Page 233 - Plastics Engineering

216 Mechanical Behaviour of Composites

180
160

140
120
N
E
2 100
s2.
2
- 80
L o

40
20

0
0 10 20 30 40 50 60 70 80 90
Angle (e)

Fig. 3.24 Variation of elastic properties for a single ply of carbodepoxy composite

(ii) Symmetric 4 Ply Laminate The same procedure is used again except that
this time the IAl matrix has to be summed for all the plies, ie

f=4
IAl = IZilf (hf - hf-1) and la1 = 1AI-l
f=1
where l~ = -0.2, hl = -0.1, h2 = 0, h3 = O.l,h4 = 0.2.

Once again, for 8 = 50" (for example)
1
=
E, = - 14.6 GN/m2
Ullh
E --- - 24.8 GN/m2
Y-
ad
1
Gxy = - 44 GN/m2
=
a66h
VXY = - =0.615 and vYx= -- - 1.045
-a12
-a12
a1 1 a22
Fig. 3.25 shows the variation of these elastic constants for values of 8 in the
range 0 to 90".