Enlargement of locally resonant sonic band gap by using composite plate-type acoustic metamaterial

• An original composite plate-type locally resonant acoustic metamaterial is proposed.
• A significant enlargement of the relative bandwidth by a factor of 3 can be obtained.
• The band gap enlargement is attributed to the locally resonant complex effect.
• The band gap is significantly dependent upon the geometrical parameters.

We numerically investigate the propagation characteristics of Lamb waves in composite plate-type acoustic metamaterial constituted of one-side cylindrical stubs deposited on a two-dimensional binary locally resonant phononic plate. Numerical results show that, with the introduction of composite plate-type acoustic metamaterial, locally resonant band gap shifts to lower frequency, and a significant enlargement of the relative bandwidth by a factor of 3 can be obtained, compared to one-side locally resonant stubbed plates. We show that the band gap enlargement is attributed to the coupling between the local resonant Lamb modes of two-dimensional phononic plate and the resonant modes of the stubs.