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 intrusive characterization of advanced materials (such as ceramics and composites) and structures (such as components for Space Shuttle main engine, high-speed civil transport, and general aviation aircraft) in hostile, high-temperature environments, and for validation of design codes. This paper presents two advanced thin-film sensor technologies: strain gauges and thermocouples. These sensors are sputter deposited directly onto the test articles and are only a few micrometers thick; the surface of the test article is not structurally altered and there is minimal disturbance of the gas flow over the surface. The strain gauges are palladium-13% chromium based and the thermocouples are platinum-13% rhodium versus platinum. The fabrication techniques of these thin-film sensors in a class 1000 cleanroom at the NASA Lewis Research Center are described. Their demonstration on a variety of engine materials, including superalloys, ceramics, and advanced ceramic matrix composites, in several hostile, high-temperature test environments is discussed. (C) 1998 Elsevier Science S.A.