Bandgap properties in locally resonant phononic crystal double panel structures with periodically attached spring–mass resonators

• The locally resonant double panel structure opens a band gap in the low frequency region.
• The band gap is the coupling between the symmetric and antisymmetric vibration modes.
• The band structure of the double panel is the evolution of that of the single plate.
• By adding springs around the resonator in a unit cell, the bandwidth gets wider.
• The band gap can be controlled by tuning the parameters.

Bandgap properties of the locally resonant phononic crystal double panel structure made of a two-dimensional periodic array of a spring–mass resonator surrounded by n springs (n equals to zero at the beginning of the study) connected between the upper and lower plates are investigated in this paper. The finite element method is applied to calculate the band structure, of which the accuracy is confirmed in comparison with the one calculated by the extended plane wave expansion (PWE) method and the transmission spectrum. Numerical results and further analysis demonstrate that two bands corresponding to the antisymmetric vibration mode open a wide band gap but is cut narrower by a band corresponding to the symmetric mode. One of the regulation rules shows that the lowest frequency on the symmetric mode band is proportional to the spring stiffness. Then, a new design idea of adding springs around the resonator in a unit cell (n is not equal to zero now) is proposed in the need of widening the bandwidth and lowering the starting frequency. Results show that the bandwidth of the band gap increases from 50 Hz to nearly 200 Hz. By introducing the quality factor, the regulation rules with the comprehensive consideration of the whole structure quality limitation, the wide band gap and the low starting frequency are also discussed.