Interface coatings for fiber-reinforced composites are an enabling technology for high temperature ceramic matrix composites. Because of their availability and relative cost, graphite fibers are preferred for many structural composite of interest for space propulsion applications. However, high temperature stable silicon carbide fibers are also of interest, even though they are higher cost. Recent work at Synterials, has suggested that a thin layer of carbon at the surface of the fiber is key to preventing corrosion of the fiber and subsequent fiber strength reduction on graphite fibers. The proposed work will evaluate three interface coatings one three graphite fibers and one silicon carbide fiber. The coating are: B4C, Si-doped BN/Si3N4 and HfC. The coatings will be evaluated by preparing mini-composites via a polymer plus CVI processing route.