Experimental And Simulation Study On Tensile Failure Of Bolt Joint Of Composite Plate And Aluminum Alloy Plate

Composite materials have the advantages of high specific strength,high specific stiffness and designable performance,and are widely used in aviation industry and other vehicles manufacturing.Mechanical joint has the advantages of convenient installation and disassembly,low cost,high reliability,represented by bolt joint,is widely used in the manufacture of aircraft and other aircraft.However,as the composite material is anisotropic,the stress concentration is easy to occur at the joint of bolted joint structure,and its failure mechanism is more complex.The bolt joint is the weak link of the whole connecting structure.The strength of the connecting structure has an important influence on the reliability of the whole structure.In this paper,the failure characteristics of the bolted connectors of carbon fiber composite laminates and aluminum alloy plates under static tensile load were studied by static tensile test.Dynamic impact loading experiments of bolted connectors were carried out to study the damage characteristics of bolted connectors under impact loading.The corresponding finite element model is established and the subprogram of composite failure criterion is written.The static and dynamic impact tensile simulation analysis of connectors is carried out,and the failure behavior of connectors is further studied.The main work and conclusions are as follows:(1)Subprogram writing and validation of composite three-dimensional Hashin failure criteria and Tsai-Wu failure criteria.The mesh size correlation of finite element model was studied to determine the optimal mesh size in the model.The static stretching experiment of composite plate with open holes is carried out,and the corresponding finite element simulation is carried out.The effectiveness of the subroutine is verified by comparing the experimental results with the simulation results.(2)Experimental and simulation study on static tensile loading failure of bolt connectors.The static tensile loading failure tests of the bolt connectors were carried out using carbon fiber laminates,7075-T651 aluminum alloy plates and TC4 titanium alloy bolts as materials.The results show that the bolt holes in the laminates are elongated along the loading direction,and the failure mode is mainly the extrusion failure around the bolt holes of the composite plates,and the bolts are cut.A composite failure criterion subroutine was written,and the static loading simulation was carried out based on Abaqus implicit analysis module by using the research method of progressive damage.The results show that the failure mode is affected by the lay-up Angle of single layer,and the failure range distribution of fiber and matrix in single layer has obvious Angle correlation.At the same time,the secondary bending phenomenon in the loading process also has obvious influence on the failure mode of the laminates.(3)Experimental and simulation study on dynamic tensile loading failure of connectors.The dynamic tensile tests of the connectors were performed at the strain rates of 1000s-1,2000s-1 and 3000s-1 by using the Hopkinson rod test device.The results show that under the three strain rates,the failure modes of connectors are the failure of bolt holes of laminates and aluminum alloy plates.With the increase of the loading strain rate,the secondary bending phenomenon has more obvious influence on the failure mode of the connectors,and it is easier to cause the failure of the pass perimeter perpendicular to the loading direction.Based on the explicit analysis module of Abaqus and the 3D Hashin failure criterion Vusdfld subprogram written,the dynamic shock loading simulation of bolt connector was carried out in the 2000s-1 strain rate dynamic shock loading.The damage behavior of connectors under dynamic load is studied,and the effectiveness of the model is verified by comparison with the experimental results.