A novel micromechanical model for predicting the failure of polymeric and ceramic matrices under an applied global tensile loading is presented. The model is based on a Weibull statistical type of approach and incorporates eleven different variables to simulate different micromechanical failure phenomenon. Through the variables, the model incorporates such phenomenon as fiber-fiber interaction; matrix-fiber interaction; damage due to processing; and local stress distribution at the interphase. The effects of the load sharing constants and shape parameter on failure are studied. A software package, used in the Windows environment, was also developed to perform a numerical analysis of the model.