13 - Multiscale Simulation of Impact Response of Carbon Nanotube/Polymer Nanocomposites

Abstract

This chapter describes a two-scale numerical model developed using the explicit FE code LS-DYNA for simulating the impact response of carbon nanotube (CNT)/polymer nanocomposites. The model is based on a representative volume element (RVE), which comprises the polymer, the CNT, and their interphase. Initially, the model is used to conduct a study on the effect of geometrical and material parameters, including the CNT content, the CNT aspect ratio, the CNT material properties, the interphase thickness, and the interphase material properties. Then, the model is used to simulate nanoindentation of the nanocomposite in an upper scale. The material properties required for the simulation of nanoindentation are extracted from the load-deflection curve of the RVE and nanoindentation theory. The simulations show that the presence of CNT significantly enhances the impact response of the polymer by increasing the impact stiffness and the energy absorbing capacity of the material. The enhancement increases with the CNT’s volume fraction and it is larger at larger impact velocities. The effect of CNT’s aspect ratio is minor. The orthotropic behavior of the CNT assigns the RVE a higher energy absorbing capacity than the isotropic behavior at small impact velocities. The prediction of impact damage at large impact velocities reveals that the CNT makes the polymer more susceptible to fracture. As far as the interphase effect is concerned, the interphase thickness had a minor effect on the total absorbed energy, although its presence affected the energy absorbed energy dissipations among the nanocomposite constituents. One of the most important contributions of the interphase on the impact response was the decrease of the energy consumed on the fracture phenomena on the impacted surface. Finally, the analysis of the macroscale specimen revealed that the energy absorption capability of the polymer was significantly enhanced by the presence of the reinforcement. Fracture took place at even lower velocity than that noted out at RVE level, whereas the unreinforced impacted areas were expected to fail first.