Page 179 - Mechanics Analysis Composite Materials

164 Mechanics and analysis of composite materials

(4.97)

i= I j= I
where, h is the total thickness of the layer (see Fig. 4.33), Le.,
h = ho + h90 ,

where

are total thickness of longitudinal and transverse plies.
Stresses in the principal material coordinates of the plies are linked with the
corresponding strains by Eqs. (3.59) or Eqs. (4.56):
&i) = (&lij) + 2$i) ),
1
diJ)= E2(&lij) + V21El(hi)), (4.98)
2
rf‘/)= G,2Yf‘/) ,

where, as earlier E1?2= E1,2/(1- VI~VZI) an1 EIVI~= -v21. Now assume that
deformation of all the plies is the same that the deformation of the whole layer, i.e.,
that

Then, substituting Eqs. (4.98) into Eqs. (4.97) we arrive at the following constitutive
equations:

(4.99)

where the stiffness coefficients are

(4.100)