Crystallographic texture evolution in high-density polyethylene during uniaxial tension

This paper presents experimental measurements of crystallographic texture evolution in high-density polyethylene subjected to very large strains in uniaxial tension (up to a true strain of 2.1). The measurements presented here differ from prior studies in three important aspects: (1) The initial texture in the sample is quite strong with a large fraction of the crystallites oriented in an unstable orientation with the crystal c-axis perpendicular to the tensile axis of the sample. (2) Rigorous methods of texture analyses, based on spherical harmonics, have been applied to produce “complete, recalculated” pole figures based on diffraction data from five incomplete pole figures. (3) The measurements were performed while the samples were kept in the deformed state. The results presented here provide several new insights into texture development in tensile straining of high-density polyethylene to large strains. There are at least three distinct preferred orientations: (i) a component with (001) aligned along the extension axis, (ii) a component with (011) aligned close to the extension axis, and (iii) a component with (010) aligned along the extension axis. Note that only the first component has been reported to be stable at high strains in previous studies. The rate of texture evolution in the present study is significantly lower than that reported in previous studies. It was also observed that the natural relaxation of strain following the tensile loading had a significant impact on the texture in the sample. It was observed that the relaxation process mitigated or eliminated the second and third preferred texture components described above, while strengthening the first.