Plasticity and thermally-induced recovery in polycarbonate

In the present paper, we present an approach combining physically-based constitutive modeling and experiments to study the thermo-mechanical response of amorphous thermoplastics whose final objective is the prediction of the thermally-induced strain recovery. The underlying thermo-mechanical mechanisms are described by elastoviscoplastic-viscohyperelastic constitutive relations allowing to account for the variation with temperature of the inter and intramolecular barriers to deformation and their abrupt change when the temperature traverses the glass transition. The model fit shows a good agreement with experimental observations on polycarbonate in terms of temperature and strain-rate dependent stress-strain response. The material kinetics with temperature is designed and introduced into the model to predict the thermally-activated strain recovery process during heating. In our approach, the intramolecular resistance of the entangled molecular chain network orientation/relaxation is used as the driving stress that continuously activates the strain recovery process during zero-stress creep above glass transition. The model predictions are shown under zero-stress creep recovery for different previous loading histories in terms of strain-rate and strain-level. The simulated results are in satisfactory agreement with experimental observations at different heating temperatures showing the relevance of the proposed approach.