Multiscale modeling assessment of the interfacial properties and critical aspect ratio of structurally defected graphene in polymer nanocomposites for defect engineering

Abstract

Low-dimensional nanocarbon reinforcements in multifunctional composites have neither defect-free conjugate structures nor efficient interfacial properties in general. Moreover, synthesizing polymer nanocomposites involves intrinsic and extrinsic structural defects, which undoubtedly degrade the properties of the nanocarbons. However, several advantages and even useful applications of such structural defects have pioneered the defect engineering of nanocarbon structures. Here, we assessed the reciprocity of the degradation of single-layer graphene and the tailoring of the interfacial load transfer by structural defects. For this purpose, we used a molecular dynamics simulation and its hierarchical bridging to a mean-field micro-mechanics model for linear elastic behavior. Crystallographic defects and oxygen functionalization were considered the representative intrinsic and extrinsic defects, respectively. Despite the notably degraded elasticity of the nanocomposites involving direct load bearing by the defected graphene, those readily governed by the interfacial load transfer were significantly improved. The contributions of both types of defects to the interface were verified using the local stress concentration on the embedded graphene during the mechanical loading of nanocomposites and an additional mode I and II decohesion test. Lastly, the critical aspect ratio of graphene that maximizes the effects of the defects on the interface stiffness of the nanocomposites was derived for defect engineering.