Wave propagation behaviors of a low-symmetry reentrant chiral structure with mass inclusion in a single material

This work proposed a low symmetry characteristics metamaterial in a single material. The structural configuration of the metamaterial is composed of the reentrant structure, chiral structure and mass inclusion. The wave propagation characteristics are investigated in terms of the Bloch-Floquet wave propagation theorem. Firstly, the band diagram of the metamaterial is analyzed. The wave behaviors of the structure are changed due to the low symmetry characteristics. The irreducible Brillouin zone (IBZ) of the proposed structure is changed. The band diagram in the whole IBZ is analyzed to get the accurate distributions of the bandgaps. Some extremum values of the dispersion surface are deviated from the boundary of the IBZ. The formation mechanisms of bandgaps are illustrated based on the analysis of the vibration mode shapes. Then, the phase velocity and group velocity of the elastic wave are calculated, showing the strong anisotropic properties. Moreover, the effects of the geometrical parameters on the bandgaps are investigated. The locations and width of the bandgaps can be tuned for by the rational design. The existence of bandgaps of the metamaterial are validated by a finite element model. Finally, a metamaterial beam sample with seven cells is made and experiment test are conducted for the vibration attenuation performance and error analysis. The proposed structure can be used for vibration attenuation in the fields of underwater vehicles.