Fiber-reinforced epoxy composites exposed to high temperature environments. Part II: Modeling mechanical property degradation

This article is part of a series on the thermo-mechanical responses of fiber-reinforced composites at elevated temperatures and it follows the first part containing experimental results. A flame-retardant system consisting of a cellulosic charring agent and an interactive intumescent additive (melamine phosphate) has been used in order to improve the post-fire mechanical performance of glass fiber-reinforced epoxy composites. The effect of one-sided radiant heat on the residual flexural stiffness of laminate coupons exposed to incident heat fluxes of 25 and 35kWm-2 was investigated. The flame-retarded coupons retained a higher percentage of their original room temperature flexural modulus after heat exposure while the control specimens showed inferior material property retention over the same exposure periods. A heat transfer (thermal) model based on Henderson's equation is used to predict the through thickness temperature profiles and subsequently the mass loss due to the resin matrix decomposition at elevated temperatures. The theoretical results from the heat transfer model are validated against experimentally obtained data and then coupled with a mechanics model that describes material property-temperature dependence in order to predict the residual flexural stiffness, after heat damage. The accuracy of the thermo-mechanical model was validated against the experimental data and a good agreement was observed