Graphite particles with a “puffed” structure and enhancement in mechanical performance of their epoxy composites

A kind of graphite particle (GP) with a novel “puffed” structure and combined with the presence of oxygen-containing functional groups, were developed in our lab. In this paper, the structure and properties of the “puffed” GPs are analyzed, and the reinforcing effects of the GPs on the mechanical properties of an epoxy resin are investigated. Nanoindentation tests showed that the elastic modulus and hardness of the GPs were reduced as compared to the graphite flakes. The effects of the GPs on the properties of the epoxy with 0.5–5.0 wt% of the GPs were investigated by three-point-bending test, fracture toughness and dynamic mechanical analysis. Microstructure of the GPs and fracture surfaces of the composites were examined by microscopy techniques. Results showed that flexural modulus, flexural strength and fracture toughness of the epoxy system with 5 wt% GPs were increased by 13%, 43%, and 28%, respectively, over the pure epoxy. Composite specimens with 5 wt% GPs also showed an apparent increase in storage modulus with respect to that of pure epoxy from DMA. Both linear elastic fracture mechanics and non-linear fracture mechanics were applied to analyze the results.