Post on 30-Mar-2018
Composite Materials
• Two or more materials combined on a macroscopicscale to form a useful material
• Ideal for structural applications where high strength-to-weight and stiffness-to-weight ratios are required
• Conventional composites limited to in-plane distributed loads
Specific Strength & Specific Modulusm x 104
0 2.5 5.0 7.5Graphite/EpoxyBoron/EpoxyGlass/EpoxyTitaniumSteelAluminum
0 1.0 2.0 3.0Tensile Strength/Density (in x 106)
m x 106
0 5 10 15Graphite/EpoxyBoron/EpoxyGlass/EpoxyTitaniumSteelAluminum
0 1 2 3 4 5 6Elastic Modulus/Density (in x 108)
Composite Product Forms
Tape - all fibers aligned in single direction
Cloth - fibers aligned in multiple (usually two) directionsPlain weave: over and under one fiber at a timeSatin weave: over several then under one fiberAS4/3501-6 6K5H
- 6000 filaments per yarn- 5 harness weave (over four under one)
• Composites referred to by type of fiber/type of matrix (AS4/3501-6)• Layers can be fiber only for later “wet” layup (adding resin), or can be “prepreg” (already containing the resin)
Representative Usage -- 1980’s
Carbon/epoxy wingskins with integral titanium splice plates,carbon/epoxy control surfaces and stabilizers (horizontal and vertical)
Representative Research, 1980’s
Integrally stiffened C/E composite wing skin (large, cocured structure)
Representative Usage -- 1990’s
C/E wing skins, stabilizers, fuselage skins, control surfaces, internal structure (F-22)
X-36 Tailless Agility Research RPV
C/E aerodynamic surfaces28% Scale (18’ length, 3’ height, 10’ wingspan, 1250 lb.)Williams International F116 engine (700 lb. thrust)
Terminology• Fibrous Composites: Fibers in a matrix
» Fibers more “perfect” properties due to diameter on order of crystal size (no slip) & fewer internal defects» Whiskers low length to diameter ratio (<100)
More “perfect” than fibers Nearly perfect crystal alignment
» Lamina - arrangement of fibers in a matrix (single layer)
• Laminated Composites: Layers of at least two different materials bonded together
» Bimetals - significantly different CTE allows thermostat» Safety glass - glass transparent & hard but brittle; polyvinyl butryal tough but scratches» Laminate - stack of lamina with various orientations of materials
Terminology (continued)
• Laminated Fibrous Composites:» Hybrid of fibrous composites and laminated composites» Layers of different fibrous composites
• Particulate Composites: particles of one or more materials suspended in a matrix of another material
» Concrete (sand and gravel in cement matrix)» Flakes
Terminology -- Family
• Common industry practice to reduce allowed orientation angles to four: 0, 45, -45, 90
• Laminates with similar number of like orientations share similar properties (belong to same family)
• Family convention: %0/%+45/%90•50/40/10 (50 % 0 plies, 40% + 45 plies, 10% 90 plies)•25/50/25 (25 % 0 plies, 50% + 45 plies, 25% 90 plies)
Terminology -- SymmetrySymmetric laminate implies that the material and orientation of layers above the laminate midplane are identical to those below.
