Abstract This paper applies acoustic analysis of Sound Transmission Loss (STL) through infinite Functionally Graded (FG) thick plate employing Hyperbolic Shear Deformation Theory (HSDT). The procedure for applying a FG plate is followed by considering the material properties are changed continually based on power-law distribution of the materials in terms of volume fraction. The main benefit of HSDT can be justified knowing the fact that, it uses parabolic transverse shear strain across thickness direction. Therefore, no need to enter the extra effect of shear correction coefficient factor. Besides, the displacement field is extended as a combination of polynomial as well as hyperbolic tangent function by neglecting the effect of thickness stretching. Furthermore, the equations of motion are obtained employing Hamilton’s Principle. To provide an analytical solution based on HSDT, equations of motion are combined with acoustic wave equations. Moreover, some comparisons are made with the known theoretical and experimental results available in literature to verify the accuracy and efficiency of the current formulation. These comparisons reveal an excellent agreement. Consequently, some configurations are presented to demonstrate which parameters appear to be effective to improve the behavior of STL including the effects of modulus of elasticity and density in the thickness direction with respect to various power-law distributions.

Abstract The main aim of this paper is to employ an extension of two-variable Refined Plate Theory (RPT2) to determine Sound Transmission Loss (STL) across laminated composite plate in contrast to external excitation. It should be noted that RPT2 known as a second type of Refined Plate Theory which includes the extension term in displacement field. To achieve this goal, firstly, the lateral displacements are expanded by considering three parts, including shear, bending and extension term to provide an analytical model based on two-variable Refined Plate Theory without considering the effect of the shear correction coefficient in governing equations. Secondly, vibro-acoustic analysis is administered by incorporating the laminated composite plate equation beside the acoustic wave equation, simultaneously. Consequently, the power transmission through the structure is specified due to a plane sound wave. Beside, in order to illustrate the accuracy of the present formulation (RPT2), the obtained STL is compared with those available in literature. However, the application of present study (RPT2) is clarified in the acoustical designs due to presenting more precise results in comparison with Classical Plate Theory. Eventually, the numerical results are achieved to determine the influences of various properties on STL.

A study on the acoustic behavior of double-walled panels, with sandwiched layer of porous materials is presented within Classical Laminated Plate Theory (CLPT) for laminated composite panels. For this purpose, equations of wave propagation are firstly extracted based on Biot's theory for porous materials, then the transmission loss (TL) of the structure is estimated in a broadband frequency. Secondly, TL coefficient of the structure is determined using Statistical Energy Analysis (SEA). In the next step, accuracy of the solution is shown with comparing the data obtained from these two presented models as well as the experimental results available in literature. Finally, the effects of parameters on sound transmission loss of double porous composite panels, especially at a high frequency range, are discussed. In addition, the results show that maximum sound energy is transferred through the waves frame (structure born) due to the porous layer bonded between the two composite panels. Therefore, material parameters that are principally related to solid phase of the foam such as Poisson's ratio, bulk density and bulk Young's modulus, have the most significant effects on the transmission loss. Meanwhile, the impacts of composite material panels and composite plies arrangement on sound transmission loss structures have been addressed in this paper.

This paper presents effects of boundary conditions and axial loading on frequency characteristics of rotating laminated conical shells with meridional and circumferential stiffeners, i.e., stringers and rings, using Generalized Differential Quadrature Method (GDQM). Hamilton's principle is applied when the stiffeners are treated as discrete elements. The conical shells are stiffened at uniform intervals and it is assumed that the stiffeners have similar material and geometric properties. Equations of motion as well as equations of the boundary condition are transformed into a set of algebraic equations by applying the GDQM. Obtained results discuss the effects of parameters such as rotating velocities, depth to width ratios of the stiffeners, number of stiffeners, cone angles, and boundary conditions on natural frequency of the shell. The results will then be compared with those of other published works particularly with a non-stiffened conical shell and a special case where angle of the stiffened conical shell approaches zero, i.e. a stiffened cylindrical shell. In addition, another comparison is made with present FE method for a non-rotating stiffened conical shell. These comparisons confirm reliability of the present work as a measure to approximate solutions to the problem of rotating stiffened conical shells.