One anticipated application for carbon nanotube is as multifunctional reinforcement 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 assess the interface be characterized using computational materials science approach. In the present work, force field molecular dynamic simulation has been applied to assess the opening mode separation of the interface in nanocomposites at the nanoscale for a CNT-polyethylene nanocompos-ites. The peak force and the energy of separation are obtained by monitoring the force on a representative graphene layer as it is 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. In order to assess the suitable sizes for nanoscale representative volume elements(RVEs) to represent the real material system, several parameters such as the length of the polymer chain have been studied to discern their influence on the measurements-peak force and energy of separation. Finally, the cohesive zones are applied within the framework of a generalized self-consistent composite cylinder model in order to investigate the impact of the interface on the macroscale effective properties of nanocomposites.