ABSTRACT
Here, we present a micro-mechanical model to describe the effects of thermal induced aging on the constitutive behavior of elastomers aged for relatively long periods. This model particularly focuses on the effects of thermal induced aging on the quasi-static mechanical response of elastomer and their inelastic responses such as Mullins effect and permanent set over time. The model describes the aging induced damage with respect to experimental studies on the process of chemical aging which suggests high detachment of original covalent bonds and formation of new bonds. Here, the strain energy of the polymer matrix in the course of aging is represented by the superposition of two independent mechanisms, (i) the original matrix with strong original bonds which is gradually decomposing, (ii) a newly formed matrix cross-linked by weak reformed bonds. Each network has its own damage mechanisms which are induced based on the applied deformation and time. The proposed mechanism is based on the experimental reports on the process of chemical aging thus is physically feasible. The model is validated with respect to a comprehensive set of experimental data designed by Johlitz et al (Johlitz et al. 2014). to capture thermal induced aging effect on constitutive behavior of elastomers. Besides accuracy, the model is relatively simple and easy to fit. It requires ten material parameters, all with clear physical meaning, which can be identified from only one set of experiment.
