International audienceThe vibroacoustic bending properties of honeycomb sandwich panels with composite faces are studied from the wavenumber modulus to the mechanical impedance, passing through the modal density. Numerical results extracted from finite elements software computations are compared with analytical results. In both cases, the homogenization method is used to calculate the global properties of the sandwich panel. As faces are made of composite material, the classical laminate theory serves as reference. With particular conditions used in the application for symmetric panel, the original orthotropic mechanical properties can be reduced simply to three parameters commonly used in vibroacoustic characterisations. Theses three parameters are the mass per unit area, the bending rigidity and the out of plane shear rigidity. They govern simultaneously the wavenumber modulus, the modal frequencies, the modal density and the mechanical impedance. For all these vibroacoustic characterisations, a special frequency called cut-off frequency separates two domains. In the first domain, below the cut-off frequency or in low frequencies, the orthotropic sandwich panel has a classical isotropic plate behaviour. In the second domain, above the cut-off frequency or in high frequencies, the out of plane shear rigidity has a great importance that changes the behaviour.Experimental measurements of the bending wavenumber modulus and modal frequencies for our own application were carried out. In the domain of the vibroacoustic, the critical frequency is also an important frequency. It depends once again on the mass per unit area, the bending rigidity and the out of plane shear rigidity. The experimental and numerical results of the article are reasonably in agreement with the analytical formula. They all confirm the evolution in frequency through different boundary conditions around the panel.The analytical modal frequencies of rectangular sandwich panels with transverse shear, in simply supported boundary conditions are well known, but in free boundary conditions it is more difficult to predict them. For experiments however, this latter condition is the most usual one. We present, in this paper, an analytical formula that we have developed for the modal frequencies of such a panel in free boundary conditions. All parameters being controlled, it is possible from dynamic measurements and with a special process to identify some honeycomb and composite mechanical properties

No abstract