Influence of strain rate on the yielding behavior and on the self heating of thermoplastic polymers loaded under tension

The effect of strain rate on the mechanical behavior of thermoplastic polymers (Polymethyl methacrylate, Polycarbonate and Polyamide 66) has been studied. Deformation tests in tension were conducted over the range of strain rate varying between 2.6 10(-4)s(-1) to 1.3 10(-1)s(-1). The Young's Modulus E and Yield stress CYST evolutions have been identified and modelled as a function of the strain rate. It has been established that, in the range of the considered strain rates, the yielding behavior of PMMA and PC is well described by the Eyring theory while for PA66 the Ree-Eyring theory is successfully used to illustrate the yielding behavior. During tensile tests the specimen surface temperatures were monitored using an infrared camera. Results reveal a significant temperature rise at large deformations for PA66 and PC. As the strain rate increases the temperature is steadily increased with deformation due to plastic work. Hence, for PC and PA66, a significant thermal softening is observed after yielding which affects the stress-strain behavior. Thermomechanical coupling during polymer deformation can be considered in the modeling of the mechanical behavior of polymers. No self-heating has been detected for PMMA.