Peridynamic Modeling of Thermo-oxidative Degradation in Polymers

Design with polymers for long-term service under high temperature requires consideration of factors such as physical aging, chemical changes, and thermo-oxidative degradation. Also, the coefficient of thermal expansion, glass transition temperature, and fracture properties experience change such as decrease in fracture strain. Such changes in the material properties cause residual stress in the oxidized layer resulting in damage in the form of cracks. The previous models in the literature are based on classical continuum mechanics (CCM) and solved using finite element methods for oxygen concentration, deformation, and failure prediction. Failure modeling within the CCM framework is cumbersome as it requires smoothness of the field variables and requires an external criterion for initiation and propagation of cracks. This chapter presents a bond-based peridynamic modeling for coupled oxidation-diffusion and mechanical deformation of epoxy resins under isothermal condition. It is a nonlocal approach and free of the smoothness requirement of the field variables. It assumes finite distance interaction among material points through bonds. The capability of this model is demonstrated through numerical simulations on isothermal oxidation-diffusion in 977-2 epoxy resin, thermo-oxidation and shrinkage in PMR-15 resin strip with and without pre-cracks, and crack propagation in a 977-2 epoxy resin and copper bimaterial configuration under oxidation.