A multi-scale modeling method suitable for SiC / SiC composite cladding tube and application thereof

Abstract

This invention relates to the field of 3D modeling technology, specifically to a multi-scale modeling method and its application applicable to SiC / SiC composite clad tubes. The method includes: performing CT scanning on the clad tube to obtain its length, radius, number of fibers, and the woven structure of the clad tube preform; drawing a macroscopic clad tube model based on its length and radius; obtaining a fiber bundle preform model and a mesoscopic matrix model based on the number of fibers and fiber paths in the macroscopic model; obtaining a mesoscopic fiber bundle unit cell model through Boolean operations based on the fiber bundle preform model and the mesoscopic matrix model; and obtaining a microscopic RVE model based on the major and minor axis radii of the fiber bundles in the mesoscopic fiber bundle unit cell model and the microstructure of the fiber bundle cross-section of the clad tube. This invention comprehensively considers the combined influence of the composite component structure and component weaving structure parameters at different scales, solving the problem of the impact of size effects on the simulation accuracy of traditional macroscopic models.

Description

Technical Field

[0001] This invention relates to the field of 3D modeling technology, specifically to a multi-scale modeling method for SiC / SiC composite clad tubes and its application. Background Technology

[0002] Fuel cladding, which holds nuclear fuel pellets, prevents radioactive fission products from leaking into the external environment through the coolant, serving as the first line of defense for reactor core safety. Fuel cladding failure due to high-energy neutron irradiation, corrosion / oxidation in high-temperature, high-pressure cooling media, complex stress, and interaction with nuclear fuel represents the most severe safety challenges facing reactor cores. Zirconium alloy cladding, with its high high-temperature strength, good corrosion resistance, small neutron absorption cross-section, and good compatibility with uranium dioxide, is an internationally accepted fuel cladding material for pressurized water reactors. However, zirconium alloy cladding fuel assemblies pose a serious safety hazard during a Loss of Coolant Accident (LOCA): the zirconium alloy reacts violently with high-temperature steam, rapidly oxidizing and producing a large amount of flammable hydrogen gas that could explode, damaging the nuclear power unit and causing nuclear leakage. To prevent such accidents, developing accident-resistant nuclear fuel cladding, enhancing its resistance to steam oxidation, reducing hydrogen production, and maintaining core integrity for extended periods under accident conditions to ensure no leakage of nuclear fuel and fission products has become a top priority for nuclear power safety development.

[0003] SiC / SiC composites are continuous SiC fiber-reinforced SiC matrix composites (SiC / SiC). They are ceramic matrix composites with strong and toughening properties obtained by adding continuous fiber-reinforcing phases to a ceramic matrix for exogenous toughening and using appropriate weak interfacial phases for matching. Through strengthening mechanisms such as fiber bridging and interfacial crack deflection, SiC / SiC composites overcome the inherent brittleness of traditional SiC ceramics, making them less prone to catastrophic damage under reactor accident conditions. Simultaneously, this material possesses a small neutron absorption cross section, excellent high-temperature chemical inertness, excellent high-temperature strength, low activation, and radiation resistance, making it considered the preferred material to replace existing zirconium alloy fuel cladding and to develop accident-resistant fuel cladding.

[0004] In simulations of SiC / SiC composite clad tubes, those skilled in the art directly utilize homogenization theory to establish macroscopic models of the clad tubes. However, this method simplifies the SiC clad tube into a multi-layer composite material, failing to reflect the fibers and fiber reinforcement effects in the model. It merely considers the overall clad tube structure in a simple homogenization manner, neglecting the structural characteristics at the mesoscopic and microscopic levels. Therefore, the model lacks accuracy.

[0005] Existing technologies disclose a three-dimensional parametric modeling method for SiC composite cladding tubes, which mainly includes the following parts: 1) setting the curve equation of the braided preform structure, defining the cladding tube radius, cladding tube length, braiding angle, and braiding density; 2) establishing a three-dimensional geometric model of the braided preform structure using parametric methods; 3) determining whether the braided preform structure has geometric overlap; if it does, returning to step 2 to regenerate the geometry of the braided preform structure; 4) determining whether the braided preform structure forms a closed loop; if it does not form a closed loop, returning to step 2 to regenerate the geometry of the braided preform structure; 5) setting the outer diameter of the cladding tube and the thickness of the substrate; 6) creating the geometry of the complete SiC composite cladding tube, using Boolean operations to distinguish between the braided preform and the substrate, and ending the modeling process. This method establishes a macroscopic model of the SiC composite cladding tube using curve formulas, but the model established by this method has a relatively detailed and complex internal structure, making mesh generation difficult and computationally intensive, which is not suitable for finite element analysis.

