Ceramic Matrix Composite Vane Subelement Fabrication

Abstract

Vane subelements were fabricated from a silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) composite and were coated with an environmental barrier coating (EBC). In order to address realistic critical design features of a turbine airfoil, the vane subelement cross section was derived from an existing production aircraft engine vane. A new fabrication technique has been developed at NASA Glenn Research Center that enables ceramic composite vanes to be constructed using stoichiometric SiC fiber in the form of a two dimensional cloth. A unique woven cloth configuration was used to provide a sharp trailing edge with continuous fiber reinforcement. Fabrication of vanes with a sharp trailing edge was considered to be one of the more challenging features for fabricating a ceramic composite vane. The vanes were densified through the chemical vapor infiltration/slurry cast/silicon melt-infiltration process. Both NDE inspection and metallographic examinations revealed that the final as-fabricated composite quality of the vanes was consistent with that typically obtained for the same composite material fabricated into flat panels. Two vane configurations were fabricated. One consisted of a thin wall (1.5 mm) shell with a continuously reinforced sharp trailing edge. The second vane configuration included a reinforcing web bridging the pressure and suction-side vane walls and the same reinforced sharp trailing edge. This paper will discuss the vane fabrication and characterization efforts.