Analysis of the Interface in CNT-Polyethylene Nanocomposites using a Multiscale Modeling Method

摘要

One anticipated application for carbon nanotube is as multifunctional reinforcemen-t material in high performance nanocomposites and the structural composites in which nanocomposites may be embedded. The performance of the composites in terms of enhanced mechanical, thermal and electrical properties is critically affected by the interfacial characteristics between the CNTs and the polymer matrix. Hence, in order to design high performance CNT-polymer nanocomposites, it is essential to understand the interface of the CNTs and the polymer. As it is difficult to directly obtain the characteristics of the interface of CNTs and polymer through experiments, it is proposed to characterize the interface using computational materials science approach. In the present work, force field molecular dynamic(MD) simulation has been applied to assess the separations of the interface in normal and sliding directions in nanocomposites at the nanoscale for a CNT-polyethylene nanocomposites. The peak force and the energy of separation were obtained by monitoring the force on a representative graphene layer as it was separated from a segment of the bulk polyethylene near the CNT interface, and subsequently used to construct cohesive zone parameters which can be transferred to higher level continuum model. Normal opening model separations and sliding mode separations were done to characterize the interface in two directions. A study of sensitivity of the force-displacement response has also been performed to investigate the influence of the temperature on the properties of interface. At the microscale, the cohesive zones were applied within the framework of a generalized self-consistent composite cylinder model and an FEM model in order to investigate the impact of the non-functionalized interface on the macroscale effective properties of nanocomposites. Functionalized interface was constructed by adding functional group between graphene sheet and the polymer. Force separation responses of functionalized interface from normal opening separations were compared with thoes of non-functionalized interface, with special emphasis placed on bond breaking and polymer griping in the functionalized cases.