Multi-axial yield behaviour of polymer foams

The yield behaviour of two densities of a ductile PVC foam manufactured by Divinycell have been investigated for a range of axisymmetric compressive a nd tensile stress states. The yield surface is found to be described adequa tely by the inner envelope of a quadratic function of mean stress and effec tive stress and a maximum compressive principal stress criterion. Under ten sile loadings the deformation of these foams is governed by cell wall bendi ng, and the uniaxial and hydrostatic tensile strengths have comparable magn itudes. Under compressive loadings the foams deform by elastic buckling of the cell walls, and the uniaxial and hydrostatic compressive strengths are again nearly equal. (C) 2001 Acta Materialia Inc. Published by Elsevier Sci ence Ltd. All rights reserved.