[0006] In the existing technology, a representative volume element (RVE) model of SiC composite material with internal shape and position defects has been established by measuring the microscopic geometric parameters using scanning electron microscopy. This model is only suitable for the simulation study of the microscopic level of SiC composite material prepared by CVI process, and cannot realize the study of the macroscopic level of SiC composite cladding tube structure. Summary of the Invention

[0007] To address the aforementioned technical problems, the main technical issue solved by this invention is that SiC / SiC composite materials consist of three structural units: fibers, interfaces, and a matrix. These structural units span from nanometer to micrometer scales, making them typical multi-component heterogeneous structural materials. However, nuclear cladding tube components prepared using SiC / SiC composite materials contain prefabricated woven structures with millimeter-scale dimensions. Simulation modeling and analysis conducted only at the macroscopic scale cannot effectively reveal the impact of the size effect of the composite structural units on the macroscopic mechanical and thermal properties of the cladding tube. Furthermore, directly constructing a refined model of the SiC / SiC composite component structure at the macroscopic scale easily leads to excessive computational load and high computational costs.

[0008] This invention provides a multi-scale modeling method for SiC / SiC composite clad tubes and its application. This method is suitable for simulation modeling and analysis of SiC / SiC composite clad tubes, comprehensively considering the combined influence of composite component structure and component weaving structure parameters at different scales, thus solving the problem of size effects affecting the simulation accuracy of traditional macroscopic models. Furthermore, this method establishes finite element models at the macroscopic, mesoscopic, and microscopic levels, each of which can run independently or collaboratively, addressing the issues of high computational load and cost associated with macroscopically refined models.

[0009] The first objective of this invention is to provide a multi-scale modeling method suitable for SiC / SiC composite clad tubes, including: CT scans were performed on the cladding tube to obtain its length, radius, number of fibers, and the braided structure of the cladding tube prefabrication. Draw a macroscopic model of the cladding tube based on its length and radius; The fiber path is obtained based on the braided structure of the cladding tube preform; The fiber bundle preform model and the mesoscopic matrix model are obtained based on the length, radius, number of fibers, and fiber path of the macroscopic cladding tube in the macroscopic cladding tube model. Based on the fiber bundle preform model and the mesoscopic matrix model, a mesoscopic fiber bundle unit cell model is obtained through Boolean operations. The major axis radius and minor axis radius of the fiber bundle are obtained based on the microscopic fiber bundle unit cell model; Obtain the microstructure of the fiber bundle cross-section of the cladding tube; Based on the microstructure of the fiber bundle cross-section of the cladding tube, as well as the major and minor axis radii of the fiber bundle, a microscopic RVE model is obtained.

[0010] Preferably, the fiber path is obtained according to the following steps: The fiber path characteristics are obtained based on the braided structure of the cladding tube preform. Based on the fiber path characteristics, the sine curve equation is fitted with the parametric equation of a circle to obtain the path equation of a clockwise fiber bundle; at the same time, the path equation of a counterclockwise fiber bundle is obtained; the fiber path is described based on the path equation.

[0011] Preferably, when obtaining the fiber bundle preform model, the working plane is first determined by the normal vector method; then the fiber bundle preform model is drawn according to the fiber path and the working plane.

[0012] Preferably, when obtaining the microstructure matrix model, the radial section of the matrix is ​​first drawn and then rotated to generate the microstructure matrix model; wherein, the radial section of the matrix is ​​obtained based on the circumferential arc length and axial length of the matrix.

[0013] Preferably, the circumferential arc length of the substrate is calculated using the following formula:

[0014] In the formula, Arc Indicates the circumferential arc length of the matrix; a Indicates the number of fibers; R Indicates the radius of the macroscopically encased tube; n This indicates the number of the smallest periodic units of a fiber.

