Molecular Dynamics Simulations of the Elastic Moduli of Polymer-Carbon Nanotube Composites

The elastic moduli of polymer-carbon nanotube composites are examined by molecular dynamics simulations of a single-walled carbon nanotube embedded in polyethylene. The overall system is modeled with a many-body bond order potential due to Brenner. Alternatively, only the carbon nanotube is modeled with Brenner’s potential and the polyethylene matrix is modeled by a united-atom potential. For these systems we perform molecular dynamics simulations to derive stress-strain curves. Here, we use the Parrinello-Rahman approach to apply external stress to a periodic system. To compare the elastic moduli of the composite with rule-of-mixtures predictions, we study three periodic systems, an infinite carbon nanotube, a finite carbon nanotube embedded in polyethylene and the polyethylene matrix itself. The results show an excellent agreement with the macroscopic rule-of-mixtures in the case of the very long nanotube and with an extended rule-of-mixtures in the case of the short nanotube.