ! !
............ P ............... P .............. P _"S" ........... ir
ir ............ "I ................ P ............ I
, ," , _J , ,, I: ' fl - ' '
, '-_ ...... ,,............ ,I
, __"7".'"-'"......,,"..........i
,' I .,_" ', _ AxialGage 1 /"
, _" "_ ..... F ...... -- .... Axial Gage 2 ri
c' _[:i-'-,''-[_i _raT:tinsv e
;" - - - G- , ........ Transverse Gage ,I
I
! | I
-2000 0 2000 4000 6000
Figure B.11.c
Strain [microstrain]
Typical Short Block Compression Test Strain Data for 2-D Braided
Material LLL, (1/4" Thick, 1.5" Long).
50
45
4O
35
•---" 30Gr)
(n 25Or)
09 20
15
10
BH2-04-5L-1
..... ".....F..... '..... ]-.... i .....II
I
I
..... ,,---,_- -,,-..... ,'-. _l • l l
..... ,"'" _,. ,:..... L...... _..._.._,...
I I I
i i _i i
I I • I
i s k
..... it" ..... I1'' ..... i- I"
l I I IIl I !
..... L ..... L ..... I.. _I-I i i
I I I
..... f ..... r ..... I---
I
!
I
J .....
!
I
I
i
I
/ .....I
II
4
I
I
I
I
I-
': iI
I
....... ---r ..... r ..... iII I
I I I
I
I I
I I
II I
I I I
I i I
.... r ..... r ..... i
I l I I
I I I I
..... I. ..... L ..... iI I I l
I I I I
I I I I
I I l l
I I l i
--- ....... r ..... r ..... iI I I
! I !
'. Axial Gage 1
Axial Gage 2
........ Transverse Gage
-12000 -9000 -6000 -3000 0 3000 6000 9000 12000 15000 18000
Figure B.12.a
Strain [microstrain]
Typical IITRI Compression Test Strain Data for 2-D Braided Material
LSS, (1/8" Thick, 1." Long).
B.10
(I)
45 _..... ,-..... ,-.....,.....I I I I
I "
l _ ', l ,I I
40 r .... _- r ..... r ..... , .....
I _1 I I
I 1_ I I
I I-- • I I35 e. ................., F "_" ,_ :I I tA I I
I I I, l l
30 b ..... _ .... _. ..... ,.....I I I_ I
I I I I
, , , % ,25 _...... _ ..... _._...,._
I I I _, l
I I I I I
I I I I I
20 b ..... ,- ..... ,..... _.,...I I I qll
I I I _l
I I I ilk
15 ,r..... ' ..... ' ..... i""-I I "_
I I
10 L .L ' I,......... I. ..... I .....
I I I I
l I I I
I I I I II
5 L ..... I. ..... i. ..... I .... i.
I I I I t
I I I I
I I I I
0
BH2_4-5M-1
.... 1 ..... "1 ..... T ..... r ..... r ..... I
I I i I I I
I I i • I I
I I I I I
.... 'I ..... _ ..... T .... r ..... I
I I I I I I
I I I I I I
I I I I I I
I I I I I
I I I I I I
I I I I I I
--I----'l--------- * @'''" " I" -- ---- -- -- IP---- -- -- -I
I I I I I I
I I I I I
I I I I I
"4 ..... 4, ..... I- ..... I'--I--I
I I I I I
I I I I I I
I I I I I I
----4--- .I- .... @ ..... I----i-I------I
I / I I I
I I I I I
I I I I
I t il
' Axial Gage 1 'I I
...... ,!
"_ - -Axial Gage 2 'I I I
I I
" - "_ _ ........ Transverse Gage! I
I I
-12000 -9000 -6000 -3000 0 3000 6000 9000 12000 15000 18000
Strain [microstrain]
Figure B.12.b Typical IITRI Compression Test Strain Data for 2-D Braided Material
LSS, (1/4" Thick, 1.5" Long).
5O
45
40
35
30
25
20
15
10
5
0
,--------,--...,.....,.....
I I I
I I I
, _-- -,-........... ,.....I • I I
........... I .....I. _ %_I
I I • I I
I I • I I
r ..... r - - - _-r ..... ,.....I I %1 I
I I _ I
L ..... L ..... !IS .... , .....I I I
I I I _I I
I I I t I
..... _ ..... _ I I_ i _l I
I I I _ I
I I I Iii II I / I
r ..... /" ......... _" t-u-
I I I qll
L ..... L ..... L ..... I_ -- --
I I I I I
l I I I
I I I I
r ..... r ..... I- ..... I- " -
t
I
..................... %_-
BH2_4-5G-1
i... ... ....... T ...... r "''" p .... - I
! I I I
I I I I
.... I I
I |
I I I
......... a ..... A .... L ..... I
I I I I
I I I I I
I I I I
.... 1 ..... '1 ....... r ..... r ..... ,I I I I !
I I I I I
.... J ..... J- A ..... L ..... L ..... II
I
I
--I ....
I
I
I
"1""
I I
I I
JI -- I J I 1I!
' 't! I
"-J ..... i-
I I I I
I I I I
I I I
I I I
I I I
..... _ ..... r ..... r ....
I I I
I I I
,Axial Gage 1
-Axial Gage 2
........ Transverse Gage
I
I
I
-I
I
I
I
"1
I
I
I
-12000 -9000 -6000 -3000 0 3000 6000
Strain [microstrain]
Figure B.]2.c Typical Short Block Compression Test
Material LSS, (1/4" Thick, ].5" Long).
9000 12000 15000 18000
Strain Data for 2-D Braided
B.11
b_
45
4O
35
3O
25
20
15
10
5
0
BH2-01-5W-1
.................... r ......... r ......... r ......... r .........| I I I
| I I I
II I I
• ----------------- ----- .... I1" ........ -r ....... -Wlp ...... ---IP-* ..... -
I I I I
I I I I
I I I
I I I I
I I I I
I I I I
......._......--.----..,.........,........., .......r.........
i i I
I I I I
I I I I
....-....- ..-...-..-,.........,... ....,.....-...,.........
