Using ultrasonic SH waves to estimate the quality of adhesive bonds in plate structures

A method using SH waves to estimate the quality of an adhesive layer in a bonded plate is presented in this paper. A mathematical analysis of SH‐wave motions in a bonded plate consistent with the experimental arrangement was carried out in full. We have found that the cutoff frequency of the second mode waves in the plate is dependent upon the thickness and the mechanical properties of the adhesive layer, and the waves in the plate resonate at this frequency. This wave resonating phenomenon was used in the experimental determination of the property of the adhesive layer. An experimental verification of the method was carried out using adhesives of several different properties. We have demonstrated that the resonant frequency of the second mode wave in the plate is dependent upon the moduli and thickness ratio between the adhesive layer and plate as predicted by the analysis.