Molecular models for creep in oriented polyethylene fibers
Abstract
Highly oriented and crystalline polyetheylene (PE) fibers have a large failure stress under rapid tensile loading but exhibit significant creep at much smaller stresses that limits applications. A possible mechanism is slip of chains due to stress-enhanced, thermally activated nucleation of dislocations at chain ends in crystalline regions. Molecular dynamics simulations are used to parameterize a Frenkel–Kontorova model that provides analytic expressions for the limiting stress and activation energy for dislocation nucleation as a function of stress. Results from four commonly used hydrocarbon potentials are compared to show that the qualitative behavior is robust and estimate quantitative uncertainties. In all cases, the results can be described by an Eyring model with values of the zero-stress activation energy Ea0≈1.5 eV and activation volume V* ≈ 45 Å3 that are consistent with the experimental results for increasingly crystalline materials. The limiting yield stress is ∼8 GPa. These results suggest that activated dislocation nucleation at chain ends is an important mechanism for creep in highly oriented PE fibers.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 12, 2020
- Source ID
- 10.1063/5.0021286
Entities
People
- Mark O. Robbins
- Thomas C. O'Connor
Organizations
- Johns Hopkins University
- National Science Foundation
- Sandia National Laboratories
- United States Army Research Laboratory
- United States Department of Energy