[0015] Preferably, the axial length of the substrate is calculated using the following formula:

[0016] In the formula, Arc Indicates the circumferential arc length of the matrix; h Indicates the axial length of the matrix; Indicates the weaving angle of the prefabricated structure.

[0017] Preferably, when acquiring the micro RVE model, the fiber distribution in the RVE unit model is obtained based on the microstructure of the fiber bundle cross-section of the shell tube, and the mathematical relationship between the length and width of the unit cell matrix and the fiber radius is determined, and the micro RVE model is drawn based on the mathematical relationship.

[0018] Preferably, the mathematical relationship between the length and width of the unit cell model matrix and the fiber radius is as follows:

[0019] In the formula, Indicates fiber volume fraction; r Indicates the fiber radius in the unit cell model matrix; c Indicates the length of the matrix in the unit cell model; d Indicates the width of the matrix in the unit cell model; The formula for calculating fiber radius is as follows:

[0020] In the formula, r Indicates the fiber radius in the unit cell model matrix; V f Indicates fiber volume fraction; S The cross-sectional area of ​​the fiber bundle is represented by N; N represents the number of fibers. The formula for calculating the cross-sectional area of ​​the fiber bundle is as follows:

[0021] In the formula, S represents the cross-sectional area of ​​the fiber bundle; and These represent the major axis radius and minor axis radius of the fiber bundle, respectively.

[0022] The second objective of this invention is to provide an application of a multi-scale model of SiC / SiC composite clad tubes in predicting the intrinsic properties of the material.

[0023] The third objective of this invention is to provide an application of a multi-scale model of SiC / SiC composite clad tubes in the analysis of materials mechanics and heat transfer.

[0024] The present invention has at least the following beneficial effects: This invention provides a multi-scale modeling method for SiC / SiC composite clad tubes and its application. This method employs a multi-scale modeling approach to establish a homogenized model of the SiC / SiC composite clad tube at the macroscopic scale, a fiber bundle unit cell model at the mesoscopic scale, and a representative volume element (RVE) model at the microscopic scale. This avoids the problems of complex structures, difficulty in meshing, or computational limitations associated with refined models. It achieves low computational cost, high computational speed, and ease of use for finite element analysis at each scale. The structural characteristics of the clad tube are expressed at each scale, thereby addressing the issue of size effects. Attached Figure Description

[0025] Figure 1 This is a flowchart of the multi-scale modeling process provided by the present invention; Figure 2 This is a schematic diagram of CT scan reconstruction of the casing tube; Figure 3 It involves using scanning electron microscopy to observe the microstructure of fiber bundles in the cladding tube; Figure 4 This is a schematic diagram of the macroscopic model of the SiC / SiC composite clad tube. Figure 5 This is a schematic diagram of the establishment of a microscopic fiber bundle unit cell model of a SiC / SiC composite clad tube; Figure 6 This is a schematic diagram of the establishment of a microscopic RVE model for a SiC / SiC composite clad tube; Figure 7 It is a microscopic fiber bundle unit cell model at different weaving angles. Detailed Implementation

[0026] In order to illustrate the technical means and effects adopted by the present invention in order to achieve the intended purpose of the invention, the following detailed description is provided in conjunction with the embodiments.

[0027] This invention establishes a multi-scale model encompassing macroscopic cladding tube scale, mesoscopic fiber bundle scale, and microscopic fiber scale, which can be used for finite element simulation calculations. The model can express the characteristics of the cladding tube at different scales, reducing the overall computational load and saving costs. The cross-scale joint model, from the microscopic fiber scale to the mesoscopic fiber bundle scale and then to the macroscopic cladding tube scale, makes the calculations more accurate. The structural parameters in the established model are all parameterized using formulas, facilitating modification.

[0028] This invention establishes a multi-scale model for SiC / SiC composite cladding, enabling analysis of structural features at different scales and improving computational accuracy. It also establishes a cross-scale joint model from the micro-fiber scale to the meso-fiber bundle scale and then to the macro-cladding tube scale, reducing the complexity of each part of the model, decreasing the number of meshes, and lowering the computational load. Each scale model can be used independently, and its structural parameters can be parameterized and adjusted.

