Molecular Dynamics Investigation of the Effects of Defects and Transverse Pressure on the Axial Tensile Behaviors of Polyethylene Crystals and Fibrils

Abstract

Experimental AFM images have revealed that the structure of ultra-high molecular weight polyethylene (UHMWPE) is porous at the fibril length scale. However, the effects of voids on the mechanical properties of PE fibers are not well understood. We employ molecular dynamics (MD) simulations to investigate the behavior of porous PE crystals under transverse pressure, which can be manifested during processing or transverse impact. We first focused on investigating the influence of the cut-off function in the Reactive Empirical Bond Order potential on the predicted properties of polyethylene crystals. Our objective was to identify the most accurate and computationally efficient implementation of the cut-off function. Through our investigation, we discovered that modifying the lower cut-off radius of the existing cutoff function yields reliable results while maintaining computational efficiency. Building upon this, we conducted MD simulations to analyze the behavior of polyethylene crystals with voids under transverse compression. Our simulations revealed that the collapse of voids is influenced by their state, whether they are vented or closed. Moreover, the strain rate significantly influences the process of void collapse. The outcomes of this study lay a solid foundation for future research endeavors, particularly in exploring the response of porous UHMWPE structures to transverse compression and axial tensile loading.