Post on 03-Jan-2016
description
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Elastic Properties of K13D2U/Epoxy Prepreg
Mark E. Tuttle, University of Washington
tuttle@u.washington.edu
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Elastic Properties of K13D2U/Epoxy Prepreg Preliminary Comments
Current design of L0 support structure involves a six-ply [0/20/-20]s laminate (used in outer castellated shell) and a three-ply [0/90/0] laminate (used in inner cylindrical tube)
The elastic properties of the [0/20/-20]s and [0/90/0] laminates will differ substantially
By measuring the in-plane properties listed below for an individual ply, in-plane elastic properties of any multi-angle laminate can be predicted using lamination theory:E1 and E2 (moduli parallel and perpendicular to fiber direction)
12 (“major” Poisson ratio)
G12 (shear modulus)
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Elastic Properties of K13D2U/Epoxy Prepreg Objectives
To measure unidirectional properties (E1, E2, 12, and G12) exhibited by the K13D2U/epoxy composite delivered by Fermilab to the UW
Use lamination theory to predict Ex and xy exhibited by a [0/20/-20]s laminate
To compare predictions to measurements obtained using a [0/20/-20]s tensile specimen machined from a prototype castellated outer shell
(…subsequently, updated FEA analyses of the L0 support structure was performed by C.H. Daly, based on measured elastic properties)
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Technical ApproachMeasurement of unidirectional properties
E1 and 12: Measured using biaxial strain gages rosettes, mounted back-to-back on a [0]6 tensile specimen
E2: Measured using uniaxial strain gages, mounted back-to-back on a [90]6 tensile specimen
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22
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Technical ApproachMeasurement of unidirectional properties
G12: Measured using biaxial strain gages rosettes, mounted back-to-back on a [45/-45]s tensile specimen
(This technique described in Whitney, Daniel, Pipes, Experimental Mechanics of Fiber Reinforced Composite Materials, Chapter 4, ISBN 0-912053-01-1)
xx
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Technical ApproachMeasurement of Ex and xy for [0/20/-20]s laminate
Ex and xy: Measured using biaxial strain gages rosettes, mounted back-to-back on a [0/20/-20]s tensile specimen machined from prototype outer castellated shell
xx
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Preparation of [0]6, [90]6, and [45/-45]s Specimens
Three flat rectangular panels with required stacking sequences were prepared using a Tetrahedron MTP Programmable Hot Press
One surface of the panels was adjacent to an aluminum plate coated with release agent (the “tool” side), while the opposite surface was adjacent to a porous teflon release ply (the “fabric” side)
Cure cycle imposed using the hot press (pressure, temperature, time) simulated the autoclave cure cycle used to produce prototype outer and inner shells
Tensile specimens were machined from these panels using a diamond-coated abrasive cut-off wheel
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Specimen Preparation - Unidirectional Tests
(Nominal) physical dimensions: [0]6 specimens: 0.0140 x 0.7450 x 7 in
[90]6 specimens: 0.0140 x 0.7450 x 6 in
[45/-45]s specimens: 0.0120 x 0.7450 x 6 in Comments:
Nominal ply thickness was 0.0024 in for [0]6 and [90]6 specimens and 0.0030 for [45/-45]s specimens
To conserve material, specimens were much thinner than is “customary”, and aspect ratios did not meet ASTM specification of 10-12
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Test Equipment
Instron Model TM-M-L table-top test frame
Vishay Series 2100 strain gage amplifiers
Mac IIci equipped with National Instruments A/D board and LabView Software package
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[0]6 Specimen
[0]6 - Specimen 4 - Raw Data
0
100
200
300
400
500
600
-600 -400 -200 0 200 400 600 800 1000
Strain (min/in)
Loa
d (l
bf) Axial Strain (Fabric)
Trans Strain (Fabric)
Axial Strain (Tool)
Trans Strain (Tool)
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[0]6 Specimen
[0]6 Specimen 4 - Stress-Strain Curves
0
10000
20000
30000
40000
50000
60000
