study, the micromechanics method is performed to estimate the laminate properties of

various laminate systems and compared with theoretical and semi-empirical solutions to

verify the transverse isotropy.

 The unit cell model is used to estimate the elastic constants and the coefficient of

thermal expansion using the FE based micromechanics method. The fiber volume

fraction was assumed to be 60%. The thermo-elastic stress-strain relations of the

composite material at macro-scale can be written as

 0o Cl C12 C13 0 0 0 E a1
 SC22 C23 0 0 0 2 a2
 03 C33 0 0 0 e3 AT a3 (2.2)
 =< -A
 23 C44 0 0 23 a23
 r31 SYM C 0 731 a31
 r12 C66 \712 a12

 The elastic constants and the CTE's in Equation 2.2 were obtained by performing

7 sets of micromechanical analyses. In the first 6 cases the temperature difference ATwas

set to zero and the unit-cell was subjected to periodic boundary conditions corresponding

to one of the macro-strains as given in Tables 1 and 2. The macro-stresses in the unit cell

were calculated as the volume average of the corresponding micro-stress components:

 1 NELM
 c =- cr) V(), i = 1,6 (2.3)
 V k=l

 In Equation 2.3, k denotes the element number, NELM is the total number of

elements in the FE model, V(k) is the volume of the kth element and Vis the volume of the

unit-cell. The average or macro-stresses are used to calculate the stiffness coefficients in

a column corresponding to the nonzero strain. In order to calculate the CTE's, the unit-

cell is subjected to periodic boundary conditions such that the macro-strains are