Micromechanical Modeling of Thermo-oxidative Degradation of High Temperature Polymer Matrix ComPosites

摘要

In this paper, oxidation of the polymer in a polymer matrix composite (PMC) used in high temperature applications is modeled using a modified Fick's law of diffusion that includes a reaction term related to the rate of oxygen consumption due to the chemical reaction between the polymer and oxygen. The model incorporates the coupling between oxygen diffusion and polymer consumption process and the resulting shrinkage at the micro-scale. It is conjectured that polymer shrinkage due to thermal oxidation may be responsible for debond to initiate and propagate along fiber-matrix interface, thereby allowing accelerated diffusion and further oxidation. In order to simulate this effect, a cohesive layer model was introduced at the interface of the polymer and fiber within the framework of finite element analysis (FEA) of a micromechanical representative volume element (RVE). Our numerical results indicate that oxygen diffusion at high temperature causes oxidation in the polymer, which indeed leads to thermo-oxidative shrinkage of the polymer that is responsible for the initiation and propagation of fiber/matrix interfacial failure at high temperatures.The results from the micro-scale FEA/RVE model were subsequently incorporated in a macro-scale laminate model through multi-scale modeling, using continuum damage mechanics. In this paper, details of the multi-scale simulation will be presented, together with some preliminary experimental data for model verification, in order to gain insight into the anisotropic nature of the thermo-oxidative degradation process and to predict its effect on long-term structural durability.