Molecular modelling of the effect of loading rate on elastic properties of CNT-polyethylene nanocomposite and its interface

Abstract

Polymer composites reinforced by carbon nanotubes (CNTs) are so attractive for many mechanical applications due to their higher strength and elastic modulus than those of polymer itself. Besides the mechanical performance of CNTs being superior, another main reason is related to the CNT-polymer interface. The interface at nanoscale level plays a key role of load transfer. These kind of polymeric materials are highly sensitive to temperature and loading rates (or strain rates), and further as the matrix with nanoparticle additives, the mechanical properties of the composite have also been found to be strongly dependent on temperature and loading rates. In this paper, specifically for the CNT-reinforced polyethylene nanocomposite, we studied the effect of loading rates on the elastic properties of the nanocomposite and its CNT-polyethylene interface by molecular dynamics (MD) modelling. Our simulated results are well agreed with the ones that are calculated on the rule-of-mixtures (ROM) and from other publications. The results show that higher loading rates lead to larger stress and Young’s modulus of the nanocomposite. And on the atomistic model with taking account of the CNT-polyethylene interface, we found that the interface thickness is independent on loading rates, while its interaction energy and Young’s modulus are related to selected CNTs, and dependent on loading rates. Both of them reach the largest value when the CNTs with the highest aspect ratios (correspondingly the highest specific surface areas) are selected and the nanocomposite being under the fastest loading rate. These results are very valuable for deeply understanding the elastic properties of CNT-polyethylene nanocomposites and their microstructural design.