Validation of material model for polypropylene (PP)

Abstract

A hyperelastic-viscoplastic material model intended for thermoplastics has been developed by SIMLab at NTNU. This model formed the basis of the thesis, where a material model for the polymer polypropylene was calibrated and validated. Four rounds of material testing were carried out. Tension and compression tests formed the basis for a calibration of the material model. Two different component tests were used for validation; stretching of a plate with a hole and plate impact tests.The calibrated model was implemented as a user-defined material model in the non-linear finite element code LS-DYNA, and numerical simulations of the tension and compression tests were carried out in order to verify the calibrated parameters. The component tests were numerically simulated with the purpose of controlling the ability of the model to predict the behaviour of the material when subjected to more complex loading cases.The calibrated material model was able to capture the main characteristics of the experimental tests. The model does, however, have limitations, as it was not able to correctly predict all strain rate effects of the material at high strain rates, like viscoelasticity. A partly recalibration of the material model was carried out to enable the model to predict the material s behaviour at high strain rates.