rule-of-mixtures

Dear all,
We are easily able to obtain mechanical properties (such as elastic modulus, Poisson's ratio and ...) of a unidirectional lamina composite by means of rule-of-mixture. 
For instance, in case of "longitudinal loading", strength of the fiber-reinforced composite for long continuous fibers will be like:
Ec=Ef*Vf+Em*Vm.

I have two main questions: 
First, are these relations (longitudinal and transverse loading) hold for bidirectional composite? if not, how can we obtain relative elastic modulus?