The Structure Design Analysis And Optimization Of Composite Battery Box For Electric Vehicles

With the development of society,the problem of environmental pollution and energy shortage is becoming more and more serious.It is imminent to build an environment-friendly society.The green-car and the auto lightweight are important directions of automobile industry development in the future,and the lightweight design of green-car also becomes a new development trend.The application of composite materials in pure electric vehicle is an important method to realize the lightweight of electric vehicle.In this paper,a long glass fiber reinforced polypropylene composite battery box is used to replace the Q235 material battery box as the research object.The feasibility of the composite battery box is discussed by the finite element analysis.The main research contents of this paper are as follows:Firstly,the mechanical properties of long glass fiber reinforced polypropylene composites were tested.Some basic experiment datum were obtained,including tensile test,three point bending test and impact toughness test.Based on these datum,the constitutive parameters of the material were obtained,which laid the foundation for the subsequent finite element analysis and structural optimization.Secondly,According to the design requirements of the battery box,the main body's material of the composite battery box is the long glass fiber reinforced polypropylene composite,the box frame and the side frame are made of the Q235 material.Under two typical working conditions of electric vehicle,the dynamic and static characteristics of the battery box are analyzed.From the preliminary analysis of the dynamic and static characteristics,it is known that the structure design of the initial model of the box frame and the side frame are not satisfied with the design requirements of the battery box.Therefore,it is necessary to carry out structural optimization analysis of the box frame and the side frame.Finally,based on the analysis of the static and dynamic characteristics of the initial model of the battery box,the topology optimization and the shape optimization of the battery box are combined.According to the results of topology optimization and topography optimization,an improved battery box model was achieved.The battery box frame and side frame structure are modified,and it is improved that to battery box modelThe results show that the maximum stress of the optimized box frame made of Q235 material under the same working condition is less than the allowable stress of Q235,and the maximum deformation is reduced by about 77%,the maximum stress is reduced by about 31%,and the natural frequency of the first order mode is raised by 36.8%,which meets the requirements of the battery structure;The mass of the box frame connection beam is reduced by 33.33%.The mass of the reinforced longitudinal beam and the side frame is reduced by 25%.The optimized composite battery box not only meets the design requirements for structural strength but also achieves the purpose of lightweight design.