Effects of Defects in Ceramic Matrix Composites (CMCs)

N06-030 Effect in Defects in Ceramic Matrix Composites (CMCs) The performance of the advanced strike fighters can be im-proved by reducing the weight of the propulsion system. The jet engines of interest are Pratt & Whitney’s F135 engine or General Electric’s F136 engine. Both engines use a common exhaust sys-tem produced by P&W. One attractive approach to reducing the weight of the jet propulsion systems is to replace high density metal nozzle components with ceramic matrix composites, specifi-cally S200 CMCs. To fully implement S200 CMC components for engine applica-tions 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 specifically, to correlate in-process, non-destructive evaluation data with S200 CMC component thermostructural performance. COI Ceramics and Pratt& Whitney have demonstrated with significant success 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. The proposed research will study existing NDE data and the appropriate representative S200 CMC material samples and NDE data, sub-scale test components and test types, and to demon-strate through mathematical composite materials analysis the ability to predict degraded CMC thermoelastic constants and re-sidual material strengths for the most typical defects. Then use those properties locally in finite element modeling thus incor-porating the NDE data into the structural models to predict the CMC component thermostructural response under required loads. Semi-automated production tools which include a graphical user interface to incorporate the selected defects into the CMC com-ponent geometry and automatically generate thermostructural analysis models. The tools will enable engineers and technicians to quickly evaluate effect of defects in CMC components.