THIN-FILM THERMOCOUPLES AND STRAIN-GAUGE TECHNOLOGIES FOR ENGINE APPLICATIONS

Advanced thin-film sensor techniques that can provide accurate surface strain and temperature measurements are being developed at NASA Lewis Research Center. These sensors are needed to provide minimally intrus ive characterization of advanced materials (such as ceramics and compo sites) and structures (such as components for Space Shuttle main engin e, high-speed civil transport, and general aviation aircraft) in hosti le, high-temperature environments, and for validation of design codes. This paper presents two advanced thin-film sensor technologies: strai n gauges and thermocouples. These sensors are sputter deposited direct ly onto the test articles and are only a few micrometers thick; the su rface of the test article is not structurally altered and there is min imal disturbance of the gas flow over the surface. The strain gauges a re palladium-13% chromium based and the thermocouples are platinum-13% rhodium versus platinum. The fabrication techniques of these thin-fil m sensors in a class 1000 cleanroom at the NASA Lewis Research Center are described. Their demonstration on a variety of engine materials, i ncluding superalloys, ceramics, and advanced ceramic matrix composites , in several hostile, high-temperature test environments is discussed. (C) 1998 Elsevier Science S.A.