EM 530 Composite Structural Analysis

Lecture Notes

Chapter 1: Introduction

Based on the text

Mechanics of Composite Materials, Robert M. Jones, 1999.

Slides courtesy of

Robert M. Jones, and Mohanned Mahdi

Motivation

http://unsilentgeneration.files.wordpress.com/2009/06/pub_gt_air

craft_composite_content_1980-2010_lg1.jpg?w=280&h=360

Course objective

• Introduce the nature,manufacture,and applications of various composite materials

• Give a through grounding in issuer of the fundamental mechanics of composite materials

• Treat a broad spectrum of analysis topics essential to basic understanding

• Compare theoretical predictions of behavior with actual measurements to validate or reject possible design analysis approaches

• Survey topics of more advanced interest

Outline

• Introduction to composite materials and structures

• Micromechanical behavior of a lamina

• Micromechanical behavior of a lamina

• Micromechanical behavior of a laminate

• Bending ,buckling, and vibration of laminated plates

• Other topics

• Computer analysis of composite structures

• Introduction to design of composite structures

THE WHAT, THE WHY , AND

THE HOW

Introduction to

composite materials & structures

Outline 1. The what

• What is a composite materials?

• Classification and characteristics

• Laminated fiber-reinforce composite materials

• Manufacturing

2. The why

• Why are composite material used instead of metals?

• Advantages (stiffness, strength , weight , cost ,etc)

3. The how

• How are composite materials used in structural applications?

• Case histories of important applications

Definition of Composite Materials

• It contains two or more physically distinct and mechanically separable materials

• It is made by dispersing one material in the other in a controlled way to achieve optimum properties

• The properties of the composite are superior and possibly unique in some specific respects to the properties of individual components

Professor Derek Hull

University of Liverpool

The what

What is a composite materials

Composite materials • Definition: Two or more materials combined on a

macroscopic scale to form a useful third material with enhanced material properties

• Properties to be improved:– Strength -- Thermal insulation

– Stiffness -- Thermal conductivity

– Weight -- Corrosion resistance

– Fatigue life -- Acoustical insulation

– Wear resistance -- Temperature-dependent behavior

Characteristics and classification

of composite materials

Classification of composite materials

• Fibrous composite

• fibers in a matrix

• Laminated composites

• layers of various materials

• Particulate composites

• Particles in a matrix

• Combinations of above

• Reinforce concrete

• Laminated fiber-reinforced composite

George H. Staab, LAMINAR COMPOSITES, Buuterworth_Heinmann, 1999.

3

Particle-reinforced

• Examples:Adapted from Fig.

10.10, Callister 6e.

(Fig. 10.10 is

copyright United

States Steel

Corporation, 1971.)

Adapted from Fig.

16.4, Callister 6e.

(Fig. 16.4 is

courtesy Carboloy

Systems,

Department,

General Electric

Company.)

Adapted from Fig.

16.5, Callister 6e.

(Fig. 16.5 is

courtesy Goodyear

Tire and Rubber

Company.)

COMPOSITE SURVEY: Particle-I

Laminated Composites

Classification of composite materials

• Fibrous composite

• fibers in a matrix

• Laminated composites

• layers of various materials

• Particulate composites

• Particles in a matrix

• Combinations of above

• Reinforce concrete

• Laminated fiber-reinforced composite

Fibrous composites

• Long fibers stronger and stiffer than bulk form

• Fibers have a more perfect structure

• Fibers

• High length-to-diameter ratio

• Near crystal-size diameter

• High strength-to-density & stiffness - to – density

• Whiskers

• Low length-to-diameter ratio

• More perfect than fibers

Compressive Strengths• Crushing, shearing and buckling effects under a

compressive load.

• where E is the tensile modulus and d/L is the reciprocal of the aspect ratio

• Larger-diameter fibers tend to resist buckling effect better than small-diameter fibers

• Ideally, fibers’ tensile strength is the same as compressive strength. However, Kevlar fibers’ compressive strength is only 20% of their tensile strength.

• Bonding condition (via matrix) can help reduce buckling effect

22

bucklingEuler 16 L

dE

Flexibility• The flexibility of a fiber, defined as k/M, can be

expressed in moment, M.

