Three-point Bending Experiment And Finite Element Analysis Of C/SiC Composites

The aerospace industry is undoubtedly of great significance to our country.It involves many cutting-edge technologies and it is closely related to national modernization,civil aviation and national defense.The advanced hot end materials used in the gas turbine engines as the heart of the aircraft have been a major problem that the international material workers have been trying to solve.Carbon fiber reinforced silicon carbide ceramic matrix composite(C/SiC)is the most widely studied,most successful and widely used ceramic matrix composite.It has important applications in the hot end parts of aircraft engines,such as nozzles,combustion chambers,turbines and blades,as well as thermal protection systems for hypersonic vehicles.The failure mechanism and interface mechanical behavior of ceramic matrix composites can reflect the influence of interface on the properties of composites,which directly affects the processing and removal mechanism of ceramic matrix composites,the failure of materials and the crack characteristics in the process of material processing.In order to fully exploit and utilize the potential properties of fiber reinforced composites and design materials efficiently,the failure mechanism and mechanical properties of the interface must be known first.Taking C/SiC as the research object,the representative volume element(RVE)model based on a single fiber and its surrounding matrix material is firstly constructed.The failure mechanism of C/SiC material under different fiber orientations was analyzed by three point bending test and finite element simulation.The influence of interface on the mechanical properties of fiber / matrix was studied.Secondly,the cohesion model is used to characterize the interface and the finite element analysis of the three point bending is carried out.The toughening mechanism,failure mode and failure mechanism of fiber reinforced composites were discussed.Finally,the numerical simulation and experimental data were coMPared to verify the constitutive model of the C/SiC interface.The deformation behavior of the interface of C/SiC composite under three point bending mode is numerically simulated and tested.The results show that the cohesive zone model is suitable for characterizing the interface behavior of C/SiC composites.Interfacial debonding strength is approximately 26-28 MPa when the fiber orientation is transverse and normal.The interfacial debonding strength increases with interface thickness until it remains stable value.When the interface thickness is about 0.2-0.3?m,the interfacial debonding strength reaches the maximum value.Comparing the three point bending experiments of different orientations(transverse and longitudinal),it shows that non-destructive fracture can be achieved when the fiber is longitudinal,and the fracture strength is much greater.In summary,the mechanical behavior and constitutive model of C/SiC composite interface are studied by three point bending test and simulation.The conclusions obtained in this study are helpful for the design,preparation and production of composite materials.