A model, based on linear elasticity and the first law of thermodynamics, was evaluated using experimentally derived data to verify its predictive capabilities. The model demonstrated that it could correctly predict the mechanical behavior of highly loaded composities if a representative adhesion energy was available. It worked well for systems where material nonlinearity was mainly due to particle debonding. The model could not, however, account for the effects of localized straining or stress concentrations on composite modulus or strength. In systems where matrix nonlinearity dominated, predictions were less satisfactory. Although the model oversimplified the debonding process, it provided a convenient mechanism for relating the composite modulus and stress-strain state to the loss of reinforcement without requiring a micromechanical description that was too cumbersome to manage. Nevertheless, the inability of the model to account for localized strains, stress concentrations, and matrix nonlinearity needs to be addressed in order to obtain better mechanical behavior predictions.