Synergistic strengthening effect of graphene-carbon nanotube hybrid structure in aluminum matrix composites

High-performance reinforcement and tailored architecture are currently explored to develop advanced metal matrix composites. In this work, aluminum (Al) matrix composite reinforced by hybrid carbon nanofillers was fabricated by a composite flake assembly process. It was found that for various carbon nanofiller volume fractions, a striking synergistic strengthening effect was achieved by employing graphene (reduced graphene oxide, RGO) and carbon nanotube (CNT) hybrid structure as reinforcement in the Al matrix. Particularly, a tensile strength of 415 MPa was achieved with the addition of 1.5 vol.% of RGO-CNT hybrid, which is significantly higher than those reinforced by individual CNT or RGO (326 and 331 MPa, respectively). The synergistic strengthening effect was attributed to the formation of a planar network of RGO and CNT, which improves the load transfer efficiency between the matrix and the reinforcement in composites. Our study highlights the importance of reinforcement architecture for enhancing the strengthening ability in composites, and provides an effective route to fully take the advantage of the superior properties of various reinforcements.