| The design process of the multi-material body structure inevitably involves the connection of heterogeneous materials.The connection technology of heterogeneous materials is one of the key technologies for realizing vehicle weight reduction.In this paper,the research on the bonding between carbon fiber composite materials(CFRP)and aluminum alloy materials(Al),clinching,and hybrid connection technologies was carried out.The finite element theory,multi-objective optimization methods,and sensitivity analysis techniques were used synthetically.The cutting performance and peeling performance are the optimization goals,and the mechanical properties of the joint are improved while the structure is lightweight.Firstly,the existing joining methods were concluded and summarized,in order to find out the development direction and the deficiency of the current joining methods.The CFRP and aluminum alloys were selected as the connected materials,the domestic and overseas research status of bonded joint,clinching and hybrid connection was summarized,at the same time,analyzed the typical application scenarios of different connection methods on the lightweight automobile body.Next,modelling parameter tests and model validation were carried out.According to the GB standard and the ASTM standard,the material parameters of CFRP,aluminum alloy,and adhesive were tested,and the material parameters were obtained to establish the constitutive model respectively.Modeling the sample and using the finite element method to analyze,the results were compared with the test to verify the effective of the material constitutive model.Thirdly,the joint performance of adhesive bonding and clinching was studied.The basic theories,force and failure modes of adhesive bonding and clinching were discussed.Established single-lap and L-peel finite element simulation models and conducted experimental verification.The two types’ mechanical and energy absorption under different factors(Adhesive bonding factors were lap length,lap width,thickness of adhesive and thickness of aluminum alloy.Clinching factors were punch diameter,fillet radius,draft angle and die depth)were analyzed and concluded.What’s more,in order to improve the performance of joint,the structure of single lap adhesive joint and clinching were designed(Adhesive joint was arc and rectangular groove structure.Clinching was multi-clinching structure).Then,Combination design of two type joining:adhesive bonding and clinching.Bonding has the problems of brittle failure,low peel strength,etc.Clinching can make up for the above defects,so the hybrid connection performance consisting of the two was studied.The hybrid joining process sequences,clinching after curing and clinching before curing,were compared.In order to ensure that the adhesive layer was not damaged,the clinching before curing process was selected first.Using a combination of test and simulation,the performance of hybrid connections was analyzed and compared with the single adhesive bonding and clinching.The results show that the hybrid joints can achieve the effective complementarity of the two joints and realize the joint failure in stages.Finally,according to the characteristics of step-by-step failure in hybrid connection,the influence of various factors on the performance of joints was considered.In this paper,step-by-step optimization techniques were used to establish two approximate models of connection methods respectively.Multi-objective optimization methods were used to optimize the design of bonded joints and clinching.The optimal Pareto solution set for the two connection methods was obtained and some optimizations were performed.The results were analyzed and verified.The results show that the accuracy of the approximating model is high,the error between the optimization result and the simulation result can be controlled within 9%,the optimal result of the stepwise optimization is the optimal result of the hybrid connection,and the stepwise optimization technique can achieve the optimal design of the hybrid joint. |
