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 as a result of thermal excursions during processing can result in rejected parts. The aim of this program is to develop a modified processing scheme that will eliminate this particular problem. In order to achieve this goal, we will focus on the 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 applying the interface coating before and after conditioning of the fiber reinforcement. The addition of this conditioning process step is expected to both reduce costs (as a result of higher yield) and improve the lifetime of the part.