Exploring the effects of temperature, transverse pressure, and strain rate on axial tensile behavior of perfect UHMWPE crystals using molecular dynamics

Ultra high molecular weight polyethylene (UHMWPE) fibers are widely used in protective structures due to their exceptional mechanical properties. Understanding how temperature, transverse pressure, and strain rate influence their mechanical behavior is critical for optimizing their performance under diverse service conditions. We investigated the combined effects of temperature, transverse pressure, and strain rate on the axial tensile behavior of perfect UHMWPE crystals using molecular dynamics simulations. Our study reveals that elevated temperatures lead to a reduction in modulus and strength due to increased thermal vibrations disrupting the crystal structure and enhancing kinetic energy. In contrast, transverse pressure improves mechanical properties by enhancing interchain interactions and stabilizing the structure. Modulus and strength increase with strain rate, reaching a plateau when the loading velocity surpasses the maximum sliding velocity of broken chains, observed at a strain rate of approximately 10(12) s(- 1). Furthermore, thermal vibration analysis revealed that the vibration frequency of carbon atoms (similar to 1 THz) aligns with this critical strain rate, providing an atomistic explanation for the transition in strain rate sensitivity. These findings provide insights into the atomistic mechanisms governing UHMWPE fiber behavior under realistic service conditions, including elevated temperatures and impact scenarios.