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Improving the Reliability of Sensor Skins for Structural Health Monitoring

I. MOHAMMAD, H. HUANG

Abstract


Fatigue cracking is one of the most common failure modes in load carrying structures. Detecting small fatigue cracks requires densely distributed sensors over a large area. By implementing multiple sensors on a flexible substrate, an engineered sensor skin that can detect small crack over a large area may be realized. Recently, we presented the implementation of such a sensor skin based on microstrip patch antenna and demonstrated that it can detect sub-millimeter crack growth. However, due to the fatigue loading, the sensor skin showed signs of either tearing or debonding from the host structure. This can cause significant reliability issues and might also cause misrepresentation of the crack in practical applications. In this paper, we investigate the inclusion of an additional flexible layer between the host structure and the sensor skin to relieve the strain transfer from the specimen to the sensors and thus improved the reliability of the sensor. Finite element simulation indicated that a 70 μm thick PDMS layer can reduce the strain transfer by up to 40%. The improvement in the reliability of the sensor was validated experimentally. The fabrication of the PDMS layer and its effect on the resonant parameters of the antenna sensor are discussed.

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