Calculation method for fatigue prediction model of three-dimensional woven ceramic matrix composite

Abstract

The invention discloses a three-dimensional woven ceramic matrix composite material fatigue prediction model calculation method, which comprises the following steps: analyzing a SiC / SiC fiber bundle composite material fatigue test result to obtain a residual stiffness degradation rule of a fiber bundle composite material; an RVE model conforming to the three-dimensional woven CMCs microstructure is established, and periodic grid division and periodic boundary condition application are carried out on the RVE model; and substituting the fiber bundle residual stiffness degradation model into the three-dimensional woven CMCs RVE model for finite element calculation, and predicting the fatigue life and residual stiffness degradation curve of the three-dimensional woven CMCs material under any peak fatigue cycle load by combining a three-dimensional Hashin failure criterion. According to the method, the influence of various damage forms of the ceramic matrix composite material under the fatigue load and different temperature environments on the SiC / SiC fiber bundle composite material is comprehensively considered, so that the prediction result can better adapt to the actual working environment.

Description

Technical Field

[0001] The invention relates to the technical field of reliability assessment of aviation composite materials, and in particular to a calculation method for a fatigue prediction model of a three-dimensional woven ceramic matrix composite material. Background Art

[0002] The upgrading of aero-engines has promoted the application of new materials such as high-temperature alloys and composite materials in engineering. The materials used in the structure of the hot-end components of high thrust-to-weight ratio aero-engines must have high specific strength, high specific modulus, high temperature resistance, oxidation resistance, and long life. Traditional nickel-based high-temperature alloy materials can no longer meet the use requirements under current design conditions. In this context, high-temperature resistant materials used in hot-end components are of great significance for improving the overall performance of the engine. In recent years, domestic and foreign scholars have gradually shifted their research focus to ceramic matrix composites (Ceramic Matrix Composites, CMCs) that exhibit excellent mechanical properties in ultra-high temperature environments. Due to their excellent high temperature resistance, corrosion resistance, and wear resistance, CMCs are regarded as ideal materials for future hot-end components of aero-engines.

[0003] Fatigue failure of internal structural parts of aircraft engines may lead to catastrophic consequences. Therefore, the fatigue life of structural parts has become a key indicator that requires special attention in the design, use and maintenance of aircraft engines. How to ensure that CMCs structures can still safely and reliably exert their mechanical properties under long-term vibration fatigue loads has become a core problem in the dynamic strength design of CMCs structures. Therefore, studying and establishing a scientific and reasonable fatigue prediction model is of great significance to improving the reliability and safety of engine components.

[0004] Commonly used CMCs structures can be divided into three categories according to the weaving structure type of their preforms: unidirectional, two-dimensional weaving, and three-dimensional weaving. Unidirectional CMCs have the ability to bear loads only in the fiber direction and are rarely used in engineering practice, but are mostly used for material performance research. Two-dimensional woven CMCs are woven by interlacing yarns in two directions. Although there is a certain load-bearing capacity between layers, they are easy to delaminate and cannot be used to make curved parts. Three-dimensional woven CMCs connect each layer through yarns, have excellent interlayer performance and strong shear and impact resistance, and can manufacture various types of rotating parts. They have been widely used in actual engineering, but there is currently no special fatigue prediction method for three-dimensional woven CMCs. Summary of the invention

[0005] The purpose of the present invention is to provide a calculation method for fatigue prediction model of three-dimensional woven ceramic matrix composite materials, which takes into account the influence of different temperature environments on SiC / SiC fiber bundle composite materials, so that the prediction results can better adapt to the actual working environment, especially in engineering applications under high temperature or extreme environments; and can greatly reduce the calculation complexity and time consumption while ensuring the prediction accuracy, thereby improving the simulation efficiency and having a high engineering application value.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A method for calculating a fatigue prediction model of a three-dimensional braided ceramic matrix composite material, the method comprising the following steps:

[0008] S1, carry out tensile tests on SiC / SiC fiber bundle composites under different temperature environments to obtain the tensile strength of fiber bundle CMCs;

[0009] S2, based on the tensile strength of fiber bundle CMCs, tension-tension fatigue tests of SiC / SiC fiber bundle composites were carried out under different temperature environments;

[0010] S3, the force-displacement data obtained from the fatigue test are processed, and the residual stiffness curve of the fiber bundle CMCs is calculated by the ratio of the maximum test force to the maximum displacement, and regularization is performed. A unified functional relationship is used to fit the variation law of the regularized residual stiffness of the fiber bundle composite material with the decay of the number of cycles, and the residual stiffness degradation model of the fiber bundle composite material is obtained;

