Synergistic effect of carbon nanotube/graphene nanoplatelet hybrids on the elastic and viscoelastic properties of polymer nanocomposites: finite element micromechanical modeling

A micromechanics procedure performed by the finite element method (FEM) was developed for the sake of examining the synergistic effects of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) hybrids on the elastic and viscoelastic properties of polymer nanocomposites. The representative volume element (RVE) approach was employed owing to its capability to consider various nano-additives with disparate dimensions and evaluate microstructure-level aspects. Constant-strain minimization method and linear viscoelastic model were utilized to predict components of elastic stiffness and creep compliance tensors. The validity of the proposed model was assessed by comparison with the well-established Halpin-Tsai micromechanical model and available experimental measurements, providing an acceptable agreement. Effects of orientation (random or unidirectional dispersion), volume content, and variation in the length and thickness of the carbonaceous nano-additives on the Young's modulus, Poisson's ratio, and creep compliance of CNT/GNP/epoxy nanocomposites were investigated. The results explicitly revealed that the CNT and GNP contributions to the mechanical reinforcement and the creep resistance in polymer are strongly associated with their distribution and volume content within the hosting matrix. Moreover, the outcomes imply that increasing the length of CNT, reducing the thickness of GNP lead to increasing Young's modulus, and decreasing creep compliance (or increasing creep resistance) of CNT/GNP/epoxy nanocomposites.