Page 237 - Plastics Engineering

220 Mechanical Behaviour of Composites

The effective elastic constants for the composite are:
1 1 1
E, = -
E, = - G --
ai1 h a22 * h ”- a66 h
-a12 -a12
uxy = - vyx = -
all a22
so

E, = 2.26 x lo3 MN/m2 E, = 2.26 x lo3 MN/m2 Gxy = 830.6 MN/m2
and
vXy = 0.36, vYx = 0.36
The stresses in the individual layers are obtained from
[::]=B.[;;,] [“]=a2.[;;,]
TBxy
TA*Y
so,
OA, = 8.71 MN/m2 and CTA, = 17.55 MN/m2

(TAX, = o MN/m2)
OB, = 2.5 MN/m2 and OB, = 4.9 MN/m2
(TB,, = 0 MN/m2)

The values of stress may be checked by simple equilibrium analysis.
(i) Force equilibrium: NA + NB = N,
OA*AA + OB~AB = Nx

(ii) Geometry of deformation:

- =-
0A.x UBx or ah = (g) OBx
EA EB
(2) UBAA + OBAB = N,

OB, = Nx/ (( 2) AA +AB) = 2.4 N/mm2

ah = (A) 2.4 = 8.8 N/m2