Multilayer Fiber Interfaces for Improved Environmental Resistance and Slip

Application of ceramic matrix composites (CMC) reinforced with carbon fibers can potentially enhance the efficiency and performance, reduce the weight, improve the durability, and lower the cost of rocket engine combustion devices and turbomachinery components used in high temperature, high-stress environments. Meeting these objectives requires improvements in fiber-reinforced CMC materials and fabrication processes, particularly improved fiber/matrix interfaces, interface deposition processes, and oxidation protection. Although carbon fibers are most desirable as CMC reinforcements, their low oxidation resistance has prevented their use in high temperature oxidizing environments. In previous work, Ultramet developed a unique and innovative process, ultraviolet-enhanced chemical vapor deposition (UVCVD), which allows deposition of dense, strain-tolerant oxides at room temperature, thus avoiding heat-induced material degradation and providing excellent material performance, including enhanced oxidation protection. However, identifying a single phase that best performs the two key functions of the interface coating, oxidation protection and interface slip, simultaneously has thus far proven elusive. In this project, the UVCVD process will be developed specifically for deposition of multilayered interface coatings in which separate components will perform these two functions, resulting in optimum composite performance.