Modeling the pullout test of nanoreinforced metallic matrices using molecular dynamics

Molecular dynamics (MD) simulations of pullout tests are developed to determine the effect of the different parameters influencing the interfacial shear strength (ISS) of carbon nanotube-reinforced metallic matrices. Unlike earlier works, the current study focuses on the effect of the cell size, cell geometry, and the potential functions adopted in the MD simulations. The basic MD cell was created in two steps. The metal atoms were initially created using the built-in tools in the molecular dynamics code "LAMMPS" guided by the specific metal lattice parameters with a pre-defined constraint of a central hole to accommodate the CNT at a later stage. The cell was equilibrated with Brownian dynamics prior to the placement of the CNT reinforcement. The CNT was then placed in the central hole. This was then followed by equilibrating the entire system prior to pulling out the CNT, to release spurious stresses arising during the build up of the cell, initially with Brownian dynamics and later with the nvt ensemble. Our ISS predictions agreed very well with earlier research work. Additionally, our results show that box-shaped MD cells are more suitable for the pullout test simulations with nvt or nve ensembles, while npt scheme produces additional forces to the system. The MD cell length was found to have insignificant effect on the pullout force.