chapter 16 avi
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Chapter 16- 2
• Composites:
--Multiphase material w/significantproportions of ea. phase.
• Matrix:--The continuous phase--Purpose is to:
transfer stress to other phasesprotect phases from environment
--Classification: MMC, CMC, PMC
• Dispersed phase:--Purpose: enhance matrix properties.
MMC: increase sy, TS, creep resist.CMC: increase KcPMC: increase E, sy, TS, creep resist.
--Classification: Particle, fiber, structural
metal ceramic polymer
Reprinted with permission fromD. Hull and T.W. Clyne, An Introduction to Composite Materials ,2nd ed., Cambridge University Press,New York, 1996, Fig. 3.6, p. 47.
TERMINOLOGY/CLASSIFICATION
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Chapter 16- 3
Particle-reinforced
• Examples:
Adapted from Fig.10.10, Callister 6e .(Fig. 10.10 iscopyright UnitedStates SteelCorporation, 1971.)
Adapted from Fig.16.4, Callister 6e .(Fig. 16.4 is courtesyCarboloy Systems,Department, GeneralElectric Company.)
Adapted from Fig.16.5, Callister 6e .(Fig. 16.5 is courtesyGoodyear Tire andRubber Company.)
COMPOSITE SURVEY: Particle-I
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Chapter 16- 4
• Elastic modulus, Ec, of composites:-- two approaches.
• Application to other properties: -- Electrical conductivity, se: Replace E by se.-- Thermal conductivity, k: Replace E by k.
Particle-reinforced
Adapted from Fig. 16.3,Callister 6e . (Fig. 16.3 isfrom R.H. Krock, ASTM Proc , Vol. 63, 1963.)
COMPOSITE SURVEY: Particle-II
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Chapter 16- 5
• Aligned Continuous fibers
Fiber-reinforcedParticle-reinforced Structural
• Examples:
From W. Funk and E. Blank, “Creep
deformation of Ni3Al-Mo in-situcomposites", Metall. Trans. A Vol. 19(4), pp.987-998, 1988. Used with permission.
--Metal: g'(Ni3Al)-a(Mo)
by eutectic solidification.
--Glass w/SiC fibersformed by glass slurryEglass = 76GPa; ESiC = 400GPa.
From F.L. Matthews and R.L.
Rawlings, Composite Materials; Engineering and Science , Reprinted., CRC Press, Boca Raton, FL,2000. (a) Fig. 4.22, p. 145 (photo byJ. Davies); (b) Fig. 11.20, p. 349(micrograph by H.S. Kim, P.S.Rodgers, and R.D. Rawlings). Usedwith permission of CRCPress, Boca Raton, FL.
(a)
(b)
COMPOSITE SURVEY: Fiber-I
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Chapter 16- 6
• Discontinuous, random 2D fibers
Fiber-reinforcedParticle-reinforced Structural
• Example: Carbon-Carbon
--process: fiber/pitch, thenburn out at up to 2500C.
--uses: disk brakes, gasturbine exhaust flaps, nosecones.
• Other variations:--Discontinuous, random 3D --Discontinuous, 1D
fibers lie
in plane
view onto plane
C fibers:
very stiff
very strong
C matrix:
less stiff
less strong
Adapted from F.L. Matthews and R.L. Rawlings,Composite Materials; Engineering and Science ,Reprint ed., CRC Press, Boca Raton, FL, 2000.(a) Fig. 4.24(a), p. 151; (b) Fig. 4.24(b) p. 151.(Courtesy I.J. Davies) Reproduced withpermission of CRC Press, Boca Raton, FL.
(b)
(a)
COMPOSITE SURVEY: Fiber-II
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Chapter 16- 7
• Critical fiber length for effective stiffening & strengthening:
Fiber-reinforcedParticle-reinforced Structural
fiber length 15sfd
t
c
fiber diameter
shear strength of
fiber-matrix interface
fiber strength in tension
• Ex: For fiberglass, fiber length > 15mm needed
• Why? Longer fibers carry stress more efficiently!
fiber length 15s fd
t
c
Shorter, thicker fiber:
fiber length 15s fd
t
c
Longer, thinner fiber:
Poorer fiber efficiency Better fiber efficiency
Adapted from Fig.16.7, Callister 6e .
COMPOSITE SURVEY: Fiber-III
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Chapter 16-
• Estimate of Ec and TS:--valid when
-- Elastic modulus in fiber direction:
--TS in fiber direction:
efficiency factor:--aligned 1D: K = 1 (anisotropic)--random 2D: K = 3/8 (2D isotropy)--random 3D: K = 1/5 (3D isotropy)
8
Fiber-reinforcedParticle-reinforced Structural
fiber length 15
s fd
tc
Ec EmVm KE fVf
(TS)c (TS)mVm (TS)f Vf (aligned 1D)
Values from Table 16.3, Callister 6e .(Source for Table 16.3 is H. Krenchel,Fibre Reinforcement , Copenhagen:Akademisk Forlag, 1964.)
COMPOSITE SURVEY: Fiber-IV
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Chapter 16- 9
Structural
• Stacked and bonded fiber -reinforced sheets-- stacking sequence: e.g., 0/90-- benefit: balanced, in-plane stiffness
• Sandwich panels -- low density, honeycomb core-- benefit: small weight, large bending stiffness
Adapted fromFig. 16.16,
Callister 6e .
Adapted from Fig. 16.17,Callister 6e . (Fig. 16.17 isfrom Engineered Materials
Handbook , Vol. 1, Composites , ASM International, Materials Park, OH, 1987.
COMPOSITE SURVEY: Structural
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Chapter 16- 10
• CMCs: Increased toughness • PMCs: Increased E/ r
• MMCs: Increasedcreepresistance
Adapted from T.G. Nieh, "Creep rupture of asilicon-carbide reinforced aluminumcomposite", Metall. Trans. A Vol. 15(1), pp.139-146, 1984. Used with permission.
COMPOSITE BENEFITS