[0011] S4, establishing a RVE finite element model of three-dimensional woven CMCs, performing periodic meshing on the RVE finite element model and assigning material properties;

[0012] S5, applying fatigue failure criteria to determine whether the model unit has failed, and counting the number and distribution of failed units; judging whether the overall structure has failed based on the unit failure results, when the failed unit forms a complete fracture surface, it is considered that the structure has lost its bearing capacity, and the process ends; otherwise, proceed to step S6;

[0013] S6, if the structure has not failed, the residual stiffness of the non-failed units under cyclic loads is calculated using the residual stiffness degradation model of fiber bundle composite materials; for the failed units, their stiffness is reduced and the material properties are reassigned according to the updated calculation results;

[0014] S7, repeating steps S5 and S6, iteratively calculating until the structure fails, and outputting the distribution of structural failure units, the number of fatigue cycles experienced, and the stiffness degradation curve results.

[0015] As a preferred example, in step S3, the residual stiffness degradation model of the fiber bundle composite material is:

[0016]

[0017] In the formula, E min (N) represents the residual stiffness of SiC / SiC fiber bundle composite material after N fatigue cycles and internal damage, E min (0) represents the initial stiffness of the material, and a' and b' are the material-related coefficients at different temperatures.

[0018] As a preferred example, step S4 further includes:

[0019] A three-dimensional woven CMCs geometric model that conforms to the microstructure of three-dimensional woven CMCs is established, and periodic meshing and periodic boundary conditions are applied to it to construct the RVE finite element model of three-dimensional woven CMCs.

[0020] As a preferred example, in step S4, the geometric parameter relationship of the three-dimensional braided CMCsRVE model satisfies the following conditions:

[0021]

[0022] Wherein, α is the surface braiding angle of the RVE model, γ is the internal braiding angle, W is the width of the square at the bottom of the RVE model, and hmodel is the height of the RVE model. The cross section of the fiber bundle is an octagon with an inscribed ellipse, L1 and L2 are the side lengths of the octagon, and a and b are the major and minor semi-axes of the inscribed ellipse of the cross section of the fiber bundle, respectively.

[0023] As a preferred example, in step S4, the periodic displacement field applied to the RVE model satisfies the following conditions:

[0024] u j+ -u j- =ε - (x j+ -x j- )=ε - Δx j

[0025] Where u represents the node displacement; superscripts j+ and j- represent the jth group of relative parallel surfaces of the RVE model; ε - represents the average strain of the RVE model; x represents the absolute position in the x direction relative to the parallel plane; Δx j Represents the distance along the x direction between the jth set of relative parallel surfaces.

[0026] As a preferred example, in step S4, the constraint equations for the three pairs of parallel surfaces of the three-dimensional braided CMCs RVE model are:

[0027]

[0028] Among them, U, V, and W are the displacements of the nodes in the x, y, and z directions respectively; subscripts I, J, K, M, N, and O represent the nodes on the corresponding surfaces; subscripts A, B, C, D, E, F, G, and H represent the vertices of the RVE model; represents the average strain of the RVE model, b is the short semi-axis length of the fiber bundle cross section, and h is the height of the RVE model.

[0029] As a preferred example, in step S5, residual stiffness and residual strength are introduced into the three-dimensional Hashin failure criterion as the fatigue failure criterion for fatigue analysis of three-dimensional woven SiC / SiC composite material units. The expression of the fatigue failure criterion is as follows:

[0030] The fiber tensile failure expression is:

[0031]

[0032] The fiber compression failure expression is:

[0033]

[0034] The matrix tensile failure expression is:

[0035]

[0036] The matrix compression failure expression is:

[0037]

[0038] The fiber and matrix shear failure expressions are:

[0039]

[0040] In the formula, σ m represents the principal stress in the m direction, m = 1, 2, 3; σ pq It represents the shear stress of the material acting on the positive p-plane pointing to the q-axis, p = 1, 2, 3, q ​​= 1, 2, 3; the subscripts T and C represent the tensile and compressive states respectively; X(N) and Y(N) represent the longitudinal and transverse strengths of the fiber bundle composite material when the number of fatigue cycles is N; S pq (N) represents the shear strength when the number of fatigue cycles of the material is N.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] First, the fatigue prediction model calculation method of the three-dimensional woven ceramic matrix composite material of the present invention comprehensively considers the various damage forms of the ceramic matrix composite material under fatigue load and the influence of different temperature environments on SiC / SiC fiber bundle composite materials. It can calculate the fatigue life and residual stiffness degradation curve of the material under any peak fatigue cycle load, so that the prediction results can better adapt to the actual working environment, especially in engineering applications under high temperature or extreme environments.

