Preparation And Optimization Of Corn Husk Fiber/Polylactic Acid Multi-layer Sound-absorbing Composite Materials

With the developing of economy,environmental pollution has become severe and closely paid attention.Noise pollution is one of the four major environmental pollutions.Noise produces many harmful effects to human normal life,work,study and health.Corn husk fiber is one of agricultural wastes,which have the largest resources in our country.But most of it was burned and the repeated utilization was not so high also caused serious air pollution.To solve the problems above,this paper using corn husk fiber with environmental PLA,to develop multi-layer acoustical composite materials.The theoretical model of sound absorption coefficient was established and sound absorption performance was optimized.Next,corn husk fiber/PLA composite material was prepared by blending hot pressing method,using corn husk fiber as reinforcing material,PLA as matrix material.Use L9(34)orthogonal test table,and the effect of fiber content,fiber length,pressing time and pressing temperature on mechanical properties of composite was analyzed through orthogonal experiments,and the optimal process conditions were achieved.When corn husk fiber length of 10 mm,corn husk fiber concentration of 50 %,pressing temperature of 170℃,pressing time of 6 min,the composite material with the best mechanical properties,its tensile strength is 639.35 MPa,the bending strength is 90.28 MPa,the impact strength is 18.4 KJ/m2.Later,corn husk fiber/PLA composite material was made according to the above optimal preparation process,using sample machine open slit on composite to make micro-slit panel.Corn husk fiber/PLA multi-layer sound-absorbing composite material was prepared by micro-slit panel,air layer,flax felt sequentially.Use L9(34)orthogonal test table,and the effect of wear rate,air layer,flax felt layer and panel thickness on sound properties of material was analyzed through orthogonal experiments,the optimal process conditions and important order were achieved.While the important order was flax felt layer>air layer>wear rate>panel thickness,and wear rate of 5 %,one layer of air layer,two layers of flax felt,panel thickness of 2 mm,made the corn husk fiber/PLA multi-layer sound-absorbing composite material’s sound properties be the best,absorption coefficient can reach 1 at 2000 Hz.Then,corn husk fiber/PLA multi-layer sound-absorbing composite material’s sound absorption coefficient theoretical formula was established by using transfer matrix method,and the results were compared with actual numerical analysis.Calculate the basic acoustic unit of acoustic impendence of multi-layer acoustical structure,derivate each acoustic unit’s transfer matrix,give the sound absorption coefficient expression of multi-layer acoustical structure,finally,compares the theoretical value with practical value.It is found that the theory of numerical curve match well with actual value,and the theoretical derivation is proved basically true.Finally,corn husk fiber/PLA multi-layer sound-absorbing composite material reasonable structure parameters were found by using genetic algorithm;make the material behave good sound absorption properties within a certain frequency band.Than compare the results with the experimental value and theoretical value.It is found that there is a good match between them.