The angular and frequency characteristics of reflectivity from a solid layer embedded between two solids with imperfect boundary conditions

In this paper, a comprehensive model of an isotropic, homogeneous, solid layer embedded in between two half-space solids with imperfect interfacial conditions is presented. The Thomson’s matrix technique for transfer of boundary conditions across a thin layer, based on recurrence formulas, coupled with separate normal and tangential rigidity representation for each interface was used. The reflection and transmission coefficients for oblique incidence of both longitudinal as well as transverse waves as a function of angle of incidence, incident frequency, interface condition, and material properties can be numerically computed through this model. Several studies of the reflection factors for a three-medium case is used to provide insight on the adhesively bonded structures. The ultrasonic quality evaluation of the commonly used aluminum–epoxy-resin–aluminum bond situation is dealt with here in detail.