Research On Mechanical Properties Of Unidirectional C/SiC Composite Under Stress-Oxidation Environment

In this paper, the unidirectional C/SiC composite is taken as example to discuss the performance of UD-CMC under stress-oxidation environment. By using finite element method(FEM), the failure process of UD-CMC under axial tensile stress is simulated. The evolving compliant interface(ECI) debonding model is applied in simulating of the tensile performance of ceramic matrix composite firstly. The effects of fiber volume fraction and shape parameter on stress-strain curves are discussed. And the whole failure process of unidirectional C/SiC composite under tensile stress is simulated. In order to verify the reliability of the model, the stress-strain of unidirectional C/SiC composite is predicted and compared with experiment results. The comparison result shows that the predicted stress-strain curves agree well with the experiment results. Also the evolution process of a long crack is simulated.Base on the research of mechanic behavior of UD-CMC under non-stress oxidation environment, the mechanic behaviors of weak interfacial bonded UD-CMC under stress-oxidation(400-900?) environment are derived discussed by taking unidirectional C/SiC composite as example. When the UD-CMC is subjected to tensile stress the matrix will crack, which provides the channel for oxygen diffusion. When the temperature is higher than 400? carbon fiber will react with oxygen. The oxidation of fiber will weaken the tensile performance of UD-CMC. When the applied stress exceeds the initial matrix cracking stress, the effect of matrix cracks on the mechanic behaviors of UD-CMC under high-temperature environment can't be neglected. In this paper, the residual modulus and residual strength of unidirectional C/SiC composite are predicted and compared with the experimental data. The comparison result indicates that the model in this paper is reasonable.At last, according to the observation of experiment, a notch-like oxidation model is proposed and used to simulate the mechanic behaviors of strong interfacial bonded UD-CMC under high-temperature. The rules of depth vary with the oxidation factors are derived. According to the function of oxidation depth, the residual strength and residual modulus are derived as well. To verify the reasonability of the model, the residual strength and residual modulus of unidirectional C/SiC composite are predicted by the notch-like oxidation model. And then, the predicted results are compared with experiment data. The errors are very small. A finite element model was built to study the mechanic behaviors of unidirectional C/SiC composite under oxidation atmosphere. The simulation results are compared with experiment data as well.