No problem is too small or too trivial
No problem is too small or too trivial if we can really do something about it – Feyman
H H 2 C-C-C{-OO H epoxy Prepregs H H-C-H -CH-C-H H H -O-}n. C-C-CH 2 H O H 2 N-R-NH 2 hardener Some specific polymers
Composites - overview Example - carbide tools (previously discussed) Co matrix phase angular WC fragments
Composites - overview Artificial combination of matrix phase & dispersed phase Matrix: metal, alloy ceramic mat'l polymer Dispersed phase: particulate fiber
Composites - metal matrix composites (MMCs) Particulates: Th. O 2 -dispersed Ni (TD Ni) sintered Al powder (SAP) Works like precipitation hardening - except strengthening maintained at hi T Improves: strength creep resistance hi T corrosion resistance
Composites - metal matrix composites (MMCs) Fibers: Conts - C, Si. C, B, Al 2 O 3 Disconts - C, Al 2 O 3 , Si. C whiskers Matrix mat'ls May get rxn betwn phases at hi T
Composites - ceramic matrix composites (CMCs) Particulates, fibers: Si. C, B, Al 2 O 3 , C, Si. C & Si 3 N 4 whiskers Matrix Improve fracture toughness: slow crack growth deflect crack tips redistribute stresses around crack tips bridge crack tips
Composites - polymer matrix composites (PMCs) Fibers: mainly - glass (GFRPs), carbon (CFRPs), aramid, others - B, Si. C, Al 2 O 3
Composites - polymer matrix composites (PMCs) Matrix
Composites - polymer matrix composites (PMCs) Very common - polyesters, vinyl esters
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
Composites non-coupled
Composites Fibers - variables amount fiber length distribution orientation Fiber orientation can be random aligned intermediate
Assignment: Review today's classnotes a. epoxies b. composites - matrix, dispersed phase c. MMCs - strengthening mechanism d. CMCs - fracture toughness improves e. PMCs - fibers f. matrix/fiber bond Read pp. 481 -507, 527 -538
Composites - polymer matrix composites (PMCs) Role of matrix in FR composites: a. transfer stresses betwn fibers b. provide barrier to environment c. protect fibers Slow crack growth deflect crack tips redistribute stresses around crack tips bridge crack tips
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