[0043] Second, the fatigue prediction model calculation method of the three-dimensional woven ceramic matrix composite material of the present invention establishes a three-dimensional woven RVE model, which can reduce the calculation complexity and time consumption while ensuring the prediction accuracy, improve the simulation efficiency, and has a high engineering application value.

[0044] Thirdly, the calculation method of the fatigue prediction model of the three-dimensional woven ceramic matrix composite material of the present invention can be used to replace the mechanical behavior response of the yarn in various types of woven CMCs structures under various complex loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is the residual stiffness degradation curve of the embodiment of the present invention; wherein (a) corresponds to a room temperature of 25° C., and (b) corresponds to a high temperature of 1100° C.;

[0046] Figure 2 is the spatial topological geometric relationship of the three-dimensional braided CMCs fiber bundle according to an embodiment of the present invention;

[0047] Figure 3 is the cross-sectional shape of the fiber bundle inside the three-dimensional braided CMCs of an embodiment of the present invention;

[0048] Figure 4 is a three-dimensional braided CMCs RVE model of an embodiment of the present invention;

[0049] Figure 5 is the periodic boundary condition of the three-dimensional braided CMCs RVE model of the embodiment of the present invention;

[0050] Figure 6 3D braided CMCs fatigue prediction stiffness degradation results of the embodiment of the present invention; (a) corresponds to 325MPa at room temperature, (b) corresponds to 310MPa at room temperature, (c) corresponds to 160MPa at high temperature, (d) corresponds to 130MPa at room temperature, and (e) corresponds to 120MPa at room temperature;

[0051] Figure 7 It is a flow chart of a method for calculating a fatigue prediction model of a three-dimensional woven ceramic matrix composite material according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0053] See also Figure 7 The embodiment of the present invention discloses a method for calculating a fatigue prediction model of a three-dimensional woven ceramic matrix composite material. The method for calculating a fatigue prediction model of a three-dimensional woven ceramic matrix composite material comprises the following steps:

[0054] S1, carry out tensile tests on SiC / SiC fiber bundle composites under different temperature environments to obtain the tensile strength of fiber bundle CMCs;

[0055] S2, based on the tensile strength of fiber bundle CMCs, tension-tension fatigue tests of SiC / SiC fiber bundle composites were carried out under different temperature environments;

[0056] S3, processing the force-displacement data obtained from the fatigue test, calculating the residual stiffness curve of the fiber bundle CMCs by the ratio of the maximum test force to the maximum displacement, and performing regularization (normalization) processing;

[0057] S4, establish the RVE finite element model of three-dimensional woven CMCs, perform periodic meshing on the model and assign material properties;

[0058] S5, apply fatigue failure criteria to determine whether the model unit has failed, count the number and distribution of failed units; determine whether the overall structure has failed based on the unit failure results. When the failed unit forms a complete fracture surface, the structure is considered to have lost its bearing capacity;

[0059] S6: If the structure has not failed, the residual stiffness of the non-failed units under cyclic loads is calculated using the residual stiffness degradation model of fiber bundle composite materials. For failed units, their stiffness is reduced, and the material properties are reassigned according to the updated calculation results. The calculation is iterated until the structure fails, and the distribution of structural failure units, the number of fatigue cycles experienced, the stiffness degradation curve and other results are output.

[0060] Step 1: Conduct tensile tests on SiC / SiC fiber bundle composite materials in an oxygen-free environment at room temperature and high temperature of 1100° C. to obtain the tensile strength of the fiber bundle CMCs in different temperature environments.

[0061] Step 2: Based on the tensile strength of fiber bundle CMCs, tension-tensile fatigue tests of SiC / SiC fiber bundle composites were carried out in an oxygen-free environment at room temperature and high temperature of 1100°C.

[0062] Step 3, the force-displacement data obtained from the fatigue test are processed, the ratio between the maximum test force and the maximum displacement is calculated, the residual stiffness curve of the fiber bundle CMCs is obtained, and regularization (normalization) is performed to eliminate the influence of the dispersion of the material.

