Lippert S., von Estorff O.

Facing the increasing demand of passengers for comfort and well-being, low noise levels inside the aircraft cabin become more and more an important development objective. Current practice for optimising the cabin noise are mainly cost- and time-intensive experimental techniques. Therefore in order to cut down development costs, efficient computational methods to predict the acoustical behaviour of aircraft fuselage and lining are highly demanded. In particular, suitable numerical models for honeycomb sandwich plates – the major design material for components of the cabin lining – are needed. In the current paper, a computational method based on a coupled model of finite elements and boundary elements to predict the sound radiation and transmission loss of honeycomb panels is presented. The honeycomb core is thereby represented by means of 3D solid elements, while 2D thin shell elements are used for taking into account the facing skins. A successful forecast of the acoustical behaviour requires not only accurate element models, but also a detailed knowledge of the material parameters which often is not available. Thus the elastic and shear modulus of honeycomb plates found in technical data sheets usually lead to an underestimation of the real values, as they are minimum quantities guaranteed by the manufacturer for dimensioning tasks. To get reliable data for the current study, the elastic properties of the facing material have been determined by standard tensile testing. Furthermore, the honeycomb core was investigated using a dynamic method to measure the complex elastic and shear modulus. The determined material properties are finally used as input data for the numerical model to predict the acoustical behaviour of a honeycomb panel. The obtained results show an excellent agreement with sound radiation and transmission loss measurements of the real panel.