Study On Simulation Method Of High Strength Steel-CFRP Adhesive/Rivet Connection Structure For Automobile

With the vigorous development of automobile industry,the problem of environmental pollution caused by automobile is becoming more and more serious.In order to reduce the energy consuming and the emission of traditional cars,lightweight design of automobile is an effective way.The application of lightweight materials in autobody is one of the most important methods to achieve lightweight.The ideal body structure is a multi-material one which is used the most suitable materials in different body areas.It is designed based on the analysis of different mechanical properties of different materials and the bearing and stress conditions of different body areas.So when the different parts connected,it is necessary to choose the way which can connect different materials.Adhesive bonding and riveting can be applied to connect heterogeneous materials.Adhesive bonding structure has the advantages of uniform stress distribution and good appearance quality,but its damage absorption effect is poor,due to the thin bonding layer.Riveting structure has a good energy absorption effect when destructed,but it has the possibility of electrochemical corrosion when used alone.Therefore,considering the form of adhesive/rivet composite connection and making full use of their strengths and avoid their weaknesses,the research of this paper is carried out.This paper is based on a co-project with a bus company.This is,Design method of frontal collision energy absorption structure of bus body and Simulation method of Steel-CFRP adhesive/rivet connection structure.It selected the widely-used Q700 high strength steel and T700 carbon fiber reinforced composites(CFRP)were selected as the connection objects,which is widely used in autobody.At the same time,it chose Araldite1?2015 adhesives and 5052 aluminum alloy pulling riveting rivets were selected to connect the objects.Finally,a kind of simulation method for High Strength Steel-CFRP adhesive/rivet structure is established.Due to the characteristics of the adhesive layer,the cohesive element was selected to simulate it,and the quadric stress criterion was used to describe the failure of adhesive.The parameters in the quadric stress criterion are determined by means of the multi-angle test of the High Strength Steel-CFRP butt joints,and the quadric stress criterion is applied to the simulation of the High Strength Steel-CFRP single bonding specimen.In the simulation model,3D solid element with eight nodes was used to simulate the high strength steel,and continuous shell element was selected to simulate the CFRP.Compared the simulation and test results with the results of the test of the single lap joints of high strength steel-CFRP,it is found that the error of maximum failure load and failure displacement is within 10%.While the error of lateral warping perpendicular to the plane of the specimen is only 11.32%,and the load displacement curves obtained by the two have a good consistency.Aiming at the establishment of the rivet molding method,3D solid element with eight nodes was used to simulate it,and the Johnson-Cook fracture strain criterion was selected to describe its failure.The parameters in the Johnson-Cook fracture strain criterion are determined by 5052 aluminum alloy plate tensile experiment.The Johnson-Cook fracture strain criterion is applied to the simulation of High Strength Steel-CFRP single riveting specimen.In the model,3D solid element with eight nodes was used to simulate the high strength steel,and the continuous shell element was selected to simulate the CFRP.High Strength Steel-CFRP single riveting specimen experiment was also done.Compared the simulation result and the experiment result,it is found that the maximum failure load and failure displacement error are within 5%.At the same time,the error of lateral warping is only 9.38%,and the load displacement curves between simulation and experiment also have good consistency.By synthesizing the simulation method of High Strength Steel-CFRP bonding and riveting,the simulation method of High Strength Steel-CFRP single adhesive/rivet specimen is carried out.Experiment of High Strength Steel-CFRP single adhesive/rivet specimen were also done.There is a good consistency between simulation result and the experiment result.Both simulation and test results show that the adhesive will fails first,and then the rivet fails.When the adhesive fails,the load error of the adhesive failure is only 6.17%,and the displacement error is only 14.58%.When the rivet fails,the load error is 11.54%,and the error of this failure displacement is only 5.92%.Besides,during the whole process,the error of lateral warping is 7.79%.All these errors are within the acceptable range,which indicates that the simulation method of the High Strength Steel-CFRP Adhesive/Rivet connection structure is effective.