Plastic Deformation of Semicrystalline Polyethylene under Extension, Compression, and Shear Using Molecular Dynamics Simulation

Abstract

Plastic deformation of the stack of alternating crystal and amorphous layers typical of semicrystalline polyethylene is studied by molecular dynamics simulation. A previous investigation of the semicrystalline layered stack undergoing isochoric extension1 is extended here to include several new modes of deformation: isostress extension, isostress compression, and isochoric shear, at 350 K and deformation rates of 5 × 107 and 5 × 106 s–1. The observed stress–strain responses are interpreted in terms of the underlying structural evolution of the material for each mode of deformation. Under tensile deformation, crystallographic slip was observed at low strains (0 < e3 < 0.08) regardless of deformation rate. Different yield mechanisms were observed for the different deformation rates. To explain the response at intermediate strains (0.08 < e3 < 0.26), we introduce the concept of “bridging entanglements”, which are temporary, physical bridges between crystal lamellae comprising entanglements involving chain se...