Research On 6061Al-CFRP Welding-rivet Hybrid Bonding Technology And Forming Control

With the increasing of global warming and other climate issues,lightweight manufacturing with low-carbon and environmentally friendly features has become a hot topic,and material lightweighting is the most important part of the lightweight process.Light alloy which was represented by aluminum alloy and carbon fiber reinforced plastics(CFRP)have attracted more and more attention because of their high strength and low density.However,how to connect aluminum alloys and carbon fiber reinforced plastics with large differences in physical and chemical properties is a major problem in the lightweight manufacturing industry and has attracted widespread attention from domestic and foreign researchers.The traditional bonding method has certain limitations on the joining of aluminum alloy and carbon fiber reinforced plastics,In this paper,a new welding-rivet hybrid bonding technology,which combines welding and riveting to realize effective connection of aluminum alloy and carbon fiber reinforced plastics,was proposed and improved.The experimental materials used continuous carbon fiber reinforced polyether ether ketone(CF/PEEK)and 6061-T6 aluminum alloy.Based on the stepped rivet structure,a new semi-penetrating structure was proposed,which not only retained the type-stepped rivets which have the advantage of heat buffering,but also reduced the processing procedures and improved production efficiency.At the same time,a method for defining the cross-sectional profile of laser-arc welding joints was proposed,which solved the problem that the traditional definition method of penetration depth and penetration width cannot accurately describe the cross-sectional profile of Low Power Laser Induced Arc hybrid(Laser-Arc)welding joints.The influence of welding parameters on the cross-sectional morphology of the weld pool of welding-rivet hybrid joints and the fracture mechanism under tensile-shear load were explored.For welding-rivet hybrid bonding,the shape of the welding joint is the most important factor affecting the quality of the bonding.Therefore,based on the new method for defining the cross-sectional profile of laser-arc welding joints,this paper built a BP neural network model optimized by genetic algorithm to realize the accurate prediction of the welding joint fusion line and the control of welding forming in the process of welding parameters welding-rivet hybrid bonding.The study found that the semi-penetrating welding-rivet hybrid bonding structure can realize the effective joining of 6061-T6 aluminum alloy and CF/PEEK material,and the welding shape is beautiful.There were three fracture modes when subjected to tensile-shear loads,namely the fracture of the welding bead,pull-out fracture and CFRP fracture.It was found that the mechanical properties and fracture mode of the hybrid joint were affected by the welding parameters and the size of the rivet.As the heat input increases and the rivet diameter raises,the joint welding area enlarges,and the fracture mode changes from the fracture at the welding bead to the pull-out fracture,eventually transformed into the CFRP fracture.When the rivet diameter was 10 mm,the tensile strength under the same parameters was the highest,the maximum tensile shear breaking load reached 2229 N,which is about 87% of the base metal strength,and the failure mode is pull-out fracture.Using the cubic interpolation fitting in MATLAB,the geometry of the welded joint was accurately fitted.The results showed that the fitting line was close to the actual contour of the welding fusion line,and the prediction accuracy is better.The average absolute percentage error(Mape)of each set of data was not more than 3%,and the standard deviation(STD)was less than 0.1.Under the optimization of the reverse prediction model,the bearing capacity of the hybrid joint was improved,and the maximum tensile shear load was 2648 N,which provided a new idea for the quality optimization and energy regulation of welding-rivet hybrid bonding.