A comparison of the micromechanics of graphene- and transition metal dichalcogenide-nanocomposites

We have previously studied the micromechanics of graphene composites by using Raman spectroscopy to map the strain in model composite systems comprising of single graphene flakes. The design rules derived from these models have then been applied successfully to bulk composites. Herein, we have adapted our approach to understand the behaviour of transition metal transition metal dichalcogenide (TMDC) reinforcements such as tungsten disulphide (WS2) and molybdenum disulphide (MoS2). Few-layer nanoplatelets were produced by mechanical exfoliation, applied to a polymer substrate and then put under uniaxial strain. Small but significant Raman band shifts were observed upon deformation. These strain-induced bands shifts were modeled using density functional perturbation theory with good correlation between the experimental and predicted band shifts. The micromechanical behaviour of these experimental systems were modeled and compared to that of graphene, with the differences being correlated nature of the interfaces and microstructures. Finally, composites were produced using WS2 nanotubes in order to assess the role of the dimensionality of the reinforcement in the mechanical performance.