Effects of Defects in Ceramic Composites

Joint Strike Fighter (JSF) and other military platforms are considering ceramic matrix composites (CMCs) for engine applications due to their potential for weight reduction and high temperature capability. The highly heterogeneous nature of fiber reinforced composites and their inherent porous structures can mask defect detection by traditional non-destructive evaluation (NDE) techniques. In order to efficiently fabricate, evaluate, predict life, and evaluate cost of these materials, improvements in material understanding are required, specifically in the area of effects of defects. Methods are required that can identify and evaluate the effects of various defects in CMCs. For this proposed program, Fiber Materials, Inc. (FMI) will demonstrate the effectiveness of an NDE method to identify performance critical flaws on silicon carbide reinforced silicon carbide (SiC/SiC) composites. A phased development plan will be used for developing the NDE method, with results confirmed by testing and fabricating an airfoil component under representative conditions. A successful program will provide technology benefits resulting from improved performance, manufacturability and reliability of CMC components.BENEFITS: Potential applications of the technologies developed in this proposed effort include military and commercial advanced gas turbine engine components, such as the Joint Strike Fighter (JSF). Advancements made in SiC/SiC materials component fabrication will extend FMI’s efforts involving C/SiC application to missile DACS thrusters, nozzles/pintles and related components. The materials and manufacturing methods developed in this and subsequent efforts will be the precursor to development of non-eroding or reusable structural materials (i.e., hot structures). Long range hypersonic missiles will benefit immeasurably from the development of non-eroding structural materials. These types of vehicles need to perform high-g maneuvers combined with a long glide, requiring a high temperature material whose structural properties will not degrade over trajectories lasting approximately several minutes.