Experimental and numerical study of through-thickness heat transfer and pyrolysis in FRP laminates under radiative heat flux

The mechanical performance of fibre-reinforced polymer (FRP) is strongly temperature dependent and governed by glass transition, pyrolysis of the polymer matrix and, in the case of carbon fibres, oxidation of the fibres. To understand the mechanical response, it is desirable to develop simplified numerical tools capable of reproducing the temperatures inside a FRP when it is exposed to a fire. A simplified one-dimensional numerical model was developed incorporating through-thickness heat conduction, boundary heat exchange, and temperature-dependent material decomposition. It uses constant thermal properties to enable rapid computational predictions while maintaining reasonable accuracy for thermomechanical applications. Carbon and glass FRP composite laminates with laid-up thermocouples were exposed to controlled radiant heat fluxes of 10, 30, and 50 kW/m 2 , enabling precise, repeatable through-thickness temperature measurements. Experimental results reveal that glass transition temperature progression occurs in depth significantly early relative to in depth pyrolysis, indicating mechanical failure and loss of structural capacity likely precedes thermal decomposition. Model validation showed that accurate material property characterisation is more critical than including complex pyrolysis chemistry for predicting glass transition progression. The framework serves as a valuable intermediate tool between analytical estimates and finite element simulations, offering practical utility for thermomechanical failure prediction.