Preparation And Performance Analysis Of Automotive Film Perforated Plate Composites

With the rapid development of the transportation industry,the problem of automobile noise has become the focus of consumers’ attention.Therefore,major automobile manufacturers have invested a lot of research and development power in reducing automobile noise.Automotive acoustic packaging is the main way of sound absorption and noise reduction in automobiles,and sound absorbing materials are an important part of automotive acoustic packaging.Therefore,designing an efficient sound absorbing material has very important practical significance.The sound absorbing material mainly comprises a porous sound absorbing material and a resonance sound absorbing material,and the porous sound absorbing material has an excellent sound absorbing effect in the middle and high frequency regions,but the sound absorbing performance in the low frequency region is poor.The resonant sound absorbing material has good sound absorbing performance in the low frequency region,but the sound absorbing effect in the high frequency region is poor.Therefore,the composite sound absorbing structure is prepared by combining the porous sound absorbing material with the resonant sound absorbing material,which has certain guiding significance for the improvement of the sound absorbing performance of the sound absorbing material.In this paper,the castor oil phytol was used to partly replace the traditional industrial alcohol.The quadratic regression orthogonal design method was used to design the castor oilpolyurethane foam and the acoustic properties were tested.Then the multi-objective optimization design of the acoustic performance(sound absorption performance and sound insulation performance)of castor oil-polyurethane foam was carried out,and the response surface model of the sound absorption performance and sound insulation performance of castor oil-polyurethane foam was established according to the test results.The improved genetic algorithm is used for multi-objective optimization,and finally the optimal solution is obtained.At the same time,the reliability of the optimal solution is verified by experiments.The average sound absorption coefficient and average sound insulation of castor oil-polyurethane foam prepared according to the optimized results were 0.515 and 10.526 dB,and the sound absorption performance and sound insulation performance are improved compared with the traditional polyurethane foam.In order to further optimize the sound absorption performance of the polyurethane foam in the low frequency region,the pine needle is added as a filler to the foam to improve the sound absorption performance.Acoustic testing,electron microscopy and flow resistance testing were carried out on pine needle-polyurethane foam.The effect of pore size on sound absorption performance was analyzed from the microstructure,and the influence of pine needle addition on foam flow resistance was also analyzed.It was found that the addition of pine needles destroyed the cell structure of the polyurethane foam,which made the cell structure inside the foam become disordered,resulting in more friction loss and heat exchange when the sound wave propagated inside the material,thus improving the sound absorption performance.At the same time,the prepared pine needle-polyurethane foam was used to prepare a composite sound absorbing structure.This paper selects polyolefin film to prepare film perforated plate,because polyolefin film has good mechanical properties and has certain sound absorption properties.The selected polyolefin film has a thickness of 1 mm,and perforated plates of different thicknesses are obtained by superposition,and drill bits of different diameters are used to obtain film perforated plates having different pore characteristics.In addition,the Matlab software is used to theoretically calculate the sound absorption performance of the perforated plate from the depth of the cavity,the thickness of the perforated plate,the perforation aperture and the perforation rate,and the theoretical calculations are compared with the experimental values,and it was found that there is good consistency.A cavity with a certain depth is excavated in the pine needle-polyurethane foam,and a prepared film perforated plate is combined with pine needle-polyurethane foam to prepare a novel composite sound absorbing structure.There are three combinations of composite sound absorbing structures: sequential structure(two perforated plates,two cavities),single perforated plate structure,and sandwich structure.The sound absorption performance of the composite sound absorbing structure is analyzed from the perspectives of cavity depth,perforated plate thickness,perforation aperture,perforation rate,pore distribution shape and combination.The composite sound absorbing structure prepared is applied to the roof and the firewall of the automobile by using the simulation software,and the statistical energy analysis(SEA)method is used to analyze the noise reduction effect.As a result,it has been found that the composite sound absorbing structure has a significant improvement in the sound absorbing performance and insulation of the acoustic packaging of the floor and the firewall.