Crystallographic texture evolution in high-density polyethylene during uniaxial tension

This paper presents experimental measurements of crystallographic texture e volution in high-density poIyethylene subjected to very large strains in un iaxial tension (up to a true strain of 2. 1). The measurements presented he re differ from prior studies in three important aspects: (I) The initial te xture in the sample is quite strong with a large fraction of the crystallit es oriented in an unstable orientation with the crystal c-axis perpendicula r to the tensile axis of the sample. (2) Rigorous methods of texture analys es, based on spherical harmonics, have been applied to produce "complete, r ecalculated" pole figures based on diffraction data from five incomplete po le figures. (3) The measurements were performed while the samples were kept in the deformed state. The results presented here provide several new insi ghts into texture development in tensile straining of high-density polyethy lene to large strains. There are at least three distinct preferred orientat ions: (i) a component with (001) aligned along the extension axis, (ii) a c omponent with (011) aligned close to the extension axis, and (iii) a compon ent with (010) aligned along the extension axis. Note that only the first c omponent 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 natu ral relaxation of strain following the tensile loading had a significant im pact on the texture in the sample. It was observed that the relaxation proc ess mitigated or eliminated the second and third preferred texture componen ts described above, while strengthening the first. (C) 2001 Elsevier Scienc e Ltd, All rights reserved.