Prediction of bulk mechanical properties of PVC foam based on microscopic model：Part II-Material characterization and analytical formulae

The bulk mechanical properties of a foam are strongly related with the modulus of elasticity and yield strength of the base material and the geometric features of the foam microstructure. This paper proposed a method to predict the bulk mechanical properties of transversely isotropic closed-cell polyvinyl chloride (PVC) foams based on the numerical analysis of microscopic models. Firstly, the elastic modulus of the base material was determined through nanoindentation and the macro compressive stress-strain curves in three orthogonal directions were measured for the Divinycell H100 foam. Then, the influence of variation of the scaling factor, which transformed an isotropic microstructure to a transversely isotropic one, on the mechanical properties were investigated numerically. It is found that the ratio of the two moduli of elasticity in the rise direction and in the transverse direction linearly depends on the scaling factor, so does the ratio of the yield strengths. Next, the relations of the bulk mechanical properties of the transversely isotropic foam in the two directions with the relative density were formulated. Finally, this method was validated by being successfully applied to foams of the same base material but different densities.