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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