Effects of graphite flake size on the properties of aligned graphene nanoplatelets covered graphite flakes/aluminum composites

Finding out the effects of graphite (Gr) flake size on the properties of Gr (Graphene Nanoplatelet (GNP))/Al composites will be helpful to design and develop various Gr(GNP)/Al composites which need to meet different application requirements. In this work, thermal conductivity (TC) and flexural strength of Gr/Al and Gr(GNP)/Al composites with different Gr flake size were investigated. Through-plane TC of Gr/Al composites is about 50% of the results predicted by EMA model. However, after introducing GNP to Gr flakes, through-plane TC of Gr(GNP)/Al composites reaches about 90% of the results predicted by EMA model. When Gr flake size are 150, 500, 850 μm, respectively, the in-plane TC of Gr/Al composites can be improved by 8.5%, 6.4%, 5.4% after introducing GNP, while the through-plane TC of Gr/Al composites can be improved by 62%, 75%, 83%. So the introduction of GNP to the Gr flake is more effective in improving through-plane TC than in-plane TC. GNP's improvement ratio on the through-plane TC of Gr/Al composites increases with the increase of Gr flake size. Furthermore, as Gr flake size increases, GNP's improvement ratio on the flexural strength of Gr/Al composites increases, which is attributed to the increase of strengthening effect of GNP on the interface region.