Modelling the indentation of low density polymer foams

The response of open-cell polyurethane (PU) foams was measured in compression, simple shear and combinations thereof. The data was fitted with Ogden's strain energy function for compressible hyperelastic solids, using one or two moduli. The Ogden function is also compared with the predictions of a micromechanics model. Finite Element Analysis (FEA) was used to predict the foam response for both plane strain indentation and the axisymmetric Indentation Force Deflection (IFD) test. Experimental deformation patterns and pressure distributions validate the predictions. The predicted relative indentation forces are about 20% less than the experimental values. Test piece geometry is shown to affect the IFD values, and interface friction to affect the deformation pattern.