• Where E is the tensile modulus, d is the fiber

diameter and k is the reciprocal of the radius of

the curvature

64

4EkdM

History of the Carbon Fiber

• The father of carbon fiber is British research chemist Sir Leslie

Philips of the Royal Aircraft Establishment ,Farnborough

• He says “we sat down one day and decided we had to do

something. From a little chemical formula written on the back of an

envelope to reality took only months and nothing could have fallen

out better according to the theory we devised. I don’t suppose initial

work cost more than a few thousand pounds”

• “we settled on the formula in autumn 1963, had an illicit can of beer

to celebrate the test result in spring 1964, got commercial production

by July 1966,and life’s been a ding-dong ever since. When you fall

on something good like this and see it used all over the world ,

satisfaction is complete”

Carbon/ Graphite Fiber

• A carbon fibers used a reinforcing material

– Filaments/fiber are long, thin strand of material about 0.0002-0.0004 in (0.005-

0.010 mm) in diameter and composed mostly of carbon atoms

– The carbon atoms are bonded together in microscopic crystals that are more or

less aligned parallel to the long axis of the fiber.

– The crystal alignment makes the fiber incredibly strong for its

size.

• Production Materials

– 1950’s – Rayon decomposition process was used to obtain fiber having 20-50%

carbon

– 1960s, polyacrylonitrile (PAN) based fiber production introduced. Contains about

55% carbon and has better properties.

– 1980’s process developed to use petroleum pitch as precursor, can produce

fiber with upto 85% or better carbon content

•

Fiber Classifications

• Carbon fibers are classified by the tensile modulus

– Low modulus, standard or intermediate modulus, high modulus,

and ultrahigh modulus

– Low modulus (34.8 million psi or 240 million kPa),

– Ultrahigh modulus 72.5-145.0 million psi (500 million-1.0 billion

kPa)

– Steel 29 million psi (200 million kPa)

• “Graphite fiber” refers to ultrahigh modulus fibers made

from petroleum pitch

– These fibers have an internal structure that closely approximates

the three-dimensional crystal alignment that is characteristic of a

pure form of carbon known as graphite.

• A 6 μm diameter carbon filament (running

from bottom left to top right) compared to a

human hair.

http://www.statemaster.com/encyclopedia/Image:Cfaser-haarrp.jpg

Graphite Fiber Production

ProcessProcess is used for making carbon fibers has many steps

– Spinning: The precursor is drawn into long strands or fibers

– Stabilizing: Fibers are heat to produce desirable molecular

structure by heating them in air or some gaseous atmosphere

– Carbonization: Heated to a very high temperature with-out

allowing it to come in contact with oxygen.

– Surface treatment: The fiber surface is slightly oxidized to

improve their ability to chemically bond better with expoxy. This

also etches and roughens the surface for better mechanical

bonding properties.

– Sizing: The fibers are coated to protect them from damage

during winding or weaving. The coated fibers are wound onto

cylinders called bobbins.

Schematic of Carbon Fiber

Production

Graphite or carbon fibers

• Precursor fiber

• Pitch

• Pan (polyacrilonitrile)

• Heat fibers in an inert atmosphere (don’t burn)

• Carbonize

• Partially graphitize

• Fiber tension is a key processing parameter

• Carbon fiber – processed below 1700 C

• Graphic fibers-processed above 1700 C

• The higher the temperature

• The higher the modulus

• The lower the strength

(some recent exceptions)

Boron Fiber

E= 60 106 psi

σ = 450 103 psi

ρ = .09 Ib/in3

http://www.specmaterials.com/images/hyborgraphic.png

Fiber or wire

Density, ρ

Ib/in3

(KN/m3)

Tensile

strength, S

103 Ib/in2

(GN/m2)

S/ρ

105 in

.(km)

Tensile

stiffness,

E 106

Ib/in2.

(GN/m2)

E/ρ

107 in.

(Mm)

Aluminium .097(26.3) 90(.62) 9(24) 10.6(73) 11(2.8)

Titanium .170(46.1) 280(1.9) 16(41) 16.7(115) 10(2.5)

Steel .282(76.6) 600(4.1) 21(54) 30(207) 11(2.7)

E-glass .092(25.0) 500(3.4) 54(136) 10.5(72) 11(2.9)

S-glass .090(24.4) 700(4.8) 78(197) 12.5(86) 14(3.5)

Carbon .051(13.8) 250(1.7) 49(123) 27(190) 53(14)

Beryllium .067(18.2) 250(1.7) 37(93) 44(300) 66(16)

Boron .093(25.2) 500(3.4) 54(137) 60(400) 65(16)

Graphite .051(13.8) 250(1.7) 49(123) 37(250) 72(18)

Fiber and wire properties

Whisker

Density, ρ

Ib/in3

(KN/m3)

Theoretical

strength, ST 103

Ib/in2 (GN/m2)

Theoretica

l strength,

SE 103

Ib/in2

(GN/m2)

S/ρ

105 in

.(km)

Tensile

stiffness, E

106 Ib/in2.

(GN/m2)

E/ρ

107 in.

