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 stop bands(band gaps). That is, vibrations in these frequency ranges cannot propagate in the PCSs. Periodic sandwich panels are typical periodic composite structures, therefore, we can design the type of the sandwich panels according to the characteristics of the periodic composite structures. The PCSs can be inserted in the propagation path to isolate or attenuate the vibrations for some certain frequencies. The work presented will provide a theoretical guidance in the vibration isolation research.By using the finite element method, vibrations in the periodic hollow steel cylinder sandwich panels and the periodic orthogonal rib stiffened sandwich panels and the transverse vibrations in binary tetrahedral periodic lattice sandwich panels are investigated in detail, The influences of the material and geometrical parameters on the band gap are discussed. The results show that:1. The band gaps can be gained in the binary periodic hollow steel cylinder sandwich panels, and the influences of physical and geometrical parameters on the distribution of the band gaps are discussed in detail. The Young’s modulus of panel and the coated layer have the greatest influences on the band gap of binary periodic hollow steel cylinder sandwich panels. The smaller the Young’s modulus, the lower the frequency band gap. Thicker and higher hollow steel cylinder with large density is favorable to gain a wide low-frequency band gap. In order to gain wider band gaps, we put periodic hollow cylinder sandwich panels in concatenation.2. The band gaps can be gained in the binary periodic orthogonal rib stiffened sandwich panels. The influences of the Young’s modulus and the density of the panels and periodic constant on the band gaps of the binary periodic orthogonal rib stiffened sandwich panels are the same as that on the binary periodic hollow steel cylinder sandwich panels. There is an optimal density of the core which will gain the widest band gap in lower frequency ranges. Higher cube with thinner rib is favorable to gain a wide low-frequency band gap. There is a comparison on the width of the band gaps and steel volumes between periodic hollow cylinder sandwich panels and periodic orthogonally rib sandwich panels. 3. The propagation of transverse vibrations in binary tetrahedral periodic lattice sandwich panels has been investigated in this dissertation. The band gaps can be gained in the binary tetrahedral periodic lattice sandwich panels. The influences of physical and geometrical parameters on the distribution of the band gaps are discussed in detail. The smaller the Young’s modulus, the lower the frequency band gap. Increasing the height of the panels or decreasing the horizontal projection length of the rod will widen the band gap in the lower frequency ranges. Young’s modulus and the density of the core hardly affect the band gap.In brief, the present investigations are expected not only to provide a theoretical basis on vibration isolation and vibration control of engineering structures, but also to promote the design and applications of periodic sandwich panels in engineering structures.