THERMOOXIDATION INDUCED STRESSES IN BISMALEIMIDE COMPOSITES: EXPERIMENT AND SIMULATION

摘要

High temperature polymer matrix composites are susceptible to thermooxidation which accelerates their degradation. Thermooxidation can lead to a drop in mechanical and thermal properties which can result in a reduced service life. The interaction of transported oxygen with matrix material forms a superficial oxidized layer adjacent to unoxidized matrix. As a result of oxidized layer shrinkage, stresses are built up in the composite. In this work, the development of shrinkage stresses based on the diffusion-reaction and elasticity models was studied using COMSOL Multiphysics. Finite element analysis and representative volume elements were used to model the coupled diffusion-reaction and oxidation state variable equations. Results were transferred to elasticity equations to calculate the spatial distribution of shrinkage stresses at any time step. Unidirectional bismaleimide composite specimens were manufactured using out-of-autoclave process. Weight loss and volumetric shrinkage under isothermal aging were recorded and compared with the results of simulation.