The polymer constitutive equations are implemented within strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. Based on the constitutive polymer model developed by Goldberg, nonlinear strain rate dependent triaxial braided composite has been analyzed. To verify the formulation, the tensile deformations of a representative polymer are computed across a wide range of strain rates. Results computed using the developed constitutive equations correlate well with experimental data.