No problem is too small or too trivial if we can really do something about it – Feyman No problem is too small or too trivial if we can really do something about it – Feyman

H 2 C-C-C{-O- -C- -O-} n C-C-CH 2 H-C-H H H epoxy H HOO H H hardenerH 2 N-R-NH 2 Prepregs 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 Artificial combination of matrix phase & dispersed phase Matrix: metal, alloy ceramic mat'l polymer Matrix: metal, alloy ceramic mat'l polymer Dispersed phase: particulate fiber Dispersed phase: particulate fiber

Composites - metal matrix composites (MMCs) Particulates: ThO 2 -dispersed Ni (TD Ni) sintered Al powder (SAP) Particulates: ThO 2 -dispersed Ni (TD Ni) sintered Al powder (SAP) - except strengthening maintained at hi T Improves: strength creep resistance hi T corrosion resistance Improves: strength creep resistance hi T corrosion resistance Works like precipitation hardening

Composites - metal matrix composites (MMCs) Fibers: Cont s - C, SiC, B, Al 2 O 3 Discont s - C, Al 2 O 3, SiC whiskers Fibers: Cont s - C, SiC, B, Al 2 O 3 Discont s - C, Al 2 O 3, SiC whiskers May get rxn betwn phases at hi T Matrix mat'ls

Composites - ceramic matrix composites (CMCs) Particulates, fibers: SiC, B, Al 2 O 3, C, SiC & Si 3 N 4 whiskers Particulates, fibers: SiC, B, Al 2 O 3, C, SiC & Si 3 N 4 whiskers Improve fracture toughness: slow crack growth deflect crack tips redistribute stresses around crack tips bridge crack tips slow crack growth deflect crack tips redistribute stresses around crack tips bridge crack tips Matrix

Composites - polymer matrix composites (PMCs) Fibers: mainly - glass (GFRPs), carbon (CFRPs), aramid, others - B, SiC, Al 2 O 3 Fibers: mainly - glass (GFRPs), carbon (CFRPs), aramid, others - B, SiC, 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 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 Matrix/fiber bond: matrix must wet fiber physical & chemical bond desirable mechanical interlocking Fibers frequently coated w/ coupling agent

non-coupled Composites coupled

Composites Fibers - variables amount fiber length distribution orientation Fibers - variables amount fiber length distribution orientation Fiber orientation can be random aligned intermediate 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 , 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 ,

Composites - polymer matrix composites (PMCs) Role of matrix in FR composites: a. transfer stresses betwn fibers b. provide barrier to environment c. protect fibers 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 Slow crack growth deflect crack tips redistribute stresses around crack tips bridge crack tips