Degradation in compressive strength of silica/phenolic composites subjected to thermal and mechanical loading

Reduction to the mechanical properties of fiber-reinforced polymer composites occurs when the material is exposed to radiant heat flux and compressive loading. A thermo-mechanical model was developed to predict the compressive strength and the failure time of silica fiber-reinforced phenolic composites. The coupling heat and mass transfer processes, generation of pyrolysis gases, and their subsequent diffusion process were considered in the model. The thermal softening, thermal decomposition of the matrix material, and phase transition of the reinforced fibers, which reduce the strength of the material, were also taken into account in the formulation of the model. Pyrolysis kinetics of phenolic resin, volume fraction of phase component, temperature profile, compressive strength, and time-to-failure of silica/phenolic composites were predicted using the developed model. The calculated temperature-dependent strength curve was compared with the experimental results measured by a high-temperature compression testing, and the agreement is good. The material fracture morphology was analyzed for silica-phenolic composite specimen after high-temperature compression testing.