J I .P .P
I i I
I I I
I I I I I
I I I I I
I I I I I
.......... l ................. [ l -- ! ...... If ........ [ ..... i . . -- I
I I I I I
I I i I I I
I I I I I I
I I I I I I
I I I I I
I I I I I I
........ L----. ...... L ......... L ......... L ...... .----L ..... .------I
I I I I I I
I I I I I I
I I I I I I
, I , I , I , I , I , I
0 1000 2000 3000 4000 5000 6000
Strain [microstrain]
Figure B.13 Typical IITRI 90 ° Compression Strain Data for 2-D Braided Material SLL.
,,¢,
U3
3O
25
2O
15
10
BH2-O2-5W-1
...... " ................. I ............ I ...... " ................ "1
I I II I I
I II
I I
I I I
I I I I
I I I I
I I I
I I I I
I I i I
I I I I
I I I I
I I I
I I I I
I I I I
I I I I I
I I I I I
I I I I I
I I I I
I I I I I
I I I I I
I I I I I
I I I I I
I I I I I
I I I I
I I I I l
I I I I I
I I 1 I I
I I I I I
, , , i , , , I , , , I , , , I , , , I
0 2000 4000 6000 8000 10000
Strain [microstrain]
Figure B.14 Typical IITRI 90 ° Compression Strain Data for 2-D Braided Material LLL.
B.12
35
3O
25
"_ 2O
U')
t.,t)
_ 15u)
10
BH2-O3-5W-1
.......... r ......... r ......... r ......... r ...................
I I I I
I I III I_
I I I
I I I I
.......... I- ......... I- ......... I- ........ I- ..................
I l I I
I I I I
I I I I
I I I I
.......... L ......... L ......... IL ........ L ..................
I I I I
I I I
I I I I
I I I I
.......... L ......... L .....................
I I I I
I I I I
I I I I
I I I l
I I I
.......... r ........ , ......... r ......... r ......... i" .........I I I I I
I I I I I
I I I I I
I I I I I
.......... r ........ r .......................................
' :I I
! !
....... _-......... _ ....................................I !
I !
, I , I , I , I , I , I
0 1000 2000 3000 4000 5000 6000
Strain [microstrain]
Figure B.15 Typical IITRI 90 ° Compression Strain Data for 2-D Braided Material LLS.
,,e
rE)
¢J3
09
45
4O
35
3O
25
2O
15
10
5
0
0
I
I
I
I
I
I
I
I
I
-r
i
I
I
I
I
I
BH2-O4-5W- 1
- r ..... i- ..... I- ..... i ...... i ...... h-
I I I I I I
I I I I I I
I I I I I I
..... r ..... _ ..... I ...... I ...... I-
I I I I I
I I I I I
I I I I I
..... r ..... _ ..... i ...... i ...... I-
I I I I I
I I I I
I I I I
..... r ..... I- ..... I ...... I-
I I I I I
I I I I
I I I I I
--I ...... I--
I I
I I I I
I I I I I
I I I I
I I I I
I I I I
-I- ..... I- .... I ...... I ...... I-
I I I I I
I I I I I
I I I I I
I I I I I I
I I I I I
l I I I l
..... t. ..... I. ..... I ...... I ...... I-
I I I I I I
I I I I I I
I I I I I I
.... _ ..... _ ..... -3 .....
I I
I I
I I I
I I
I I
I I
I I
I i
I I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
.... J ..... J
I
I
I
I
I
I
I
I
I
I
I
I
.... '=4 ..... 4
I I
I I
I |
I I
I I
I I
.... _ ..... J
I I
I I
I I
2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
Strain [microstrain]
Figure B.16 Typical IITRI 90 ° Compression Strain Data for 2-D Braided Material LSS.
B.13
70 r ..... r ....I I
I I
I I I
,_,. ,_n__ __-,.....
i '!!Rt_ _ . _k ....v_
BH2-11-3A-1
l I
I I
-I- ..... I-
I I
I I
I I
I I
_ eL ..... I--
I
I
I
I
.......... I_
I
I
I
I
I
I
I
I
..... i .... Ii_ ,I
---I-
| I
I !
I I
I I
..... i" ..... i ...... I ...... I ..... --I ..... "l ..... "l ..... "1
I I I I I i I I
I i I I I I I
I I I I l
I I I I
I .... I .... _ -- I i i I _
I I I i
I I I I I
I I I I t I
I I 1% II I.....,......,...... .....I I ', \I II I
I | I I I II
I I I _ II
..... i .... J ..... J ..... J .....
O I I I I s
I I I II
I I I I I I
I I I II I
I I _ /! !
I I I I I
I I II l I
I I I I I I
"" ...... i- ExtensometerI
' ' Axial GageI I
--I ..... I-- "1
' ' ........ Transverse GageI I
I I
_ II
-4000 -2000 0 2000 4000 6000 8000 10000 12000 14000 16000
Strain [microstrain]
Figure B.17 Typical Tension Test Strain Data for Stitched Uniweave Material SU-1.
O'}
CO
oO0
Figure B.18
BH2-12-3A-1
70 r ..... r .......... r ..... I ...... I ...... I ..... If ..... _ ..... _ .....
I I l I I I _ I I I
I I I I I I _ I I II
I | I I I I I I
60 ' ' ' ' ' ' ' ' ' '!,..... F..... : : : : : :.1" : :I _l. l I I I I I _ _ I
, % , , , , _ l j_r'l , I
5O L. _ . .I.. .......... L ..... I ...... I ...... _ ..... _---- --J ......... _ ..... J
' _ ' ' ' ' ' ' ' 'i 'l, - , , , , ,, % , , , , _ _,_ , , ,I I I I I I _P" / I / I I I
40 ,. \ _. ,- , ---' ...... '---_---' ..... -'..... -'..... 'I .... I ......... I ..... I''" _ Ij_/ /I I I I I, .., , , , _'/,:__----' I
i I _ i I I _....L
, % , , , .,_" -'i-- -- "-,-- , , ,
30 r ..... ,x......... F ..... ,.... -_ .... ,..... -,..... -' ..... -' ..... ;I I _I I I _I II III III I I, ,, , , i', , ,I _ ql I i / i I I I i I
i I • i I/ I I I II
20 r ..... r-. ........ r .... _ ..... ,..... !-'1 Extensometer I_I I I I I _ I II I _ I I I I • I
10 ' ' _ Il I _ I I l I, , %-_" __7"1 ........ Transverse Gage I'
I I I I I I, , _/ : : : ':[ : : _,0 I,,, I ...... I,,,I,,,I,,,I,,,I,,,I,,,I,,,I
-4000 -2000 0 2000 4000 6000 8000 10000 12000 14000 16000
Strain [microstrain]
Typical Tension Test Strain Data for Stitched Uniweave Material SU-2.
