1. Last class -
Creep, relaxation, recovery
PVC
silicones
polycarbonate
aramid
epoxy
Today –

2. Some specific polymers
H2C-C-C{-O C O-}nC-C-CH2
H-C-H H
epoxy O
Some specific polymers
hardener
H2N-R-NH2
Prepregs

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

4. Composites - overview
Artificial combination of
matrix phase & dispersed phase
Matrix:
metal, alloy
ceramic mat'l
polymer
Dispersed phase:
particulate
fiber

5. Composites - metal matrix composites (MMCs)
Particulates:
ThO2-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

6. Composites - metal matrix composites (MMCs)
Fibers:
Conts - C, SiC, B, Al2O3
Disconts - C, Al2O3 , SiC whiskers
Matrix mat'ls
May get rxn betwn phases at hi T

7. Composites - ceramic matrix composites (CMCs)
Particulates, fibers:
SiC, B, Al2O3 , C, SiC & Si3N4 whiskers
Matrix
Improve fracture toughness:
slow crack growth
deflect crack tips
redistribute stresses around crack tips
bridge crack tips

8. Composites - polymer matrix composites (PMCs)
Fibers:
mainly - glass (GFRPs), carbon (CFRPs), aramid,
others - B, SiC, Al2O3

9. Composites - polymer matrix composites (PMCs)

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
Matrix/fiber bond:
matrix must wet fiber
physical & chemical bond desirable
mechanical interlocking
Fibers frequently coated w/ coupling agent

12. Composites
non-coupled
coupled

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