A computational study of the interplay between viscoplasticity and hardening for impact-loaded uniform density foams

Foam-like materials have been studied extensively for applications requiring energy absorption and blast mitigation. This work analyzes the interplay between viscoplasticity—quantified by the rate-dependence and viscosity parameters—and various hardening rules for uniform density foams when they are subject to blast-like impact loads. The foam is modeled using a simple viscoplastic extension of the rate-independent elastoplastic model developed by Deshpande and Fleck and a flexible hardening rule that exhibits different qualitative hardening regimes. The constitutive model is implemented as a VUMAT in ABAQUS. The underlying elastoplastic wave mechanics under these different scenarios is also examined. The results presented here indicate a qualitative change in the foam response depending on the amount of viscoplasticity and the type of hardening behavior. Additionally, this study attempts to answer whether or not ratedependency is always beneficial for mitigation of applied loads. The results presented in this work has important implications for the design of impact-resistant foams.