(Mm)

Copper .322(87.4) 1.8(12) .43(3.0) 13(34) 18(124) 5.6(1.4)

Nickel .324(87.9) 3.1(21) .56(3.9) 17(44) 31(215) 9.6(2.4)

Iron .283(76.8) 2.9(20) 1.9(13) 67(170) 29(200) 10.2(2.6)

B4 C .091(24.7) 6.5(45) .97(6.7) 106(270) 65(450) 71(18)

Sic .115(31.2) 12(83) 1.6(11) 139(350) 122(840) 106(27)

AL2 O3 .143(38.8) 6(41) 2.8(19) 196(490) 60(410) 42(11)

C .060(16.3) 14.2(98) 3(21) 500(1300) 142(980) 237(60)

Whisker Properties

Matrix Materials

• Metals

Metals can be made to flow around an in-place fiber system by

diffusion bonding or heating and vacuum infiltration, E.G.,

Aluminum, Titanium, and Nickel-chromium alloys

• Carbon

Carbon can be vapor deposited on an in-place Fiber system or

liquid material can be infiltrated around the fibers and carbonized

place by heating

• Ceramic

Ceramic material can be cast from a molten slurry around

stirred-in fibers with random orientation or with preferred

orientation because of flow or vapor deposited around a bed of

in-place fibers.

Matrices• Thermosetting polymeric resins – epoxy,

polyester, phenolics, polurethane, polyimides

• Thermoplastic resins – polyamide (nylon),

polypropylene (PP), poly ether ether ketone

(PEEK)

• Elastomers – silicone, neoprene (CR), NBR,

SBR

• Metal matrix

• Ceramic matrix

Polymer Matrices

Polymers

Thermosets Thermoplastics Elastomers

Non-crystalline Crystalline

Polymer Matrix Materials

• Polymers ≡(poly ≡many) (mer ≡ unit or molecule)

– Rubbers ≡ cross-linked polymers which have a semi

crystalline state well below room temperature.

• Thermoplastic ≡ resins or plastic compounds which can

be repeatedly softened by heating and hardened by

cooling,E.G., Nylon, Polyethylene, Polysulfone

• Thermosets ≡ resins which are chemically reacted until

almost all of the molecules are irreversible cross-linked

in A 3-D Net-work, E.G, Epoxies, Polyamides

Polymer systems

Thermosets

• Most of the polymer matrices are thermosets (75%)

• Thermosets are cured using curing agents or

hardeners to form a network structure (cross-linked)

• Thermosets are brittle at room temperature and

have low fracture toughness values (KIC = 0.5 -1.0

MPa m1/2)

• Thermosets are suitable for high temperature

application as they have higher softening

temperatures and better creep resistance than

thermoplastics

Polyester• Developed in 1833, consisted of unsaturated linear

polyester molecules dissolved in styrene (styrene is a cross-linking monomer).

• Curing can take place when an organic peroxide (e.g. MEKP) is added to the polyester resin. Free radicals are then created during the chemical reaction which leads to a formation of a 3-dimensional network structure.

• Polyesters are fairly easy to process as they are relatively inexpensive and have low viscosities. The shrinkage which occurs on curing is around 4-8% (pretty high).

Terminology• Shelf life or storage life – the length of time that

unmixed resins can be stored

• Pot life – resins into which the initiator has been mixed

• Inhibitor – molecules which absorb free radicals are added to resin mixture to slow down or prevent further cross-linking reaction

• A-stage – referring to resole and nonvolac resins

– Resole: a low molecular mass material, only heat is needed to covert the resin to the C-stage

– Nonvolac: hardener is needed to achieve the C-stage

• B-stage – a rubbery phase, the resin mixture is partially soluble and partially cured

– Prepreg: pre-impregnated tape (B-stage)

• C-stage – resin mixture is cured to a fully cross-linked condition

Epoxy• Developed in 1939, was mainly for coatings and

adhesives.

