Honeycomb sandwich panels are much stiffer than uniform isotropic panels of similar mass. In this paper experimental modal densities of rectangular sandwich panels under nearly free-free boundary conditions are studied. In the literature, the modal density has been deduced from the real part of the mobility averaged over randomly chosen driving points on the panel. This mobility function is subsequently used to calculate band-averaged loss factors of these panels using the steady state input power method. According to the theoretical studies conducted by various researchers, it has been observed that there is a discrepancy between the theoretical and experimental results for the modal density of honeycomb core sandwich panel. The theoretical modal density of such panels increases with increasing frequency; however, experimental results show a decreasing trend above a certain frequency. There are no experimental results reported in the literature of the modal density of foam-filled honeycomb core sandwich composite panels. In this paper, foam-filled honeycomb core sandwich composite panels of different core thickness are investigated to determine their modal densities and their corresponding fundamental modes of core cell vibration. An in-depth theoretical study of the modal density of these panels is underway, and hence only experimental results are discussed in this paper. Since an impedance head was used to measure the mobility, the necessary corrections to exclude the mobility of the impedance head have been applied to plot only the correct value of the real part of the mobility. These corrections, which were applied to measured values of the mobility, were for the mass and stiffness of the impedance head.
展开▼
