Electroelastic gap waves between dissimilar piezoelectric materials in different classes of symmetry

Shear surface waves guided by a gap between dissimilar piezoelectric half-spaces that belong to different classes of material symmetry are systematically investigated. It is shown that at most two surface waves can be guided by the structure. Equations for calculating surface wave velocities of propagation and corresponding existence conditions are obtained in closed form. For some special cases, surface wave velocities are derived explicitly. It is shown that despite the presence of a characteristic length in the problem (that is, the gap width) a non-dispersive surface wave independent of the wavelength and gap width can be guided by the structure. Electroelastic wave components and existence conditions of this non-dispersive wave are obtained. It is demonstrated that both the gap width and the dielectric permittivity of the gap have significant influences on the dynamic behaviour of the structure so that even small gaps cannot always be simplified and modelled as permeable, impermeable or absorbent with infinitesimal width.