Im new to this forum and this is my first post. For several years I have successfully modeled composites but only had to use elastic anisotropic material properties. I have a new project which involves a 25 cycle compression test of a helmet. The helmet is made of several layers of Dyneema (UHDPE fibers) reinforcing thermoplastic PU. Around the edge of the helmet is a carbon/epoxy reinforcing strip. I have to cycle the helmet 25 times under a load of 300 lbs to determine any permanent plasticity. Im not sure what material model to use for the Dyneema/PU. I am about to suggest a cyclic compression test to get experimental results but being new to thermoplastic behavior am not sure how to represent the results mathematically. Thanx for any help!