Interaction of oxidation, stress and damage in high temperature polymeric matrix composites

Polymeric matrix composites with long term durability requirements at high temperatures must be designed to resist degradation due to physical aging, chemical changes and thermo-oxidation. This study focuses on the interaction between oxidation and damage. The oxidation layer growth in a neat resin depends upon the relative dominance of the oxygen diffusion rate in oxidized region and the reaction rate in the un-oxidized region. Oxidation in fiber-reinforced composites is orthotropic with axial direction of fiber being the preferred oxidation growth direction. Transverse oxidation growth correlates with growth rates observed in neat resins after accounting for the fiber volume. Close coupling is observed between discrete crack growth rates and oxidation layer growth rates in axial direction. Damage evolution and the interaction of damage and oxygen diffusivity is critical for oxidation prediction in composite materials. In this paper, the interaction between strain field and its effect on oxygen concentration fields and the nature of damage evolution during oxidation are described.