Molecular Dynamics Simulation of the Effects of Layer Thickness and Chain Tilt on Tensile Deformation Mechanisms of Semicrystalline Polyethylene

We performed molecular dynamics simulations to investigate the effects of layer thicknesses of both crystalline and noncrystalline domains and chain tilt within the crystalline lamellae on tensile deformation mechanisms of the lamellar stack model of semicrystalline polyethylene. For equal thicknesses of crystalline and noncrystalline regions, similar stress-strain profiles were obtained with two different initial orientations of the crystal stem relative to the tensile direction. Repeated melting/recrystallization transitions were observed, at the slower strain rate of 5 X 10(6)s(-1), characterized by oscillating stress strain profiles. With increasing thickness of the crystalline regions, these oscillations occurred less frequently. For systems with initially tilted chain stems in the crystalline domain, decreasing the thickness of the noncrystalline region increased the number of short bridge segments in the noncrystalline region connecting the two crystalline regions and induced significant shear stresses, rearrangements in the crystalline region, and the strain hardening during the tensile deformation.