Monte Carlo Simulation of Uniaxial Tension of an Amorphous Polyethylene-like Polymer Glass

Abstract

Atomistic Monte Carlo (MC) simulations of uniaxial tension of an amorphous linear polyethylene (PE)-like polymer glass have been carried out. A united-atom model has been used where PE chains are represented by beads connected by flexible springs. Highly efficient end-bridging MC moves have been used to first equilibrate the polymer in the melt and then cool to a temperature below its glass transition temperature. A mix of efficient MC moves has also been used to simulate the deformation dynamics. Upon uniaxial deformation the stress response to the strain is initially linear elastic, subsequently as the strain increases further yielding is observed, and finally strain hardening is developed. The simulated Young modulus and Poisson ratio take realistic values. Furthermore, the temperature and strain rate dependencies of stress−strain curves have been investigated, and the results are in qualitative agreement with the experimental observations. Chain conformation and energy and stress partitioning with increasing strain are followed in detail. During the deformation the chains adopt more extended conformations, and the fraction of dyads in the trans state increases. In the elastic region mechanical work done on the sample is primarily stored as nonbonded internal energy, whereas from the yield region onward the intrachain contributions start to play a role.