What are ceramic matrix composites (CMCs) and how are they applied in aerospace?

CMCs combine ceramic fibers with ceramic matrix for high-temperature structural capability. Materials: Silicon carbide/silicon carbide (SiC/SiC) - Most common for aerospace; Carbon/carbon (C/C) - Highest temperature but oxidation-limited; Oxide/oxide - Lower temperature, better oxidation. Properties: Temperature capability to 1300-1500C (vs 1100C for superalloys), 1/3 density of nickel superalloys, and Good specific strength at temperature. Processing: Chemical vapor infiltration (CVI), Melt infiltration, and Polymer infiltration and pyrolysis. Applications: Turbine shrouds (GE LEAP - first production), Combustor liners, Turbine vanes (under development), and Exhaust components. Challenges: Brittle matrix (requires environmental barrier coating - EBC), High cost (~$1000/lb vs $20/lb superalloy), Manufacturing variability, Joining and attachment design, and Limited design database. Benefits: Enable higher turbine temperatures (efficiency gains), Reduce or eliminate cooling air requirements, and Weight reduction in hot section. CMCs are enabling technology for next-generation engines with 10+ years development required.