Understanding the Durability of SiC Based Ceramic Matrix Composites (CMCs) for Gas Turbine Engine Hot Section Components

Silicon carbide fiber reinforced silicon carbide ceramic matrix composites (SiCf/SiC-CMCs) are being used in the fabrication of gas turbine engine hot section components due to their light weight and excellent thermal and chemical stabilities at high-temperature. These superior properties enable significant enhancements in engine efficiency and reduced fuel burn, emissions, and cooling requirements. In support of NASA’s Aeronautics Mission under various programs at Glenn Research Center, different types of composites have been developed and assessed for a high temperature (2700 °F) SiCf/SiC CMC system for turbine engine applications. These composites have creep-resistant SiC fibers, advanced 3D weaves, 2700 °F-capable hybrid SiC matrices, and durable environmental barrier coatings (EBCs). These efforts have resulted in improvements in the overall CMC thermomechanical and environmental durability. In order to study the role of different constituents and processing variables, a single fiber tow CVI (chemical vapor infiltration) SiC/SiC mini-composite can be considered the basic architectural feature of woven and laminate SiC/SiC CMCs. Moreover, the mini-composite mechanical and tensile creep damage behavior represents the creep behavior of 0° fiber tows in the axial loading direction of a macro-composite or component. In addition, a large number of mini-composite samples can be fabricated at relatively low cost within a short time, which makes them attractive for obtaining a robust set of experimental data and studying constituent behavior. In this presentation, the mini-composite approach to study damage mechanisms that limit CMC life in extreme environments including exposure to steam will be presented. The effects of constituent type and volume fraction on the CMC durability, which will help influence CMC design, will be discussed.