• Many different structures available today are derived from bisphenol acetate and epichlorohydrin.

• Epoxy is more expensive and is more viscous than the polyester resin making it very difficult to process

• A higher curing temperature (up to 180oC) with two to three stages of curing will be required.

• The shrinkage is much smaller than for polyesters (1-4%)

• In general, epoxies are stiffer and stronger, but more brittle than polyesters. Epoxies also retain their properties better in high temperatures than polyesters do.

Phenolics

• Developed in 1872, known as phenol-

formaldehyde.

• A resole is produced by reacting a phenol with an

excess amount of aldehyde in the presence of a

basic catalyst. (one-stage resin)

• A nonvolac is generated when excessive phenol is

reacting with an acid catalyst. (two-stage resin)

• Low cost, excellent heat resistance and good

balance of properties

Thermoplastics• Are linear polymers, don’t cross-link, might be branched

• Have superior toughness to thermosets

• Polypropylene and polyethylene are similar in origin and manufacture. PP is cheaper than PE. PP is harder, more rigid and has a higher stress cracking resistance than PE. Polycarbonate is an amorphous, transparent material, has good impact resistance, can be used up to 140oC.

• Polyamide (e.g. Nylon) has a high m.p. (260oC) and maintains its properties to about 150oC.

• Polyetheretherketone (PEEK) is a semi-crystalline polymer having 20-40% crystallinity. PEEK has a high Tg (143oC) and m.p. (343oC), good toughness (6 MPa m1/2) and good solvent resistance

Elastomers• Rubber-like elasticity – can be stretched more than

200%.

• In general the suitable temperature range for an

elastomer is between -50oC and 120oC.

• Natural rubber –cis-polyisoprene

• Styrene-butadiene rubber (SBR)

• Acrylonitrile-butadiene rubber (NBR)

• Chloropreene (CR)

• Polysiloxane (Silicone)

• Vulcanization – cross-link chemical chains using

sulfur.

Laminated Composites

• Bimetals

– Thermostat

• Clad metals

– Copper-clad Aluminum wire

• Laminated glass

– Safety glass

• Plastic-Based Laminates

– Formica

Particulate Composite

• Particles and Matrix can be either metallic or nonmetallic

• Nonmetallic in Nonmetallic – Concrete

– Polycrystalline Graphite

• Metallic in Nonmetallic – Rocket propellant

– Aluminum paint

• Metallic in Metallic – Lead in copper alloys and steel

• Nonmetallic in Metallic – Cermets (Reactor control rods)

Mechanical Behavior

• Most engineering materials

– Homogeneous

Properties independent of position in Body.

– Isotropic

properties independent of orientation at a point in the body

• Composites

– Inhomogeneous (Heterogeneous)

properties depend on orientation at a point in the body

Consequences of Heterogeneity

• Study composites VIA

– Micromechanics

Interaction of constituent materials is examined on a

microscopic scale

• Macromechanics

– Composite presumed Homogenous and effects of constituent

materials are detected on an Average Macroscopic scale

Mechanical Behavior

ASTM dog-bone tension specimen

Laminated Fiber-Reinforced

composite materials

Laminated Fiber-Reinforced composite

• Also called filamentary composites

• Lamina –basic building block

– Flat (but sometime curved ) arrangement of unidirectional

or woven fibers in a matrix

• Fibers

– Load –carrying agent

• Matrix

– Support and protect fibers

– Transfer load between broken fibers

Fiber-reinforced laminae

Effect of a broken fiber

Various stress-strain behaviors

Laminate

• Laminae with various

orientations of their

principle material

directions

• Bonded with lamina

matrix as “Glue”

• Can tailor directional

dependence of laminate

stiffness and strength to

match the loading

environment

Reason for Lamination

• Must bond laminae together to achieve maximum bending stiffness

• Recall the two-beam problems from basic mechanics of materials:

Possible deformation of two bonded layers

Bimetallic Strip

Thermal stresses

in isotropic and composite material

Terminology • Lamina-singular-one layer or ply

• Laminae-plural-more than one lamina, layers ,or ply

• Laminate-collection of laminae bonded together

• Principle-A law or fact

• Principle-main

• Criterion-singular

• Criteria-plural

• Data-plural (so data are)

