Improved Quality Assessment for Turbine Engine Components With Potential Applications to Ceramic Matrix Composite (CMC) Materials

Abstract

Demand for improved power from turbine engines has resulted in the development of ceramic matrix composite (CMC) materials that can withstand extreme temperature environments and maintain the damage tolerance required for space vehicles and next generation turbine engines. CMC components allow higher temperature operation and increased power over nickel-based superalloy components due to their reduced weight and temperature stability. The use of CMCs allows a potential increase in turbine engine temperatures to above 1400°C. This temperature increase results in improved performance, which translates into increased efficiency, better power to weight ratios, and improved reliability with both significant fuel savings and reduced life cycle costs. Evaluating CMC component quality is difficult due to variations in the fiber/matrix properties and variations in fabrication related parameters. Further, there is limited information on operational and remaining life characteristics. These factors produce significant challenges to existing inspection methods. Determining the reliability of CMC components is a complex process and requires an understanding of both manufacturing variability and damage effects that can occur throughout the life of the component. Consequently, a nondestructive inspection capability is required that can reliably evaluate CMC components during manufacturing, provide acceptance/rejection criteria for determining “fitness for use” and be useful for assessing operational damage effects. New nondestructive testing capabilities, Photon Induced Positron Annihilation (PIPA) and Distributed Source Positron Annihilation (DSPA), have demonstrated the potential ability to detect and quantify fabrication flaws and manufacturing quality for metallic, composite and ceramic components that are used to improve performance and power to weight ratios in high temperature turbine engine applications.