Analysis of the high strain compression of open-cell foams

Abstract

The high strain compression of open-cell foams is analysed, using a lattice model with tetrakaidecahedral cells. The buckling of elastic cell edges, under combined bending and torsional loads, is analysed, and the deformed shapes predicted. The stress-strain relation and Poisson's ratio are predicted for strains up to 70%, for compression in the [001] and [111] directions of the BCC lattice. The prediction for [111] compression is closest to experimental stress-strain curves for polyurethane foams, especially when the cell shape anisotropy is taken into account. A plateau in the compressive stress-strain curve is not predicted, whereas one is observed for compression along the foam rise direction. Reasons for this are discussed; there is a small contribution from the polymer non-linearity, but irregular cell structures need to be analysed. The deformation, both of individual cells and of the PU foam, is compared with the theory.