Study On Mechanical Properties Of Multi-connection Models Of Titanium Alloy And CFRP Panel

With the problem of excessive energy consumption and environmental pollution become increasingly serious,lightweight structures such as automobiles and aircraft based on lightweight materials have become the mainstream of research.In the field of structural manufacturing,connection is an indispensable way to inherit force and motion.Connection mainly includes mechanical connection,welding and bonding.In addition,the connection between metal and nonmetal often adopts mechanical connection and bonding.In this paper,Titanium alloy and CFRP single lap joints are taken as the research objects.Three kinds of connection modes,mechanical connection,bonding and hybrid connection,are studied respectively.The main research contents and achievements are as follows:(1)The bonding pressure and the thickness of the adhesive layer in the bonding process have been studied experimentally.The results show that when the thickness of the adhesive layer in the range of 0.1mm-0.3mm,the optimum joint strength is 1123.6N when the thickness of the adhesive layer is 0.2 mm.When the bonding pressure varies from 1000 N to 2500 N,the optimum bonding strength is 9135.7N at 2000 N.(2)The finite element simulation of mechanical joints,bonding and hybrid connection is carried out by using ABAQUS software,and the failure process of the lap joints have been analyzed and compared.The end of the adhesive layer of the bonded joints first fails,then the crack extends to the middle until the adhesive completely fails.The mechanical joint mainly bears the load at the center of rivet.The double-rivets riveted joint which parallel to the tensile direction has two rivets carrying unevenness,and the rivets near the tensile direction are relatively large.In the process of hybrid joint,the adhesive layer bears the load first,and then transfers to the rivet.The rivets can prevent the crack extension in the adhesive layer and increase the joint strength and fracture toughness.(3)The effects of bonding,single and double nails,and double nails' positions on the mechanical properties of the riveted and hybrid joints have been investigated experimentally.Found that with the increase of the number of rivets,the joint strength and toughness of riveted joints increase significantly while the hybrid joints strength decreases.During the tensile process,the adhesive layer bears the load first.After the adhesive layer fails,the rivets can also bear part of the load.The rivets delayed crack propagation and improved the joint strength and fracture toughness.The position of rivets can hardly affect the joint strength.Comparing the experimental results with the finite element analysis results,the difference is small,indicating that the experimental model in this paper is credible.In addition,the influence of rivet holes on the bonded joints was studied,and the corresponding holey bonding experiments have been carried out.Due to the stress concentration around the holes,the bonding strength decreases.With the number increasing of holes,the weakening effect on the joint strength is more obvious.Compared with bonded,riveted and holey bonded joints,the hybrid joint not only improve the joint strength and fracture toughness,but also reduce the number of rivets and achieve the purpose of light weight.