Multiscale modeling of the interface effects in CNT-epoxy nanocomposites

This paper presents a hierarchical multiscale simulation framework for investigating the interface effects in polymer nanocomposites. In this framework, the load transfer ability of the interface in carbon nanotube (CNT)-epoxy nanocomposites is evaluated using molecular dynamics (MD) simulations by adopting an atomistic graphene-polymer interface model in which the cured epoxy matrix with various crosslink densities is constructed by using a dynamic crosslinking algorithm. The interfacial behavior between CNTs and the epoxy matrix has been characterized in both normal opening mode and sliding mode separation in terms of the force-separation responses at the nanoscale. Key factors, e.g. the crosslink density of the epoxy network in the matrix, the system temperature, the separation mode and functionalization, has been investigated on their effects on the load transfer ability of the CNT-epoxy interface. Further, by employing embedded cohesive zone model in finite element analysis, the macroscale effective material properties of the CNT-epoxy nanocomposites have been evaluated under the nanoscale interface effects. It is observed that covalent functionalization between CNT and polymer matrix can dramatically improve the load transfer ability of the interface at the nanocale, thereby enhancing the effective mechanical properties of the nanocomposites at the microscale. This work will assist in deepening our knowledge about the load transfer ability of the interface and the corresponding strengthening mechanisms in CNT reinforced epoxy nanocomposites.