Modeling of the mechanical behavior of amorphous glassy polymers under variable loadings and comparison with state-of-the-art model predictions

The objective of this work is to model the mechanical behavior of glassy polymers during non-monotonic loadings involving softening/hardening characteristics, transient effects and plastic instabilities. The microstructure of a glassy polymer has a strong influence on the mechanical properties and it is typically described by network models. The present state of modeling amorphous glassy polymers is revealed through reviewing state-of-the-art network models. To evaluate the models, several numerical examples are presented. It is found that the models are able to capture the monotonic loading accurately, but for transient effects after loading rate changes and for long-term behavior, their responses deviate significantly from the experimental data. In order to improve the predictions under these conditions, a new constitutive model is proposed in this work. The numerical treatment of the proposed model associated with both the ODE-solver and finite element method is discussed. The model is calibrated to the experimental data for various states of deformation. The numerical results indicated that the proposed model is able to predict experimental response under long-term and repeated loadings well.