A hierarchical micromechanics framework for properties of discontinuous carbon fiber composites containing graphene nanosheets

The elastic moduli of polymer composites reinforced by aligned discontinuous carbon fibers (DCFs) and graphene nanosheets (GNSs) along the longitudinal and transverse directions are evaluated. To this end, a hierarchical micromechanics framework based on the Mori–Tanaka method and simplified unit cell model is developed. The model captures the GNS agglomeration and interaction between the GNS and the surrounding polymer. The effects of the amount and dispersion type of GNSs, size and stiffness of GNS/polymer interphase, volume fraction and aspect ratio of discontinuous fibers on the macro-mechanical properties of DCF/GNS/polymer multiscale composites are examined. Both longitudinal and transverse elastic moduli of aligned DCF-reinforced composites can be enhanced by adding GNSs into the polymer matrix. The GNS has a higher effect on the macro-mechanical properties as the DCF aspect ratio decreases. The elastic moduli of multiscale composites with agglomerated GNSs are decreased over those of multiscale composites with uniformly dispersed GNSs. To confirm the validity of the model, the predictions are compared to the experimental data.