Morphology of Highly Textured HDPE (High Density Polyethylene)

摘要

High density polyethylene (HDPE) specimens were subjected to high orientation producing deformations below the melting point using either a rolling mill or a channel-die. After appropriate annealing protocols, the crystallographic and morphological textures were examined using wide-angle x-ray diffraction pole figures, two dimensional small-angle x-ray scattering and transmission electron microscopy. Although the two deformation patterns resulted in very similar crystallographic textures, the details of the morphological arrangements of crystalline lamellae were different. Quantitative considerations of the 2-D SAXS patterns led to the conclusion that lamellae which are inclined to the macroscopic orientation direction reflect a shear process within the individual lamellae, rather than a rigid rotation inside the surrounding amorphous material. The crystalline part can deform by slip, twinning or stress-induced martensitic transformation. The goal is to simulate the texture evolution at large deformations and compare results to the experimental ones. The simulation is done by a Relaxed Hybrid model which accounts for the inextensibility of lamellae in the chain direction and by a Self-Consistent model. The amorphous behavior is included in a composite formulation of both models. Keywords: Strain rate; Plastic flow. (AW)