[0063] In order to further describe the attenuation law of the residual stiffness of the fiber bundle composite material with the number of fatigue cycles, a unified functional relationship can be used to fit it, and the function is shown in Formula 1:

[0064]

[0065] In the formula, E min (N) represents the residual stiffness of SiC / SiC fiber bundle composite material after N fatigue cycles and internal damage, E min (0) represents the initial stiffness of the material, and a' and b' are the coefficients related to the material at different temperatures.

[0066] Step 4: The mechanical properties of the load-bearing yarns in the three-dimensional woven SiC / SiC composites are consistent with those of the SiC / SiC fiber bundle composites. An RVE finite element model of three-dimensional woven CMCs is established, and the model is periodically meshed and assigned material properties.

[0067] The established three-dimensional braided CMCs RVE model has a geometric parameter relationship as shown in Equation 2:

[0068]

[0069] Wherein, α is the surface braiding angle of the RVE model, γ is the internal braiding angle, W is the width of the square at the bottom of the RVE model, and hmodel is the height of the RVE model. Considering the real shape of the fiber bundle inside the material, and in order to simplify the calculation, the cross section of the fiber bundle is regarded as an octagon of an inscribed ellipse, the major semi-axis of the inscribed ellipse in the cross section of the fiber bundle is a, the minor semi-axis is b, and the side lengths of the octagon are L1 and L2, respectively.

[0070] The periodic displacement field of the RVE model is shown in Equation 3:

[0071] u j+ -u j- =ε - (x j+ -x j- )=ε - Δx j (3);

[0072] Where u represents the node displacement; superscripts j+ and j- represent the jth group of relative parallel surfaces of the RVE model; ε - represents the average strain of the RVE model; x represents the absolute position in the x direction relative to the parallel plane; Δx j Represents the distance along the x direction between the jth set of relative parallel surfaces.

[0073] For the three pairs of parallel surfaces of the RVE model, the constraint equations are shown in Equation 4:

[0074]

[0075] Among them, U, V, and W are the displacements of the nodes in the x, y, and z directions respectively; subscripts I, J, K, M, N, and O represent the nodes on the corresponding surfaces; subscripts A, B, C, D, E, F, G, and H represent the vertices of the RVE model; represents the average strain of the RVE model, b is the short semi-axis length of the fiber bundle cross section, and h is the height of the RVE model.

[0076] Step 5: Apply fatigue failure criteria to determine whether the model unit has failed, and count the number and distribution of failed units; determine whether the overall structure has failed based on the unit failure results. When the failed unit forms a complete fracture surface, the structure is considered to have lost its bearing capacity.

[0077] The three-dimensional Hashin failure criterion is used as the fatigue failure criterion of the three-dimensional braided SiC / SiC composite element. The three-dimensional Hashin static strength failure criterion is shown in equations (5) to (9):

[0078] Fiber tensile failure (σ1>0):

[0079]

[0080] Fiber compression failure (σ1<0):

[0081]

[0082] Matrix tensile failure (σ2>0):

[0083]

[0084] Matrix compression failure (σ2<0):

[0085]

[0086] Matrix-fiber shear failure (σ1<0):

[0087]

[0088] In the formula, σ m Represents the principal stress in the m direction, m = 1, 2, 3; S pq (N) represents the shear strength when the number of fatigue cycles of the material is N, p = 1, 2, 3, q ​​= 1, 2, 3;.

[0089] Based on the static strength failure model of this criterion, residual stiffness and residual strength are introduced to develop a failure criterion suitable for fatigue analysis. The specific expressions are shown in equations (10) to (14):

[0090] Fiber tensile failure:

[0091]

[0092] Fiber compression failure:

[0093]

[0094] Matrix tensile failure:

[0095]

[0096] Matrix compression failure:

[0097]

[0098] Fiber and matrix shear failure:

[0099]

[0100] In the formula, σ m represents the principal stress in the m direction, m = 1, 2, 3; σ pq It represents the shear stress of the material acting on the positive p-plane pointing to the q-axis, p = 1, 2, 3, q ​​= 1, 2, 3; the subscripts T and C represent the tensile and compressive states respectively; X(N) and Y(N) represent the longitudinal and transverse strengths of the fiber bundle composite material when the number of fatigue cycles is N; S pq (N) represents the shear strength when the number of fatigue cycles of the material is N.

