Wave propagation in water-immersed adhesive structure with the substrates of finite thickness

In previous theoretical studies on the adhesive structure, the substrate is mostly considered as a semi-infinite solid space and corresponding theoretical derivation is rarely related to the thickness of the substrate. In the paper, based on the transfer matrix method, we studied in the water-immersed trilaminar plate-like adhesive structure with the substrates of finite thickness and the perfect/sliding interfaces in the case of plane longitudinal wave incidence and deduced the expressions of reflection and transmission coefficients of longitudinal waves. In order to verify the accuracy and applicability of the deduced formula, this formula was firstly applied to the water-immersed steel–epoxy resin–steel adhesive structure with perfect interfaces and the calculated result was compared with the existing data. Taking the water-immersed aluminum–epoxy resin–aluminum adhesive structure with perfect/sliding interfaces as an example, the impacts of incident angle and frequency on the reflection and transmission characteristics of the longitudinal wave were then analyzed. Finally, the theoretical method was experimentally verified and the experimental results were well consistent with the numerical calculation results. The reflection and transmission coefficient curves of longitudinal wave showed the obvious resonance when the longitudinal wave was normally incident. Regardless of the substrate thickness, the frequency of acoustic waves or the incident angle, it can only confirm whether a sliding interface exists, but the interface to slide cannot be determined.