Abstract

Surface oxidation degrades the durability of polymer marix composites operating at high temperatures due to the presence of strong coupling between the thermal oxidation and structural damage evolution. The mechanism of oxidation in polymer matrix composites leads to shrinkage and damage growth. The thermo-oxidative behavior of composites introduces changes in diffusion behavior and mechanical response of the material. This study presents the derivation of peridynamic formulation for the thermo-oxidative behavior of the polymer matrix composites. As a demonstration purposes, isothermal aging of a unidirectional composite lamina is presented by using peridynamics. Oxidation contributed to the damage growth and its propagation.

Introduction

The thermo-oxidative environment results in growth of the thermo-oxidative layer and changes in material properties. The degradation mainly occurs on the surface layer, and it leads to weight loss and shrinkage of the oxidized layer. Therefore, prediction of long-term durability requires the consideration of both the oxidative changes and damage evolution.

The previous studies on the investigation of coupled thermo-chemo-mechanical models such as those of Zohdi [1], Wang [2], Gigliotti [3-4], Oskay [5] and Liang and Pochiraju [6] utilized finite element method (FEM) for the solution of the field equations in conjunction with a damage variable for monitoring material stiffness degradation. Zohdi [1] developed a FE model to address the coupling of thermo-chemo-mechanical processes in multiphase solids. The model is general enough to predict the loss of structural integrity of heterogeneous solids exposed to environmental attacks: diffusion, reactions, production of heat, changes in the stress field. Wang [2] considered a micromechanics FE model to develop high-temperature constitutive equations of polymer matrix composites with oxidation reaction, damage and degradation. Based on the irreversible thermodynamic theory, the model predicts oxygen concentration, mass loss and oxidation induced stresses.