ENME207 L25

Composites

composites

matrix reinforced with fibers to get desired properties

anisotropic

properties not uniform in all directions

composite pros

tailored properties, fatigue resistant, light, less thermal expansion, stealth, corrosion resistant

Composite cons

expensive, envirosensitive, limited coupling

Matrix

continuous phase, transfers stress, protects phases (MMC, CMC, PMC)

Dispersed phase

fibers, reinforcement, enhance matrix properties, load bearing

Fiber types

monofilaments, woven fibers (multi filament), short fibers, whiskers, particulates

MMC

metal, increases yield, TS, creep

CMC

ceramic, increases Kic, toughness

PMC

polymer, increases E, yeild, Ts, creep, E/p

carbon fiber reinforcement

increase strength, stiffness, cost

decrease densite

glass reinforcement

increase strength, density

decrease cost, stiff

organic reinforcement

increase cost, strength, stiff tough

ceramic reinforcement

increase cost, strength, stiffness

whiskers

strongest, thin single crystal

fibers

polycrystalline, amorphous

failure

fails when fibers fail, but load still carried by matrix (nit all fibers fail at same time → becomes shorter) 

parellel alligned

k = 1

Perpendicular aligned

k = 0

random 2D aligned

k = 3/8

random 3D aligned 

k = 1/8

unidirectional

aligned fiber <60%

woven

cloth more 1 fiber <40%

chopped strand

<10%

structural

stacked/bonded fiber reinforced sheets