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.

Mechanical properties and local mobility of atactic-polystyrene films under constant-shear deformation

“…a rather slight increase of Young's modulus with pressure has been found. 19 The temperature and strain-rate dependencies of the stress-strain characteristics have been investigated by Li et al 20 They performed atomistic Monte Carlo simulations of uniaxial tension of an amorphous linear polyethylene-like glassy polymer. They found that with increasing strain in the elastic region mechanical work is stored as non-bonded internal energy, and that in the yield regime the intra-chain contributions start to play a role.…”

Deforming glassy polystyrene: Influence of pressure, thermal history, and deformation mode on yielding and hardening

“…24,[26][27][28] Also other simulation techniques are applied to study the deformation of polymers, such as Monte Carlo algorithms or variants of energyminimization methods for PE-alike, 29 polypropylene, 30,31 poly͑oxypropylene͒, 32 PC, [33][34][35] and PE. 36,37 As the simulation studies are limited to only small time and length scales, numerical agreement is often only possible by means of extrapolation over orders of magnitude.…”

Monte Carlo Simulation of Uniaxial Deformation of Polyethylene‐Like Polymer Glass: Role of Constraints and Deformation Protocol

“…In spite of problems such as small system sizes and huge cooling and deformation rates, MD has proved to be a useful tool in studying deformation behavior of amorphous polymers 12, 15, 16. Although Monte Carlo (MC) simulation does not contain any dynamics, this tool is also starting to be used for the study of polymer deformation 17–22. Various lattice‐model MC simulations have been used to study the deformation behavior of polymeric models 19–22.…”

“…3‐D off‐lattice MC simulations of PE‐like crosslinked networks have been performed by Chui and Boyce 17. The authors of the present paper recently simulated the uniaxial extension of multichain PE‐like systems employing a mix of very local atomic and more collective MC moves 18…”

“…In many simulations of deformation, the strain is prescribed by changing monomer positions affinely with the box size 15, 17, 18, 23. Such a simulation protocol is not very efficient for polymers since it affects the hard degrees of freedom of the polymer molecules, i.e., bond length and valence angles.…”