B.14
BH2-13-3A-1
7O
6O
50
4O
30
..... i i r i ;..................... i10
0
-4000 -2000 0 2000 4000 6000 8000 10000 12000 14000 16000
Strain [microstrain]
Figure B.19 Typical Tension Test Strain Data for Stitched Uniweave Material SU-3.
7O
6O
5O
"N 4O
(/3
(t3
3003
2O
10
0
-4000
BH2-14-3A-1
t ..... f" - -i" ..... i ...... I ...... J ..... "1 ..... "l ..... "l ..... "i
| | a I I I I I I i
I i a i i i i | I l
i I l I l I I i I I
i I I I I I I I D
IN4 .... I'= .... _ ..... I-= ..... I ...... I ...... I ..... =,1 ..... -- =,l -- ._='4-- --_'.1 ..... 4I I I
I I I I I _ I II _li I • I I I I I
I 11 I . l I I I I I I I
=..= =I,= ........... i. ..... i= ..... i.=..==l ..... ,,4 .... d..w==.=l..===J
I L I . I I I I I ! I
I • f • I I i I I I I II L I . I I I I i _ ..... I
I L -- I . I I I I,_P /I I /I I I
I I = I I I I I I I
, _, . , , , //q : : , ,l _ l I I _ I I I I I
I I " I I I I I I I I, a - , , _ .... :..... -..... -___ , ,i" ..... ," .......... F ..... ,.... ,...... ,..... "3..... "5..... ; ..... ",, , _ - , , j', --:- .... -, ..... --:- - - , ,I f " I I I I I I I l. ,_ . , ,,j" : : : : , ,' '\- ' I',,...... ,,..- -- ..... ,,-- ometer
I I " I I I 1 I '
iF" ..... P'- ............. I ...... I ..... _1--- I'l
" : " ' ' ' ' I\. ....... Transve.e,i
i
I I --- l l I l I
, , _/ : ', : : I . . . I,I,,,I ...... I,,,I,,,I,,,I,,,I,,, I,,, I,,, I
-2000 0 2000 4000 6000 8000 10000 12000 14000 16000
Strain [microstrain]
Figure B.20 Typical TensionTestStrainData for Stitched UniweaveMaterialSU-4.
B.15
BH2-15-3A-1
........................ i..........i.....iI I !
I l l I l i I
60 ,. -. __. ..... ,...... ,.... ,.. - .4..... -, ..... -4.....I - I I I I I I I I
I I I I I I I I I I
, % , _ , , , , , /, , ,
,. , _ , , , , ._:/_, , ,50 L-_.--,- ........._ '-..... '...... '...... '..... _'J.... "J..... "J..... J
I I I I I I I ...., --I-- __
I _l_ I I I I I I I I
I • I J I I I I _I I I I l
' I ' J l l ' l _! ' ' '
L j I.. JL IL ..... | .... I ...... i_r_ _ _ .,I ..... J ..... J ..... J,'-- C, ......... , ,'" ' ' ' ' '40- , , _I , , ,/r _ , , ,_ , _, , , , , , ,
_0 ' iL "1 , , ..'_I__.... a..... J ...... , , i30 r ..... ,",.... -r ..... ," ..... ,..... _ ..... ,- -- -- ", ..... -, ..... " ..... "
I f _ I I I I I I I I
l I II I I I I I I I20 ' ' \ .-I I"r ..... r - II " - "1" ..... r .... _1- _ H£. ..... !- -I Extensometer I"I I I I I I I, , _ :1 , /', ', :1 I,' ' 't 1 , jS" , , ! I ..... Axial Gage I iI- ..... I- ............ I ...... I ...... I- - .4
I I _l I I I I I10 ..... _ ....... Transverse Gage i
I I I I I I I
0
-4000 -2000 0 2000 4000 6000 8000 10000 12000 14000 16000
Strain [microstrain]
Figure B.21 Typical Tension Test Strain Data for Stitched Uniweave Material SU-5.
...,¢¢d}
.¢..=,
cO
120
100
8O
6O
4O
2O
Figure B.22
BH24)5-3A-1
............. ,....... r ...... "1....... ,............. 1 ....... ,I I ' I I
I I I I I
I I I I I
I I I I I
I I I II
'I-
F'--':' ...... ,;...... :.,............_ u._...... T, ,'
_, , , ,I I I I I l i
I I I _ l I I
p -- -- -- -- -- " ....... I" ...... P ...... "1 ....... I ..... r ...... 'I ....... I
I I I I I I I '
I I I I I I
I I __ii i_.=_ IIL II I IF, I I I
I I I I I I ' I
I I I I I I I I
I I I I I I I
I I ' I I ! I I
I I I I I I I I
, I I I I I l i
IIIN ............. III......./_ ii:]IIN ..... .4 ....... , ....... IN ...... Extensometer'4....... Ii Ill
I A.'_ I I I / I
I I I I I /I, ,Y'i i i ..... _x,_,_0e:".................. i'......i'......':: I',, , , , , ,,........ Transverse Gage, I I I I I
0 ' 4_... ! -- . I , , , I , , , I , , , I , , , I , , , II I I I I I 1 I ! I I I I I I I I , I I I I I
-2000 0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Typical Tension Test Strain Data for 3-D Woven Material TS-1.
B.16
120 r .......I
I
I
I
I
100 r ......I
I
I
I
80 ,_
_ ',I
_ 60 _-
_ ',I
40 r ......!
!
!
I
20 _I
!
!
