Torsion properties of high density polyethylene foams

High density closed-cell HDPE foams (450-950 kg/m(3)) were prepared by compression molding, and torsion rectangular tests were performed to measure their shear modulus in order to study: (1) the relationship between the modulus as a function of the density, and (2) to determine the effect of thin skins. Based on the assumption that the twist stiffness (product of shear modulus and moment of inertia) of the foams is the sum of the twist stiffness of the skin layers and the core part, several structural foam models are proposed. We found that structural foam models give better results than uniform foam models, indicating that thin skins have an important effect of the shear modulus of polymer foams.