[0101] Step 6: If the structure has not failed, the residual stiffness of the non-failed units under cyclic loads is calculated using the residual stiffness degradation model of the fiber bundle composite material; for the failed units, their stiffness is reduced and the material properties are reassigned according to the updated calculation results.

[0102] Through iterative calculations, the failure process of each unit in the structure is continuously monitored until the entire structure fails. The final output includes data such as the distribution of failed units, the number of fatigue cycles experienced, and the stiffness degradation curve of each unit.

[0103] Examples

[0104] 1. Carry out tensile tests on SiC / SiC fiber bundle composites under different temperature environments to obtain the tensile strength of fiber bundle CMCs.

[0105] 2. Based on the tensile strength of fiber bundle CMCs, tension-tensile fatigue tests of SiC / SiC fiber bundle composites were carried out under different temperature environments.

[0106] 3. Process the force-displacement data obtained from the fatigue test, calculate the ratio between the maximum test force and the maximum displacement, obtain the residual stiffness curve of the fiber bundle CMCs, and perform regularization (normalization) to eliminate the influence of the dispersion of the material. In order to further describe the attenuation law of the residual stiffness of the fiber bundle composite material with the number of fatigue cycles, a unified functional relationship can be used to fit it, such as Figure 1 shown.

[0107] 4. The mechanical properties of the load-bearing yarn in the three-dimensional woven SiC / SiC composite material are consistent with those of the SiC / SiC fiber bundle composite material. The RVE model of the three-dimensional woven CMCs is established by referring to the spatial topological geometric relationship of the three-dimensional woven CMCs RVE model. The spatial topological geometric relationship of the three-dimensional woven CMCs RVE model is as follows: Figure 2 As shown in Figure 2, the cross-sectional shape of the fiber bundle inside the 3D braided CMCs is as follows: Figure 3 As shown in Figure 2, the established RVE model is as follows: Figure 4 shown.

[0108] The model is periodically meshed and given material properties and periodic boundary conditions. Figure 5 shown.

[0109] 5. Use fatigue failure criteria to determine whether the model unit has failed, and count the number and distribution of failed units; determine whether the overall structure has failed based on the unit failure results. When the failed unit forms a complete fracture surface, the structure is considered to have lost its bearing capacity.

[0110] The three-dimensional Hashin failure criterion is adopted as the fatigue failure criterion for three-dimensional braided SiC / SiC composite elements. Based on the static strength failure model of this criterion, the residual stiffness and residual strength are introduced to develop a failure criterion suitable for fatigue analysis.

[0111] 6. If the structure has not failed, the residual stiffness of the non-failed units under cyclic loads is calculated using the residual stiffness degradation model of the fiber bundle composite material; for the failed units, their stiffness is reduced and the material properties are reassigned based on the updated calculation results.

[0112] Through iterative calculation, the failure process of each unit in the structure is continuously monitored until the entire structure fails. The final output includes data such as the distribution of failed units, the number of fatigue cycles experienced, and the stiffness degradation curve of each unit. The calculated stiffness degradation curve is as follows: Figure 6 shown.

[0113] Depend on Figure 6 As is known, the overall agreement between the simulation and test results is good, but the deviation is large in the initial stage. This is because in the early stage of fatigue loading, the material damage evolves faster and the stiffness decreases more rapidly, but the analysis step set in the calculation process is fixed, and the rapid changes in material damage cannot be accurately captured in real time, resulting in a certain error with the test results. With the continuous action of fatigue loads, the damage of the material gradually stabilizes, and the agreement between the simulation results and the test results is significantly improved. Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products.

[0114] Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0115] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0116] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0117] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0118] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0119] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for calculating fatigue prediction model of three-dimensional braided ceramic matrix composite materials, characterized in that: The method comprises the following steps: S1, carry out tensile tests on SiC / SiC fiber bundle composites under different temperature environments to obtain the tensile strength of fiber bundle CMCs; S2, based on the tensile strength of fiber bundle CMCs, tension-tension fatigue tests of SiC / SiC fiber bundle composites were carried out under different temperature environments; S3, the force-displacement data obtained from the fatigue test are processed, and the residual stiffness curve of the fiber bundle CMCs is calculated by the ratio of the maximum test force to the maximum displacement, and regularization is performed. A unified functional relationship is used to fit the variation law of the regularized residual stiffness of the fiber bundle composite material with the decay of the number of cycles, and the residual stiffness degradation model of the fiber bundle composite material is obtained; S4, establishing a RVE finite element model of three-dimensional woven CMCs, performing periodic meshing on the RVE finite element model and assigning material properties; S5, applying fatigue failure criteria to determine whether the model unit has failed, and counting the number and distribution of failed units; judging whether the overall structure has failed based on the unit failure results, when the failed unit forms a complete fracture surface, it is considered that the structure has lost its bearing capacity, and the process ends; otherwise, proceed to step S6; S6, if the structure has not failed, the residual stiffness of the non-failed units under cyclic loads is calculated using the residual stiffness degradation model of fiber bundle composite materials; for the failed units, their stiffness is reduced and the material properties are reassigned according to the updated calculation results; S7, repeating steps S5 and S6, iteratively calculating until the structure fails, and outputting the distribution of structural failure units, the number of fatigue cycles experienced, and the stiffness degradation curve results.