01,,,
-2000
BH24)6-3A-1
I
.......i.......i...........,,, -I I I
....... ,...... _ ...... -: .....I I I
I I I
! I I
' ' i, , , I , , , I ...... i
0 2000 4000 6000 8000 10000 12000 14000
....... 0....... r ...... "1 ....... i ....... r ...... 1 ....... i
i i i I i i i
i i i i i I i
i i i i i i i
i i i i i i i
i i i i i I i
- --&- .... -I ...... I" ...... .1 ....... o....... r" ........... - ".7"_- " "--' I
I I I I I I
I I I I I
/.,, , ,," , , , ,I I I I I I
..... I.......... .1 ...... "1 _ .... r ...... "! ....... I
I I I I I
I I I I I I
I I I I I I
I I I I I
I I I I I I
--I ..... I ..... 4 ..... I ....... I- ...... 4 .......
I / I I I
I I I I I
I I I I
I I
I I
...... I- ...... .4 .......
t'Extensometer i,
Axial Gage i
........ Transverse Gage II
!
, , , I , , , I , , , I
Strain [microstrain]
Figure B.23 Typical Tension Test Strain Data for 3-D Woven Material TS-2.
(/)
(,'3
cO
120
100 .....
80 .....
60
40
2O
0 I , , ,
-2000
BH2_)7-3A-1
............. I....... r ...... "1 ....... , ....... r ...... 1 ....... I
I I I I I I I
I I I I I l I
I I I I I I I
I I I I I l I
i i i i ii i
...... I....... l" ...... "! ....... I ....... I" ...... I ....... I
I I I I I / i i
FI I I I I I
# I I I I I I
I I I I I I I I
-- -- _1 ..... I....... i" ...... .1 ....... I ..... I" ...... .1 ....... II
I I I I I I
I I I I _11_ II I If I I I I I
..... /: : , ,f I I I I I
, , 17"--2-; _ _-_- , ,
I I I I I I I
I I I I I I I
....... 1 ....... I- ..... .41 ....... II ....... ...... I- ...... 4 ....... II
ExtensometerI I I I I
I ! I I I
.................... - ....... Axial GageI I I I
I I I I I
I I I I I/ i i i i---..I I I l - = = • = = = _ -- - - I
, , , t , , , I , , , I , , , I , , , I , , , I , , , I
0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Figure B.24 Typical Tension Test Strain Data for 3-D Woven Material OS-1.
B.17
BH2-O8-3A-1
120 r ............. ,....... r ...... "1....... ,....... r ...... 1 ....... ,I I I I I I I I
I I I I I I I I
I I I I I I I I
I I I I I I I I
I I , , , , , ,I00
f--
I I I I I I I I
I I I l I I I I
I I I I I I I I
I I I I I I I I
80 ' ' ' ' ' ' ' 'r -- -- I i i i ....... I ....... _ " i I -- -- -- _ -- -- i I " " -- I .... I I -- r ...... _ -- I I I I -- -- I
I I I I I I I I
I I I I I I I I
I I I I I I I
I I I I I I
I I I I I
(I) S t "
I I I I I II I I I
G'_ I I I II
, , , J/ ' , , :40 . ............ ,....... _,_.... 4 ....... ,....... _ ...... 4 ....... ,
, , , _ i "_--_-- ,
,' ,, _ : _ Ex_om_t_ ',I I I I,' , , , ..... i,
,"............/,,---7,'.....,i......i,'....... _.......T ao ve -e":'I
I I I I I
I I I I I
0 I ...... I , . , I , , , I , , , I , , , I , , , I , , , I
-2000 0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Figure B.25 Typical Tension Test Strain Data for 3-D Woven Material OS-2.
BH2_9-3A-1
120 r ............. ,....... r ...... 1 ....... ,....... r ...... 1 ....... ,I I I I I I I I
I I I I I I I I
I I I I I I I I
II I I I I I I
I I IlOO _- , f "ll I I , I........ " .............. "" ....... I....... f'''''--1 ....... I
80 i , , , , J__ __, __.,.......-J.I
I
s I I I I I I I
._ I I I I I I II
...... I....... I- ...... .4 ..... I....... I- ...... -I ....... I
_--- I I I I I I I
I I I I I II
I I l l l I II
I I I I I I I I I
I I I l I I II
40 _............. ,....... _ .... _....... ,.............. _....... ,I I I ..... I
, ometer '
" E _' ' ' ...... 'i ..... Ax'_alGa 'I I I I I ' I
i ge ,i20 ,,-............I I I I
I 1 I i I I I,,' ! ........TI
l 1 l l l , lI J I I I I . - I
0 I ...... I , , , I , , , J I l , I ' ' l I ' I ' I l I ' J
60
-2000 0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Figure B.26 Typical Tension Test Strain Data for 3-D Woven Material LS-1.
B.18
120
100
I
I
80 r ......!
I
] 'i
!
60 ,,.......
,!!
!
4o ,. ......I
I
I
I
20 ,,- ......!
I
!
I
0 I , , ,
BH2-10-3A-1
r ............. i ....... r ...... "! ....... =....... r ...... "! ....... oi I I i l I | I
l I I I l I l I
l l O I I i l !
l I I I I ! O I
l I l l I I | I
pi i w=== i..o= ..... l "''= p === w = " "l = = "" "====I " = = " = P = " " = -- = _ = " e " = = =1
I I I I I I I I
I I I I | I I I
l I I I i I O I
I I I I I I I
l I I l I l I
...... I l ....... _ I _ .... _ I I ..... I I ...... _ I I .... _ I I I .... I
I I I I I l l
I I I I I I I
I I l I¢ • I I
'I¢ I I I _'_ m, q I I
k- ...... I ....... I- ...... .4 -- _f_'_ -- - --I ....... I- ...... 4 ....... I
I , , ,_ , ' ' 'I i i iJ$'-- i i ' i
I I I I I I I
I I I I I I I
I I l I l l I
iiiii I........................... I ....... I- .... 4 ....... I--
I I I I
i ' -- --, ExtensometerI I I I
I I I I
' ' ' ' ....... ti............ I- ...... 4 ....... I
I I I
Ill ,I' 1" ," ........ Transverse Gage /+I . - II
, . , I , . , I , . . I . , , I , , , I , . . I , . , I
-2000 0 2000 4000 6000 8000 10000 12000 14000
Strain [microstrain]
Figure B.27 Typical Tension Test Strain Data for 3-D Woven Material LS-2.
