MSUComposites2009

8/7/2019 MSUComposites2009

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Composite Materials for Aircraft Structuresomposite Materials for Aircraft Structures

Dr. Douglas S. Cairns,Lysle A. Wood Distinguished Professor

Department of Mechanical and Industrial EngineeringMontana State Universit

ME 463 Composites,


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Lysle Wood Professor

Goals of the Professorship

technology nationally and in MontanaProvide support for aerospace related faculty

eve opment

Enhance student learning opportunities for aerospace

Design and Analysis of Aircraft Structures 13-2


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Cairns Background

Began composites career in 1978 as a Staff Engineer at the University of Wyoming Characterization of compression fatigue mechanisms of F18 vertical stabilizer

(AS1/3501-6) for Navy , , -

Navy and Army Senior Engineer, Hercules Aerospace, Magna UT (designed and analyzed space and

aircraft structures manufactured from composite materials) Ph.D. in Aeronautics and Astronautics, MIT, thesis on damage resistance and

damage tolerance due to impact damage in carbon/epoxy and kevlar/epoxystructures, research sponsored by FAA

Manager of Composites Technology, Hercules Materials Company

US largest manufacturer of structural carbon fibers ma er a s or m ary an commerc a aerospace pr mary s ruc ura app ca ons

Radius Engineering Board of Directors since 1988 Joined Mechanical and Industrial Engineering at Montana State University in 1995,

began working on wind turbine blade structures,


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Introduction

Com osite materials are used more and more for

primary structures in commercial, industrial, aerospace,marine, and recreational structures



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Composites:

Composites materials consist of a fibrous reinforcements

bonded together with a matrix material

Occur naturally in your bones, in wood, horns etc. Allow the stiffness and strength of the material to change

with direction of loading



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The Hierarchy for Advanced Structural Materials

Begin as laboratory curiosity

Aerospace) Applications to stuff rich people buy

Applications to things you and I can afford

ey ssump on: aw ma er a s are u ma e y

inexpensive and materials synthesis is ultimately

inexpensive



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Case History- Aluminum

At one time, more rare than gold and silver; Kingsand Queens wanted aluminum lates

Very Expensive Applications Art Deco furnishings in the 1920s and 1930s

ary a rcra ur ng

Stuff that rich people buy (Post WW II through 1960s)

General Aviation

Boats

Bicycles

y Aluminum BBQ grills at K-Mart

Aluminum shower curtain rods at hardware store



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Composites:

Carbon Fibers



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Radius Engineering- Salt Lake City, Utah

Radius developedthe Trek carbonfiber bicycle used byRadius developed Swix carbon fiber

Lance Armstrongski poles; have been used by Goldmedal Olympic skiers since 1990s



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Discussion Objective

Provide a brief introduction to composite materialsand structures in Air lane Structures



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Composites are Damage Tolerant

F18 Midair Collision (Circa 2002, no injuries)



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Composites are Damage Tolerant (cont.)



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Composites are Damage Tolerant (cont.)



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Composite Vertical Stabilizer and Rudder Damage



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Composition of Composites

Fiber/FilamentReinforcement CompositeMatrix

Good shear properties High strength High strength

Low density

Good shear properties

Low density



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Carbon is the Emperor

Typical large

tow properties



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The Emperors New ClothesTwo Basic Facts Hamper Application of Carbon Fibers to Primary Structure

Carbon Fiber is expensive; about 8X-10X E-glass

Much more sensitive to fiber mis-ali nment frommanufacturing process



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Not Just An Academic Exercise

Design and Analysis of Aircraft Structures 13-18Consequence of Misalignment in Large, Composite Structure


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The Emperors New ClothesTwo Basic Facts Hamper Application of Carbon Fibers to Primary Structure

updated 3:56 p.m. MT, Fri., Aug 14, 2009Boeing Co. has discovered another problem with its long-delayed 787 jetliner,

prompting the aircraft maker to halt production of fuselage sections at a factory in Italy.

The Chicago-based company found microscopic wrinkles in the skin of the 787s

June 23, spokeswoman Lori Gunter said Friday. Boeing has started patching the areas.

The plane, built for fuel efficiency from lightweight carbon composite parts, is a priorityor oe ng as s rugg es w w n ng or ers am e g o a recess on.

http://www.msnbc.msn.com/id/32415601/ns/business-aviation/



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Difficult to Control Manufacturing Defects inProduction



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Shorthand Laminate Orientation Code

Tapes or Undirectional Tapes

[45/0/-45/902/-45/0/45

Each lamina is labeled by its ply orientation.

Laminae are listed in sequence with the first number representing thelamina to which the arrow is ointin . Individual adjacent laminae are separated by a slash if their angles

differ. Adjacent laminae of the same angle are depicted by a numerical

subscript indicating the total number of laminae which are laid up in

[45/0/-45/90] s

sequence a a ang e.

Each complete laminate is enclosed by brackets. When the laminate is symmetrical and has an even number on each

side of the plane of symmetry (known as the midplane) the code maybe shortened by listing only the angles from the arrow side to the

Tapes or undirectional tapes


midplane. A subscript S is used to indicate that the code for only onehalf of the laminate is shown.


