A visco-hyperelastic constitutive description of elastomeric foam

This study focuses on the constitutive modelling of finite deformation in elastomeric polyurethane foams-in particular, PORON-4701-59-25045-1648 (0.4g/cm(3) density) and PORON-4701-59-20093-1648 (0.32g/cm(3) density). Their mechanical properties under compression, for engineering strains up to about 80%, are characterized over a range of strain rates between 10(-2) and 10(3)/S. Dynamic compression is applied using a split Hopkinson pressure bar device. Experimental results show that the behaviour of elastomeric foam is sensitive to strain rate and can be described by a visco-hyperelastic material model. In this model, the quasi-static response is defined by compressible hyperelasticity, whereby the strain energy potential is assumed to be representable by a newly proposed polynomial series with three independent parameters. Strain rate sensitivity is characterized by incorporating a nonlinear Maxwell relaxation model with four parameters. The (seven) material parameters in the constitutive model are determined from highspeed mechanical testing methods tailored for high-compliance materials. A comparison of predictions based on the proposed frame-independent constitutive equation with experiments shows that the model is able to describe the rate dependent behaviour of the elastomeric foams examined. (C) 2004 Elsevier Ltd. All rights reserved.