In silico tensile tests and design of hierarchical graphene fibres and composites

In this contribution, we apply a hierarchical fibre bundle model (HFBM), previously developed to estimate the mechanical properties of multiscale carbon nanotube (CNT)-based structures, to the case of graphene macroscopic cables. The nonlinear elastic properties of graphene and its exceptional intrinsic strength, with mean Young's modulus of 1TPa, third-order elastic stiffness of -2.0TPa and intrinsic strength of 130GPa, are drawn from recent experimental studies. The model allows to derive macroscopic characteristics like strength, stiffness, toughness as a function of hierarchical structure, starting from statistically distributed properties at the nanoscale and without the introduction of additional ad hoc parameters. The influence of the presence of defects in the graphene bundles is evaluated. We also analyse the properties of graphene-reinforced composites, including the influence of the volume fraction of a ductile polymeric matrix. We show that the composite properties can be engineered to optimize strength and/or stiffness, and that the present model can be a useful tool to help pursue this objective