Acoustic Performance Analysis Of Automobile Bio-based Polyurethane Porous Materials Based On Acoustic Black Hole

With the development of modern society,the automobile ownership in China is further advanced.Vehicle noise has greatly bad on people’s lives and the environment,and vehicle interior noise has a greater impact on the comfort of drivers and passengers.Polyurethane,as one of automobile noise reduction materials,has been used to reduce the vehicle interior noise and improve the vehicle environmental quality.Due to the depletion of petroleum resources and the strengthening of environmental awareness,it is great significance to find a substitute for petroleum polyol.In addition,the acoustic performance of bio-based polyurethane has no obvious advantages compared with traditional petroleum-based polyurethane.It is of important significance and engineering practicality to improve the application effect of bio-based polyurethane in automobiles by changing the appearance of polyurethane.In response to the national green environmental protection theme,rapeseed oil polyol and coconut oil polyol are used as substitutes for petroleum polyols to prepare rapeseed oil and coconut oil-based polyurethane.The influence of the coconut oil polyol and rapeseed oil polyol’ contain on the acoustic properties,mechanical properties,microstructure and aging properties of polyurethane were analyzed.The Study showed that rapeseed oil polyols enhance the acoustic properties of polyurethane and weaken its mechanical properties.The influence of the raw material of polyurethane on the acoustic and mechanical properties was also analyzed.The contents of rapeseed oil polyol,diphenylmethane diisocyanate,and deionized water were used as design variables.The average sound absorption coefficient and Young’s modulus were optimized targets.The response surface Box-Behnken design method was used to design the experiment.According to the experimental results,the mathematical model between the design variables and the optimization goal was established.Finally,the best formula of rapeseed oil and coconut oil-based polyurethane was determined,and the polyurethane with good comprehensive properties(acoustic and mechanical properties)was prepared and verified.The cell structure,acoustic properties and mechanical properties of the optimized sample and the pre-optimized sample as well as the petroleum-based polyurethane were compared.The acoustic black hole(ABH)was applied to the polyurethane,and the influence of the ABH structure on the acoustic performance of the polyurethane was analyzed.The effect of the function coefficient and cut-off thickness of one-dimensional and two-dimensional ABHs on the sound absorption coefficient of polyurethane were analyzed.The result showed that the one-dimensional and two-dimensional ABH structure reduced the mid-and low-frequency acoustic performance and improved the high-frequency acoustic performance of porous materials.The functional coefficient and cut-off thickness of the one-dimensional ABH structure have a great influence on the sound absorption performance of the material in the whole frequency range.The functional coefficient and cut-off thickness of the two-dimensional ABH structure only affect the mid-and low-frequency sound absorption performance of the material.One-dimensional and two-dimensional ABH polyurethane were applied to the room and vehicle.The changes in sound pressure level in the vehicle were compared when there was petroleum-based polyurethane,rapeseed oil and coconut-based polyurethane,and ABH polyurethane,respectively.The results showed that rapeseed oil and coconut oil-based polyurethane and petroleum-based polyurethane had almost the same effect on noise.The ABH polyurethane greatly reduced the noise.