Molecular dynamics study of the reinforcement effect of graphene in multilayered polymer nanocomposites

We conducted comprehensive molecular dynamics simulations of the nanoindentation of graphene reinforced composites to study the effect of graphene as a reinforcement and coating material. Three different cases are considered: (i) single and multilayered graphene layers used to coat a polyethylene (PE) substrate, (ii) graphene layers embedded into a PE block forming a multilayered system, and (iii) graphene layers randomly embedded into a PE block forming a nanocomposite. The study focused on the reinforcement mechanism and the fracture behaviour associated with increasing the number of graphene coating layers, changing interlayer spacing distance, orienting graphene-PE layers with respect to the indentation direction, and changing graphene dispersion in the composite. The results of our study reveal that the indentation resistance of a single-layer graphene coated PE is fourteen-fold the indentation resistance of pure PE. They also indicate that the indentation resistance of the multi-layered embedded graphene arrangement can be effectively controlled by appropriately selecting the separation distance between the graphene layers. They further show the strong influence of the orientation and the arrangement of graphene layers on the mechanical response of the nanocomposite. These findings are useful in designing graphene-based nanocomposites with tenable performance. (C) 2017 Elsevier Ltd. All rights reserved.