Physics-based Life Prediction Model Incorporating Environmental Effects for SiC/SiC Ceramic Matrix Composites

Continuous fiber-reinforced SiC/SiC ceramics matrix composite (CMC) material is being considered in an advanced gas turbine engine intended for an aircraft or an industrial power generation system, for high temperature capability, possibly with added protection from environmental or thermal barrier coating. CMC engine parts in military/commercial vehicles allow engines to operate at higher temperatures than what a typical superalloy with or without a barrier coating can withstand, and it also significantly reduce engine weight. A successful insertion of CMC’s, particularly in Air Force’s aircraft engines, will also need to sustain aggressive corrosive environment due to “salt” attack on top of considerable damage caused by oxygen and moisture in the combustor fuel. Multidisciplinary physics-based analytical modeling proposed here deals with microstructural damages occurring due to environmental effects, such as, oxidation, recession etc., and it could be an important tool for designing and continually monitoring the health of these critical components in service. Demonstration of such a life prediction tool, which will correlate actual thermochemical and micromechanical damage processes with mechanical response, will shorten the mechanical design and analysis process of CMC components, thereby lowering cost and leading to higher reliability. These benefits will also be relevant for other NASA, DOE and DOD supported CMC application programs for power generation industries where higher temperature and lesser quality fuel will cause these damages to become more severe. BENEFIT: The application of CMC engine parts in military war fighters allows engines to operate in higher temperatures and will reduce the engine weight significantly. Analytical modeling strategy in CMC gas turbine engine design and application is an important complement to test investigation, which reduces test costs and shortens the design-to-production cycle of CMC engines. The proposed development of the micromechanical modeling technique and structural analytical tool will enable its transition to JSF and other military aircraft propulsion systems. Future use may involve hypersonic aircraft and the J-UCAS propulsion systems for weight reduction and enhanced life expectancy. Ceramic matrix composites also leverage large economic and social benefits in commercial application. Catalytic converters alone in the power generation industry enable a $38 billion pollution control business each year and have reduced air pollution by 1.5 billion tons since 1975. Demonstration of commercially available GENOA software, that can successfully predict the composite thermo-chemically-oxidization behavior, will provide the military, the aerospace industry and power generation plants with a verified analytic/design tool. Successful demonstration/verification of a life prediction analytical methodology for engine composites under service environment would reduce future certification costs of an advanced engine structure fabricated with CMC material database for future engine components.