• Axis-singular

• Axis-plural

• Modulus-singular

• Moduli –plural

• Phenomenon –singular

• Phenomenon-Plural

Manufacturing / Fabrication of

Composites

Some slides in this section are courtesy of

Richard Chung, Chemical and Materials Engineering Dept., San Jose State University

Initial Forms of Composite Materials

• Fibers

– Individual

– Roving

– Tow

– Unidirectional

– Woven

• Matrix

– Resin

– Metal

– Carbon

– Ceramic

• Preimpregnated fiber systems

– Tape

– Cloth

– Braid

Woven roving composite

2-D woven Fabrics

Thermosetting Resin Matrix• Hand lay-up

• Hand spray-up

• Vacuum bag/ Autoclave molding

• Match-die molding

• Resin transfer molding

• Filament winding

• Pultrusion

• Braiding

• Preform/molding compounds(SMC, BMC)

Laminate

Hand Lay-up

Hand Spray-up

Vacuum Bag/ Autoclave Molding

Autoclaves

Match-die Molding

Resin Transfer Molding

Filament Winding

Pultrusion

Braiding

• Advantage of Joint-Braiding Composite

• Seamless, thickness uniformity, fiber

density uniformity

• Angle of braiding yarn can be controlled

from 10 to 80 degree

• Multi-node complicated jointing composite

(Max. 10 layers by our experience)

• Various kind of application of joint part

Preform/Molding

Compounds(SMC, BMC)

Sandwich Structure

Thermoplastic Resin Matrix

• Fibers

• Tapes

• Electrostatic charge

• Powder

• Stamping

Metal Matrix

• Powder metallurgy

• Metal processing methods

– Rolling

– Forging

– Extrusion

– Drawing

– Die casting

Ceramic Matrix• Glass forming

– Pressing

– Sintering

– Drawing

• Particulate forming

– Powder pressing

– Hydroplastic forming

– Tape casting

• Cementation

• Drying/Firing

Manufacturing steps

1. Lay up

• Arranging of fibers in laminae and laminae in laminates

2. Curing

• Drying or polymerization of thermoset-matrix material

• Unaided

• Heat and/or pressure

• Consolidation of thermoplastic-matrix material

3. Machining

4. Assembly

Laminate Layup

Laminate layup Procedures

• Layup of tape and/or cloth– Hand

– Automated

• Filament winding

• Molding – Male and female

– Injection

• Roll forming

• Pultrusion

Composite tape layup methods

Hand layup of Boron-epoxy layer

The most basic fabrication method for thermoset composites is hand layup, which

typically involves laying dry plies or prepreg plies by hand onto a tool to form a laminate

stack. Here, technicians at Liberty Aerospace (Melbourne, Fla.) hand lay carbon/epoxy

prepreg for a general aviation part. Source: Liberty Aerospace

Source:http://www.compositesworld.com/cdn/cms/SB09_compositesthematerials_h.jpg

Automatic Tape-laying operation

• This automated fiber placement (AFP) machine, developed by Ingersoll Machine Tools

(Rockford, Ill.), is used by Goodrich Aerostructures (Chula Vista, Calif.) to produce the

inner fixed structures for the new GEnx jet engines that will power Boeing 787 passenger

jets. It replaces much slower manually intensive hand-layup techniques used previously

(see photo below). Source: Goodrich Aerostructures

• Source: http://www.compositesworld.com/cdn/cms/SB09_compositesthematerials_n.jpg

Fiber or Tape Placement

• http://www.compositesworld.com/cdn/cms/fraunhofer_fiber_placement_web.jpg

Unidirectional Tape problem areas

Filament Winding

http://www.freepatentsonline.com/7124797-0-large.jpg

http://i.ytimg.com/vi/NxspMPEsIk8/0.jpg

Compression Molding

Compression Molded Aerospace Part

• The Airbus A380 leading

wing edge is compression-

molded using a Ticona-

supplied thermoplastic CFRP.

http://www.sae.org/dlymagazineimages/8547_9499_ART.jpg

Continuous-belt,

chopped fiberglass roving, smc machine

Roll-Forming Process

for structural shapes

Pultrusion

Combination of manufacturing processes

Fabrication methods: relative costs and rates

Curing

Curing

• Thermoset-matrix materials

– Add heat to speed the natural chemical reaction of

polymerization with heat (catalyst) and pressure

– Volatiles usually given off during curing

– Chemical hardeners are used with some epoxy resins

• Thermoplastic –matrix materials

– Add heat to fuse constituents

– No volatiles because no chemical reaction

– Add pressure to consolidate constituents

• Cocuring is curing of two or more parts simultaneously

and in contact to fasten them together permanently

Polymer systems

Curing of thermoset-matrix composites

• Generally, the higher the temperature, the shorter the cure

time

• Heat required because:

