Design And Mechanical Properties Analysis Of Vehicle Body Composite Joint Structure

So far,domestic and foreign vehicle companies have many years of historical experience in applying composite materials to the secondary load bearing structure and the main load bearing structure of vehicle body,and the technology application is relatively mature.With the development and wide application of integral molding technology and co-curing technology,the number of parts and fasteners has been reduced to a certain extent,which greatly optimizes the assembly process and reduces the delivery time,but the load transferred between the remaining parts will be larger.However,in particular parts of the vehicle and considering the needs of individual design and routine maintenance,these connections need to be considered in relation to the intended reserved parts of the interface.As a result,the connection between the adjacent components of composite structure is not around the topic,the composite connection structure becomes the key of the whole structure of the core parts,to connect the structural strength and failure mechanism analysis has great significance to explore the structural stability and durability,provide reliable basis for the optimization of composite connection structure.In this paper,based on the importance of composite joint structure in the dynamic vehicle body,the single bolt joint and new mortise and tenon joint strength of composite joint structure in different layings were investigated.Based on the structure of composite material related theory,appropriate stiffness degradation theory and three-dimensional progressive damage theory,through the experimental analysis and finite element simulation method,the paper analyzed the connection strength properties and failure to validate the new link rationality and efficiency of mortise and tenon joint structure,and compared with the experimental results in the existing literature.The specific contents are as follows:(1)The test method is adopted to test the connection strength of different connection forms under different layering scheme design.It is found that in the case of the same layering,the connection bearing strength of the connection structure is successively from large to small:The mortise and mortise are adhesive≈Ultimate stretching of veneer>There is no adhesive mortise and mortise>There is no glue in mortise and mortise>There is no tenon and no glue>Lap joint without sleeve and adhesive>Single branch ultimate stretching>No sleeve and no glue for lap joint;At the same time,ABAQUS finite element analysis software was used for auxiliary verification.(2)With the change of layering ratio and the increase of layering angle selection range,the failure modes of test connectors gradually transition from tensile failure and splitting failure to extruding-shear failure and extrusion failure,and the safety and reliability of connectors are getting higher and higher.According to A and B series of experimental data and phenomena,the best laminate angle design proportion is 0~o,±45~o,90~o laminates account for 40%,50%,10%,respectively.(3)For the connected structure under axial tensile load,the ratio of fiber layering along axial direction 0~o is higher,which can improve the overall tensile strength;When the ratio of±45~olamination is high,the local compressive strength of the connection hole increases,so the corresponding lamination should be designed according to the specific bearing mode.Reasonable layering sequence and layering angle ratio can greatly improve the bolt connection strength of the laminate test connector and at the same time improve the stress caused by the hole opening.(4)Will stretch-different degree damage interface obtained by shear test macro microscopic observation,it is concluded that:destruction of extrusion on connection hole type,hole for bolt by compression buckling deformation of fiber bundles,and then squeeze the resin from uniform distribution into clusters,in the adhesive fiber bundles from resin matrix tensile damage fracture,pulls in junction plane between the adhesive can effectively delay delivery.