Determination of mode II interlaminar fracture toughness enhancement of unidirectional carbon fiber-reinforced matrix composites with graphene and multi-walled carbon nanotubes

Carbon fibre-reinforced composites are widely applied in various engineering fields and have exposed specific stress-bearing shortages under strong impact in different environment. So, composites with interlaminar toughness enhancement methods have been considered. In this paper, the carbon fibre-reinforced composites' interlaminar fracture toughness is tested with two kinds of complements under two different densities adding in the middle layer based on those nano materials' toughness enhancement conclusions that former researchers have obtained. The specimens' scale satisfied the ASTM D7905/7905M-14 standard and all the experiment process is conducted under the standard conditions. All the data from the specimens are considered to be valid, but given that the too-low or too-high value may contain accidental factors, both the highest and lowest values are deleted during the data processing. From the results, the MWCNTs group under the 1.0g/m² adding density behaved better than the Graphene group compared with the Control group and the energy release rate increased 138.04% and 88.70% respectively, which is very pleasant. While for the 0.5g/m² adding density, neither the MWCNTs nor the Graphene obtained enhancement, which means that the density is not suggested. The toughness enhancing mechanism is analysed to be the more energy release needed when pulling the MWCNTs out and the adhesive among the nano materials and matrix.