– Some catalysts and/or hardeners do not react below a critical

temperature

– Molecular mobility necessary for contact of reactive groups

– Drives off solvent (volatiles) and water

• Otherwise, voids occur

• Must do before pressure applied

– Must resin flow to obtain uniform distribution

• Pressure required to:

– Consolidate (debulk) fiber and matrix system

– Squeeze out excess resin

Curing cycle

Resin behavior during curing

• Before curing

– Initial form of composite laminate is laminae laid adjacently in

A B-staged condition (partially cured to reduce resin flow during

laminating or molding)

– Resin is semi-sold with negligible strength and stiffness

• Gradually increase temperature

– Resin cross-linking begins and is significant by the gel

temperature (temperature at which viscosity is so high that no

further dimensional change occurs)

– Progressive cross-linking causes solidification

– However , elevated temperature lowers stiffness

Matrix cross-linking Vs. Temperature

Resin behavior during curing, continued

• At highest temperature

– Cross-linking is nearly complete

– Resin is solidified but of low stiffness because of temperature

• During subsequent temperature excursions

– No further cross-linking unless pervious maximum temperature

is exceeded

Autoclave for rocket motor cases

Rocket motor case

Manufacturing defects

• Interlaminar voids (air, no resin , delaminating)

• Excess matrix voids and porosity

• Inclusion of foreign matter

• Excess resin between layers

• Incomplete curing of resin

• Damaged fibers

• Incorrect orientation of laminae directions

• Wrinkles or ridges (improper compaction)

• Unacceptable joints in layers

• Variation in thickness

The why

Why are composite materials used instead of

metals ?

The why

Advantages

• Strength and stiffness

• Cost

• Weight

• General

Strength and

stiffness advantages

Advantages of

Fiber-reinforced composites

• Strength and stiffness

– Specific strength =

– Specific modulus=

• Cost

– Better in weight –sensitive applications

– Better in usual high scrap page applications

(double tapered wing spar with holes)

– Easier fabrication

– Going down with higher production and new technology

density

strength

Density

ModulusElastic

Translation form

constituents to lamina to laminate

Comparison of composite forms

Tensile strength and stiffness

Stiffness versus strength

• Stiffness is often equally important and

sometimes even more important than strength

Cost Advantages

Predicted cost of fiber

Cost versus pounds used

Composites down metals up

Elements of cost

• Raw material cost

• Design cost

• Fabrication cost

• Assemble cost

• Operating cost

• Maintenance cost

• Salvage value

Initial cost

Life-cycle cost

Materials utilization factor

• M.U.F = Amount of raw material

Amount of material in final part

• Metals : up to 15 to 25

• composite: 1.2 to 1.3

Doubly tapered wing spar

Raw Material cost

Machining cost

Scrappage

Layup cost

Titanium

High

Very high

Very high

None

Graphite- epoxy

High

Very low

Very low

Moderate

Fundamental fabrication difference

between composite and metal structures

Tooling

• CTE of tool need Not match part

– Both must be known and predictable

– Tool must be dimensionally compensated

• For great precision, but few parts

N-C machined Aluminum

• For great precision, but few parts

N-C machined Steel

• For good accuracy with many parts electro-formed

Nickel

• For rapid fabrication and few parts graphite-epoxy

Advantages of composite tooling

over metal tooling

(High-Temperature fiberglass – reinforced plastic tooling)

• Shorter fabrication time

• Weight 25% less

• Faster cure times (less mass to heat)

• Coefficient of thermal expansion of tool matches part

• Easier to repair (but less durable)

• Suitable for low-volume production runs

• Suitable for prototyping stage where shape changes are

common

Composite Tooling

• Graphite-epoxy tooling

– Susceptible to

• Surface damage (more than fiberglass)

