Abstract
Structural health monitoring refers to the interdisciplinary engineering field whose objective is to monitor and evaluate the integrity of mechanical structures. Often times, structural health monitoring diagnostics utilize piezoelectric (lead zirconate titanate) transducers bonded to the surface of the structure monitored. Nonetheless, unexpected variations in the mechanical properties of the adhesive film could affect the dynamic behavior of the system and potentially mischaracterize the fitness for service of a structure. In this article, we presented an analytical model to describe the dynamic coupling between the structure and the lead zirconate titanate transducer that includes the adhesive layer. An electromechanical impedance–based method capable of assessing the integrity of the adhesive bondline was developed based on the proposed analytical model. Our study found that the phase angle of the transducer’s electrical admittance was correlated to the mechanical impedance of the adhesive film following a power law behavior. Validation of the proposed model was carried out both by testing transducers bonded to aluminum plates and through a numerical parametric study. In the future, the method proposed could be used to detect preexisting defects in the adhesive bondline, to estimate the adhesive’s thickness at manufacturing, and to monitor the degradation of the adhesive material during the life of the system.
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