Effects of cell irregularity on the high strain compression of open-cell foams

The high strain compression of low-density open-cell polymer foams has been modelled by finite element analysis. We used a Voronoi method to generate periodic structures with different degrees of randomness of the cell size and shape, then to investigate the influence of this randomness on the response of Voronoi open-cell foams to high strain compression. It is found that, although the reduced compressive stress-strain relationship and the Poisson's ratio vary in different directions for individual samples, the models are, on average, isotropic. A highly irregular foam has a larger tangential modulus at very low strains and a lower effective stress at high compressive strains than a more regular foam. The geometrical properties were investigated and used to predict the compressive stress-strain relationships for random open-cell foams with different degrees of cell regularity. For irregular low density foams, strut bending and twisting (the "springs-in-parallel" model) dominate the mechanical response at low strains and strut buckling (the "springs-in-series" model) becomes the main deformation mechanism at large compressive strains. (C) 2002 Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.