Effect of transition layer using mesophase pitch on mechanical properties of carbon/carbon composites

The mesophase pitch was used as transition layer between fiber and matrix of 2D carbon/carbon (C/C) composites. The effect of the transition layer on the mechanical properties of C/C composites was investigated by comparing with three kinds of manufactured C/C composites, that is, no transition layer, normal pitch as transition layer and mesophase pitch as transition layer. The results show that the mechanical properties are improved by using pitch transition layer, and the flexural strength and laminar interface shear strength (LISS) of C/C composites using mesophase pitch are improved by 44% and 15% respectively than that of C/C using normal pitch. The analysis of fractured surface shows that the bonding strength of intra-bundle and inter-bundle of fibers is different by using mesophase pitch, which cause crack to deflect during fracture. Therefore the strength and toughness are improved simultaneously.