"3
¢,o
cO
6O
5O
4O
3O
2O
10
BH2-11-5G-1
--I ......... "_ ......... --I .........
I I
I I
I
I
I
--'!---------- ....
I
j' o!
! !
! !
! !
! !
0 e
I--
I I I
I I I
I I I
I I I
I I I
I I I
I I I
, , i jI I I
I I
I I
!
!
!
!
!
!
!
!
I ' I I I
I ] I I i
! !
j i i.......... I .......... I .........
--_= i i IJ , i ,
I lI
I I I I
! I l l
I
, J , ,
......... I------., d- ----I ......... "4 ......... -4 .........
, / , i ii_ I I I
/ I I I
/ I I I.......... I ......... ,,4 ......... =4 .........
I
l
,Axial Gage 1
Axial Gage 2
0 2000 4000 6000 8000 10000 12000
Figure B.28
Strain [microstrain]
Typical Short Block Compression Test Strain Data for Stitched Uniweave
Material SU-1.
B.19
BH2-12-5G-1
60 .......... r ......... ,.......... , ................... _ .........I I I I I
I I I I I
I I i I I
I i I I I
! i I I I
_V .......... _ ......... ,- ......... ,......... ......... ....., , 1.- J /
I
40
3O
2O
10
0
I II I I I
! I I _ I I
I I I I I I
I I I I I I
/ /I I I I
I I I I I I
I I I I I
I I I I I
I I I I I I
/ /I I I II I I I I I
I I I I I I
I I I I I
I I I I I I
/ /! I I I
I I I i m • I
' ' ' li", , , Axial Gage! I
, , I "" - A×_G_e2, ,-I:I I I
I I I I I II I I I I Ii I i i i I
, , , I , , , I , , , I , , , I , , , I , , , I
0 2000 4000 6000 8000 10000 12000
Figure B.29
Strain [microstrain]
Typical Short Block Compression Test Strain Data for Stitched Uniweave
Material SU-2.
6O
50
4O
"5
30
u')
2O
10
Figure B.30
BH2-13-5G-I
"¢ T 'i" -i ......... "i ......... "I
I I I I I I
I I I I I I
I I I I I I
II
4 _ 4 ', ',I I I I I
I I I I I
I I I I I I
I I I I I I
I I I I I
I I I I I
I I I I I
=P ......... I=
I I
I I
!
I
I
I I
I I
! II I
!I I I
I I I I
I I I I
I I I I
I I I I
I
I
II
I I
....... I .......... I .........I I
I I
I I
I I
I I
I I
I
Axial Gage 1 t "Axial Gage 2 " ]I
!
I I
i I
0 2000 4000 6000 8000 10000 12000
Strain [microstrain]
Typical Short Block Compression Test Strain Data for Stitched Uniweave
Material SU-3.
B.20
6O
5O
4O
30
2O
10
Figure B.31
BH2-14-5G-1
I
I
I
I
I
I I
I I
I I
I l
I I
I
I
i
I
I
...... P- ......... I--
! I
!
!
! I
! I
I I i I
.k , ÷ :I I I I
I I
! I I
I I I
I I I
I I I
I I I
I i i
i I i I
I I I I
I I I I
.... i ......... _ ......... _ ......... 4
I | I I
I I I I
I I I I
I I I I
I I I I
...... I- ..... I .......... I ......... -4 ......... -I ......... -I
II I I I I
I I I I . I
, , ,Axial Gage 1 ,I I
.......... I .......... i ..........
, , , ,Axial Gage 2! I I
I I I
I I I I I I
2000 4000 6000 8000 10000 12000
Strain [microstrain]
Typical Short Block Compression Test Strain Data for Stitched Uniweave
Material SU-4.
6O
5O
4O
o_ 30
u0
2O
10
0
Figure B.32
BH2-15-5G-1
"l ......... "1
! I I I I
I I I I I
I I I I i
.......... P ......... I .......... I ......... "a-- "a ......... "I
I
, , , ,b,/ , ,, , , i>- , ,, , , _/ , i ,
.......... r" ......... ,.......... ,.... IJ"- - - "I ......... "_......... "_, , , // , ,, , ,_y ,, , ,f I I I
, , _r , , ,, , f/, , , ,
.............................! ::.........i..........i.........:,, ,_j_-: ', , ,! ! !
..................',..........',.........i--::-:.........i" I I I ' ,Ax_
i i i I i i
Gage 1'' 'I
........ I- ......... I.......... I ......... _ --_>'_ .....i........ I _-,_x_G_e=,:,I I I I I I
I I I I I I
I I I I I II I I I I I
, , , I , , , I , , , I , , , I , , , I , , , I
2000 4000 6000 8000 10000 12000
Strain [microstrain]
Typica] Short Block Compression Test Strain Data for Stitched Uniweave
Material SU-5.
B.21
Figure
90
80
70
60
50
40
30
20
10
0
0
B.33
BH2-O5-5G-1
........ r ........ i i
I i i i I i
I I I I I I
I I I I I I
i.=i.ip==._i=.iilii..i==.nii...i=..==9='--i=i'--i9--=ili'iiI_
I I I I I I
I I I / I II I I I I
lllillllllll II IIIIIII III I _ _'='= =='_
I I I I I I
I I I I I
I I I I I
I I I I I
I I II I I
I I I I I I
| I I I I I
I I I I I!
I I I I I
......... I ......... 4 ......... _ ......... 4
I I I I
I I I I I I
I I I I I I
I I I I I I
| I I I I I
' I..................,......... ,AxN Gage 1 -.,I I
I II
, I L._ageI
-I .......... I ......... ---[.
I I I
I I I I I I
I I I I I I
2000
Typical Short
Material TS-1.
4000 6000 8000 10000 12000
Strain [microstrain]
Block Compression Test Strain Data for 3-D Woven
1/1
ffl
9O
8O
7O
6O
5O
4O
3O
2O
10
0
BH2-06-5G-1
........ i "_ ........ "_ ................... r-- ! ...................
