Scanning Laser Doppler Vibrometry for the characterization of the damping loss factor in honeycomb panels

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Scanning Laser Doppler Vibrometry for the characterization of the damping loss factor in honeycomb panels

Martarelli, Milena / Santolini, Claudio / Sassaroli, Andrea

In the aeronautic field the noise control has become very important in the last years. For this reason, damped panels are used in the interior of aircrafts and helicopters, with the aim to acoustically isolate the cabin. The damping factor of these panels must be accurately characterized with rapid and reliable test methods. One of the parameters used to describe the panel damping is the damping loss factor, which represents the capability of the structure to damp the interior vibration coming from the outside of the environment. In this paper two algorithms for the loss factor estimation has been compared, i.e. the Power Injection Method (PIM) and the Least Square Complex Exponential Method (LSCEM), taken as reference. Both of them are based on experimental data measured by means of a Scanning Laser Doppler Vibrometer (SLDV). This experimental technique allows us to perform an accurate and high-spatial density measurement of the surface velocity of the structure. The two methods for the experimental determination of the material loss factor have been applied to a linear structure with low damping ratio as a steel rod and a steel plate in order to test the stability of the loss factor calculation in dependence on test parameters. Afterwards, having determined the optimal experimental parameters via the previous analysis, they have been applied to a typical honeycomb panel used in aeronautics applications.