The Vehicle Composite Tailgate Design And Development

As the requirements for energy saving and emission reduction of automobiles become increasingly stringent,the use of lightweight materials to achieve vehicles lightweight is an important way to solve energy and environmental problems.As a large-scale automobile doors&closures,the traditional metal tailgate assembly has many parts and high weight.It is an inevitable trend to replace the traditional metal tailgate with composite tailgate to achieve lightweight.In this paper,the systematic research on the material selection,structural design and optimization,injection molding process analysis and performance verification of tailgate is carried out,which provides reference and guidance for the engineering design and development of composite vehicle tailgate.The main work of the thesis is as follows:The application and development of fiber reinforced composite materials were understood,the application status and key technical difficulties of composite materials in automotive interior and exterior decoration were analyzed.Considering the material cost,process and performance,the plastic tailgate materials studied in this project were selected:long glass fiber reinforced polypropylene composite for inner panels;pure polypropylene for outer panels,and inner and outer panels were bonded together with an adhesive.The typical working conditions of the traditional metal tailgate were analyzed,and the main performance parameters of the tailgate were determined to guide the structural design of the composite tailgate.The design difficulties and requirements of the automobile tailgate are analyzed systematically.Then the topological structure of the composite tailgate is determined by topology optimization.The thickness of each component of the composite tailgate is determined by size optimization.The arrangement and size of the ribs are determined by shape optimization,and finally realized the integration,modularization and lightweight design of the composite vehicle tailgate.Finally,the composite tailgate parts were reduced by 71%compared with the traditional metal tailgate,and the weight was reduced by 3.15kg.The injection molding simulation of the composite tailgate was carried out,and the causes and solutions of the injection molding process defects were analyzed.Then Taguchi orthogonal test method is used to optimize the injection molding process parameters of composite tailgate,and the main process parameters:mold temperature,melt temperature,holding pressure,holding time and cooling time are selected as test factors.The warping deformation is the optimization objective.The five-factor four-level L16(4~5)orthogonal test scheme is designed.Then the simulation result data is analyzed by the range analysis method and the variance analysis method.The order of process parameter significance that affects the warpage deformation is holding time,holding pressure,mold temperature,cooling time,melt temperature;when the amount of warpage is minimum,the process parameters are mold temperature is 60°C,melt.temperature is 220°C,and holding pressure is 90%of filling pressure,holding time is 20s,cooling time is 15s.The element mapping strategy of composite structure simulation is introduced.Based on this strategy,Moldflow and Abaqus are used to map the results of the Moldflow analysis to the structural analysis model.Then the performance parameters of the composite tailgate are analyzed.The results show that the transverse stiffness,torsional stiffness,bending stiffness and mode frequency of the composite tailgate meet the performance requirements,and compared with the metal tailgate,the transverse stiffness,torsional stiffness,bending stiffness and modal values are improved.This proves the rationality of the composite tailgate structure designed.