[0029] The technical solution of this invention mainly includes the following steps: 1) Determine the macroscopic shell tube length, inner diameter, outer diameter and other dimensions, and draw the macroscopic shell tube model; 2) Determine the major axis radius, minor axis radius, fiber bundle spacing and other dimensions of the microscopic fiber bundle unit cell model, and draw the microscopic fiber bundle unit cell model; 3) Determine the fiber radius, unit cell model length, width, height, fiber volume fraction and other dimensions in the microscopic RVE model, and draw the microscopic RVE model; 4) Complete multi-scale modeling.

[0030] See Figure 1 As shown, this invention provides a multi-scale modeling method suitable for SiC / SiC composite clad tubes, including: S1. Perform CT scans on the cladding tube to obtain its length, radius, number of fibers, and the braided structure of the cladding tube prefabrication; and obtain the microstructure of the fiber bundle cross-section of the cladding tube. See Figure 2 As shown, the model baseline was determined based on CT scan images of actual SiC / SiC composite clad tubes, providing a basis for the establishment of the finite element model. (See also...) Figure 3 As shown, with the aid of tools such as scanning electron microscopy, the fiber distribution in the RVE unit model was found.

[0031] S2. Draw a macroscopic model of the cladding tube based on its length and radius. See Figure 4 As shown, a macroscopic SiC / SiC composite cladding tube model was established by measuring the dimensions of the SiC / SiC composite cladding tube, such as the length H, radius R, and number of fibers a.

[0032] S3. Obtain the fiber path based on the braided structure of the precast cladding tube; The fiber bundle preform model and the mesoscopic matrix model are obtained based on the length, radius, number of fibers, and fiber path of the macroscopic cladding tube in the macroscopic cladding tube model. Based on the fiber bundle preform model and the mesoscopic matrix model, a mesoscopic fiber bundle unit cell model is obtained through Boolean operations. The fiber path is obtained according to the following steps: The fiber path characteristics are obtained based on the braided structure of the cladding tube preform. Based on the fiber path characteristics, the sine curve equation is fitted with the parametric equation of a circle to obtain the path equation of a clockwise fiber bundle; at the same time, the path equation of a counterclockwise fiber bundle is obtained; the fiber path is described based on the path equation.

[0033] When obtaining the fiber bundle preform model, the working plane is first determined by the normal vector method; then the fiber bundle preform model is drawn according to the fiber path and the working plane.

[0034] When obtaining the micromatrix model, the radial section of the micromatrix is ​​first drawn and then rotated to generate the micromatrix model; wherein, the radial section of the micromatrix is ​​obtained based on the circumferential arc length and axial length of the matrix.

[0035] The circumferential arc length of the microstructure is calculated using the following formula:

[0036] In the formula, Arc Indicates the circumferential arc length of the microstructure; a Indicates the number of fibers; R Indicates the radius of the macroscopically encased tube; n This indicates the number of the smallest periodic units of a fiber.

[0037] The axial length of the microstructure is calculated using the following formula:

[0038] In the formula, Arc Indicates the circumferential arc length of the microstructure; h Indicates the axial length of the microstructure; Indicates the weaving angle of the prefabricated structure.

[0039] In this embodiment, a parametric curve is constructed to describe the fiber path based on the structural characteristics of the fiber-woven prefabricated body, as follows: First, the path features of the prefabricated shell tube structure obtained by CT scan reconstruction are found. The features are approximately a sine curve rotating around a cylinder in a three-dimensional coordinate system. Therefore, the equation of the sine curve is fitted with the parametric equation of the circle to obtain the path equation of one of the clockwise fiber bundles as shown in equations (1), (2), and (3). Similarly, the path equation of one of the counterclockwise fiber bundles is shown in equations (7), (8), and (9).

[0040] The equation for the clockwise curve is as follows: (1) (2) (3) The normal vector of the curve in the clockwise direction is determined as follows: (4) (5) (6) In the formula: Represents the azimuth coordinates in a rectangular coordinate system; Indicates the radius of the cladding tube; This represents the amplitude of the helical fiber after it has been fitted to a sine curve; Indicates the number of fibers in the clockwise direction; It indicates the weaving time and, together with the weaving speed, controls the weaving length; Indicates the weaving speed, which, together with the weaving duration, controls the weaving length; The normal vector representing the curve in the clockwise direction; This represents the time parameter, used to output the normal vector at the corresponding time.

