Bimodal reinforcement of graphite flake and graphene nanoplatelet in Cu matrix composites: Anisotropy of the thermo-mechanical properties and failure mechanisms

Abstract

Bimodal reinforcement consisting of powders of large graphite flake (GF) and small graphene nanoplatelet (GNP) were used to fabricate (GF + GNP)/Cu composites to reduce the anisotropy of the thermal and mechanical properties in GF/Cu composites. In this study, we investigated the effects of GNP addition on the anisotropy of the thermal and mechanical properties and the deformation behavior of (GF + GNP)/Cu composites. The 2 θ > value was used to evaluate the alignment of the reinforcing phases (GF, GNP), by which the variations in the coefficient of thermal expansion (CTE) and thermal conductivity (TC) of the composites were analyzed. With increasing GNP volume fraction, the angle (θ) at which the GF deviated from the in-plane direction increased. As a result, the anisotropy of the CTE in the in-plane and through-plane directions increased, whereas the anisotropy of the TC and mechanical strength decreased. Cracking was observed in both the specimens compressed along the in-plane and through-plane directions, whereas kinking was observed only in the specimens compressed along the in-plane direction. The deformation behavior and mechanical properties of the composites with bimodal reinforcement in the in-plane and through-plane directions were strongly dependent on the change in the alignment of the GF with the addition of GNP. The results clearly revealed the role of bimodal reinforcement in controlling the anisotropy of the thermal and mechanical properties of the (GF + GNP)/Cu composite, providing guidelines for optimizing the thermomechanical properties of high-performance (GF + GNP)/Cu composites.

Keywords

• GF/Cu composite
• Graphene nanoplatelet (GNP)
• Bimodal reinforcement
• Coefficient of thermal expansion (CTE)
• Mechanical property