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



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



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



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



Chapter 16- 6

• Discontinuous, random 2D fibers


• 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



Chapter 16- 7

• Critical fiber length for effective stiffening & strengthening:


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



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 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



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



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



Chapter 16-

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Core Problems:

Self-help Problems:

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