Adhesive bond degradation sensor

Alan R. Wilson; Christina Olsson-Jacques; Richard F. Muscat

doi:10.1117/12.469047

13 November 2002 Adhesive bond degradation sensor

Alan R. Wilson, Christina Olsson-Jacques, Richard F. Muscat

Proceedings Volume 4934, Smart Materials II; (2002) https://doi.org/10.1117/12.469047
Event: SPIE's International Symposium on Smart Materials, Nano-, and Micro- Smart Systems, 2002, Melbourne, Australia

Abstract

Early detection of adhesive bond degradation using sensing elements embedded within the 100um bond-line of aluminium epoxy adhesive joints has been demonstrated. Sensing elements of varying heights were fabricated at the ends of narrow conductors on a flexi-circuit carrier. This construction simulates the active sensing region on a patented silicon adhesive bond degradation sensor and has been used to characterize the sensing elements without the expense and time associated with fabricating the complete integrated silicon sensor. The highest elements on the flexi-circuit serve both as electrical pickup studs, providing a circuit from the flexi-circuit to the top aluminium plate, and as spacers to ensure that the shorter sensing elements do not contact the aluminium plate. The non-contacting sensing elements are thus arranged to be close to the metal/adhesive interface and are sensitive to any change in conductivity in this region due to release of ions as the interface is degraded by the environment. Accelerated aging tests were performed on flexi-circuit sensors embedded in the bond-line of double cantilever beam specimens. The specimens were immersed in 50° C water and pre-loaded to just initiate a crack. Load on the specimen was then maintained by applying a constant load point displacement with a very low velocity to ensure that the environment would degrade the bond-line in advance of the crack front. The change of load and the conductivity measured by the sensing elements were then logged with time. The onset of bond degradation was detected approximately 10-20 mm ahead of the crack tip.

Citation Download Citation

Alan R. Wilson, Christina Olsson-Jacques, and Richard F. Muscat "Adhesive bond degradation sensor", Proc. SPIE 4934, Smart Materials II, (13 November 2002); https://doi.org/10.1117/12.469047

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