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

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 mo-lecular 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 angstrom/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.