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Shorthand Laminate Orientation Code

Fabrics and Tapes and Fabrics

[(45)/(0)/(45)]

Midplane

When plies of fabric are used in a laminate. Theangle of the fabric warp is used as the ply directionan le. The fabric an le is enclosed in arentheses

[(45)/0(-45)/90]

Fabrics

to identify the ply as a fabric ply. When the laminate is composed of both fabric and

tape plies (a hybrid laminate). The parenthesesaround the fabric lies will distin uish the fabric

Midplane

plies from the tape plies. When the laminate is symmetrical and has an odd

number of plies, the center ply is overlined toindicate that it is the mid lane.

Tapes & Fabrics



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Fatigue Performance of Composites ExceedsThat of Metals

(Reference only)1.00

Maximum

25/50/25/ Gr/Ep0.75

cyclicstress/ultimate

stress

0.50

Room0.25

7075-T6 aluminum

,

dry R = -1.0 K1 = 3.0

0102 103 104 105 106 107


Cycles to failure


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Reduced Corrosion Problems WithAdvanced Composites

Advanced composites do not corrode like metalsthe combination of corrosion and fati ue crackinis a significant problem for aluminum commercialfuselage structure.



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Corrosion Case History Aloha Airlines

Low time airframe (but many Ground-Air-Ground cycles, 89,090


Operated in moist, warm environment (chemical processes exponential

with temperature)


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767 Exterior Composite Parts



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Honeycomb Usage



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SummaryAdvantages and Disadvantagesof Composite Materials

Advantages Disadvantages

Weight reduction(approximately 20-50%)

Some higher recurring costs

Higher nonrecurring costs

Corrosion resistance

Fatigue resistance

Higher material costs

Nonvisible impact damage Tailorable mechanical

properties Repairs are different than

those to metal structure

a es roug o se

Lower assembly costsfewer fasteners etc.

Isolation needed to preventadjacent aluminum partgalvanic corrosion



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Material and Process Specifications

Materialspecifications

Processspecifications

Supplier qualification Fiber requirements

Storage and handling Cure cycle

repreg requ rements

Fiber volume

Resin chemistry

ayup an agg ngprocedures

In-process quality control

Forms (tape, fabric)

Cure cycle

Quality controls

Acceptable anomalies

Splicing

Manufacturing characteristics Incoming and receiving tests



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Building Block Approach

ElementsJoints

Coupons

Environment

RT/Ambient

Small Panels

FullAirplaneStructure

Subcomponents

(Thousands)

(Hundreds)(Dozens)

Large Panels

Components

Coupons and Elements

Mechanical properties

Interlaminar properties

Large Panels and Test Boxes

Validate design concepts tress concentrat ons Durability Bolted Joints Impact damage characterization

Provide substantiating data for

material design values Demonstrate compliance with criteria

Materials

The effects of temperature and moisture

Analysis

Thermal and moisture strains calculated

nv ronmenta actors

models to predict strain values


are accounte or n es gn va ues anstrength properties.

critical condition.


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FAA/JAA Requirements forMaterial Allowables

FAR 25.613 Material Stren th Pro erties

Statistical basis

Environmental effects accounted for

MIL-H-17B

FAR 25.615 Desi n Pro erties

A basis for single load path

B basis for redundant structure

FAA AC 20-107A

JAR 25.613 25.615 and 25.603 similar to


FAA regulations


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FAA/JAA Regulations That GovernStructural Materials

FAR 25.603 Materials

Suitability and durability established by tests Conform to specifications that ensure strength

Takes into account environmental conditions

FAR 25.605, Fabrication Methods

sound structure (repeatability)

New methods must be substantiated by tests

FAR 25.609, Protection of Structure Protected against deterioration or loss of strength


. , . , .regulations

FAA/JAA Ad i i Th G


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FAA/JAA Advisories That GovernComposite Materials

FAA AC 20-107A Com osite Aircraft Structure

Presents an acceptablebut not the onlymeans forcertifying advanced composite structure

FAA AC 21-26, Quality Control for the

Manufacture of Composite Structure

Presents an acceptablebut not the onlymeans for

complying with the quality control requirement ofFAR 21

JAA ACJ 25.603, Composite Aircraft Structure


Similar to FAA AC 20-107A

St th R d ti f


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Strength Reduction ofAdvanced Composite Materials

Pristine Materials

Processing anomalies

Surface irregularities

Splicing

Reduction

of theallowable

Waviness

Inclusions

Voids

Stress

Visible damage

Nonvisible damage

Repair (holes, etc.)Allowable

es gn

Environment

Allowable strain

region

Strain


777 C it P i St t


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777 Composite Primary StructureCertification

Sequence Load Description Sequence Load Description

1 Limit roof Load 4 Strain surve

a. Up bendingb. Up bending/unsymmetricc. Down bendingd. Down bendin /

56

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Fatigue spectrumStrain surveyUltimate load strain survey

a. Stall buffet

2

Unsymmetrice. Stall buffet (unsymmetric)

Strain survey 8

b. Up bendingc. Down bending

Destruction test -


Fatigue spectrum3 down bending


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787 Airplane

Approximately 50% of the airframe is made from composites; avery bold move in the commercial aircraft industry



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Boeing 787 Dreamliner Logistics



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