Structural Design And Performance Study Of Polymer Matrix Soft And Hard Alternating Layered Of Sound Absorbing Materials Based On Low Frequency Noise Reduction

Noise pollution is one of the most urgent problems in modern industry.Sound absorbing materials are the most extensive,simple and effective means of noise control.Polyurethane foam?PUFM?is a typical porous material of noise control,which has the advantages of anti-seismic buffer and low cost,but its low-frequency sound absorption effect is not ideal.In order to solve this problem,this paper designed a variety of damping layer structure,including doped inorganic filler of nitrile rubber?NBR?composite materials and structure of microperforated panel?MPP?resonance,and PUFM as porous structure of soft layer,through legal were double layer and interlayer,multi-layer cycle structure and a series of polymer soft hard alternate layered absorption material,aimed at using porous sound absorption and resonance absorption mechanisms such as to promote the combination of low frequency sound absorption performance.The details are as follows:PZT/NBR composites were prepared by mechanical blending with NBR as the matrix and lead zirconate titanate?PZT?as reinforcing filler.The effects of PZT content change and NBR thickness variation on dynamic mechanical properties and sound absorption properties were studied.The results show that with the increase of PZT volume fraction,the damping factor of the composite increases first and then decreases.Due to the influence of two different damping contribution mechanisms,the sound absorption performance will also change.When the content of PZT is 20 vol.%,The damping factor tan?of the composite material reaches a maximum of 1.26,the glass transition temperature Tg was-14.2?,and the sound absorption coefficient reaches a maximum of 0.23 at 1600Hz.With the increase of thickness,the PZT/NBR composite material is in the low frequency range of 400 to 1000 Hz.The sound absorption effect is improved.When the thickness is increased from 10 mm to 40 mm,the maximum sound absorption coefficient of the composite material is increased from 0.08 to 0.24.The PZT/NBR composites was used as the damping hard layer,the PUFM composties was used the porous soft layer,and preparation of the sound absorption composites with double-layer,sandwich layer and multi-layer periodic structure.The PZT/NBR-PUFM composites with with double layer,sandwich layer and multi-layer periodic structure were prepared.The structure order was studied.The influence of different structural parameters such as filler dosage and type,soft and hard layer matrix,soft and hard layer thickness,PUFM cell size and layer thickness ratio on sound absorption performance.The results show that the structural order has a great influence on the sound absorption performance of PZT/NBR-PUFM double-layer structure materials.When the rubber layer faces the sound source,the average sound absorption coefficient of the double-layer structure material in the range of 500?1600 Hz is improved from 0.09 to 0.50;the addition of PZT can make the characteristic absorption peak of NBR-PUFM double-layer structure material shift to the low frequency direction;the rubber matrix and foaming material also have an effect on the sound absorption performance of the double-layer structure material,compared with other materials,the NBR-PUFM composites with the double-layer structure exhibited the best sound absorption effect,and the maximum sound absorption coefficient reached 0.91 at630 Hz,and the PZT/NBR-PUFM composites with double-layer structure can also improve the low-frequency sound absorption performance when used the PUFM with smaller cell size;The thickness of the foamed material has a significant effect on the sound absorption performance of the double-layer structure material.As the thickness increases,the sound absorption band of the PZT/NBR-PUFM composites with double-layer structure gradually moves toward the low frequency direction.When the thickness of the PZT/NBR composite is 1mm and the PUFM thickness is 40 mm,the maximum sound absorption coefficient of the double-layer structural material reached 0.9.The NBR-PUFM composites with sandwich structure had higher sound absorption efficiencies than the composites with double-layer structure.Under the condition of 1:8:1 layer thickness,the maximum sound absorption coefficient is increased by about 20%;the amount and type of fillers affect the sound absorption performance of NBR-PUFM composites with sandwich structure material,and the average sound absorption coefficient of the composites with sandwich structure is increased by 8%using Ce O₂as the filler.For the NBR-PUFM composites with multilayer periodic structural,when the thickness of the PUFM is 10mm,the average sound absorption coefficient in the range of 200?800 Hz is obviously improved with the increase of the number of periodic units.MPP was prepared from aluminum plate and polylactic acid as raw materials,and combined with cavity to obtain MPP-AG resonant structure;PUFM was filled into the cavity of MPP-AG resonant structure to obtain MPP-PUFM stratified structural material;MPP-AG resonance structure was laminated with the NBR-PUFM composites,and the MPP-AG-NBR-PUFM multilayer structural material and the NBR-PUFM-MPP-AG multilayer structural material were respectively obtained according to the structural order.The effects of structural parameters such as perforated plate material and thickness,perforation rate,cavity depth,foam type and thickness and structural alternating sequence on sound absorption performance were studied.The results show that for the MPP-AG resonant structure,the resonant structure with lower perforation ratio has better sound absorption performance at low frequencies.With the increase of cavity depth,the effective sound absorption bandwidth of MPP-AG resonant structure gradually increased and the characteristic peak gradually moved toward low frequency.The influence of the kinds of MPP material on the MPP-AG resonance structure is not obvious,and the maximum of sound absorption coefficient of the MPP-AG resonance structure of the two different materials is 3%;with the increase of the MPP thickness,the characteristic sound absorption peak of the resonance structure gradually moves to the low frequency,and the maximum of sound absorption coefficient is reduced from 0.93 to 0.43.The foaming material have influences on the sound absorption property of the stratified structural material.Compared to other mateials,the composites material stratified structure with PUFM has the best sound absorption effect,the maximum sound absorption coefficient reached 0.87.With the thickness of PUFM increases,the characteristic absorption peak of MPP-PUFM layered structure material will gradually move to low frequency;MPP-PUFM layered structure material with smaller cell size have better low frequency sound absorption properies.Under the same thickness condition,the MPP-AG-NBR-PUFM composites with multi-layer structure can improve the mid-low frequency sound absorption performance,and the average sound absorption coefficient in the range of500?1600Hz is raised from 0.58 to 0.66.The NBR-PUFM-MPP-AG composites with multi-layer structure exhibited excellent low-frequency sound absorption performance,and the maximum of sound absorption coefficient at 400 Hz reaches 0.94,and the high-frequency coefficients are also improved.