Nanoscale metal-graphene nanolayered composites are known to have ultra-high strength due to the ability of graphene to effectively block dislocations from penetrating through the metal-graphene interface. The same graphene interface can deflect generated cracks, thereby serving as a toughening mechanism. In this talk, the role of graphene interfaces in strengthening and toughening the Cu-graphene nanolayered composite will be discussed. In-situ TEM tensile testing of Cu-graphene showed that the dislocation plasticity was strongly confined by the graphene interfaces and the grain boundaries. The weak interfacial bonding between Cu-graphene induced an interesting stress decoupling effect, which resulted in independent deformation of each Cu layer. MD simulations confirmed such independent deformation of each Cu layer and also showed that the graphene interfaces effectively block crack propagation as delamination occurs at the Cu- graphene interfaces to allow for elastic strain energy dissipation. Bending fatigue testing was also conducted on Cu-graphene nanolayered composites that indicated ~5 times enhancement in robustness against fatigue-induced damage in comparison to the conventional Cu only thin film. Such an enhancement in reliability under cyclic bending was found to be due to the ability of the graphene interface to stop fatigue-induced crack propagations through thickness of the thin film, which is contrary to how a metal only thin film fails under cyclic loadings.
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