Low-Cost, Polymer-Derived Interface Coatings for CMC Applications

The need for low density, high temperature materials in space has driven evaluation and implementation of carbon-carbon, ceramics and ceramic matrix composites (CMC) for structural applications. The thermal, mechanical, and chemical properties of ceramic matrix composites make them attractive both for next generation and retrofit applications. CMC?s require a fiber matrix interface coating to impart toughness, but the high cost of current interface coatings ? from 30 to 70% of the cost of a CMC part - has severely limited overall adoption of CMC?s. Low cost oxidation resistant coatings are the third leg of the CMC material triad (fiber-interface-matrix) needed to realize full commercial potential. Starfire polymer based coatings can reduce interface coating costs by 95%. In Phase I, these coatings exhibited desirable interface properties (thin, uniform, debonding). The phase II effort will optimize these interface coatings such that they will protect the fiber from oxidation and support an oxygen sealing feature against both matrix micro-cracking and impact damage. The interface coatings will be validated for hypersonic, rocket, and turbine engine applications.