Study On Mechanical Behaviors Of SiC_f/Ti Composite Under Tensile And Fatigue Loads

With the rapid development of high-tech aviation technology,the application of metal matrix composites in aeroengine has attracted much attention.Metal matrix composites in aeroengine experience complex and changeable loading conditions.So this paper focus on the mechanical behaviors of metal matrix composites under tensile and fatigue loads,in order to lay the theoretical foundation for its more extensive applicaton.In this paper,SiC_f/Ti composite is taken as an example.Experiments of metal matrix composites under axial and off-axis loading have been conducted.The mechanical property of SiC_f/Ti composite under static tension loads has been studied by SEM and energy analysis.By using the finite element method with continuous cohesive zone interface model,the failure behavior and matrix crack process of metal matrix composites under axial tensile stress is simulated.The effects of fiber volume fraction and interface parameters are discussed.The stress-strain of SiC_f/Ti composite is predicted and compared with experiment results.The comparison result validates the reasonability and reliability of the model in this paper.Based on the analysis of axial tensile properties,a mesoscopic mechanic model is developed to describe the off-axis property of metal matrix composites involving cohesive zone model.Besides,a finite element model is adopted,considering the tensile-shear coupling effects of interface under off-axis loads.The simulation result shows that off-axis angle is the key factor.Both the results of mesoscopic mechanic model and the finite element model are compared with experimental data.The comparison result indicates that finite element method can well simulate the off-axis behavior of metal matrix compsotes.Last but not least,the fatigue hysteresis behavior of metal matrix composites under tensile-tensile cycle loads is studied.According to the observation of experiment,high peak stresss,medium peak stress and low peak stress conditions are analyzed and the fatigue hysteresis loop is predicted.The fatigue damage process of metal matrix composites is directly described by calculating its fatigue hysteresis dissipation and damping ratio.By combining the fiber statistical failure criterion and the maximum strain failure criterion,the fatigue life of SiC_f/Ti composite is predicted.