[0041] The equation for the counterclockwise curve is as follows: (7) (8) (9) The normal vector of the counterclockwise curve is determined as follows: (10) (11) (12) In the formula, Represents the azimuth coordinates in a rectangular coordinate system; Indicates the radius of the cladding tube; This represents the amplitude of the helical fiber after it has been fitted to a sine curve; Indicates the number of fibers in the clockwise direction; It indicates the weaving time and, together with the weaving speed, controls the weaving length; Indicates the weaving speed, which, together with the weaving duration, controls the weaving length; Indicates phase, used to control the relative positions of the peaks and troughs of clockwise and counterclockwise spiral fibers; The normal vector representing the curve in the clockwise direction; This represents a time parameter used to output the normal vector at the corresponding time. The length of the braided preform is derived from the length H of the cladding tube, the braiding angle is set as parameter θ, the number of braided fibers a is derived from the CT scan reconstructed image, the braiding speed v and braiding duration t, and the phase f are all determined by these parameters, as shown in the following formula: (13) (14) (15) In this embodiment, in order to draw the cross section perpendicular to the fiber bundle path direction, the position of the working plane is determined by the normal vector method. That is, the path direction equation of the fiber bundle is differentiated and substituted into the starting coordinates to obtain the normal vector equation of the node along the fiber bundle direction. Combined with the node coordinates, the working plane where the cross section of the fiber bundle is located can be obtained. Equations (4), (5), and (6) can be used to obtain the normal vector of the fiber bundle in the clockwise direction, and equations (10), (11), and (12) can be used to obtain the normal vector of the fiber bundle in the counterclockwise direction. Thus, the working plane is obtained. The cross section of the fiber bundle is drawn as an ellipse on the working plane, and its major axis radius is determined to be R. a The minor axis radius is determined to be R. b And a fiber bundle model is formed by sweeping, see Figure 5 As shown in the middle image. In this embodiment, the radial section of the matrix is ​​drawn and a rotation operation is performed to generate the matrix model. See [link to documentation]. Figure 5 As shown. Circumferential arc length of the substrate. It is related to the number of fibers 'a' in the preform and the radius 'R' of the cladding tube. Determine the length of the smallest periodic unit of the fiber; even n times its length, periodic characteristics still exist. Different unit cell lengths can be selected according to requirements, determined by formula (16). The axial length of the matrix has a trigonometric function relationship with the prefabricated weaving angle and the circumferential arc length of the matrix. The circumferential arc length of the periodic unit and the prefabricated weaving angle are used to determine the axial length of the matrix. The axial length of the matrix can be calculated and determined by formula (17), thus ensuring the periodicity of the microstructure model.

[0042] Based on the fiber bundle prefabricated model and the mesoscopic matrix model, Boolean operations are used to form a periodic unit model of the overall mesoscopic braided structure. (See [link]) Figure 5 As shown in the diagram on the right.

[0043] The formula is shown below: (16) (17) In the formula, Indicates the axial length of the matrix; Indicates the circumferential arc length of the matrix; It is represented as a positive integer, taking the values ​​1, 2, 3, ...

[0044] S4. Obtain the major axis radius and minor axis radius of the fiber bundle based on the microscopic fiber bundle unit cell model; Based on the microstructure of the fiber bundle cross-section of the cladding tube, as well as the major and minor axis radii of the fiber bundle, a microscopic RVE model is obtained.

[0045] When obtaining the microscopic RVE model, the fiber distribution in the RVE unit model is obtained based on the microstructure of the fiber bundle cross section of the shell tube, and the mathematical relationship between the length and width of the unit cell matrix and the fiber radius is determined. The microscopic RVE model is then drawn based on the mathematical relationship.

[0046] The mathematical relationship between the length and width of the unit cell model matrix and the fiber radius is as follows:

[0047] In the formula, Indicates fiber volume fraction; r Indicates the fiber radius in the unit cell model matrix; c Indicates the length of the matrix in the unit cell model; d Indicates the width of the matrix in the unit cell model; The formula for calculating fiber radius is as follows:

[0048] In the formula, r Indicates the fiber radius in the unit cell model matrix; V f Indicates fiber volume fraction; S The cross-sectional area of ​​the fiber bundle is represented by N; N represents the number of fibers. The formula for calculating the cross-sectional area of ​​the fiber bundle is as follows:

[0049] In the formula, S represents the cross-sectional area of ​​the fiber bundle; and These represent the major axis radius and minor axis radius of the fiber bundle, respectively.

