Gradient Interphase, 3-D Fiber Architecture CMC's, Phase I

A clear need exists for the next generation of Ceramic Matrix Composites (CMC) for Thermal Protection Systems (TPS), propulsion hardware, and other high temperature applications. No "off-the-shelf" materials and/or processes capable of meeting NASA's goals are available, yet completely integrating a unique combination of commercially available or nearly commercially available technologies can meet NASA's goals. The basic elements of the proposed approach focus on refining 3-D fiber architectures, instituting semi-conductor industry controls on the CVI process, forming a gradient interphase between the matrix and fibers, and relying on molecular level modeling results to predict thermal stability. Both 3-D woven and 3-D braided preforms will be designed and manufactured to control the resultant pocket size and shapes to reduce voids during infiltration. Pulsed CVI with an improved out-gas control system will both form a gradient interphase that reduces the CTE mismatch induced internal loads between fiber and matrix and provide a more perfect microstructure while improving processing speed. CMC test articles will be compared to previous work on molecular level thermal modeling for Phase I. Phase II will deliver optimized design and manufacturing processes capable of making impact tolerant, long fatigue life, high temperature CMC's. More »