Ceramic Composite Attachments for Transmission of High-Torque Loads

The use of fiber-reinforced ceramic matrix composites (FRCMC) for advanced turbopump (T/P) hot-section components offers a number of potential advantages relative to the use of “conventional” materials. Among these advantages are reduced weight, enhanced life with reduced maintenance, and improved performance achievable by increasing the turbine inlet temperature. FRCMC are, however, emerging materials, and their design and analysis present unique challenges. These composites have relatively low thermal expansion coefficients and low strain-to-failure characteristics, and they have nonlinear, anisotropic properties. These characteristics particularly complicate the design of attachments to mating metallic components within a T/P. In an ongoing program, an FRCMC stator and rotor for a rocket engine T/P are being developed for eventual ground test demonstration. The rotor attachment is designed to transmit high-torque loads and provides an example of a design methodology that is compatible with current analytical capabilities. The approach used and described herein applies an empirically derived materials properties data base in combination with macromechanical analysis to reach a solution to this design challenge. This example demonstrates both the capabilities and the limitations of current design and analysis practices and provides direction for future development. A curvic coupling was chosen to meet the specific design goals and will be fabricated and tested to verify the design.