Study On Hole-clinching For CFRP And Aluminum Alloy Sheet

Carbon fiber composites have excellent material properties,such as high specific modulus,high specific strength and so on.They have attracted more and more attention in the automotive industry.At present,most of the vehicle body is still sheet metal.The connection between carbon fiber composites and metal materials is an important factor affecting the service performance of the body structure.In this paper,hole-clinching for joining CFRP and Aluminum Alloy Sheet is studied.The main research contents include tensile properties of CFRP sheets with hole,forming properties of joints and unidirectional tensile properties of joints.Emphasis is placed on the analysis of joint forming damage,joint failure and damage evolution process of prefabricated CFRP sheets.Uniaxial tensile mechanical properties and damage modes of perforated CFRP laminates were studied.tensile tests were carried out on three kinds of perforated CFRP laminates,[0]₁₆,[0/90]_4s,[45/-45]_4s.The load-displacement curves,strain fields and fracture modes of three kinds of laminates are obtained.Based on continuum damage mechanics,a three-dimensional CFRP material model was established,and a finite element model of prefabricated CFRP laminates was established to simulate the unidirectional tensile experiment.The progressive damage process of three kinds of CFRP sheets under single tension was analyzed,including matrix damage process,delamination damage process and shear damage process.Forming process of clinching joint between prefabricated CFRP and aluminium alloy was studied.The size of clinching die and the alignment device are determined.Clinching test of prefabricated holes CFRP plate and aluminium alloy was carried out.There are three diameters of sheet metal including 8.0mm,8.2mm,8.4mm,The influence of lower plate aperture on neck thickness,self-locking value and bottom thickness is analyzed by experiment.then the clinching finite element model is established to study the damage of CFRP sheets with different layers during joint forming.including three layers[0/90]₃?[45/-45]₃ and[45/90/-45/0/90/45].Single-tension mechanical properties and joint failure of clinched joint between prefabricated CFRP and aluminium alloy were studied.Tensile tests were carried out on the joints of CFRP with hole diameters of 8.0mm,8.2mm,8.4mm,laminated forms of[45/-45]₃,[0/90]₃ and[45/90/-45/0/90/45],The influence of the diameter of circular hole and the form of lamination on the bearing capacity and failure mode of CFRP laminates is analyzed.There are two failure modes in the joint,one is the fracture of the upper plate of aluminium alloy leading to the fracture of the joint neck,the other is the peeling failure of the joint caused by the failure of the CFRP plate.The finite element model of joint tension was established to simulate the unidirectional tension process,and the damage of CFRP plate under the failure modes of joint neck fracture and joint peeling failure was analyzed.