Electromechanical hybrid metamaterial for the control of ultrasonic guided waves

Abstract

Last years, a growing number of research has been devoted to the control of the behavior of Phononic crystals and Metamaterials through for instance tunability of the frequency position and/or width of a band gap. This can be achieved by using active materials such as piezoelectric materials. Here, a new class of hybrid metamaterials (HMMs) is proposed to tune the dispersion of guided Lamb waves. The studied HMM is made of a single homogeneous piezoelectric plate on which metallic electrodes are laid on. These electrodes are very thin in comparison to the plate thickness and allow changing locally the electric boundary conditions (EBCs). It is shown, experimentally and theoretically, that by simply modifying the EBCs, coupling between some modes can be induced, leading to the opening of a gap at the edge or within the first Brillouin zone. Moreover, a hybridization gap is observed for the first symmetrical Lamb modes, involving the electrical resonance associated to an inductive electrical circuit connected on electrodes. Such a system opens important perspectives for the development of SAW devices for radiofrequency applications.