An acoustic metasurface composed by unidirectional fiber composite materials

Acoustic metasurfaces are artificial materials of subwavelength thickness capable of manipulating reflection, transmission and absorption of acoustic waves. Acoustic metasurfaces have important values for space limited application fields. At present, the strategy for the design of acoustic metasurfaces depends on the metamaterials. Therefore, we propose a scheme by designing a kind of non-metamaterials acoustic metasurface to manipulate the wavefont in fluids. Based on this idea, a new type of reflection acoustic metasurface composed by the unidirectional fiber composites with periodicity is studied. Through homogenization theory and optimization method of micromechanics the fractions of composites unit cells are designed in order to obtain the effective mechanical and acoustics prosperities of unit cells to satisfy the densities and longitudinal velocities of discrete metasurfaces needed, as well as the impedance matching condition. Finally, the gradient longitudinal velocity of the acoustic metasurfaces needed is achieved. Using Bloch-Floquet analysis, the relationship between longitudinal velocity and frequency is studied. The band diagrams exhibit the broadband characteristics of the designed metasurfaces. Simulations of reflection control are studied for the designed metasurfaces with normally incident plan wave. Excellent wavefont manipulation effects are observed in broadband frequencies. Accordingly, it is verified that longitudinal modes are the most important factors for wave manipulation under normally incident waves. The research work provides a novel idea and potential method for the design and physical implementation of the acoustic metasurfaces as well as the other acoustic wave manipulation devices.