Research On Mechanical Properties Of Ceramic Matrix Composites Under Stress-Oxidation Environment

SiC/SiC composites have become important candidates for hot sections of aero-engine due to their high temperature resistance,oxidation resistance,low density and high strength.The high temperature,oxidative atmosphere which exists in the hot parts directly promotes the oxidation of materials,and leads to the decline of mechanical properties,while the existence of stress aggravates this process.Therefore,the topic of this paper is to study the tensile properties of SiC/SiC composites under high temperature stress-oxidation environment,which can provide a reference for the design and use of SiC/SiC composites.Firstly,an oxidation kinetics model of unidirectional SiC/SiC composites under high temperature stress-oxidation environment was established,based on the classical mass transfer theory,the oxidation mechanism of SiC/SiC composites and the matrix crack model.In this model,the oxidation behaviors of C interface,SiC matrix and fiber were considered comprehensively.The model can be used to simulate the internal structure evolution of composite under high temperature stress-oxidation environment.The mass change rate of materials was selected as the parameters to measure the oxidation degree.By comparing with the experimental results,the validity of the model was verified.On the basis of oxidation kinetics model,this paper established a prediction model for residual tensile properties of SiC/SiC composites under high temperature stress-oxidation environment by taking the degration of components' properties into account.The residual strength and stiffness of the composites which were oxidized for a certain time can be predicted through this model.The comparison between the predicted results and the experimental data shows that this model can effectively reflect the degradation law of the tensile properties of actual materials,and has certain theoretical application value.At last,by modifying the oxidation parameters which related to the oxidation mechanism of components in water vapor environment,the stress-oxidation kinetics model and residual tensile property prediction model of SiC/SiC composites in high temperature and steam atmosphere were established.The Degradation Laws of oxidation and tensile properties of materials in water vapor environment were proposed,which laid a foundation for further research.