Research On Lightweight Design Of Composite Battery Pack For Electric Vehicle

In recent years,with the great investments in industry,education and research,China has made great achievements in the field of new energy vehicles,especially the electric vehicles(EV).And the superior development of electrification keeps promoting the transformation and sustained development of the "New four modernizations" for future automotive.In addition to the R&D of core technology about battery,motor and control,more attention should be paid to the advanced lightweight design methods,which combine multi-material application,structure optimization and process improvement.Under the background that the subsidy has been reduced and the mileage range has become the development bottleneck,the lightweight design for the "heart" traction battery pack of EV can not only improve the energy density of the pack and mileage range,but also improve the comprehensive performances of the vehicles,such as the safety.At the same time,the combination of lightweight and electrification is more conducive to the construction of a low-carbon society.Hence,the composite material with excellent weight reduction effect is applied to the battery pack in this paper.And the finite element analysis and optimization are performed to verify its weight reduction potential and application prospect.This paper is sponsored by National Key R&D plan of China(2016YFB0101601)-Integrated Multi-Objective Optimization Design of Structure,Material and Performance for Electric Vehicle with New Structure.For the battery pack,under the constraints of five static and modal performance analysis values of metal battery pack,the composite multi-step optimization design and performance verification of SMC composite upper cover plate and carbon fiber reinforced plastic(CFRP)battery box are performed.Finally,while achieving 46.15% high weight reduction ratio,the stiffness,strength and modal performance have been improved,and the performance under multiple working conditions can also meet the requirements.The main research contents of this paper are as follows:1.Test of CFRP and SMC composite samples and simulation benchmarkingIn order to obtain reliable simulation parameters for composite battery pack,the parameters and curves of 48 K unidirectional carbon fiber composite are firstly obtained through the RTM process laminate production and sample test.And this material is mainly applied to the battery box under severe working conditions.Meanwhile,the parameters of SMC composite material are also obtained for the further analysis of the upper cover plate under simple load.Furthermore,the simulation and test benchmarking of CFRP components including square tube and car hood is also carried out to verify the reliability of complex anisotropic material parameters.2.Finite element analysis of metal battery packAccording to the principle of constant stiffness design,the finite element model of a metal battery pack is established.Five kinds of static analysis and constrained modal analysis conditions with high calculation efficiency are determined to extract the product performance parameters,which are applied as the constraints for the optimization design of the composite battery pack.3.Structure optimization design of composite battery packAccording to different working conditions and based on the concept of multi-material design,SMC composite material with better comprehensive performance and cost advantage is applied to the upper cover plate,and topography and size optimization based on modal frequency are carried out to determine the optimal structure form.Then,CFRP with excellent comprehensive performance is applied to the battery box and composite material modeling is carried out to perform multi-step optimization that includes free size,size and stacking sequence.In the process of size optimization,the battery pack reinforced bracket is set as design variable to achieve better weight reduction effect.4.Performance verification of composite battery pack under multiple working conditionsUnder the guidance of the national and enterprise standards,the optimized composite battery pack is analyzed under the various conditions,including random vibration,mechanical impact,extrusion,sphere impact for bottom plate and drop.And the reliability of the optimization method based on static and modal analysis is verified.The research significance of this paper is: the appropriate lightweight composites are selected based on the distinguishing characteristics and requirements of the components for battery pack.According to the concept of constant stiffness design,the efficient optimization of the component structures considering the common working conditions is carry out,and the final multi-condition performance analysis results verify the reliability of the optimization scheme.This scheme has a certain reference value for the lightweight application of composite materials in battery pack and other components of new energy vehicles.