The formulation of a new three-dimensional micromechanical model for fiber reinforced material is presented. It is based on the relaxation of the coupling effect between the normal and shear stresses. The simplicity of the model lends itself very well to the inclusion of nonlinear behavior while maintaining the three-dimensional capability. Present nonlinear capabilities that have been added to the model include a thermoelastic-plastic analysis employing the Prandtl-Reuss flow relations with a strain hardening parameter and both isotropic and kinematic hardening. Results from the present analysis are compared in different cases with their counterparts from finite element solutions and experiment. In addition, this micromechanical analysis is extended to model a weak fiber/matrix bond.