The Structure?Molding Process And Material Design And Optimization Of Composite B-Pillar With Ply Drop-off

With the regulations and the consumer market putting a high value on automobile energy consumption and vehicle safety performance,how to achieve the goal of lightweight and high strength in the existing automotive structure and material system has become a hot research topic in the field of automotive.The composites have excellent material properties and the unique laminated plate forming process which can cut plies at the specific location to form the composite ply drop-off structure.The ply drop-off structure can easily achieve the stiffness tailoring which can minimize the use of material.In this paper,in order to achieve lightweight and meet the safety requirements of the car,the composite drop-off structure with variable stiffness is proposed to be applied to the B-pillar.In this paper,the mechanical properties of the ply-drop off structure,the molding process parameters,the B-pillar structural characteristics and the optimum design of laminate layup are studied,the main contents and results include:(1)In this paper,based on the stress-strain relationship of composite laminates,the mechanical analysis method of composite ply drop-off structures is expounded theoretically.In this paper,the three-dimensional simulation model of the ply drop-off structure is established by using the finite element methods,and the mechanical properties are analyzed.From the interlaminar stress distribution,the causes and mechanism of interlaminar stress concentration are analyzed;(2)The stress concentration of the ply drop-off structure may lead to the early failure of the laminate.This paper carried out the parametric studies of molding process to reduce the stress concentration.The study of molding process parameters include:covering ply design,drop angle and the stagger distance.The guiding principles for the design of the ply drop-off structure are obtained;(3)According to the performance requirements of B-pillar structure,this paper analyzes the two conditions of side impact and roof crush of a vehicle,and obtains the relationship between the safety performance and the B column deformation mode under the two conditions.According to the variable stiffness requirements of the B-pillar and the guiding principles of the process parameters obtained in the previous chapter,the partition design of the composite B-pillar with drop-off structure is carried out.(4)Taking into account the crashworthiness and lightweight requirements of B-pillar structure under the conditions of roof crush and side impact,the optimal design of the number of plies,the ply angle and order in each sublaminate were carried out.Finally,in the foundation to meet the molding process requirements,61.4%lightweight was achieved,and the maximum capacity increased by 20.2%in roof crush,the intrusion distance and intrusion velocity were decreased by 9.4%and 7.4%in side impact.By introducing the composite ply drop-off structure,the crashworthiness of the B-pillar structure is improved,and a substantial lightweight is achieved.The research provides the ideas and methods for the applications of composite materials in the vehicle structure,and provides a great potential for the combination of structure,process and material for automobile lightweight.It has a strong application value in engineering.