Vibro-acoustic characteristics of eccentrically stiffened functionally graded material sandwich cylindrical shell under external mean fluid

Abstract

The main objective of this research work is focused on acoustic radiation analysis of functionally graded material (FGM) sandwich cylindrical shell structure reinforced by periodically eccentrically ring stiffeners. In the analysis, two common types of FGM sandwich cylindrical shell are considered, which include one with FGM face shell and homogeneous ceramic or metal core, and the other with FGM core and homogeneous face shell. Given the structure is immersed in a mean flowing fluid of velocity tangential to the accoustically deformed boundary and it is excited by a radial point force. The ring stiffeners are assumed to be identical and uniformly spaced, and the in-plane flexural and out-of-plane torsional motions of the ring stiffeners are employed to accurately describe the force moment coupling between the stiffeners and the shell. Fluid-structure coupling is considered by imposing velocity continuity condition at fluid-structure interfaces. By applying the Poisson summation formula and the Fourier transformation technique for periodic ring stiffeners FGM shell structures, the sound pressure level (SPL) about structural acoustic radiation performance index is expressed in a superposition form of space harmonics for a given wave number. The validity of the proposed theoretical model is verified by comparisons with previously published numerical results. Based on the developed theoretical mode, the influences of the FGM properties, gradient index, sandwich type, the size of ring stiffener, external mean flow and skin-core-skin ratios type on the structural acoustic radiation performance have been investigated. In addition, the results show that under the same skin-core-skin ratio and thickness, the acoustic radiation performances of type C seem better, and the larger the section size of ring stiffened, the greater the influence of structure acoustic radiation characteristics, whereas the magnitudes of the SPL curves increase with the increasing values of Mach number.