Session: 12-10-03: General: Mechanics of Solids, Structures and Fluids

Paper Number: 112860

112860 - Characterizing High-Speed Impact Behavior of UHMWPE Through Molecular Dynamics Simulation 

This research aims to build a molecular dynamics simulation model with the objective of a fundamental understanding on the mechanics of ultra-high-molecular-weight-polyethylene (UHMWPE) fibers at atomic scales under extremely high-rate transverse impact loading condition. MD simulations of high-velocity impacts on carbon-based polymers are relatively rare. The most common materials studied are graphene sheet. In recent studies, ballistic impacts of polyethylene were studied via large-scale MD simulations to investigate the dissipated energy, deformation and fracture response, and temperature and pressure evolutions during impact. It was found that entanglement density, interchain friction, and chain mobility are influential factors on the ballistic behavior of the thin PE film. It was also observed that even under hypersonic speed impact, chain scission was not observed to be a significant mechanism in dissipating the energy of the PE film. These observations have provided important insight into the ballistic impact behavior of amorphous PE film. However, the microstructure of the impacted object is not a representative of real UHMWPE fiber. Another shortcoming of these simulation is that the exact role of each of these influential factors was not quantitatively analyzed. Therefore, in order to fully understand the underlying mechanisms of energy dissipation during ballistic impact, a highly representative MD model that takes into account the shish-kebab structure of the UHMWPE fiber is needed, which is the objective of this research. Therefore, in this research, ballistic impact simulation using molecular dynamics simulation method will be conducted for the UHWMPE fiber at microscale. Unlike most of the existing works, where the focus has been on the ballistic impact resistance of amorphous polyethylene, our research will consider exclusively the shish-kebab structure of the UHMWPE macro-fibril. Both the extended chain crystals that consist of the shish and epitaxial crystals that consist of the kebab will be investigated through molecular dynamics simulation method. In the ballistic impact simulations, a diamond projectile that represents a rigid projectile will be used to impact the polyethylene at various velocities. Two different types of potential energy function will be compared to reveal the energy dissipation mechanisms involved in the ballistic impact. The first type of potential energy function is given by the polymer consistent force field (PCFF) based on CFF91(consistent force field) with additional parameters specified for polymer materials. The PCFF and COMPASS (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies) force fields have the same functional form. The proposed MD simulation will be conducted by using the open-source MD code Large-scale Atomic/Molecular Massively Parallel Simulator (Lammps).

Presenting Author: Guodong Guo Texas A&M University HECM

Presenting Author Biography: Dr. Guodong Guo is an Instructional Assistant Professor in Multidisciplinary Engineering Department of Texas A&M University. Dr. Guo received his PhD degree from North Carolina State University. His research interests lie in the broad field of solid mechanics, composite structures, sensors, and actuators. His research findings have been published in prestigious journals including Composite Structures and Technology, International Journal of Impact Engineering, Composite Structures, Smart Materials and Structures, etc. At undergraduate level, Dr. Guo teaches various courses in structural mechanics, system dynamics, and mechanical design.

Authors:

Guodong Guo Texas A&M University HECM
Shah Alam Texas A&M University-Kingsville