Yu D., Liu Y., Qiu J., Wen J., Zhao H.

In the last decade, the propagation of elastic or acoustic waves in periodic composites, known as phononic crystals, has received much attention. The emphasis was laid on the existence of complete elastic/acoustic band gaps in which sound and vibration are all forbidden. This is of interest for applications such as frequency filters, vibrationless environments for high-precision mechanical systems or design of new transducers. With the idea of phononic crystals, most periodic structures such as beams and plates are designed. Vibration band gaps in the periodic structures have been found both theoretically and experimentally. But most of the work considered only the free vibration in vacuum. It is often necessary to compute the vibration of marine structures that are in contact with a dense fluid. This information can be useful in designing marine vehicles that exhibit reduced acoustic signatures and self-noise characteristics. In this paper, we studied the flexural vibration band gaps in periodic plates with fluid loading. The structures comprise continuous elements of two different material and geometrical types connected in alternating sequence. The effective mass density is introduced due to the fluid loading effect. And the effective wavenumber of the flexural wave through the plates is obtained. So we can calculate the complex band structure to investigate the gap frequency range and the vibration reduction in band gap by transfer matrix method easily. Furthermore, the effect of the fluid material parameters on the band gaps is considered. The existence of flexural vibration gaps in periodic plates gives a new idea in vibration control of plates with fluid loading. The findings will be significant in the application of phononic crystals.