Page 198 - Plastics Engineering

Mechanical Behaviour of Composites 181

Example 3.5 Calculate the transverse modulus of the PEEWcarbon fibre
composite referred to in Example 3.2, using both the simplified solid mechanics
approach and the empirical approach. For PEEK v,,, = 0.36.
Soiution From equation (3.13)
3.8(400)
E2 = = 5.4 GN/mz
0.3(3.8) + 0.7(400)
Using the Halpin-Tsai equation

E2 = 3.8 [ 1 + 2(0.3)(0.97)] = 8.5 GN/mz
1 - (0.3)(0.97)

Using the Brintrup equation
EL = 3.8/(1 - 0.36*) = 4.37 GN/m2

(4.37)400
E2 = = 6.2 GN/m2
400( 1 - 0.3) + 0.3(4.37)
Some typical elastic properties for unidirectional fibre composites are given in
Table 3.4,

Table 3.4
ljpical elastic properties of unidirectional fibre reinfd plastics
Fibre
volume
fraction, EI E2 GIZ
Material Vf (GN/m2) (GN/m2) (GN/mz) "12
GFRP 0.6 40 9 4 0.31
(E glasdepoxy)
GFRP 0.42 32 7 3.1 0.35
(E glasdpolyester)
KFRP 0.6 79 4.1 1.5 0.43
(Kevlar 491epoxy)
CFRP 0.6 125 9 4.4 0.34
(carbon/epoxy)
CFUP 0.62 497 5.3 5.6 0.31
(carbon HWepoxy)
GFRP - Glass Fibre Reinforced Plastic
KFRP - Kevlar Fibre Reinforced Plastic
CFRP - Carbon fibre Reinforced Plastic