A dynamical model of light fibrous materials

Damping induced by fluid entrainment in porous media is the major mechanism of vibroacoustic energy dissipation within aircraft cabins. Although such systems are often satisfactorily modelled using an equivalent fluid formula tion with a mass enhancement to represent the porous frame, at propeller bl ade pass frequencies for example, the reactive forces generated by the fram e stiffness and damping also become significant and the structure must be a nalysed as a full two phase system. In this paper, two different fibrous ma terials commonly used as fuselage thermal insulation are considered and a s imple seismic experimental test configuration is modelled to verify the ana lysis method. The structural frame properties are determined through vacuum testing and the specific fluid induced effects are developed from flow res istivity measurements. A finite element model of the two-phase system is fo rmulated and the response of the model is shown to compare excellently with experimental test results carried out under atmospheric conditions. (C) 19 98 Elsevier Science Ltd. All rights reserved.