Investigating the influence of pull-out speed on the interfacial properties and the pull-out behavior of CNT/polymer nanocomposites

Abstract

Carbon nanotubes (CNTs) improve the fracture toughness of nanocomposites and composite materials by bridging the crack growth path using the pull-out mechanism. Achieving the ability to estimate the dynamic fracture toughness of these materials, the effects of pull-out speed on the pull-out behavior and the critical interfacial shear stress (CISS) between CNT and epoxy resin are investigated in this paper. Employing the molecular dynamics (MD) simulation, the optimized unit cells consisting of epoxy resin containing a single-walled CNT are prepared. Appropriate boundary conditions are applied to the ensembles and the pull-out simulation is performed for the pull-out speeds in the range of 0.0015–0.0050 Å/fs resembling medium-rate loading. The effect of the pull-out speed on the maximum pull-out force is studied. It is revealed that by increasing the pull-out speed, the maximum pull-out force decreases. The corresponding average pull-out force–displacement curves are independent of the pull-out speed and are approximately similar. Based on these simulations, the pull-out speed affects the pull-out energy in the specified speed range. The variations of the pull-out energy and the CISS relative to the changes in the CNT length and diameter are also partially affected by the pull-out speed.