Complex-Shaped SiC/SiC Ceramic Matrix Composites via Novel, Non-Woven Preforming, Phase II

The use of ceramic matrix composites (CMCs) has the potential to increase the life and operating envelope of turbine engines. While great strides have been made in mechanical properties, CMCs still suffer from limitations in terms of shape capability, especially with complex-shaped parts such as turbine blades. Using high-strength fibers that have been woven into a fabric causes problems due to the nature of the fabric. The issues of greatest concern with regard to the preform are joining structures perpendicularly to other structures, poor interlaminar shear strength, and creating features with small characteristic dimensions such as wall thickness and radius of curvature. In Phase I, Ultramet demonstrated the fabrication of complex-shaped silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC) CMCs using a novel, non-woven preforming technique. This technique allowed the fabrication of a near-net-shape turbine blade containing thin walls, thin internal ribs, small radii of curvature, and small features, and the blade was bonded to a perpendicular support structure. Testing showed the material to have isotropic properties, and a shear strength of 8 ksi was measured. Phase II will focus on improving the tensile strength of the composite and the toughening effect of the reinforcing phase.