Graphene quality dominated interface deformation behavior of graphene-metal composite: The defective is better

When nano-scaled reinforcements (“nanofillers”) are incorporated into a metal matrix, the enhancement in mechanical properties may well exceed those predicted by the “rule-of-mixtures”, owing to the rich interplay between the nanofiller and the various crystalline defects in the metal matrix. However, how the nanofillers and their interfaces with the matrix affect the deformation and failure mechanisms of the composites still remains elusive. In this study, we fabricated bulk nanolaminated composites from both near-pristine, high quality (HQ) graphene and defective, low quality (LQ) graphene. Ex situ and in situ compression tests of micro-pillars fabricated from the bulk composites revealed that the defective graphene nanosheets located at the interfaces possessed significantly higher shear strain accommodation and strain stiffening ability during deformation, resisting the graphene interlayer shearing/strain localization. The different deformation behaviors of the interface regions rendered a strong correlation between the macroscopic tensile behavior of the composites and the graphene quality, with LQ graphene-Cu composite both stronger and more ductile than the composite reinforced by HQ graphene layers. This study provides the first quantitative estimate of graphene/metal interfacial shear strength and shear accommodation capability (both as a function of the graphene quality), and suggests that the macroscopic mechanical properties of the graphene-metal composites can be fine-tuned by meticulously designed interfaces.