Constitutive Modeling of Elastic‐Plastic Open‐Cell Foams

Abstract

Elastic-plastic foams are commonly used in engineering practice in the core of structural sandwich members and in energy absorption devices dissipating the kinetic energy of an impact without generating high stresses. Due to complexities involved in both the geometry and the loads, the analysis often requires a complete material constitutive model. Studies of the postyield constitutive modeling of foams under multiaxial stresses do not exist. A failure criterion describing the failure surface at the onset of plasticity for open-cell, isotropic foams idealized as linearly elastic–perfectly plastic is employed here in a plasticity-based formulation to obtain the postyield constitutive matrix. The model is valid when the material experiences zero hardening and deforms according to the associated flow rule. The first assumption appears realistic for open-cell foams at small to moderate strains, while the second needs further investigation.