Advanced Process Schemes for Improvement of the Dimensional Stability of Ceramic Matrix Composites

Ceramic matrix composites (CMC) are being developed for turbine engine exhaust structures on the Joint Strike Fighter (JSF) and other advanced military platforms. One of the primary candidate material systems for manufacturing components in the exhaust structure is a polymer-derived matrix composite that uses a silicon carbide based fiber reinforcement. These CMC components can be complex shapes that require very precise dimensional tolerances. Deviations from as-molded and machined dimensions resulting from thermal excursions during processing can result in rejected parts. The aim of this program is to further develop and implement a modified processing scheme that will eliminate this particular problem. In order to achieve this goal, this program will focus on the thermal conditioning of the fiber reinforcement. Precise control of the thermal history of the reinforcement will result in improved dimensional stability. As a provider of interface coatings used in this type of ceramic composite, we will also investigate the effects of this thermal conditioning on the interface coating. The inclusion of this optimized process step is expected to both reduce the manufacturing cost (as a result of higher yield) and improve the lifetime of CMC components