[0050] In this embodiment, for the fibers in the fiber bundle structure, a microscopic RVE unit is determined. The unit cell size of the microscopic RVE model is the same as the radius R of the major axis of the fiber bundle in the mesoscopic fiber bundle unit cell model. a and the minor axis radius R of the fiber bundle b With the aid of tools such as scanning electron microscopy, the fiber distribution in the RVE unit model can be identified, such as... Figure 6 Left figure, determining fiber volume fraction V fThe fiber radius r is determined by the number of fibers N and its relationship with the cross-sectional area S of the fiber bundle. The formula for calculating the cross-sectional area S of the fiber bundle is shown in Equation (18), and the formula for calculating the fiber radius r is shown in Equation (19). The mathematical relationship between the length c and width d of the unit cell matrix and the fiber radius r is shown in Equation (20). The graph is drawn as follows. Figure 6 As shown in the figure on the right.

[0051] (18) (19) (20) This invention provides an application of a multi-scale model of SiC / SiC composite clad tubes in predicting the intrinsic properties of the material.

[0052] This invention provides an application of a multi-scale model of SiC / SiC composite clad tubes in the analysis of materials mechanics and heat transfer.

[0053] In this embodiment, the model is used for finite element calculations: By inputting the material parameters of the SiC matrix, PyC interface layer, and SiC fibers into the material, the microscale RVE model can be used for calculation, thereby predicting the material performance parameters of the fiber bundle structure at the mesoscale, including mechanical properties and thermal transfer properties, for subsequent calculations. The material performance parameters of the SiC matrix and the fiber bundle structure predicted in the previous step are called into the micro-fiber bundle unit cell model, and the material performance prediction simulation is performed again to obtain the mechanical properties and heat transfer properties of the macro-clad tube model. The performance predicted in the previous step is imported into the macroscopic homogenized cladding tube model to carry out mechanical and heat transfer simulations, and to simulate the overall structural performance. In microscopic simulations, parameters such as fiber arrangement and volume fraction in the microscale RVE model can be changed to take into account the influence of relevant parameters on fiber bundle performance. In microscopic simulations, the fiber bundle weaving angle in the microscopic fiber bundle unit cell model can be changed, such as... Figure 7 As shown, the influence of the fiber bundle braiding angle on the performance of the cladding tube is considered. The microscopic model can be plotted into a local part of the macroscopic model, and the safety of the structure can be examined from a multi-scale perspective by using the response results of the microscopic fiber bundle unit cell model in the macroscopic model. The micro-level RVE model can be plotted within a local part of the meso-level model, and the safety of the structure can be examined by the response results of the micro-level RVE model in the meso-level model.

