Method for calculating gaseous diffusion and oxidation evolution of ceramic matrix composite (CMC) structure

A method for calculating gaseous diffusion and oxidation evolution of a ceramic matrix composite (CMC) structure, comprising:

• determining a temperature and a load distribution in a structural member;
• determining a matrix crack distribution in the CMC structure by, according to a temperature field and a stress field, based on a matrix cracking model, calculating a matrix crack density and a matrix crack width related to a temperature and a stress in the CMC structure;
• based on the matrix crack distribution, averaging a total amount of gaseous diffusion in a gas flow channel to establish an equivalent diffusion coefficient model of a fiber bundle composite scale related to the matrix crack distribution based on the matrix crack width and the matrix crack density in fiber bundle composites with an axial length;
• establishing a representative volume element (RVE) model of woven CMCs by conducting image recognition on an X-ray computed tomography (XCT) scan image of a meso-structure of the woven CMCs used in the structural member, describing a warp direction by a cosine function, describing weft yarns in a form of a straight line, and observing to obtain geometric parameters to establish the RVE model;
• establishing an equivalent diffusion coefficient model of a RVE scale to characterize a gas flow of the CMC structure, by, based on pore characteristics, regarding the fiber bundle as a homogeneous material, and substituting the equivalent diffusion coefficient model of the fiber bundle composite scale into the yarn of the RVE model to establish the equivalent diffusion coefficient model of the woven CMCs on the RVE scale;
• calculating a distribution of a gas concentration in the CMC structure by calculating the distribution of the gas concentration of each element in the CMC structure in a transfer direction using a finite difference method;
• calculating a distribution of oxidation products in the structure by calculating a growth thickness of an oxide at cracks and pores in each element according to the gas concentration;
• and
• calculating sealing conditions comprising changes in the crack width and a pore characteristic quantity of the gas channel, substituting a new gas channel characteristic quantity into the averaging and establishing steps, calculating a new equivalent diffusion coefficient field to realize recalibration of the gas channel, and repeating calculation of the distribution of the gas concentration and the calculation of the distribution of oxidation products to realize a calculation of distribution of the oxidation products in the structural member at different times.