Research On Preparation And Topology Optimization Method Of Plant Oil Polyol Polyurethane Porous Composite Materials In Vehicles

Automotive acoustic packaging is a technical method to effectively control the noise,vibration and harshness（NVH）of the vehicle.Under the requirements of environmentally friendly materials for vehicles,it is urgent to develop green and renewable acoustic packaging materials.Polyurethane（PU）porous materials,as one of the indispensable passive noise reduction materials in automotive acoustic packaging,will inevitably develop towards high efficiency,safety and environmental protection.Plant-based PU porous materials have been extensively studied for their excellent mechanical properties and potential acoustic performance.Therefore,from the perspective of theoretical research or engineering applications,the research of plant-based PU porous sound-absorbing materials for vehicles is beneficial to the development of environmentally friendly automotive acoustic packaging.In this paper,an abundant and renewable palm oil polyol（POP）was selected as the raw material for the preparation of plant-based PU,and then a palm oil-based PU sample was successfully prepared by means of replacing the partial petroleum polyol.The effect of the POP on the microscopic morphology,acoustic properties and mechanical properties of the PU was analyzed,and compared with the traditional PU.The results showed that POP increases the content of closed pore ratio in the microstructure of PU,affects the airflow resistivity and porosity,thereby improving the low-frequency sound absorption performance of the sample.The high closed pore ratio enhances the compressive performance while reduces the tensile properties.In order to better grasp the acoustic characteristics of different porous acoustic models,the paper analyzed and sorted out the Biot-Allard theoretical model,empirical model,analytical model and semi-phenomenological model.Then,based on the MATLAB App Designer platform,developed seven types of porous acoustic models simulation software,and the models included Delany-Bazley（DB）、Delany-Bazley-Miki（DB-Miki）、Attenrough、Johnson-Champoux-Allard（JCA）、Johnson-Champoux-Allard-Lafarge（JCAL）、Wislon和Biot-JCA.The software can calculate the complex wavenumber,characteristic impedance,sound absorption coefficient,normalized dynamic bulk density,normalized surface impedance,and normalized bulk modulus of the porous acoustic model.In order to obtain the acoustic parameters of tortuosity,viscous characteristic length and thermal characteristic length of palm oil-based PU,this paper proposed an inverse method based on the difference algorithm（DE）.First,the JCA rigid acoustic model was used to reverse the acoustic parameters of two palm oil-based PU,ordinary PU and metal foam,which named PU1,PU2,PU3 and PU4,respectively.Within the allowable range of error,the results of the inverse estimation showed that the inverse sound absorption curve of the PU2 material fits well with the experimental sound absorption curve,and the inverse parameter error of the PU3 material is the smallest.Then,the reverse estimation results of the two different thicknesses of PU3 materials indicated that the increase in thickness is beneficial to improve the accuracy of the reverse estimation,and compared with the reverse estimation results of the PU foam in the literature,the viscosity characteristic length error in this paper is lower,which verifies the reliability of the inverse method.The dynamic density and dynamic bulk modulus of palm oil-based PU porous material(PU-P₄₉)characterized by the JCA model were interpolated by the solid isotropic material with penalization（SIMP）,and then the method of moving asymptote（MMA）is used to topologically optimize the PU-P₄₉ in the two-dimensional muffler and three-dimensional distribution in the car cabin.The transmission loss curve of the muffler showed that the topology result of the PU-P₄₉material improves the transmission loss（TL）value of the muffler at 340 Hz,and the TL value is higher than the topology result of the fiber material based on the DB model.The optimized sound pressure level curves of the three positions in the car cabin showed that the topology distribution of the PU-P₄₉ material in the three positions of the car roof domain,the floor domain and the surrounding domain of the car effectively reduces the sound pressure level of the target point at the optimized frequency.Therefore,the topology distribution of palm oil-based PU porous materials can provide certain guidance for the arrangement of acoustic packaging.