ABCCBA
Antisymmetric laminate implies that the material of layers above the laminate midplane are identical to those below, but the orientations are of opposite sign
ABC-C-B-A
Terminology -- Balance
Balanced laminate implies that for every +θ oriented layer there exists a -θ oriented layer of the same material
[45,0,90,-45,0,90] balanced, unsymmetric
[45,0,90,-45,90,0,45] unbalanced, symmetric
[10,0,45,-45,-10,38,-38] balanced, unsymmetric
[45,-45,0,90,0,-45,45] balanced, symmetric
Laminate Shorthand Convention
Disregarding material hybrids, the convention is to list the plies in stacking order, referencing the orientation
[45,-45,0,0,45,-45,90,-45,45,0,0,45,-45,90,-45,45,0,0,-45,45]
==> [±45,02,±45,90,+45,0]s (30/60/10)
Remove one of the centerline 0 plies:
[45,-45,0,0,45,-45,90,-45,45,0,0,45,-45,90,-45,45,0,-45,45]
==> [±45,02,±45,90,+45,0]os (26/63/11)
Lamina Coordinate System
Coordinates 1,2,3 are principal material directionsCoordinates X,Y,Z are transformed or laminate axes
Effect of Orientation on Mechanical Properties
AS4/3501-6: E1 = 20E6 psi, E2 = 1.0E6 psi, ?12 = 0.3, G12 = 1E6 psi? xy,x is a coefficient of mutual influence -- a measure of shear in xy-plane due
to normal stresses in x-direction
Properties of Inorganic FibersFiber (Mfr.) ρ (g/cm3) σ Mpa (ksi) E Gpa (msi) Diameter (µm) Use temp. (C)AluminaFiber FP (duPont) 3.9 1.38 (200) 380 (55) 21 1316PRD166 (duPont) 4.2 2.07 (300) 380 (55) 21 1400Sumitomo 3.9 1.45 (210) 190 (28) 17 1249
MulliteNextel 440 (3M) 3.1 2.70 (250) 186 (30) 12 1426Nextel 312 (3M) 2.7 1.55 (225) 150 (22) 12 1204
b-SiCNicalon (Nippon Carbon) 2.55 2.62 (380) 193 (28) 10 1204SiC WhiskerVLS (Los Alamos) 3.2 8.3 (1200) 580 (84) 4-7 1400SiC MonofilamentSCS-6 (Textron) 3.05 3.45 (500) 410 (60) 140 1299Berghof 3.4 3.45 (500) 410 (60) 100 1259
Si3N4TNSN (Tonen) 2.5 3.3 (362) 296 (43) 10 1204
GraphiteT300 (Amoco) 1.8 2.76 (400) 276 (40) 10 >1648T40R (Amoco) 1.8 3.45 (500) 276 (40) 10 >1648
Elastic Constants of High Performance FibersFiber only in resin
Fiber E1 E2 ? t G12 ?? ν12 E1 E2 1 2 # Filaments Densitymsi msi ksi ksi ksi msi msi ksi g/cm3
Carbon/GraphiteAS4 34 1.2 520 13 260 0.3 34 1 520 3000 1.8T40 41 1 820 17 410 0.2 41 1 100 12 1.8Celion 6K-SKRSY 34 1.2 450 13 225 0.3 34 1.2 450 6000 1.8Celion 12K 30 1.2 245 12 122 0.3 34 1.2 200 12000 1.77ACP 31 .5 500 12 250 0.3 31 .5 1000 12000 1.8
Silicon CarbideSCS-6 60 30 500 26 250 0.17 50 25 400 1 3.1Nicalon 15 2 203 6.3 102 0.2 15 2 1000 500 2.6FP-5 23 23 84 9 42 0.3 55 55 1000 210 3.9FP-25 19 55 54 7 27 0.3 55 55 210 3.9
GlassE-glass 11 5 500 4 250 0.3 11 2 1000 12000 2.5S-glass 12.4 1 665 5 333 0.3 15 2 1000 1000 2.5
KevlarKevlar 49 17 1 250 6.5 125 0.28 17 1 250 1000 1.4
Properties of Metal and Ceramic Whiskers
Material Melting point Density Tensile Strength Young’s Modulus(F) (lb/in3) (ksi) (msi)
Iron 2768 0.284 1902 42Copper 1951 0.320 426 14Silver 1732 0.374 256 17Silicon 2538 0.084 554 23Al2O3 3700 0.143 4000 62BeO 4660 0.103 1900 50B4C 4400 0.091 2000 70SiC 4870 0.115 3000 70Si3N4 3450 0.115 2000 45Graphite 6600 0.060 2850 102
Glass Fiber Reinforcement
“E” lectrical “S” tructural QuartzCost/lb $1.00 $5.00 $100.00
TensileStrength, ksi 350 450 130Modulus, msi 10.6 12.6 10
Density, lb/in3 0.092 0.090 0.078
Dielectric Constant 6.33 5.34 3.70(conduct energy)
Loss Tangent 0.001 0.002 0.0002(absorb energy)
Graphite Fiber Reinforcement
Standard High Strain High Modulus Ultra High ECost/lb $18-35.00 $40.00 $65.00 >$275.00
TensileStrength, ksi 450 600 250-400 250-400Modulus, msi 34 35-45 50-55 75-120
Density, lb/in3 0.059 0.059 0.059 0.059
Advanced Composites Fiber Comparison
Fiber Fiber CompositeFiber Price ($/lb) Modulus (msi) Density (lb/in3)
