| Excessive exposure to noise will bring physical and psychological harm to people.With the popularity of vehicles,people spend more and more time with them.Excessive noise in a vehicle will have negative impacts on the physical and mental health of drivers and passengers,which puts forward higher requirements on the NVH(Noise,Vibration,Harshness)performance of a vehicle.Acoustic packaging plays an important role in improving the NVH performance of vehicles.Traditional acoustic packaging materials are a series of petroleum products such as petroleum-based polyurethane porous materials and polyester non-woven fabrics.The extensive use of petroleum products will seriously consume non-renewable resources and is not conducive to sustainable development.Under the goal of " Carbon Neutrality and Emission Peak " proposed by Chinese government,it has become an urgent task to develop and promote environmentally friendly acoustic packaging materials.Soybean oil epoxy resin porous material is a kind of environmentally friendly material with good acoustic performance and high content of bio-based components.This paper focuses on soybean oil epoxy resin porous materials,and conducts research around five aspects: material preparation,formulation optimization,microstructure modeling,performance simulation,and application of the material.In this paper,epoxy soybean oil was used as the main raw material to prepare soybean oil epoxy resin porous materials.The reaction mechanism was analyzed,the feature analysis and tests of acoustic and mechanical properties were conducted among materials with different "epoxy-curing agent" ratios.The results show that the material proposed in this paper is an acoustic packaging material with excellent sound absorption performance and outstanding comprehensive properties.Its sound absorption performance is better than that of petroleum-based polyurethane porous materials which are widely used in vehicles,and it has fair mechanical properties.The content of bio-based component in its raw materials can reach up to 67.77%,which is much higher than that in bio-based polyurethane porous materials.Taking epoxy soybean oil,1-methylimidazole and sodium bicarbonate as design factors and average sound absorption coefficient as response,the response surface experiment was designed and the fitting equation was built.Amount of these three factors were optimized based on the Simulated Annealing algorithm.The result shows that when 74.365 g epoxy soybean oil,0.801 g 1-methylimidazole and 9.815 g sodium bicarbonate were used,the average sound absorption coefficient of the material is the largest.The result were verified by experiment.Based on the Bravais space lattice,a new method for build the microstructure model of porous materials is proposed.And using the affine transformation method,a method for build microstructure model of porous materials with ellipsoidal cells is proposed.These two methods are suitable for build microstructure models of soybean oil epoxy resin porous materials as well as all kinds of foaming porous materials.The microstructure details and the size distribution of cells and pores of the model fit the real foaming porous materials well,which can reflect the characteristics of uneven sizes and positions of cells and pores.Using the microstructure model building method proposed in this paper,models with different structural characteristics were built and sound absorption performance of them was analyzed by viscous-inertial flow simulation and JCA acoustic model.The effects of different structural characteristics on the sound absorption performance were studied.The results show that the smaller the cells,the better the sound absorption performance in the medium frequency,and the worse the sound absorption performance at high frequency.The more widespread the size distribution of the cells and pores,the better the sound absorption performance.For porous material with ellipsoidal cells,when the sound incident direction is parallel to the stretching direction,the sound absorption performance decreases gradually with the increase of cell aspect ratio,while when the sound wave incident direction is perpendicular to the stretching direction,the sound absorption performance changes very little.Using soybean oil epoxy resin porous material to design the impedance composite muffler and use it in the intake system of a truck.Conduct simulation to study the improvement of sound transmission loss.The results show that the sound transmission loss of the intake system is significantly improved after the installation of muffler,which can effectively reduce the noise of the intake system.In addition,the design method of the perforated tube muffler is given,and the impedance composite muffler is designed by laying soybean oil epoxy resin porous material with different thickness in the chamber of the perforated tube muffler.The influence of material thickness on the performance of the muffler was analyzed by conducting simulation.Results show that laying a proper thickness of porous material will slightly weaken the peak value of the sound transmission loss of the muffler,but can significantly improve the valley value,so that the muffler can obtain stable noise reduction performance in a wide frequency range. |
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