A combined thin film/thick film approach to realize an aluminum-based strain gauge sensor for integration in aluminum castings

There is currently a large demand for aluminum components to measure the mechanical and thermal loads to which they are subjected. With structural health monitoring, components in planes, vehicles, or bridges can monitor critical loads and potentially prevent an impending fatigue failure. Externally attached sensors need a structural model to obtain knowledge of the mechanical load at the point of interest, whereas embedded sensors can be used for direct measurement at the point of interest. To produce an embedded sensor, which is automatically encapsulated against environmental influence, the sensor must be able to withstand the boundary conditions of the host component's manufacturing process. This embedding process is particularly demanding in the case of casting. Previous work showed that silicon-based sensors have a high failure rate when embedded in cast aluminum parts and that using aluminum as a substrate is preferable under these circumstances. In the present paper, we present the fabrication process for the combination of a thick-film insulation and a thin-film strain gauge sensor, on such an aluminum substrate. The sensor is capable of withstanding high temperatures of at least 600 °C for over 20 min and a subsequent embedding in a gravity die casting process.