2. The fatigue prediction model calculation method of three-dimensional woven ceramic matrix composite material according to claim 1 is characterized in that: In step S3, the residual stiffness degradation model of the fiber bundle composite material is: In the formula, E min (N) represents the residual stiffness of SiC / SiC fiber bundle composite material after N fatigue cycles and internal damage, E min (0) represents the initial stiffness of the material, and a' and b' are the material-related coefficients at different temperatures.

3. The fatigue prediction model calculation method of three-dimensional woven ceramic matrix composite material according to claim 1 is characterized in that: Step S4 further comprises: A three-dimensional woven CMCs geometric model that conforms to the microstructure of three-dimensional woven CMCs is established, and periodic meshing and periodic boundary conditions are applied to it to construct the RVE finite element model of three-dimensional woven CMCs.

4. The fatigue prediction model calculation method of three-dimensional woven ceramic matrix composite material according to claim 3 is characterized in that: In step S4, the geometric parameter relationship of the 3D braided CMCs RVE model satisfies the following conditions: Wherein, α is the surface braiding angle of the RVE model, γ is the internal braiding angle, W is the width of the square at the bottom of the RVE model, and h is the height of the RVE. The cross section of the fiber bundle is an octagon with an inscribed ellipse, L1 and L2 are the side lengths of the octagon, and a and b are the major and minor semi-axes of the inscribed ellipse of the cross section of the fiber bundle, respectively.

5. The fatigue prediction model calculation method of three-dimensional woven ceramic matrix composite material according to claim 3 is characterized in that: In step S4, the periodic displacement field applied to the RVE model satisfies the following conditions: u j+ -u j- =ε - (x j+ -x j- )=ε - Δx j Where u represents the node displacement; superscripts j+ and j- represent the jth group of relative parallel surfaces of the RVE model; ε - represents the average strain of the RVE model; x represents the absolute position in the x direction relative to the parallel plane; Δx j Represents the distance along the x direction between the jth set of relative parallel surfaces.

6. The fatigue prediction model calculation method of three-dimensional braided ceramic matrix composite material according to claim 3 is characterized in that: In step S4, the constraint equations for the three pairs of parallel surfaces of the three-dimensional braided CMCs RVE model are: Among them, U, V, and W are the displacements of the nodes in the x, y, and z directions respectively; subscripts I, J, K, M, N, and O represent the nodes on the corresponding surfaces; subscripts A, B, C, D, E, F, G, and H represent the vertices of the RVE model; represents the average strain of the RVE model, b is the short semi-axis length of the fiber bundle cross section, and h is the height of the RVE model.

7. The fatigue prediction model calculation method of three-dimensional braided ceramic matrix composite material according to claim 1 is characterized in that: In step S5, the residual stiffness and residual strength are introduced into the three-dimensional Hashin failure criterion as the fatigue failure criterion for fatigue analysis of the three-dimensional braided SiC / SiC composite material unit. The expression of the fatigue failure criterion is as follows: The fiber tensile failure expression is: The fiber compression failure expression is: The matrix tensile failure expression is: The matrix compression failure expression is: The fiber and matrix shear failure expressions are: In the formula, σ m represents the principal stress in the m direction, m = 1, 2, 3; σ pq It represents the shear stress of the material acting on the positive p-plane pointing to the q-axis, p = 1, 2, 3, q ​​= 1, 2, 3; the subscripts T and C represent the tensile and compressive states respectively; X(N) and Y(N) represent the longitudinal and transverse strengths of the fiber bundle composite material when the number of fatigue cycles is N; S pq (N) represents the shear strength when the number of fatigue cycles of the material is N.

Images