Punch indentation of polyurea at different loading velocities: Experiments and numerical simulations

Punch indentation experiments are performed on 10 mm thick polyurea layers on a steel substrate. A total of six different combinations of punch velocity, punch size and the lateral constraint conditions are considered. Furthermore, the time integration scheme for a newly-developed rate-dependent constitutive material model is presented and used to predict the force–displacement response for all experimental loading conditions. The comparison of the simulations and the experimental results reveals that the model is capable to predict the loading behavior with good accuracy for all experiments which is seen as a partial validation of the model assumptions regarding the pressure and rate sensitivity. As far as the unloading behavior is concerned, the model predicts the characteristic stiff and soft phases of unloading. However, the comparison of simulations and experiments also indicates that the overall model response is too stiff. The results from cyclic compression experiments suggest that the pronounced Mullins effect needs to be taken into account in future models for polyurea to improve the quantitative predictions during unloading.