Durable high temperature materials are required for hypersonic engine and structural thermal protection systems. In particular, 2700ºF or greater capable structural materials that can survive stresses on the order of 10 ksi (70 MPa) for at least 100 hours in an oxidizing environment have been identified as an enabling material for future hypersonic vehicles with a long term desired target of 3000ºF. As these applications are structural, a strong degree of damage tolerance is desired, and thus ceramic matrix composites are the primary choice due to the desire for reduced weight, high temperature strength and oxidation resistance. Silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC) composites are believed to be the most suitable solution due to meeting the requirements with the exception of creep at the highest temperatures/loads. The proposed effort will modify the SiC fiber preform by the addition of a fraction of more creep resistant carbon fibers. The Phase I will encompass engineering the appropriate level of hybridization in a C-SiC/SiC composite, producing and evaluating the ceramic composite material for hypersonic vehicle applications, including stress rupture at temperatures of 2700ºF or greater.