TECHNOLOGY AREA(S): Air Platform, Materials/Processes, Weapons ACQUISITION PROGRAM: NAE Chief Technology Office

OBJECTIVE: Develop and demonstrate a physics-based erosion model for gas-turbine grade ceramic matrix composites (CMCs).

DESCRIPTION: CMCs are currently being considered for use in hot-section hardware of advanced aero engines with goals of increased performance and efficiency. Concerns exist regarding the degradation of CMCs due to life- limiting phenomena associated with thermal, mechanical, chemical, and environmental effects. Of particular concern is erosion by small particles such as sand, dust, and other fine erosive objects ingested into hot-sections of engines. Since CMCs are brittle in nature and some sections of CMC components such as airfoils are in a thin configuration, erosion generates a varying degree of damage from localized micro-fracture to significant material removal, depending on the severity of erosion events. Consequently, erosion in CMC hardware can result in a reduction in load-carrying capacity, a premature component life, and a loss of related functions. Significant science and technology activities have modeled erosion behavior in metallic, polymeric, and coating materials systems [Refs 1-3]. However, despite its importance and demand, to date no pertinent model exists able to describe erosion phenomena of CMCs. Erosion in CMCs has shown to be very complex due to the random and violent nature of erosion events coupled with the materials� architectural and constituent complications [Refs 4,5]. As a consequence, an emerging need exists to develop an innovative physics-based erosion model for CMCs. The model, at a minimum, is to be able to predict the rate and shape of material removal with respect to type of materials for given erosion conditions. The approach is also expected to leverage overall experimental and fabrication efforts/iterations and to contribute to the improvement of the design of CMCs that are more durable and reliable against erosion. In general consideration, but not limited, target materials are gas-turbine grade CMCs, erosive particles are silica or ceramic-based and random in shape with varying sizes of 50-200 micrometers, and particle velocities are in a range of Mach 0.2 to 2.

PHASE I: Design and develop an initial erosion model concept and demonstrate feasibility for the CMC material systems. The Phase I effort will include prototype plans to be developed under Phase II.