Last class -

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Last class -
Creep, relaxation, recovery
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Some specific polymers
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Composites - overview
Example - carbide tools (previously discussed)
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Composites - overview
Artificial combination of matrix phase
dispersed phase
Matrix metal, alloy ceramic mat'l polymer
Dispersed phase particulate fiber
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Composites - metal matrix composites (MMCs)
Particulates ThO2-dispersed Ni (TD
Ni) sintered Al powder (SAP)
- except strengthening maintained at hi T
Improves strength creep resistance hi T
corrosion resistance
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Composites - metal matrix composites (MMCs)
Fibers Conts - C, SiC, B, Al2O3 Disconts - C,
Al2O3 , SiC whiskers
May get rxn betwn phases at hi T
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Composites - ceramic matrix composites (CMCs)
Particulates, fibers SiC, B, Al2O3 , C, SiC
Si3N4 whiskers
Improve fracture toughness
slow crack growth deflect crack
tips redistribute stresses around crack
tips bridge crack tips
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Composites - polymer matrix composites (PMCs)
Fibers mainly - glass (GFRPs), carbon (CFRPs),
aramid, others - B, SiC, Al2O3
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Composites - polymer matrix composites (PMCs)
Matrix
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Composites - polymer matrix composites (PMCs)
Very common - polyesters, vinyl esters
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Composites
Role of matrix in FR composites a. transfer
stresses betwn fibers b. provide barrier to
environment c. protect fibers
Matrix/fiber bond matrix must wet fiber
physical chemical bond desirable mechanical
interlocking
Fibers frequently coated w/ coupling agent
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Composites
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Composites
Fibers - variables amount fiber
length distribution orientation
Fiber orientation can be random aligned
intermediate