Influence of oxidation inhibitor on carbon-carbon composites: 7. Studies on work of adhesion and fracture toughness of carbon-carbon composites

The objective of this study was to examine the effect of oxidation inhibitor contents on the work of adhesion, fracture toughness, and impact strength of the unidirectional carbon-carbon composites (C/C composites). The molybdenum disilicide (MoSi₂) used as an oxidation inhibitor was impregnated with phenolic resins to improve the anti-oxidation properties of the composites in different concentrations of 4, 12 and 20 wt%. Based on Wilhelmy equation, the work of adhesion of C/C composites was calculated by contact angle methods. Fracture toughness and impact strength were measured by three-point bending test for the critical intensity factor (T_IC) and Izod test method, respectively. As a result, the composites made with MoSi₂ resulted in an increasing of both fracture toughness and impact strength. Especially, the composites made with 12wt% MoSi₂ content showed the highest value of London dispersive component, W_A^L, in work of adhesion, resulting from improving the interfacial adhesion force among fibers, filler, and matrix in this system.