Propagação de ondas mecânicas em quasicristais fonônicos unidimensionais segundo a sequência de fibonacci com espelhamentos simétrico e antissimétrico

Abstract

The goal of this work is to investigate the changes resulting from the modifications in the arrangement of the one-dimensional phononic crystals where the constituent materials are spatially organized according to the symmetric and anti-symmetric mirrored quasiperiodic Fibonacci sequences. In this work, we study phononic quasicrystals composed of two different materials, lead and epoxy, surrounded by two semi-infinite layers composed of a third material, aluminum. These crystals have properties that can be adjusted according to the stacking of their components, and can give rise to the acoustic bandgaps. Because of this, phononics are currently a highly attractive research field and have several applications, mainly in sensors, filters, acoustic insulators, among other areas. By applying continuity conditions at the interfaces, the transmission spectra of the incident sound wave were calculated numerically by employing the transfer-matrix method. We studied the effects of the incidence angle and the spatial arrangement of the structure. Our results show that the propagation of longitudinal (or p) and transversal (or s) acustic waves are almost similar because the wave speed for longitudinal mode is only about half the wave speed of the transversal one. Besides, some effects are obtained by varying the incidence angle and the quasiperiodicity, which has origin on the long-range correlations of the arrangements symmetric and antisymmetric of the mirrored Fibonacci sequence. It is possible to observe some aspects that highlight the potential for technological applications demonstrated by the structure, such as the presence of wide phononic bandgaps, for application in ultra-wide bandgap systems, and transmission multi-peaks in bandgap regions without the need to introduce defects.