Mechanical properties of graphene platelets reinforced syntactic foams

Graphene platelets (GPs) are two-dimensional thin plates containing few layers of graphene sheets. Compressive and tensile behaviors of epoxy-based syntactic foams with pristine GPs as additives are discussed in this article. Four sets of syntactic foams containing 0, 0.1, 0.3, and 0.5 vol.% of GPs were fabricated and tested. The volume fraction of microballoons in all syntactic foam samples was kept constant at 30%. Results indicated that the compressive and tensile moduli of the syntactic foams were significantly improved as compared to samples that did not contain GPs. The addition of GPs also enhanced the tensile strength while the compressive strength was only slightly increased. Optimal property improvements were obtained for very low filling fraction of approximately 0.3 vol.%. Samples with higher volume fraction of GPs (0.5%) showed deterioration in mechanical properties when compared to other GP containing samples. Transmission microscopy study indicated formation of voids enclosed by undispersed GPs in the samples which could explain the decline of the properties. High matrix porosity could also play an important role in this observation. Utilizing surface modified GPs could allow incorporation of higher volume fraction of GPs homogeneously, thus improving the mechanical properties of the syntactic foams.