Effects Of Fastener Parameters On Tensile Properties Of C/SiC Composite Joint Structures At High Temperatures

Ceramic matrix composites exhibit excellent high temperature mechanical properties and thermo-physical properties,which make them widely used in aerospace and aeronautical fields.The hybrid Ceramic Matrix Composite(CMC)and alloy bolted joints are common connection structures for high temperature application of ceramic matrix materials.In high temperature environments,the thermal expansion mismatch between CMC and superalloy will result in changes of initial assembly parameters,which will then affect the load bearing capacity of the joints.In addition to the assembly parameters of the fastener,the size parameters of bolt are also important factors affecting the bearing capacity of ceramic matrix composite bolt joints.Therefore,it is of great significance to investigate the influence of bolt parameters on high temperature load bearing capacity of ceramic matrix composite-superalloy bolted joint for its application in aerospace field.Firstly,a nonlinear constitutive model of2 D C/SiC ceramic matrix composites suitable are introduced for stress analysis.On basis of the material model,Tsai-Wu theory and material stiffness degradation rules were utilized to implement a progressive damage analysis of C/SiC composites bolted joint.A procedure for the damage analysis was provided.Secondly,finite element models are established for simulation of uniaxial tension performances of the CMC and superalloy bolted joint structure by using finite element software ABAQUS.The influence of thermal expansion mismatch on bolt assembly parameters and high temperature tensile properties of bolted joints are studied.The results showed that the thermal mismatch between CMC and superalloy plates will result in reduction of bolt-preloads and bolt-hole clearances of CMC plate.When the initial bolt-hole clearances are small,the gap between bolt and CMC hole will be changed to minor interference from clearance fit at high temperatures.When the initial clearance is larger than 0.8%,the final failure will increase first and then decrease,and finally increase with the rise of temperature.Finally,based on the established finite element model,the effects of bolt parameters on tensile strength at room temperature and 750?are studied for the CMC-superalloy bolted joint structures.The results showed that when the bolt diameter,bolt head diameter and bolt head thickness are respectively 5mm,9.5mm,and 2.8mm at room temperature,and 5mm,9.8mm,and 2.8mm at 750?,the final failure loads reach the maximum values for the given ranges of bolt parameters...