A microstructure-based model of transport parameters and sound absorption for woven fabrics

A microstructure-based model is proposed to describe the transport parameters and sound absorption perfor-mance of idealized periodic woven fabrics. With proper hypotheses and simplifications, transport parameters, including permeability, tortuosity, viscous characteristic length and thermal characteristic length, are explicitly expressed as functions of fiber diameter and porosity. The unknown control coefficients introduced in the analytical model are fitted by performing multiscale numerical simulations over the representative unit cells. Subsequently, these transport parameters are submitted into the well-established Johnson-Champoux-Allard (JCA) model of porous media to calculate the acoustic impedance and sound absorption coefficient of the woven fabric. Compared with the corresponding transport parameters of a non-crimp fabric, the tortuosity is enlarged and viscous characteristic length decreases significantly, while the viscous permeability and thermal charac-teristic length remain almost unchanged, resulting in slightly improved performance in sound absorption. The fiber diameter, porosity, and thickness of a woven fabric comprehensively determine its capability to absorb sound. For enhanced energy dissipation (and hence sound absorption) via viscous-thermal boundary layers on fiber surfaces, the fiber diameter and porosity should be selected from an appropriate range such that the characteristic pore size of the woven fabric lies in the order of submillimeter. With the increase of sheet thickness, the sound absorption coefficient in the low frequency band is significantly improved.