A model for predicting composite material strength degradation under elevated and high temperatures is proposed. This model is based on the morphology of the mixture of materials in different states. The degradation of resin-dominated shear strength can be well described by the rule of mixture while the degradation of nominal compressive strength tends to follow the lower bound of strength defined by the inverse rule of mixture. Composite materials under tension may exhibit fiber- or resin- dominated behavior. In a lower temperature range, strength is dominated by the fiber tensile strength, while at higher temperatures, tensile components may exhibit resin- dominated failure in joint regions. The parameters required in the model can be obtained on the basis of kinetic analysis of dynamic mechanical analysis results. The fitting of experimental curves of material strength degradation is not necessary. The proposed modeling scheme can easily be incorporated into structural theory to predict mechanical responses and time-to-failure. © 2009 SAGE Publications