Molecular Dynamics of Bond Breaking and Tensile Failure in Crystalline Polyethylene

Abstract - Crystalline polyethylene (PE) can sustain very large tensile loads along the polymer-chain direction, but failure ultimately requires loss of carbon-backbone connectivity. This project uses reactive molecular dynamics to identify when bond-breaking-related damage begins during chain-axis tension and to test how the predicted failure sequence changes with molecular structure and interatomic potential. The current poster reports the completed AIREBO-M comparison between a pristine 4×4×8 orthorhombic PE crystal and the same crystal containing one controlled backbone-carbon defect. Both systems were relaxed, equilibrated at 300 K, and stretched along the crystallographic c-axis at an engineering strain rate of 2.0×10^9 s^-1 while transverse pressure was maintained near zero. In pristine PE, the maximum smoothed tensile stress was 172.4 GPa at 40.13% strain. The first sustained geometric C–C coordination-loss event, used here as a proxy for bond-breaking-related damage, occurred at 40.30%; operational fracture followed at 40.95%, and near-total load loss at 41.97%. With one backbone- carbon defect, the axial modulus decreased from 263.3 to 253.4 GPa and UTS decreased to 163.1 GPa at 39.87% strain. The first additional coordination-loss event occurred at 40.00%, followed by operational fracture at 40.85% and near-total load loss at 41.76%. Thus, within AIREBO-M, the defect lowers stiffness and peak strength more strongly than it shifts the final failure window. Matched simulations with a reactive neural-network PE potential are ongoing.