I I I I I I
I I I I I I
! I I I I I
.......... I" ......... l .......... l ......... 9 ......... 9 ......... "_I
I I I I I I
I I I I I I
I I I I I I
.......... l- ......... I.......... I......... 9 ......... 9 ......... "I
I I I I I I
I I _1 / I I I
l I /I / I I I
___I I
, , , ' ____, ................... r = ......... i ......... i ......... 9 ......
I I I I
I I i I I I
I I
.... _.__ ................... O- .................. I......... ,.4 ......
I I I I
I I I I I II I
I I I I
I I I i i !
' ' - Ax_ Gage I "i.................. I.......... I......... = =
I I
,' ', ', - - ,Axial Gage 2 / :' I I I ....... / -- I
I I I I I I1,,,i,,,i,,, ,,,, I.,, ,0 2000 4000 6000 8000 10000 12000
Strain [microstrain]
Figure B.34 Typical Short Block Compression Test Strain Data for 3-D Woven
Material TS-2.
B.22
9O
8O
7O
6O
U')
_ 50
_ 40
30
20
10
0
0
Figure B.35
BH2_7-5G-1
..... r ......... * .......... I ...... "_ ..............
! I I _ I I
| ! t I I
| ! I / I I
I I I I I I
| | I I I I
I I I I I I
! 1 I I
I I I I
I I I I
i I I I I
I I | I I
I I I I I
I I I I I
I I I I
I I I I
I I I I I
| I I I I
I I I I I
t I ! I I
I I * | I
I:'-- _I
I
I
!
¢
I
' ' I........ ,.......... ,. ,Axial Gage 1
I I
! ! I
, , , ,Axial Gage 2_ _ _ L- .I .......... I .........
| I I
! I I I I
I I I I I
2000 4000 6000 8000 10000 12000
Typical Short
Material OS-1.
Strain [microstrain]
Block Compression Test Strain Data for 3-D Woven
9O
8O
7O
6O
5OU')
U)
4O-i,.-,
(.f)
30
20
10
0
0
Figure B.36
BH2_8-5G-1
! I
I I
I |
...... I" ......... e-
l I I
I I I
I I I
I I I I
I I I I
I ! !
....... t- ............ I ......... ,4--- .......
I I I
I I I
I I I I
...... J--- -I .......... I ......... -4 .........
I I I
t- -I .......... I ......... "1 -'---_ ....... "1
I I I I ,/_ l
I I I I I I
I I I I I I
......... I ........... "l ......... "1/I I I I
I I I I I
I I I I I I
......... I .......... I .... "1 ......... "1 ......... "1
I I I I
I I I I
I I I I
...... "1 ......... "1 ......... "1
I l
I I
I l
"I ......... "1
I I
I I
I I
"4 ......... ,4
I I
l I
I I
I I
i I
.,x, olI_iAxNGage2 _i
I I
I I
!
I I I I
' ' II I
I I
I I I
.I. ........ I .......... I .........
I I I
I l I l
I I I I
2000 4000 6000 8000 10000 12000
Typical Short
Material OS-2.
Strain [microstrain]
Block Compression Test Strain Data for 3-D Woven
B.23
90
8O
7O
60
3x 5Oin
_ 4o
3O
2O
10
Figure B.37
BH2_9-5G-1
.......... _ ......... i.......... i ......... _ ......... _ .........
l I I I
I I I
, 7, 7, ..... ",.........I I I i
.................... I.... )_ "" ":............ ', ,, ..... ..........I I I I
I I
f t
.................,_.,...../...:..........'.... ,! I !/ , _ : : ,
/ ,/ , , ,
, .t -72_ ....... ,,......... -;..... -:........., / /, , , ,V" / ' ' ' '
i, "2"-":-'" .... ',......... I ..... I .........I I !......e_._:/....'__-- ,.......b........I - AxmJGagel -
" :A I/ Axial Gage 2,,# L I I n,- .- - -/- - - ......... .......... ......... ,i i
._ / . , t II/ , , ' J i
I i i i im i i i i, , , i , , , i , , , t , , , i , , , i , , ,
2OOO
Typical Short
Material LS-1.
4000 6000 8000 10000 12000
Strain [microstrain]
Block Compression Test Strain Data for 3-D Woven
90
80
70
6O
._z. 50
U)
40,,.,,o')
30
2O
10
0
0
Figure B.38
BH2-10-5G-1
I I I I I
I I I I I
I I I | I
...... I- .... --- I -I ........... ----- .....
I I I I !! I I I I
I I I I I
I I I I I
I I I I
! ! ! !
I I I I I
I I I I I
| I I I I
I I I I I
I I I I
I I I I
I I II I i I I
I I I I I
I|
,Axial Gage 1
.Axial Gage 2
I
I
'!I
I
I
I
II
I4
I
I
I
4
I
I
I
-4
I
I
I
I
!
2000 4000 6000 8000 10000 12000
Typical Short Block
Material LS-2.
Strain [microstrain]
Compression Test Strain Data for 3-D Woven
B.24
Appendix C Boeing Specifications
Copies of two Boeing specifications are included in this appendix for reference. The
first specification, BSS 7260, illustrates the modified ASTM D695 compression fixture
used for the compression interlaminar shear tests described in Section 13.1. The second
specification, BSS 7273, describes the procedure used for the double cantilever beamtests described in Section 14.1.
C.1
1/
General llote z
The inside faces of the assembled fLxtu[e shall ClOlm within _+ 0.00l inch and sh.ll be maintained to• finish of 32 Ra or better Xn accordance v_th MiSZ B 46.1.
1/ OPTION: Relieve interior of bolting tangs 8 minimum of 0.02 inch.
IIODIFZED D6gS CONPRESSION F_XTURE /'OR TYPE IllAND TYPE IV CCO(PRESSION TESTS
rLgute 13
BSS
7260
Page 26
ORIGINAL ISSUE:x-m R|V,
;._-_; REVISED:. "C" 12-23-_8
C2
SCOPE
This standard describes the procedures for Mode I interlaminar fracture toughness
testing of materials by applying a constant tensile crack opening displacement rate
to a constant width and height double cantilever beam test'specimen. The fracturing
surfaces are pulled away from each other without sliding or shearing.
