A microstretch description of electroelastic solids with application to plane waves

A continuum microstretch model is introduced for electroelastic media on the basis of a biaxial stretch deformation including microrotation. Strain measures, microinertia and electric multipoles are expressed in terms of angle and axis of microrotation and a couple of stretch variables. The linearization of balance laws allows us to state a differential system for seven field variables, as occurs in the simpler micropolar case. This approach is applied to the propagation of plane monochromatic waves adopting two geometric configurations, where an applied electric field is orthogonal to the wavenumber vector. The dispersion equations are obtained in both cases. In addition to the classical purely longitudinal or transverse waves, a set of coupled microstructural modes is found, which show the dependence on the microinertia, electric quadrupole and the orientational angle of the axis of microrotation. A numerical example is shown to discuss wave properties and their occurrence on finite or unbounded wavenumber ranges