Analysis Of Sound Absorption Performance Of Multilayer Composite Nonwovens

In recent years,in the field of sound absorption and noise reduction,nonwovens have gradually become the research focus of textile sound absorption materials due to their high porosity and large specific surface area.However,the sound absorption effect of nonwovens in low frequency band is poor.To improve its low frequency sound absorption performance,the best sound absorption band can only be moved from high frequency to low frequency by increasing the thickness.This method leads to heavy materials and waste of resources.In this topic,preparing light,thin and high porosity,small diameter material and compositing it with the traditional spunbonded non-woven fabric,the sound absorption performance of the composite material in low frequency band is significantly improved.Without changing the thickness,the low frequency sound absorption performance of nonwovens is significantly improved.It has certain research significanceThis topic uses high molecular weight polyacrylonitrile as the electrospinning raw material,and controlling the spinning conditions to obtain electrospun nanofibers with different structural parameters film.Based on spunbonded nonwovens,the obtained PAN nanofiber film,spunbonded non-woven fabric,and aluminum perforated board are composited to obtain single-layer,double-layer and three-layer composite materials respectively,and the sound absorption performance of the impedance tube is tested.Main research contents:(1)Single layer nonwoven: The effect of structural parameters on the sound absorption performance of single-layer nonwovens was analyzed by measuring the sound absorption performance through impedance tube.(2)Multilayer composite nonwovens: Based on the measured sound absorption coefficient,analyzing the effects of the material type,fiber diameter and porosity on the sound absorption performance.(3)Mathematical theoretical model: Based on the Rayleigh model,combined with the propagation equation of sound waves in the medium and the acoustic boundary conditions at the cross-sectional abrupt interface,and obtained the theoretical model of sound absorption of single layer porous material and double layer composite material.(4)By carrying out the numerical simulation,explored the influence of the structural parameters of each material on the sound absorption performance and the sound absorption performance was verified by experiments.And the correctness of the mathematical theoretical model is further verified.The results show that:(1)Single layer electrospun fiber film: Under the same cavity depth,the smaller the diameter of the material and the smaller the aperture,the better the sound absorption performance in the middle and low frequency bands;Increasing the porosity of the material can move the sound absorption resonance frequency of the material to low frequencies,and increase the sound absorption coefficient in the full frequency range.(2)Double layer composite sound absorption: For the double-layer composite nonwovens,the sound absorption performance gradually increases with the decrease of the fiber diameter of the sound-absorbing cover layer and is proportional to the material porosity of the sound-absorbing cover layer;For perforated plate and nonwoven composite double-layer material,the sound absorption performance of the composite material is improved in the whole frequency band,especially the sound absorption coefficient in the low frequency band.(3)Three-layer composite material: Compared with single-layer and double-layer composites,the sound absorption performance has been significantly improved in the full frequency band,and the growth of the sound absorption coefficient in the low frequency band is more significant.And its sound absorption coefficient increases with the increase of the porosity of the interlayer material.(4)Verification of mathematical theory model: The mathematical simulation is carried out by combining the sound boundary condition formula of each material and the structural parameters of the material.The trend of the acoustic absorption curve of the theoretical model is consistent with the experimental results.The relationship between the structural parameters of the material and the sound absorption coefficient is consistent with the experimental results.The theoretical model calculated by the average pore diameter can predict the sound absorption trend of the material in each frequency band.However,due to the different pore diameters and interconnection of the porous material,the above-mentioned sound absorption theoretical model has certain limitations.The theoretical value and the actual measured value exist.Certain differences have no reference value for the value of the sound absorption coefficient.