Title: Mechanical Properties of Polymer Networks using LAMMPS
Presenter: Timothy Sirk
Affiliation: U.S. Army Research Laboratory
Abstract: Atomistic simulation of chemically cross-linked polymer networks will be discussed, including their construction, equilibration, and considerations in computing thermodynamic, transport and mechanical properties. We present molecular dynamics (MD) results from epoxy networks, which are commonly used in high performance composites and adhesives that involve high-impact loading conditions or ballistic collisions. We show that the glass transition temperature (Tg) of the network can be estimated from MD simulation using volumetric and mechanical data, and the elastic modulus exhibits well-known characteristics of a viscoelastic solid, such as a strong sensitivity to strain rate near the Tg. Further, the Young's modulus at relatively low experimental strain rates can be recovered from high strain rate MD results through the construction of a 'master curve' via the Williams-Landel-Ferry equation. This presentation will also include practical aspects of LAMMPS use in equilibrium and non-equilibrium simulations.