Prediction of Mechanical Properties of EPON 862 (DGEBF) cross-linked with Curing Agent W (DETDA) and SWCNT using MD Simulations

Abstract

The present study focuses on the prediction of mechanical properties of single-walled carbon nanotubes (SWCNT) reinforced epoxy resin (DGEBF) cross-linked with curing agent W (DETDA). The MD models of the reinforced epoxy were built using the amorphous module of Material Studio (Accelrys Inc.). The COMPASS force field was used in the simulations. The amorphous structure was achieved by using periodic boundary conditions and then subjecting to an energy minimization using an ensemble of the constant-volume and temperature (NVT). The structures were equilibrated for 100 picoseconds (ps) and then followed by MD equilibrations at room temperature for another 200 ps. Since at room temperature most of the atoms are in static mode, the atoms were excited using simulation temperatures above the glass transition temperatures. In an attempt of finding global energy minimum, simulated annealing runs were then carried out starting at elevated temperatures at atmospheric pressure using the ensembles of the constant number of particles, constant-pressure and constant temperature (NPT). The molecular structure temperature was then gradually lowered to a room temperature. Each subsequent simulation was started from the final configuration obtained at the preceding temperature. Density of the epoxy at each temperature was calculated from the average specific volume and glass transition temperature (Tg) was estimated based on the discontinuity in the slope of the density-temperature plot. The amorphous structures obtained at room temperature were analyzed to determine the fundamental mechanical properties of the SWCNT reinforced EPON 862-W. Calculations of fundamental mechanical material properties of single-walled carbon nanotube (CNT) were performed using molecular dynamics simulations via Material Studio. A simple but effective technique of extrapolation was adopted to compensate for the problem of CNT distortion because of smaller lattice sizes. Property calculations were performed at each density value and extrapolated to the actual value of density equal to 1.9 gm/cm 3 . A similar extrapolation technique was employed to overcome the issue of achieving exact theoretical