APPLICABLE DOCUMENS_
The current issue of the following references shall be part of this standard to theextent herein indicated.
ASTH E4 Verification of Testing Machines.
BAC 5317 Fiber Reinforced Composite Parts
COBTENTS
Not applicable to this specification.
DEFINITIONS
a. Area Method Interlaminar Fracture Toughness - The total interlaminar fracture
energy combining several initiation and arrest events.
b. Brittle Crack Propagation - A sudden crack propagation with the absorption of
no energy other than that stored elastically in the body.
c. Crack Starter - Nonbondable release sheet material (typically FEP for 250F and
350F curing systems and Kapton coated with a release agent llsted in BAC 5317for materials with higher processing temperatures) inserted between the middle
prepreg plies during layup allowing initiation of interply cracking.
Crack Tip Position - Position from which a crack will begin propagating.
Crack Tip Sharpness - a qualitative measure of the crack tip depth or radius.Crack tip sharpness is a function of the material, where a brittle material
produces a sharp crack tip (shallow tip/small radius] and a ductile materialproduces a less distinct crack tip (greater tlp depth/large radius].
f. Ductile Crack Propagation - Slow crack propagation that is accompanied by
noticeable plastic deformation and requires energy to be supplied from outsidethe body.
d.
e.
ACTIVE PAGES: (1) Rev. B (2) Rev. B (3} Rev. B (4) Bey. B (5) Bev. B (6) Rev. B
ORIGINAL ISSUE: REV.:
ENG _ _ ,
FSC_ NO. S13_S-I_ IIIV,lI
X 502
"B" 10-21-88
GIC INTERLAMINAR FRACTURE TOUGHNESS
FTR_ R- RF.7 NP_I_('_n t'_D_ T_'rq
ROE'J'WOSPECIFICATION SUPPORT STANDARD
BSS7273
I of 6
C.3
5
S.1
DEFZIZTIOSS (Continued)
g. Fiber Bridging - A phenomena where fibers begin to delaminate from both the
top and bOttOm surfaces. Two crack tips are crested which may iacrease theapparent fracture toughness.
h. Znitiation Znterlaminar Fracture Toughness - A measure of the minimum energy
level required to resist crack initiation.
i. Surface Energy Interlaminar Fracture Toughness - A measure of the energy level
associated with a materials resJqtance to delamination and crack propagation.
TEST SPECIMEN REQUIREME_I'S
PANEL PREPARATION
a. A laminate test panel shall be layed up using an even number of prepreg pliesas illustrated in Figure 1. Cured laminate thickness shall be 0.16 + 0.01 inch.
The number of plzes shall be determined from the cured ply thickness--ascalled out in the referenced specification. All plies shall be oriented in _hezero direction.
b. A crack starter ply shall be placed between the middle plies as shown in
Figure 2.
c. Panels shall be bagged and cured in accordance with the applicable process
specification for the material.
Variable
dimensionbased on
number of
specimens
required
±
T
e Trime
• t o13.0 • 2.0
Trim
3.0
13.0,2.0
15.0*2.0
All dimensions in inches
I,-,-,Insort of
FEF or Kaptoncoated with
a release
agent listedin BAC 531?
0 beg.
Fiber
direction
DCB SPECIMEN AND PANEL GEOMETRY AND DIMENSIONS; PLAN VIEW
Figure 1
BSS
7273
Page 2
ORIGINAL ISSUE:S-12-83
REVISED: "B" 10-21-88
C4
5.2
S
S.1
6.2
SPEC IHEN PREPARATION
Nachine specimens to the dilensions as sho_m in Figure 2.
Oo
LOAD (P DETAIL !
TOP ¥11_
LOAD IP) °_14----- t
CONSTANT WIDTH AND HEIGHT DGUBLIt CANTZLEVZR BEAN (IX:B) SFZCI_N
Figure 2
• 0a 1 lqm_r/_.ePMmTuS
TEST NACHINE
Testing shall be perforned vith a constant displacement rate test nachLne. TestmechLne shall be verified Ln accordance vith ASTM R4.
SPZCI_N GRIPS
Triangular specimen grips, as shorn in Figure 3. are attached to the upper and loverbean halves as disFlayed in Figure 4.
IIOT£J A11 dimansioeo in incites /Ill
/ f 1
," ]__rigure 3
BSS
7273Page 3
ORIGINAL ISSUE: 5-12-83 REVISED: "B" 10-21-88
C.5
6.2
7
7.1
SPECIMEN GRIPS (Continued)
CRACK TIP
POSITION
ALl dLmt'nS_Onl An inches
kGRIPS
POSITIONS OF THE TRIANGUALAR SPECIMEN GRIP IN THE DCE SPECIMEN
Figure 4
PROCEDURE
PARAMETERS/MEASUREMENTS
a. A minimum of five specimens shall be tested for each desired temperature.teapersure shall be 75 + 10P.
b. A crosshead speed of 1.0 inch/mln shall be maintained to product a loaddeflection curve.
]Room
c. To measure crack tip position, each crack arrest position shall be marked onthe edge of the specimen during loading with a visible urking pen. k IOxmagnifying glass is recommended to visually observe end "ark t_e crack tipposition. Each crack tip position vail correspond to an individual load llneas shown in Figure S.
**'0"** Be sure to note whether bridging of fibers between u;perCAUTION and lower surfaces occurs. Thl8 phenomena can significantly******* affect the results since sore than one crack tip is _rscturing.
d. The area llIustrated in Figure 5 represents the energy absorbed between twoknown crack length pomltLons.
Ignore first Peak, or mmnualLycrack aOout 0.5 knch. since the
f_p crack starter gzvmS • false
crack tzp sharpness that ts
not a functzon at the natarsa_. Crack Tkp Poo&tkon x
CrossJ_ed OefkectLon ( Sh. )
AREA METHOD LOAD DEFLECTION CURVE AND DATA DETERMINATION
Figure S
BSS
7273
Page 4
ORIGINAL ISSUE:l-NMO lilY.
