Predicting anisotropic crushable polymer foam behavior in sandwich structures

An anisotropic elastic-plastic, viscoelastic-damage model was developed to predict the multiaxial crushing behavior of polymer foams used in the core of sandwich structures. This model was based on pressure vessel experiments on Divinycell H100, whereby the post-yield response of the foam was characterized by anisotropic hardening during plastic flow, as well as damage and viscoelastic hysteresis. Post-yield properties from uniaxial compression/tension and simple shear material hysteresis experiments were used to develop three-dimensional material constitutive equations for the foam. Plastic flow was governed by the Tsai-Wu failure criterion, which was verified to accurately predict yielding of the foam in the triaxial pressure experiments. The solution methodology proved to be very effective in predicting the hysteresis response of the foam under triaxial compression, triaxial compression-tension, and triaxial compression-shear. Good agreement was found between theoretical predictions and experimental results.