Research On Vibration Attenuation And Sound Insulation And Optimal Design Of Periodic Sandwich Plates

Periodic structures are periodically arranged with characteristics of band gaps (stop bands). That is, elastic waves in these frequency ranges cannot propagate in the periodic structures. Therefore, this kind of structure has advantages in vibration attenuation and sound insulation.Periodic sandwich plates are typical periodic structures. Band structures of lots of sandwich types are calculated by element finite software COMSOL. Among them, corrugated sandwich and grid sandwich are found to be the proper sandwich types which exhibit band gaps. Vibration responses of these two types of sandwich plates are calculated and compared with band structure. Influences of geometry and material parameters on stop bands are systematically investigated. Regulating mechanism of stop bands is analyzed based on the vibration mode of unit cell and optimal design suggestions are proposed. Band structures of grid sandwich plates with added mass are also calculated and influences of elastic modulus and mass density are discussed. The research results show that:1. Elastic wave with frequency among band gaps got remarkable attenuation when propagating in corrugated sandwich plates and grid sandwich plates, which proves the wide range of applications in vibration attenuation and sound insulation. The location and width of stop bands are decided by geometry and material parameters.2. To the corrugated sandwich plates, the widest stop bands can be gained when choosing proper thickness of panels. Inclination angle of corrugated panels has a great influence on stop bands, which will disappear when inclination angle is larger than60°. Elastic modulus has a greater influence on stop bands than mass density. The widest stop bands can be gained when choosing proper elastic modulus ratio of face panels and core panels. Stop bands can be widened by putting unit cell with different geometry or material parameters in series.3. To the grid sandwich plates, the widest stop bands can be gained when choosing proper thickness of panels. Periodical length has a much greater influence on stop bands than core thickness. The location of stop bands will be higher and the width of stop bands will decrease when periodical length is increasing. Elastic modulus has a greater influence on stop bands than mass density. Stop bands will disappear when elastic modulus of face panels is larger than core panels. The location of stop bands for triangular grid sandwich plates is higher than that for square and hexagonal grid sandwich plates.4. Comparing with band structure of grid sandwich without added mass, band structure of grid sandwich with added mass is cut down in somewhere, and band gap of local resonance type is found. The location of band gap of local resonance type is decided by elastic modulus and mass density of added mass. The width of band gap of local resonance type will be larger when the mass density of added mass is increasing.