Polymer matrix composites (PMC's) perform well under many loading conditions and situations. Exposure of PMC's to fire is a concern due to their inherent material degradation at elevated temperatures. The elevated temperature response of PMC's to combined thermal and mechanical loads are especially of concern.

PMC thermal and mechanical properties undergo transformations at elevated temperatures. Some of these effects are reversible if the maximum temperatures are lower than approximately 200C. The stiffness is significantly reduced at elevated temperatures but if the applied temperature is under the thermal degradation temperature of the matrix, the stiffness should be recoverable upon cooling. Some effects like the endothermic decomposition of the matrix are not reversible effects.

This study focuses on reversible properties in the temperature range from room temperature to about 200C. Thermally these effects alter the thermal conductivity and specific heat. Reversible elastic effects considered are the off axis stiffness reductions as functions of temperatures.

Thermal profile predictions were conducted using a finite difference code that included convection and radiation effects on the front and back faces of the composite. These predictions were shown to be in good agreement with experimental data.

A modified classic laminate analysis (CLT) was implemented to predict the failure times of the composites under combined thermal and mechanical loading. The Budiansky-Fleck micro-buckling analysis technique was used as the failure function of the [0] surface plies. A finite element analysis (FEA) analysis was also performed and showed good agreement with the experimental data.