Modeling of the behavior of semi-crystalline polypropylene at elevated strain rate and temperature

A non-linear viscoelastic model comprised of two components, a rubber-like hyperelastic component and a viscoelastic time-dependent relaxation spectrum was used to model the behavior of semi-crystalline PP at rates and temperatures close to that found in the thermoforming process. Temperature dependence was introduced through time-temperature-superposition (TTS) using WLF. The hyperelastic constants were identified from equibiaxial tensile experimental tests while the time-dependent relaxation spectrum was characterized through a temperature-frequency sweep analysis from a strain controlled DMTA test. Results show that the developed model is capable of simulating the behavior of semi-crystalline PP fairly well.