Economical Fabrication of Thick-Section Ceramic Matrix Composites, Phase II

No timely and cost-effective methods now exist for fabrication of thick-section (>=2), continuous fiber-reinforced ceramic matrix composites (CMCs). Application of such CMCs can enhance the efficiency and performance, reduce the weight, improve the durability, and lower the cost of aerospace propulsion systems, particularly those used in high temperature, high-stress environments. Achieving these benefits requires development of matrix infiltration techniques capable of efficiently producing thick parts. The quality of such parts will also depend on implementation of improved fiber/matrix interfaces and interface deposition techniques. Carbon fibers are of particular interest as CMC reinforcements because they are relatively inexpensive, have higher strength and stiffness and lower density than oxide or non-oxide ceramic fibers, and retain their mechanical properties at very high temperatures. The main drawback of carbon fibers is their low oxidation resistance, which has prevented their extensive use in high temperature oxidizing environments. Oxide interfaces can potentially impart sufficient protection, as well as provide other essential interface functions related to load transfer between fibers. In Phase I, Ultramet demonstrated a unique and innovative process for depositing oxide interfaces, specifically ultraviolet-enhanced chemical vapor deposition (UVCVD), throughout thick fiber preforms. Ultramet also successfully achieved rapid infiltration of carbide matrices into thick-section (1) fiber preforms, up to 98% dense, using an innovative melt infiltration process and obtained initial mechanical properties and oxidation performance of the resultant composites. In Phase II, Ultramet will optimize material selection and processing parameters to produce low-porosity carbon/silicon carbide (C/SiC) thick-section CMCs having optimal strength, stiffness, and oxidation performance, and scale up the processing to fabricate components up to 14 diameter x 2.5 thick.