Modeling EPS Foam
I'm trying to model the Expanded Polystyrene (EPS) Foam used for bicycle helmets. I've been using the ANSYS built in Foam, Expanded Polystyrene material provided by GRANTA Materials Data for Simulation. While this material has worked, I'm concerned that it doesn't seem to exhibit any plastic deformation. I'm hoping to introduce crushability of the foam.
I have tried incorporating EPS stress-strain data from research papers into the built-in model as uniaxial test data, but I'm still not see any plastic deformation. I believe this is because I'm not including plastic failure models and I'm wondering if there are any resources in this area?
I have tried using bilinear kinematic hardening properties, but the material fails (this may be due to incorrect values used). Specifically, I'm wondering what plasticity models should be included in the material in order to see a plastic deformation when the helmet impacts a surface?