後藤 健

Carbon fiber-reinforced carbon matrix composites (C/Cs) are usually used with anti-oxidation coating applied on their surface, The data about bonding strength between the coating and C/C substrate are indispensable for material design of C/Cs for various high temperature structures. Standardized measuring methods to evaluate the bonding strength, however, have not been established and the scratch method or the indentation method have attempted to be used. The results by these methods do not give quantitative bonding strength and are useful only for relative comparison of specimens with same geometry. In this paper, the bonding strength between SiC coating and C/C substrate with various coating conditions was attempted to be measured by specially designed shear load method. The experimental results by a this method were discussed in terms of thermal and mechanical loading conditions by using finite element analyses.

In a development study of the air-turbo-ramjet (ATR) engine for a space plane, carbon-carbon (C/C) composites are attempted to be applied to the tip-turbine structure mainly taking advantage of high specific strength at elevated temperature. This disk has rather complicated shape and thus the joining structure is expected to be used. For the joint between fan blades and a fan disk, the dovetail joint is appeared to be useful but it is indispensable to maintain sufficient durability against extremely high centrifugal force to design optimally material property as well as the joint geometry. Tensile tests were carried out on simplified dovetail joint models made of three type of two dimensionally reinforced C/C composites. The effect of stacking pattern and various geometrical parameters was examined so as to fined an optimal structure. The result of the tensile test suggests that fracture of the dovetail joint be controlled by the average stress criterion, which implies stress concentration near the shoulder is almost relaxed during failure process of the C/C composites. It is also shown that AE signals are extremely useful to identify durability limit of the dovetail joint especially when the fracture mode is shear.