Experimental and numerical investigation on the fundamental natural frequency of a sandwich panel including the effect of ambient air layers

Due to the advanced lightweight characteristic of sandwich structures, ambient air can significantly affect their natural frequency. In order to clarify the importance and magnitude of this effect, the natural frequency of a sandwich panel surrounded by air layers using experiment and numerical simulation was investigated in this study. The experiment setup based on modal testing was proposed with the feature of simulating air layers around the sandwich panel. The numerical simulation was formulated on the basis of fluid-structure interaction analysis. The experimental and numerical simulation results correspondingly demonstrated that the fundamental natural frequency of sandwich panel tends to decrease to be less than 25% of the frequency neglecting the air effect when the air layer thickness becomes thinner than 3 mm.