Numerical Analysis And Experiment Research On The Propagation Of Vibrations In Periodic Sandwich Panels Based On The Band Theory

Periodic composite structures (PCSs) are made of two or more elastic materials periodically with characteristics of band gaps. That is, vibrations in these frequency ranges cannot propagate in the PCSs. As a special type of PCSs, periodic sandwich panels can be designed according to the material parameter and structure parameter to isolate or attenuate the vibrations for some certain frequencies.In this thesis, the band gaps and vibration transmission property of the periodic hollow steel cylinder sandwich panels, polypropylene hollow sheet and aluminum honeycomb panel are investigated numerically and the influences of the geometrical parameters and the material parameters on band gaps are discussed. Besides, the vibration transmission property of the periodic hollow steel cylinder sandwich panels and polypropylene hollow sheet is studied experimentally. The acceleration frequenty responses obtained in the experiments are compared with that of numerical simulations and the band gap distributions. The main conclusions are as follows:1.The periodic hollow steel cylinder sandwich panels, polypropylene hollow sheet and aluminum honeycomb panel exhibit the characteristics of band gaps.There is a certain frequency region in the vibration transmission curve, in which the vibration attentuates and the attenuation region is consistent with the band gap.It explains that the vibration transmission in certain frequency ranges can be regulated to reduce the vibration and noise by using the band gap characteristics of the periodic hollow steel cylinder sandwich panels.2.For the periodic hollow steel cylinder sandwich panels, the larger the Young’s modulus or the smaller the density of the panel, the higher the frequency of band gap and the wider the band gap. Larger density of the core is favorable to gain a wide low-frequency band gap. Periodic sandwich panels composed of long steel, wide thickness tube, large diameter tube and thin thickness panel are more likely to obtain low-frequency band gaps. For the polypropylene hollow sheet, with the decreasing of the length of the cell, the center frequency and the wide of the band gap increase. For aluminum honeycomb panel, with the increasing of the height of the core and the minimum period dimension, the center frequency and the wide of the band gap increase.3.The experimental acceleration-frequency responses of the periodic hollow steel cylinder sandwich panels and polypropylene hollow sheet present some certain frequency ranges in which the acceleration amplitudes attenuate up to40%-70%. The more periods, the more obvious attenuation. The frequency domain is consistent both with that of the numerical results and band gap. It concludes that periodic structure has better vibration isolation performance.4.The experiment results show that,with increasing of the height of the periodic hollow steel cylinder sandwich panels’s steel tube, or decresing of the thickness of periodic hollow steel cylinder sandwich panels’s panel, the starting frequency for the attenuation of the acceleration-amplitude frequency response curve decreses and so it is the center frequency. This is the same as that of the numerical analysis.