Page 169 - Mechanics Analysis Composite Materials

154 Mechanics and analysis of composite materials

A,,,, ,GPa
t 40

120

100

80

60

40

20

0‘ I
0 15 30 45 60 75 90
Fig. 4.20. Dependencies of tensile (A!I and shear (AM)stiffnessesof a unidirectional carbon-poxy
layer on the orientation angle.

0153046607590
Fig. 4.21. Dependencies of coupling stiffnesses of a unidirectional carbon-epoxy layer on orientation
angle.

sin’ 4 cos’ 4
I
G12 =-- cos44 sin44 ksin2 4 c0s2 4
ET El E2 El
In connection with this, a question arises as to what angle should be substituted into
this equation to provide the most accurate result. The answer is given in Fig. 4.24,
which displays the strains in principal material coordinates of a carbon-epoxy layer