Finite Element Analysis Of Fiber Push-out Of C/SiC Composites

C/Si C composites are one of the most widely and successfully used ceramic matrix composites, and it has huge development potential in the aerospace field recently. Its excellent material performance is closely related to the interface, whose toughening form, failure mechanism and stress conditions directly affect the mechanical properties and application of C/Si C composites. So how to measure the interface shear strength of C/Si C composites is one of the key problems of the interface research.The single fiber push-out method can response the real material performance of the interface and has caused lots of attention in the recent years. Based on the mesoscopic mechanics theory, this paper used push-out test and numerical simulation together to test the interface shear strength and analyze the relevant influence factors. Main work of this paper is as follows:Firstly, the formation, damage and failure mechanism of the interface of C/SiC composites were summarized and studied. The cylindrical fiber push-out theory model of the C/SiC composites and a bilinear interface constitutive model of the interface were established, which provide the theoretical foundation for the research of the interface characteristics during the push-out process and interface mechanical properities.Using the FEM software ABAQUS, an axi-symmetric finite element model was used to simulate the single fiber push-out process of C/Si C composites. The mechanical properties and the process of failure and damage of the interface were analyzed, and the interface shear strength is about 35 MPa. In order to analyze the behavior of the debonding and failure process, the thermal residual stress caused in the curing process, the interface roughness, the thermal expansion coefficient of fiber and matrix, the curing temperature, the anisotropic of the fiber and so on were taken into consideration.According to the fiber push-out simulation, the fiber push-out test was designed, and the test equipment Nano Indentation G200 was adopted. The work-piece is one-dimensional C/SiC composites and its thickness is 100 microns. Through the output load-displacement curve, the interface debonding process can be known, the maximum debonding force is about 73 m N and the interface shear strength is around 35 Mpa. The simulation results consist with the test results, which verified the rationality of the simulation model.In conclusion, this paper studied the process of interface debonding and failure of the C/SiC composites, the interface shear strength and its relevant influence factors.This research plays an important role in the interface constitutive research.The results can be used for the parameters optimization of the design of the interface and the composites. In addition, the conclusions provide an effective method and a theoretical rule for the manufacture and machine of the C/SiC composites.