Structural Intensity Formulation and Measurements Validation in the Case of Composite Multi-Layered Panels

Author: Simon F.   Pauzin S.  

Publisher: S. Hirzel Verlag

ISSN: 0001-7884

Source: Acta Acustica, Vol.92, Iss.2, 2006-03, pp. : 256-268

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Abstract

The active structural intensity is a vector quantity that allows to know the transmission paths of mechanical energy through structures and to localize the vibration sources and sinks. While the measurement of structural intensity is generally applied to isotropic beams and panels, this paper deals with intensity on anisotropic multilayered panels, as those used in aeronautic domain. The theoretical approach is described with the hypothesis of far field. The error due to finite difference approximation is analysed. So, we show off that, in the case of a field with plane waves in a preponderant direction, the intensity can be investigated with a probe composed of only two sensors. After a reminder of the methodology, this paper shows the comparison between experimental and theoretical results in a wide frequency range on a panel composed of a core in Nomex honeycomb and symmetrical fibreglass laminates. Then, the effect of very important damping, local and spatial, is shown on a dissymmetrical multilayered panel. Finally, experiments are conducted on the mechanical deck of VASCo, a representative helicopter cabin (structure in sandwich composite) excited by 4 random shakers mounted on the fastening locations of the gear box. We point out that energy is propagated from each source on a narrow surface towards the middle of the mechanical deck, which is in accordance with the near acoustic pressure field radiated by the structure into the cabin.