Browsing by Subject "Phononic crystals"

Now showing 1 - 6 of 6

Open Access
AVBVICVII ferroelectrics as novel materials for phononic crystals
(Taylor and Francis Inc., 2017) Palaz S.; Oltulu, O.; Mamedov, A. M.; Özbay, Ekmel
In the present work the acoustic band structure of a two-dimensional (2D) phononic crystal (PC) containing a semiconducting ferroelectric - AVBVICVII (A = Sb, Bi; B = S, Se, Te; C = I, Br, and Cl) was investigated theoretically and numerically by the plane-wave-expansion (PWE) method. Two-dimensional PC with square lattices composed of semiconducting ferroelectric cylindrical rods embedded in the organic/inorganic matrix is studied to find the existence of stop bands for the waves of certain energy. This phononic bandgap - forbidden frequency range - allows sound to be controlled in many useful ways in structures that can act as sonic filters, waveguides or resonant cavities. Phononic band diagram ω = ω(k) for a 2D PC was plotted versus the wavevector k along the Г-X-M-Г path in the square Brillouin zone (BZ). The band diagram shows four stop bands in the wide frequency range. The unusual properties of matrix and ferroelectric properties of AVBVICVII give us ability to control the wave propagation through the PC in over a wide frequency range. We study the 2D composites by solving the basic acoustic wave equation and use Bloch wave analysis to identify the band gaps.
Open Access
Band structures of metacomposite based phononic crystals in quasi-Sierpinski fractals
(Scientific Society of the Silicate Industry, 2021-05-29) Oltulu, Oral; Özer, Zafer; Mamedov, Amirullah M.; Özbay, Ekmel
In this paper, we investigated the bandgaps of two-dimensional phononic crystals with quasiSierpinski carpet unit cells in a metacomposite based solid–solid phononic crystal. Finite element method was used to analyze the properties of two-dimensional phononic bandgaps (2D PBGs) in a quasi-fractal structure. Two new types of quasi-Sierpinski fractal unit cells whose constituents are homogeneous and isotropic were proposed to obtain larger full bandgaps. The results show that the PBGs of the proposed quasi-Sierpinski fractals are suitable to tune the PBG’s without changing the size of the phonic crystal. The new quasi-Sierpinski fractals also retain the selfsimilarity as in the third-order Sierpinski fractal unit cell. The investigated quasi-fractals can be easily modified to increase the filling fraction of the constituents, which can be effectively used to enlarge existing PBG by preserving degree of self-similarity structure.
Open Access
Ferroelectric based fractal phononic crystals: wave propagation and band structure
(Taylor & Francis, 2020-04) Palaz, S.; Özer, Z.; Mamedov, Amirullah M.; Özbay, Ekmel
In this study, the band structure and transmission in multiferroic based Sierpinski carpet phononic crystal are investigated based on finite element simulation. In order to obtain the band structure of the phononic crystal (PnC), the Floquet periodicity conditions were applied to the sides of the unit cell. The square lattice PnC consists of various piezoelectric inclusion in a rubber matrix with square and circular cross section.
Open Access
Multiferroic based 2D phononic crystals: band structure and wave propagations
(Taylor & Francis, 2019-08) Palaz, S.; Özer, Z.; Ahundov, C.; Mamedov, Amirullah M.; Özbay, Ekmel
In the present work the acoustic band structure of a two-dimensional phononic crystal containing an organic ferroelectric (PVDF- polyvinylidene fluoride) and muliferroic material (LiVCuO4) were investigated by the plane-wave-expansion method. A two-dimensional PC with square lattices composed of LiVCuO4 cylindrical rods embedded in the PVDF matrix are studied to find the existence of stop bands for the waves of certain energy. This phononic bandgap – forbidden frequency range – allows sound to be controlled in many useful ways in structures that can act as sonic filters, waveguides or resonant cavities. Phononic band diagram ω = ω(k) for a 2D PC, in which non-dimensional frequencies ωa/2πc (c-velocity of wave) were plotted versus the wavevector k along the Γ-X-M-Γ path in the square Brillouin zone show four stop bands in the frequency range 0.01–8.0 kHz. The ferroelectric properties of PVDF and unusual properties of multiferroic LiVCuO4 give us the ability to control the wave propagation through the PC in over a wide frequency range.
Open Access
Topological insulator based locally resonant phononic crystals: wave propagation and acoustic band gaps
(Taylor and Francis Inc., 2016) Oltulu, O.; Simsek S.; Mamedov, A. M.; Özbay, Ekmel
ABSTRACT: In the present work the acoustic band structure of a two-dimensional phononic crystal (PC) containing an organic ferroelectric (PVDF- polyvinylidene fluoride) and topological insulator (Bi2Te3) were investigated by the plane-wave-expansion (PWE) method. Two-dimensional PC with square lattices composed of Bi2Te3 cylindrical rods embedded in the PVDF matrix are studied to find the existence of stop bands for the waves of certain energy. Phononic band diagram ω = ω(k) for a 2D PC along the Г-X-M-Г path in the square Brillouin zone show four stop bands in the frequency range 0.01–8.0 kHz.
Open Access
Two-dimensional phononic band structure of archimedean-logarithmic spiral-based slabs
(Taylor & Francis, 2019) Palaz, S.; Oltulu, O.; Mamedov, Amirullah M.; Özbay, Ekmel
We present band structure results for elastic waves in periodic composite materials consisting of a spiral scatterer shape embedded in a uniform silicon matrix. The material of the scatterer is tungsten as a high density material. The phononic band structure of two-dimensional solid phononic crystal is studied numerically by finite element method to obtain dispersion relations. We find full band gaps at relatively low frequencies for a low filling ratio. Due to spatial inhomogeneity, the unique structural characteristics of the spiral structure lead to localized modes. Hence, the proposed model geometry introduces a phononic crystal to cover a wide range of stopbands starting from low frequencies. The results could give a possibility to design effective filters for the low frequency range.