Deformation mechanisms in oriented high density polyethylene

Abstract

The deformation behaviour of single crystal texture HDPE has been examined in tension as a function of the orientation of the tensile axis with respect to the chain direction. Over most of the orientation range examined, it was found that slip processes parallel to the chain direction were the dominant modes of deformation. Fibrillar slip becomes relatively more important than chain slip as the strain increases and as θ0, the initial value of the angle between the tensile axis and the chain direction, decreases. Lamellar slip was only observed over a limited range of orientations due to the high initiation stress required for the process. At low θ0 values, lamellar separation accounted for a substantial part of the applied strain. Stress-induced martensitic transformation, which was observed in samples with θ0>26°, cannot account for an important fraction of the strain although the resolved shear stress required for the activation of the martensitic transformations is of the same order of magnitude as that required for chain slip.