The Thermo-structural And Tensile Strength Analysis Of C/SiC Composite Bolted Joints

Ceramic matrix composites have been widely used in the thermal structure of aircraft because of their high temperature resistance,wear resistance,high temperature creep,thermal conductivity and low thermal expansion coefficient.In aircraft structure,ceramic matrix composites are inevitably connected with metal parts.When this type of joint structure is used at high temperature environment,the mismatch of thermal expansion coefficients between ceramic matrix composite and metal will lead to the additional thermal stress in the joint area and change the connection parameters of joint,so that the structure will be damaged in advance.Therefore,it is of great significance to study the influence of temperature on the ceramic matrix composite and metal bolted joint structure and its application in aerospace.First,in order to realize the stress calculation and failure analysis of the 2D woven C/Si C composites in the ceramic matrix composite bolt joint structure,this paper uses the macroscopic phenomenological constitutive model to describe the nonlinear characteristics of the stress strain curve of the 2D woven C/Si C composite,and combines the Tsai-Wu strength theory as the failure criterion of the ceramic matrix composite.The material model is embedded into the ABAQUS finite element model by UMAT subroutine.The finite element simulation of the loading and unloading processes of the flat plate and the tension process of the plate with a hole are carried out,and the validity of the UMAT subroutine is verified by comparison with the experimental results in literature.Secondly,the heat transfer model of single screw bolt joint structure composed of 2D woven C/Si C ceramic matrix composite and high temperature alloy GH4169 is firstly established by using the finite element software ABAQUS.The transient temperature field of the model under a given thermal boundary load is obtained by calculation.The results of the temperature field are introduced i nto the stress field analysis,and the thermo mechanical coupling analysis of the model is realized by combining the UMAT subroutine of the material model.By studying the thermal stress field of the bolt joint structure under the effect of thermal load,the influence of the transient thermal loads on the pre-tightening force and bolt-hole clearance of the structure is discussed.Finally,the strength analysis of bolt joint structure of the 2D woven C/Si C ceramic matrix composite material and high temperature alloy was carried out with different pre-tightening forces and different bolt-hole clearance,and the influence of different pre-tightening force and bolt-hole clearance on the tensile properties of the structure was studied.The strength analysis of the bolt joint structure under different temperature conditions is carried out to discuss the variations of the joint strength with the pre-tightening force and bolt hole clearance,and the strength analysis of the bolt joint structure with different pre-tightening force at 750? is carried out.