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.