• Penetration of release agents

• Delamination

– Too porous- leaks

• Ceramic tooling

– For low CTE

– Not porous

– Costs less than graphite for tool itself, but more for other

equipment

The How

How are composite material used

in structural application

The How

important Applications

• Replacement pieces

• Military Aircraft

• Civil Aircraft

• Space

• Automotive

• Commercial

Applications of composites

Hierarchy of development

• Demonstration pieces

• Replacement pieces

• Production pieces

• All –composite Airplane

Lockheed composite work in the 1920’s

Wooden Aircraft fuselages via molded sheets of

Glue-coated plywood in concrete tube with inflated rubber Bags

Replacement pieces

• Boron-Epoxy

– F-111 Stabilizer

– F-111 Fuselage

• Graphite- Epoxy

– F-5 Fuselage

– A-7 Access door

– A-7 Speed Brake

Military Aircraft Applications

of composite material

Production pieces • Boron-Epoxy

• F-111 wing pivot fitting doubler

• F-14 Horizontal Stabilizers

• F-15 Horizontal & vertical stabilizers

• Graphite- Epoxy • S-3A Spoilers

• F-16 horizontal & vertical stabilizers

• Space shuttle payload bay doors

• F-18

• Harrier

• Kevlar –Epoxy • spirit

Wing pivot Fitting

boron-epoxy doubler

Wing pivot fitting modification

cost comparison-new Aircraft

Wing pivot fitting modification

cost comparison-new Aircraft

F-14 Horizontal stabilizer

F-15 Horizontal and

vertical stabilizers

S-3A Graphite Spoiler

S-3A Metal Spoiler

S-3A Graphite Spoiler

Limited production S-3 spoiler

weight summary

F-16 Stabilizer

F-18 composite materials Applications

Deo RB, Starnes IHJR, Holzwart RC, Low-Cost Composite materials and

Structures for Aircraft application. NATO RTO AVT Panel spring symposium and

specialists' meeting Loen, NORWAY, 2001.

F-18 Graphite-epoxy usage

AV-8B Harrier

Civil Aircraft Applications

of Composite materials

Commercial Aviation Applications

• Boeing 737 spoilers

• L-1011 vertical fin

• McDonnell Douglas Dc-10 vertical stabilizer

• Boeing 757

• Boeing 767

• McDonnell Douglas MD-11

• Boeing 7J7

Composites Applications

• High percentage of composite in Airplane necessary to

realize potential

– Pyramiding

– Weight reductions

• Structure ≈ 30% total weight

• Payload ≈ 10% total weight

Stiffer& stronger materials yield

• Larger Payload

• Longer range

• Higher fuel efficiency

737 spoilers flight hours

747 seat strut

• Aluminum forging

– 7075-T73 $8/Ib(1980)

• Injection molded lexan

– Glass fibers in polycarbonate matrix

– 2 to 2-1/2 mm diameter pellets $ 1.45/Ib (1980)

– Less raw material cost

– Less fabrication cost

– Lower weight

– 2/3 minute per strut

– 40 KSI strength

L-1011 vertical fin

L-1011 vertical fin

Aluminum versus graphite –epoxy

DC-10 Vertical Stabilizer

• Primary structure

• FAA certification

• Flight evaluation (kc-10 and DC-10)

• Interchangeable with metal fin

• Carbon-epoxy spar box structure

• 187 Ibs. Less than 1,006 Ib. metal structure (30-45%

more weight savings if not interchangeable)

• Area 10 SQ. FT. less than Av-8B wing

• 60 components autoclave cured to form main pieces

• Heater bars used to final assembly

• Aluminum sprayed on outer surface for lightning

protection and antenna ground plane

Boeing 757 use of composites

Boeing 767 use of composites

MD-11 COMPOSITES USE

• Redesigned DC-10

• More composites, but still primarily metal

• Kevlar wing-to-fuselage fillet

• Graphite-epoxy parts (-2,500 Ib):– Elevators

– Center engine inlet duct

– Outboard flaps

– Wing trailing edges

– Horizontal stabilizer

– Winglets

– Tail cone

– Ailerons

• Some Aluminum-lithium floor beams (-340 Ib)

All-composite Aircraft

• Mosquito

• WinDecker eagle

• Lear fan 2100

• Beech starship

• Rutan voyager

• Avtek 400

• Piaggio p-188

• Williams V-Jet

Starship use of composites

• Essentially an all-composite Aircraft

• Graphite –epoxy sandwich with nomex honeycomb core

• Fuselage

• Wing

– For separate airfoil shapers for efficiency

Spaceship One