The Compression of Closed-Cell Polymer Foams

Abstract

The tensile response of oriented polyethylene and polystyrene films provides material data for the modelling of closed-cell polymer foams. We analyse a Kelvin foam, with 60% of the polymer in the cell faces, compressed in the [001) direction. Cell edges bend and compress axially, while cell faces act as membranes. The tensile strains across some face diagonals are 40% of the foam compressive strain, so tensile yielding can occur. The predicted Young's moduli are slightly low, because compressive face stresses are ignored, but the Poisson's ratio is correctly predicted. The predicted yield stresses for polyethylene foams are close to experiment. Polystyrene extruded foams may collapse in compression when face yielding commences.