-600 -400 -200 0 200 400 600 800 1000
Strain (min/in)
Str
ess
(psi
) Axial Strain (Fabric)
Trans Strain (Fabric)
Axial Strain (Tool)
Trans Strain (Tool)
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[0]6 Specimen
[0]6 Specimen 4
0
10000
20000
30000
40000
50000
60000
0 100 200 300 400 500 600 700 800 900
Average Axial Strain (min/in)
Str
ess
(psi
)
E1 = 59.5 Msi
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[0]6 Specimen
[0]6 Specimen 4
0
50
100
150
200
250
300
350
0 100 200 300 400 500 600 700 800 900
Ave Axial Strain (min/in)
-1*A
ve T
rans
Str
ain
(in
/in)
12 = 0.39
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[90]6 Specimen
[90]6 Specimen 2
-200
0
200
400
600
800
1000
1200
1400
-500 0 500 1000 1500 2000 2500
Strain (min/in)
Str
ess
(psi
)
Axial Strain (Fabric)
Axial Strain (Tool)
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[90]6 Specimen
[90]6 Specimen 2
-200
0
200
400
600
800
1000
1200
1400
-200 0 200 400 600 800 1000 1200 1400 1600 1800
Average Axial Strain (min/in)
Str
ess
(psi
)
E2 = 0.806 Msi
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[45/-45]s Specimen
[45/-45]s Specimen 3 - Stress-Strain Curves
0
1000
2000
3000
4000
5000
-3000 -2000 -1000 0 1000 2000 3000
Strain (min/in)
Str
ess
(psi
) Axial Strain (Fabric)
Axial Strain (Tool)
Trans Strain (Fabric)
Trans Strain (Tool)
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[45/-45]s Specimen
[45/-45]s Specimen 3
0
1000
2000
3000
4000
5000
0 500 1000 1500 2000 2500
Average Axial Strain (min/in)
Str
ess
(psi
)
Ex = 2.32 Msi
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[45/-45]s Specimen
[45/-45]s Specimen 3
-500
0
500
1000
1500
2000
-500 0 500 1000 1500 2000 2500
Average Axial Strain (min/in)
-1*A
ve T
rans
Str
ain
(in
/in)
xy = 0.95
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[45/-45]s SpecimenCalculation of G12
The shear modulus implied by these measurements is*:
(Whitney, Daniels, Pipes, Experimental Mechanics of Fiber Reinforced Materials, Chapter 4, ISBN 0-912053-01-1)
MsiMsiE
Gxy
x 595.0)95.1(2
32.2
)1(212
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Summary of Measured Unidirectional Properties and Predictions for a [0/20/-20]s Laminate
Summary of measured unidirectional properties:
E1 = 59.5 Msi 12 = 0.39
E2 = 0.806 Msi G12 = 0.595 Msi
Predicted properties for a [0/20/-20]s laminate:
Ex = 38.4 Msi xy = 3.0
Ey = 1.08 Msi Gxy = 4.55 Msi
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[0/20/-20]s Specimen
[0/20/-20]s Laminate
0
5000
10000
15000
20000
25000
30000
35000
-3000 -2000 -1000 0 1000
Strain (min/in)
Str
ess
(psi
) Axial Strain (Fabric)
Trans Strain (Fabric)
Axial Strain (Tool)
Trans Strain (Tool)
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[0/20/-20]s Specimen(Predicted Ex = 38.4 Msi)
[0/20/-20]s Laminate
0
5000
10000
15000
20000
25000
30000
35000
0 100 200 300 400 500 600 700 800
Average Axial Strain (min/in)
Str
ess
(psi
)
Ex = 43.7 Msi
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[0/20/-20]s Laminate
0
500
1000
1500
2000
2500
0 100 200 300 400 500 600 700 800
Average Axial Strain (min/in)
-1*A
ve T
rans
Str
ain
(in
/in)
xy = 3.1
[0/20/-20]s Specimen(Predicted xy = 3.0)
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Sensitivity StudyVariation in Exx for [0/+/-]s Laminates
20
25
30
35
40
45
50
55
60
65
0 5 10 15 20 25 30 35 40
Angle (degrees)
Axi
al M
odul
us E
xx (
Msi
)
Predicted
Measured
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Sensitivity StudyVariation in xy for [0/+/-]s Laminates
0.35
0.85
1.35
1.85
2.35
2.85
3.35
0 10 20 30 40
Angle (degrees)
Poi
sson
Rat
io,
xy
Predicted
Measured
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Sensitivity StudyVariation in Eyy and Gxy for [0/+/-]s Laminates
0
2
4
6
8
10
12
0 5 10 15 20 25 30 35 40
Angle (degrees)
Mod
uli
(Msi
)
Eyy
Gxy
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Discussion
Only one measurement has been made for all specimen types; results obtained are not valid in a statistical sense
Specimen thickness is smaller than is customary, and in-plane aspect ratios are lower than ASTM specifications
Nevertheless, comparisons between measurement and prediction for a [0/20/-20]s laminate are reasonable
Given material costs, measured properties are sufficient for present purposes