5-12-83REVI_dEO. °B" ,].0-21-88
C.6
?.2
?.2.1
7.2.2
CALCULATIOK OF SURFACE ENERGY INTERLAHINAR FRACTURE TOUGHNESS
AREA I4ETHOD
• . Are• method GIC interl•nin•r toughness l• calculated from the follovin?foreul•.
At•• Interl•nin•r Toughne•s -
where
E
A
B - specinen vidth (in.)
E (in-lb/in. 2)A x a
• re• of the load deflection curve be tmmen the initial
and final crack positions.
crack length corresponding to E, initial crack tip to final crack tip(in.)
b. To obtain the energy involved in fracture (ln-lb/inl), the area under the curve• t two crack length position• seen in Figure 5 •hall be nea•ured.
c. Ignore 1st peak in calculation, or manually crack about 0.5 inch, since the PEPcrack •tarter gives • false crack tip sharpness that is not • function of thematerial.
d. The area illustrated in Figure $ represents the energy absorbed between two
known crack length positions.
INITIATION M_THOD
Initiation Method
GIC interlaaln•r toughness is calculated from the following fornula:
GIC m
where
p
a •
3PY GIC is in inch-pound/inch2
fracture load measured In pounds at the bott_ of the small savtoothezcursion8 (arrest) or fracture load •t tip of Jawtooth excursion(initiation)
crack length measured visually in inches and recorded manu•lly at itscorresponding load position on the chart (arrest or initiation cracklength)
specimen width in inches (e specimen constant)
calculated crosshe•d deflection in inches corresponding to lo8d value P.
These parameter• are •born in Figure 6.
8SS
?2?3
Page 5
ORIGINAL ISSUE:a m iEv iwmm
5-12-03 REVISED: *E" 10-21-88
C7
7.2.2 INITIATIONMETROD (Continued)
To measure the crosshead deflection Y for the GI_ initiation calculation, it isnecessary to obtain the load-deflection curve or_g_n by deliberately unloading alon9the dashed line as seen in Figure 6.
,wJ
/f
J
/
f/ Crack Length (
Selected at this IPol ; t _on
I R
CROSSHEAD DEFLECTION (in.)
INITIATION MZTNOD LOAD'DEFLECTION CURVE AND DATA POINT DETERMINATION
Figure 6
ItEPOEI'IIIG
Report specimen identification, teat temperature, and GIC to the nearest in-lb/ln 2.
BSS
7273
Page 6
ORIGINAL ISSUE:i-m Ally.
S-12_83REVISED:- • 10-21-88
C8
Form ApprovedREPORT DOCUMENTATION PAGE OMBNo.0704-0188
_ data _ode¢l. and co_q0t_r_ngand r.._. g t_p.oolmct©n¢=_lor .rn&t_n_._end co.n'cnp._s ,eg_udi_Ot_m ou_ est=rrate o__ olher ,t_cec=d Ibis c°l_c_°n o_=nlorrnaton.k'_<E'_g Sugg_lnlOr_tot_ ¢h= iouc0e_,to W_h_gton H_OClUa_I _,rv_. L_eclorate _o¢iraor_.._ _rat_ons and Reports, 1215 J_ierl_=n DavusH_ghway,Surle1204.Arlington,VA 22202-4302, and tothe O(fce, of Mana0_t and BuOy, Pa_e_o,rk Reductcm Prolect Io704-0188), Washm,gton. DC 20503.
1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
July 1994 Contractor Report4. TITLEANDSUBTITLE
Test Methods for Textile Composites
6, AUTHOR(S)
Pierre J. Minguet, Mark J. Fedro, and Christian K. Gunther
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
Boeing Defense & Space GroupHelicopters DivisionPhiladelphia, PA 19142
g, SPONSORINGI MONITORINGAGENCYNAME(S)ANDADDRESS(ES)
National Aeronautics and Space AdministrationLangley Research CenterHampton, VA 23681-0001
5. FUNDING NUMBERS
NAS1-19247
WU 510-02-12-09
8. PERFORMING ORGANIZATION
REPORT NUMBER
10. SPONSORING/MONITORINGAGENCY REPORT NUMBER
NASA CR-4609
11. SUPPLEMENTARYNOTES
Langley Technical Monitor: C. C. Poe, Jr.Final Report - Task 7
12a,DISTRIBUTIONI AVAILABILITYSTATEMENT
Unclassified-Unlimited
Subject Category 24
12b. DISTRIBUTION CODE
t3, ABSTRACT (Maximum 2OO word$)
Various test methods commonly used for measuring properties of tape laminate composites were evaluated todetermine their suitability for the testing of textile composites. Three different types of textile composites wereutilized in this investigation: 2-dimensional triaxial braids, stitched unkveave fabric, and 3-dimensional interlockwoven fabric. Four 2-D braid architectures, five stitched laminates, and six 3-D woven architectures were tested.All preforms used AS4 fibers and were resin-transfer-molded with Shell RSL-1895 epoxy resin. Ten categoriesof material properties were investigated: Tension, Open-Hole Tension, Compression, Open-Hole Compression,In-Plane Shear, Filled-Hole Tension, Bolt Bearing, Interlaminar Tension, Interlaminar Shear and InterlaminarFracture Toughness. Different test methods and specimen sizes were considered for each category of test.Strength and stiffness properties obtained with each of these methods are documented in this report for all thematerial systems mentioned above.
14. SUBJECTTERMS
Textile composites; Braiding; Weaving; Stitching; Mechanical testing; Tension;Compression; Shear; Bearing; Fracture toughness
17. SECU RITY CLASSIFICATIONOF REPORT
Unclassified
NSN 7540-01-280-55(X)
18. SECURITY CLASSIFICATIONOF THIS PAGE
Unclassified
19. SECURITY CLASSIFICATIONOF ABSTRACT
15. NUMBER OF PAGES
228
16. PRICE CODE
All20. LIMn'ATION OF ABSTRACT
Standard Form 298 (Rev. 2-89)Preecribe¢li_yA_ISI Std. Z39-t8298-1C_