1. 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

2. 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

3. Composites - overview Example - carbide tools (previously discussed) Co matrix phase angular WC fragments

4. 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

5. 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

6. 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

7. 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

8. 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

9. Composites - polymer matrix composites (PMCs) Matrix

10. Composites - polymer matrix composites (PMCs) Very common - polyesters, vinyl esters

11. 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

12. non-coupled Composites coupled

13. 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

14. 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 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

15. 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