Acoustic Metasurface Design Based On Fiber Composites

Acoustic metasurface is a new ultra-thin periodic structure with sudden phase change rising in recent years.In theory,it can manipulate the direction of acoustic wave propagation.The relevant research has never stopped.It has important values and broad prospects for space limited application fields.Therefore,at present,the strategy for the design of acoustic metasurfaces mainly depends on the metamaterials,which has the problems with narrow bandwidth and difficult microstructure design for extreme physical parameters.To solve this problem,this paper puts forward the idea of using non hyperstructured periodic materials for acoustic wave regulation,and introduces fiber composites into the field of metasurface design.Its periodicity and designability provide the possibility for acoustic wave manipulation.In this paper,firstly,the prediction of elastic properties of fiber composites is studied,including unidirectional fiber composites and two-dimensional triaxial woven fabrics composites.For the unidirectional fiber composites,the commonly used mixing rate formula,empirical formula,semiempirical formula and homogenization method are listed;For the two-dimensional triaxial woven fabrics composites,through the basic theory of composite elasticity and micromechanics,the unit cell geometry model is established.The theoretical analysis model is used for prediction,and the prediction results are consistent with the existing experimental results.Then,the principle of sound wave manipulation is deduced based on the generalized Snell law.With the help of composite micromechanics method,the components of unidirectional fiber composite unit cells are designed through homogenization prediction method and optimization method,so that the cells have specific equivalent sound velocity and equivalent density,and meet the characteristic impedance matching,so as to form the sound velocity gradient distribution required by the metasurface.The energy band structure analysis and directional reflection simulation of unit cell are carried out by using the finite element software COMSOL,which verifies the broadband characteristics and reasonable effectiveness of the metasurface manipulate acoustic wave of unidirectional fiber composite.Compared with the acoustic metasurface based on metamaterials,the acoustic metasurface of unidirectional fiber composites does not need microstructure design.The flexible designability of composites can achieve a broader range of physical parameters and a larger spatial coverage scale.It has obvious advantages in the regulation of large wavelength acoustic waves with small-size structures.It is expected to break through the bottleneck of physical preparation of metasurface due to the size limitation of microstructure.The research on the metasurface of the unidirectional fiber composites provides a new idea and method for the design of other acoustic wavefront manipulation devices.