Functionally graded graphene reinforced composite structures: A review

Owing to their superior mechanical properties, e.g. exceptionally high Young's modulus, high strength, large specific surface area, and good thermal conductivity, graphene and its derivatives such as graphene platelets (GPLs) are excellent reinforcing nanofillers for composite materials. The most recently developed functionally graded graphene platelets reinforced composite (FG-GPLRC) where GPLs are non-uniformly dispersed with more GPLs in the area where they are most needed to achieve significantly improved mechanical performance has opened up a new avenue for the development of next generation structural forms with an excellent combination of high stiffness, light weight and multi-functionality. Research activities in this emerging area have been rapidly increasing since it was first proposed in 2017. The present paper (i) briefly reviews the mechanical properties of graphene and graphene composites; (ii) summarizes the characteristics of functionally graded materials (FGM) and reports the fabrication of FG-GPLRC; (iii) discusses the existing micromechanics models for the prediction of effective mechanical properties of GPLRC; (iv) presents a comprehensive review on the mechanical analyses of FG-GPLRC structures; and (v) discuss the key technical challenges and future research directions.