[0054] In summary, the multi-scale joint model of this invention, from the micro-fiber scale to the meso-fiber bundle scale and then to the macro-shell tube scale, can reduce the complexity of each part of the model, express complex structures in a concise and clear way, and has a small number of meshes, resulting in less computation during calculation, thus providing convenience for finite element analysis. This invention can predict material properties at the micro-fiber bundle scale by performing finite element calculations using a micro-fiber scale model, and predict material properties at the macro-cladding tube scale using a fiber bundle scale model. It connects multi-scale models into a whole, and only requires the material property parameters of the micro-level model to complete the entire finite element calculation, reducing the need for experimental data. It can also be compared with the results obtained from macro-level experiments to ensure the accuracy of the model.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-scale modeling method suitable for SiC / SiC composite clad tubes, characterized in that, include: CT scans were performed on the cladding tube to obtain its length, radius, number of fibers, and the braided structure of the cladding tube prefabrication. Draw a macroscopic model of the cladding tube based on its length and radius; The fiber path is obtained based on the braided structure of the cladding tube preform; The fiber bundle preform model and the mesoscopic matrix model are obtained based on the length, radius, number of fibers, and fiber path of the macroscopic cladding tube in the macroscopic cladding tube model. Based on the fiber bundle preform model and the mesoscopic matrix model, a mesoscopic fiber bundle unit cell model is obtained through Boolean operations. The major axis radius and minor axis radius of the fiber bundle are obtained based on the microscopic fiber bundle unit cell model; To obtain the microstructure of the fiber bundle cross-section of the cladding tube; Based on the microstructure of the fiber bundle cross section of the cladding tube, as well as the major and minor axis radii of the fiber bundle, a microscopic RVE model is obtained; The fiber path is obtained according to the following steps: The fiber path characteristics are obtained based on the braided structure of the cladding tube preform. Based on the fiber path characteristics, the sine curve equation is fitted with the parametric equation of a circle to obtain the path equation of a clockwise fiber bundle; at the same time, the path equation of a counterclockwise fiber bundle is obtained; the fiber path is described based on the path equation. The path equations of a clockwise fiber bundle are shown in equations (1), (2), and (3): （1） （2） （3） The path equations of a counterclockwise fiber bundle are shown in equations (7), (8), and (9): （7） （8） （9） In the formula, Represents the azimuth coordinates in a rectangular coordinate system; Indicates the radius of the cladding tube; This represents the amplitude of the helical fiber after it has been fitted to a sine curve; Indicates the number of fibers in the clockwise direction; It indicates the weaving time and, together with the weaving speed, controls the weaving length; Indicates the weaving speed, which, together with the weaving duration, controls the weaving length; Indicates phase, used to control the relative positions of the peaks and troughs of clockwise and counterclockwise spiral fibers; When the micro-RVE model is obtained, the fiber distribution in the RVE unit model is obtained based on the microstructure of the fiber bundle cross section of the shell tube, and the mathematical relationship between the length and width of the unit cell matrix and the fiber radius is determined. The micro-RVE model is then drawn based on the mathematical relationship. The mathematical relationship between the length and width of the unit cell model matrix and the fiber radius is as follows: In the formula, Indicates fiber volume fraction; r Indicates the fiber radius in the unit cell model matrix; c Indicates the length of the matrix in the unit cell model; d Indicates the width of the matrix in the unit cell model; The formula for calculating fiber radius is as follows: In the formula, r Indicates the fiber radius in the unit cell model matrix; V f Indicates fiber volume fraction; S The cross-sectional area of ​​the fiber bundle is represented by N; N represents the number of fibers. The formula for calculating the cross-sectional area of ​​the fiber bundle is as follows: In the formula, S represents the cross-sectional area of ​​the fiber bundle; and These represent the major axis radius and minor axis radius of the fiber bundle, respectively.

2. The multi-scale modeling method suitable for SiC / SiC composite cladding tubes according to claim 1, characterized in that, When obtaining the fiber bundle preform model, the working plane is first determined by the normal vector method; then the fiber bundle preform model is drawn according to the fiber path and the working plane.

3. The multi-scale modeling method suitable for SiC / SiC composite cladding tube according to claim 1, characterized in that, When obtaining the microstructure matrix model, the radial section of the matrix is ​​first drawn and then rotated to generate the microstructure matrix model; wherein, the radial section of the matrix is ​​obtained based on the circumferential arc length and axial length of the matrix.

4. The multi-scale modeling method suitable for SiC / SiC composite cladding tubes according to claim 3, characterized in that, The circumferential arc length of the substrate is calculated using the following formula: In the formula, Arc Indicates the circumferential arc length of the matrix; a Indicates the number of fibers; R Indicates the radius of the macroscopically encased tube; n This indicates the number of the smallest periodic units of a fiber.

5. The multi-scale modeling method suitable for SiC / SiC composite cladding tubes according to claim 4, characterized in that, The axial length of the matrix is ​​calculated using the following formula: wherein Arc represents the circumferential arc length of the base body; h represents the axial length of the base body; represents the preform braid angle.

6. The application of a multi-scale model of SiC / SiC composite clad tube constructed by the method described in any one of claims 1 to 5 in predicting the intrinsic properties of the material.

7. The application of a multi-scale model of a SiC / SiC composite clad tube constructed by the method described in any one of claims 1 to 5 in the analysis of materials mechanics and heat transfer.

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