Effects of Defects in Ceramic Composites (CMCs)

N06-030 Effect in Defects in Ceramic Composites. The performance of the Joint Strike Fighter can be improved by reducing the weight of the propulsion system. The JSF is powered by either Pratt & Whitney’s F135 engine or General Elec-tric’s F136 engine. Both engines use a common exhaust system produced by P&W. One attractive approach to reducing the weight of the JSF propulsion system is to replace high density metal nozzle components with ceramic matrix composites. To fully implement S200 CMC components for engine ap-plications several technical hurdles need to be achieved. Some of those hurdles are at the materials science level others purely at the manufacturing and process control level. The focus of this effort is at the manufacturing level. It is specifi-cally, to correlate in-process, non-destructive evaluation data with S200 CMC component thermostructural performance. COI Ceram-ics and Pratt& Whitney have demonstrated with significant suc-cess that they can dimensionally locate and estimate the size and type of defect using various NDE methods. Some of those NDE methods investigated for S200 CMCs in the referenced work have included, air scan and water-coupled ultrasonics, front flash thermography, microwave, real-time ultrasonic camera. Non-destructive evaluation of manufactured parts will be important in reducing manufacturing time and cost while produc-ing the best end item parts. COI Ceramics Inc., Pratt & Whitney Inc. and the U.S. Air Force Research Laboratory have done sev-eral studies of various NDE methods for in-process inspection of S200 CMC flaps and seals for the JSF common exhaust nozzle. MR&D’s objective in the proposed research will be to exe-cute a Phase I program to study existing data and to develop the appropriate representative S200 CMC material samples and NDE data (with the most likely defects and with out defects), test samples and test types, and to demonstrate through mathematical composite materials analysis the ability to predict degraded CMC thermoelastic constants and residual material strengths for the most typical defects. Then use those properties locally in fi-nite element modeling thus incorporating the NDE data into the structural models to predict the CMC component thermostructural response under required loads.