E-glass 1 10.6 0.07S-glass 5 12.6 0.07Aramid 15-50 18.0 0.05Standard Graphite 17-35 34.0 0.06High Strain Graphite 40 42.0 0.06High Modulus Graphite 65 50.0 0.06Ultra-High E Graphite 275-650 75.0 0.06
Representative Properties of Unfilled Resins
* PC: polycarbonate, PS: polysulfone, PPO: polyphenylene oxide**Load specimen at room temp., heat until extensive creep
Thermoplastics* ThermosetsPC PS PP Polyester Epoxy-BPA Epoxy-CA Phenolic
Yield Strength, ksi 9 10 9 11 12 19 9
Tensile Modulus, msi 3.4 3.6 3.8 3.5 3.6 7.8 4.5
Elongation, % 80 50 30 4.5 4 3.5 2
Tg, C 150 190 210 155 170 190 -F 302 374 410 311 338 374 -
Heat Distortion**, C 132 174 130 140 155 175 170
Continuous Use, C 120 150 115 125 145 150 160Temp. F 248 302 239 257 293 302 320
Desired Characteristics of Matrix Resins
Mechanical & Thermal:High strengthHigh elastic elongationHigh shear strengthHigh modulusHigh heat distortion temp.Low creep at use temp.High toughness/impact strengthThermal expansion near fiberResistance to thermal degradationLow thermal conductivity
Chemical Properties:Good bond to fiber (directly or
with coupling agent)Resistance to solvents & chemicalsLow moisture absorption
Processing Characteristics:Low enough melt or solution viscosity
and surface tension to permit thorough fiber wet-out
Good flow characteristicsRapid cure or solidificationSuitable for precoated reinforcementCure temp. not greatly above use temp.Low shrinkage during and after noldingLong shelf life and pot life
Other Factors:Low costLow densityLow dielectric constant
Comparison of Thermoset and Thermoplastic Resins
Stepwise cure possible to permit Viscosity varied only by increase in control of viscosity & handling temperature and/or shear rate
Thermosets Thermoplastics
Most used Most suited to automated production
No flow under heat and pressure Softening and/or melting points so flowafter cure; scrap discarded readily under heat and pressure;
remolding of scrap usually possible
Amorphous May be crystalline
Applied to reinforcement as low High viscosity even in the melt;viscosity liquids or varnishes reinforcement by dry or melt compounding
Phenolics and most polyimides emit No volatiles emitted during moldingvolatiles on curing (not epoxies orpolyesters)
Comparison of Thermoset and Thermoplastic Resins
Thermosets Thermoplastics
Post curing often necessary for Post molding shrinkage may be severeoptimum properties due to slow crystallization
Higher strength, modulus and Tougher, less brittle and lower costaverage use temperature
Used with continuous fiber and Used mostly with discontinuous fiberdiscontinous fiber (usually >1/4”) (length usually <1/2”), though much
activity in last 10 years on TP prepregs
Low tensile elongations Relatively high tensile elongationspossible with some plastic yielding
Variability in mechanical properties High variability in mechanical properties
Maximum Useful Temperature of Representative Resin Based Composites
Density MaximumMaterial (lb/in3) Temp. (F)
E-glass/epoxy 0.072 350Boron/epoxy 0.075 350Graphite/epoxy 0.059 350
E-glass/polyimide 0.072 600Boron/polyimide 0.075 600Graphite/polyimide 0.059 600
Borsic/aluminum 0.100 600Borsic/titanium 0.130 1200
Composite Materials Overview Homework Assignment (40 pts)
a) Type a 4 page essay/report (not including a title page) on the various types
of composite fibers, matrices, their relative properties, uses, characteristics.
Include both thermoset and thermoplastic matrices.
b) Include references to content, figures, tables, etc.
c) Use the lecture notes as one reference, other references could be your
textbook, other documents on the course web page, and so on.
d) For an extra 10 pts, discuss the difference between carbon and graphite
fibers.