Molecular Dynamics Simulations of Polymer-Nanotube Composites

Abstract

The structure and mechanical properties of nanocomposites composed of (10,10) carbon nanotubes in an amorphous polyethylene matrix have been modeled with molecular dynamics simulations. Two systems were studied, an infinite nanotube (via periodic boundaries) and a finite capped nanotube 6 nm in length. In the infinite case the modulus in the direction of the nanotube is given by the upper bound of the rule of mixtures, as expected under isostrain conditions for a well-aligned fiber-reinforced composite. In the finite case, no load transfer is observed at low strain, consistent with the weak nanotube-polymer adhesion and a subcritical nanotube length. The simulations predict that regions of amorphous polymer close to the bulk density remain around the nanotubes at relatively large strains, and that the density decrease during strain results primarily from chain disentanglement and alignment in regions between nanotubes.