Optimization Design Of A Cfrp Rear Longitydinal Arm Of Automobile Chassis

Taking the lightweight requirements in the automobile industry into account,carbon fiber reinforced composite(CFRP)materials are attracting more and more attention for their high specific strength and high specific stiffness.The rear longitudinal arm is one of the main structures of car chassis.Design of the rear longitudinal arm with CFRP can reduce its weight effectively.However,the application of CFRP materials have also brought great challenges to the optimization design process,such as complex multiple loading conditions and a large number of design variables.In this dissertation,light-weight design for a chassis longitudinal arm of a new energy car was implemented by using laminated carbon fiber reinforced composites.Firstly,epoxy resin/T700 was selected as the material for the rear longitudinal arm.The mechanical properties of the selected CFRP material were measured.Then,based on the classical laminated plate theory,an optimum combination of discrete variables and an optimum stacking sequence of laminates were obtained by finite element analysis with commercial CAE software ABAQUS.The Tsai-Wu failure criterion was used for failure prediction.The designed composite longitudinal arm was lighter than the steel one by 30% without weakening its stiffness and strength.Research results demonstrates that the composite longitudinal arm could be well developed based on expert knowledge combined with finite element analysis,which provides a useful reference for application of advanced composites on light-weight design of main load-bearing structures of new energy car chassis.Next,by developing add-on functions of ABAQUS with Python,the global ergodic search for thickness ratio of different ply-angles was carried out to find the effective range and the optimum solution.Finally,in order to solve problem of long running time under multi working conditions,the tree-based algorithms,such as XGBoost,Dart,Random Forest,were introduced into the thickness ratio calculation.Considering both of the running time and the computation accuracy,if calculating 0 or 10 cases under the new condition,the accuracy rate of Tsai-Wu factor can reach 96.3% and 98.3%(compared with 1 failure value).In the case of reducing the amount of data under the existing working conditions by half,the accuracy rate can reach 95%(compared with the failure value 1),with the cases under the new working conditions increased to 40.