Abstract
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.
