Constitutive modeling of the rate- and temperature-dependent macro-yield behavior of amorphous glassy polymers

The rate- and temperature-dependence of the macro-yield behavior, as one of the important concerns for the investigation and application of amorphous glassy polymers, is very significant below and near the glass transition temperature (T-g). Two molecular chain microstructures, i.e., sub-entanglement (SE) and topological entanglement (TE) and their evolution, are introduced as the inherent micro-mechanisms for the rate- and temperature-dependent macro-yield performance. With the introduced entanglement microstructures-based internal variables, an elasto-viscoplastic finite deformation constitutive model of amorphous glassy polymers is proposed to describe its rate- and temperature-dependent macro-yield response. The rate-dependence of T-g and its effect on the microstructures' thermo-mechanical state and evolution are also taken into account. Comparing with the experimental results of PMMA in literature, the proposed model shows a good capability to simulate and predict the macro-yield behavior at various strain rates (from 0.0003 s(-1) to 0.1 s(-1)) and temperatures (from room temperature to T-g). This work illustrated that the introduction of SE and TE as the inherent micro-mechanisms is a reasonable interpretation for the macro-yield behavior of amorphous glassy polymers.