Sound Radiation and Vibration of Composite Panels Excited by Turbulent Flow: Analytical Prediction and Analysis

Joana Rocha

doi:10.1155/2014/316481

Abstract

The present study investigates the vibration and sound radiation by panels exited by turbulent flow and by random noise. Composite and aluminum panels are analyzed through a developed analytical framework. The main objective of this study is to identify the difference between the vibroacoustic behaviour of these two types of panels. This topic is of particular importance, given the growing interest in applying composite materials for the construction of aircraft structures, in parts where aluminum panels were traditionally being used. An original mathematical framework is presented for the prediction of noise and vibration for composite panels. Results show the effect of panel size, thickness of core, and thickness of face layers on the predictions. Smaller composite panels generally produced lower levels of sound and vibration than longer and wider composite panels. Compared with isotropic panels, the composite panels analyzed generated lower noise levels, although it was observed that noise level was amplified at certain frequencies.

Highlights

The shift towards composite aircraft fuselage and wing structures and the overall use of new concepts of materials in aircraft manufacturing carry the need of a better understanding of structural and acoustic behaviors associated with these types of materials
This study considers the case of a turbofan aircraft at cruise flight conditions, a situation in which interior noise levels are governed by the transmitted turbulent boundary layer noise into the cabin
Since face layers are thicker and this panel has a higher aspect ratio, this effect is more visible in composite Case 4 than in composite Case 3

Summary

Introduction

The shift towards composite aircraft fuselage and wing structures and the overall use of new concepts of materials in aircraft manufacturing carry the need of a better understanding of structural and acoustic behaviors associated with these types of materials. Previous studies have been conducted to understand the dynamic, vibration, and noise radiation properties by composite panels; most studies did not consider the turbulent flow excitation in the analysis. Several authors [10,11,12,13] have investigated analytical methods to determine the sound transmission loss of sandwich structures, considering the case of an infinite plate excited by a plane wave. In [22], a hybrid analytical one-dimensional finite element method is derived, which uses FEM approximation in the thickness direction and analytical solutions in the plane directions, reducing the number of finite elements required In this context, the present study addresses this problem through an analytical approach. A discussion is presented on the comparison of the vibroacoustic behaviour of composite panels compared to traditional isotropic panels

Theoretical Formulation

Structural Vibration and Sound Radiation Results

Conclusions