A finite element study on the CNT size effect on the nonlinear response of polymer nanocomposites

Abstract

The effect of carbon nanotube (CNT) aspect ratio on the elastic–viscoplastic response of polymer nanocomposites with and without interphase region is studied using the finite element method. Also, the interfacial debonding between the constituents of the nanocomposite is considered in the simulation. To characterize both the polymer and the interphase zone, an elastic–viscoplastic constitutive relation is used. The CNT is modeled as an isotropic elastic material. A phenomenological cohesive relation that allows for separation is employed to model the interface between the polymer and the CNT phases. The effects of CNT aspect ratio, interface strength and interphase thickness on the nanocomposite stress–strain behavior are analyzed. It is observed that the polymer nanocomposite stress carrying capacity significantly decreases with increasing CNT aspect ratio in the presence of both interphase zone and debonding. The results indicate that in the presence of the interphase and debonding, with increasing the aspect ratio, the main concern is dominated by debonding at the interface between the CNT and interphase, while the plasticity of matrix is the chief concern at low CNT aspect ratio. Furthermore, it is found that in the absence of interphase, the strength of nanocomposite is improved with increasing CNT aspect ratio.