A failure model for damage accumulation of cross-linked polymers during parallel exposure to thermal aging & fatigue

A multi-stressor damage accumulation model is presented to describe the effects of concurrent thermal aging and fatigue on the failure behavior of cross-linked polymers. Accordingly, the kinetic equations describing the environmental and mechanical damages were individually derived and then coupled into a generic failure model that describes the damage accumulation through a multi-dimensional manifold. Assuming the constitutive behavior of the material is provided by a modified network alteration constitutive model, our model can predict the exact failure properties of cross-linked polymers in the course of aging at different times and temperatures. We hypothesized that the accumulation of damage during aging correlates to the loss of toughness which consequently results in the prediction of the failure point during the aging. To validate the model, a comprehensive set of experimental data has been provided. After fitting with limited experimental data, the model predictions were benchmarked against other data and show good agreement. The proposed model is inexpensive, is relatively easy to implement and has a few material parameters which allow a fast fitting.