Sound Transmission Analysis of Viscoelastic Composite Multilayered Shells Structures

Abstract

In the development of aircraft comfort, one of the main issues is the sound transmission analysis to estimate the insulation capability of aeronautical panels. In this work, a higher-order shell finite element is proposed for the passive noise insulation analysis of composite laminated structures embedding viscoelastic layers. Starting from the Principle of Virtual Displacements, the present Finite Elements are obtained by making use of higher-order Layer-Wise theories, employing the Mixed Interpolated Tensorial Components (MITC) method to avoid the shear locking effect and taking into account the frequency dependence of the viscoelastic material through the use of a fractional derivative model. The Rayleigh integral method is considered for the evaluation of the acoustic insulation of the panels. Numerical studies are carried out to demonstrate that the present shell finite element is an efficient and accurate tool for the sound transmission analysis. Different lamination sequences, different boundary conditions and various radius to thickness ratios are taken into account.

Analytical higher-order-theories for noise reduction analysis of viscoelastic composite multilayered shells

“…Rectangular sandwich shell panels are considered, taking the structural data from the work of Valvano et al., 24 the geometry and material properties are summarized in Table 1. The sandwich shell is loaded by a plane wave applied to the bottom surface Ptrue(α,β,z,ωtrue)=P0true(α,β,−h/2,ωtrue)=1 N/m2, the load is constant on frequency.…”

“…In order to introduce the displacement kinematic assumptions, in this work the generalized Galerkin method is employed, as well described in the book of Washizu, 30 and the three-dimensional mechanical displacements u=(u,v,w) are expressed as: where the three-dimensional displacements can be approximated by a proper choice of the functions in the shell reference surface bold-italicud(α,β), for the shell reference system see Figure 1, and of the functions along the thickness bold-italicgd(z), moreover the accuracy depends also on the number of terms N. In this work the attention is focused on advanced shell kinematic models well-known in literature as Layer-Wise models (LW). In order to easily implement this modeling, the Legendre polynomial are used and, in particular, an higher-order cubic expansion LW 3 has taken into account: in which the used polynomials are function of ζ , locally defined: −1≤ζ≤1, for more details refers to the work of Valvano et al., 24 and the superscript k indicates the kth layer, it means that the polynomial is defined layer-by-layer. To consider a lower kinematic model LW ith , the higher-order terms bold-italicujth, with j>i, are set to zero.…”

“…23 The sound transmission FEM analysis of multi-layered composite viscoelastic shells is investigated in the paper of Valvano et al. 24…”

Simulation Analysis of Cylindrical Shell Cavity Noise with Melamine Foam Lining

“…Because precision instruments and their payloads are usually placed in the fairing cylinder section, the internal sound field of the high-speed railway vehicle body, aircraft fuselage, and some heavy machinery can be converted into a similar noise reduction study in the fairing cylinder section cavity. erefore, the acoustic vibration characteristics and the noise in the cylindrical shell cavity have attracted extensive attention of researchers [3][4][5].…”

“…e sound insulation performance of the cylindrical shell itself is very limited, so passive noise reduction is used to further enhance the noise reduction performance of the cylindrical shell. Valvano et al [5] developed an accurate shell finite element model for the passive sound insulation analysis of composite laminated structures embedding viscoelastic layers. Engberg and Korde [13] took the cylinder section of a satellite fairing as the research object, established the cylindrical shell correlation model, and studied the influence law of acoustic overlay on the noise reduction effect.…”