High-strength and high-toughness ceramic-based composite cladding tube gradient structure and design method thereof

Abstract

The invention discloses a high-strength and high-toughness ceramic matrix composite cladding tube gradient structure and a design method thereof.The composite cladding tube gradient structure is composed of a multilayer gradient woven SiC fiber preform and a ceramic matrix, and the design method comprises the steps that a, single-layer preform models with different inner diameters and different weaving angles are established; b, establishing a multi-layer composite cladding tube model with a gradient braided structure; c, carrying out entity grid division on the multi-layer composite cladding tube model; d, defining damage criteria of the SiC fiber preform and the ceramic body; e, setting boundary conditions of the multi-layer composite cladding tube model; and f, the structural design of the high-strength and high-toughness composite cladding pipe is determined. The multi-layer composite cladding tube designed by the invention has the characteristics of high strength and high toughness at the same time, overcomes the defect of insufficient toughness of a ceramic-based composite cladding tube, and realizes structural optimization of a ceramic-based composite material.

Description

Technical Field

[0001] The invention relates to the field of ceramic-based composite cladding tubes, and specifically provides a high-strength and high-toughness ceramic-based composite cladding tube gradient structure and a design method thereof. Background Art

[0002] In 2012, the U.S. Department of Energy proposed the concept of accident tolerant fuel (ATF), which aims to improve the ability of fuel elements in nuclear reactors to tolerate severe accidents. Compared with the traditional UO2-Zr alloy fuel system, ATF can delay the reactor core loss of coolant accident (LOCA) for a certain period of time, while maintaining or improving fuel performance under normal operating conditions. Ceramic matrix composites, especially SiC f / SiC composite materials, due to their excellent high-temperature mechanical properties, corrosion resistance and radiation resistance, have become one of the candidate materials for innovative accident-tolerant fuels and are expected to be used in Generation IV advanced nuclear reactors and light water reactors (LWRs).

[0003] Current nuclear grade SiC f / SiC composites use multi-layer two-dimensional fiber weaving to improve the inherent brittleness of the matrix and achieve toughening effect. However, due to the limitation of weaving process, most of the fiber preforms in each layer are prepared by the same weaving angle. Although this improves the SiC f / SiC composite materials have good mechanical properties, but there are still some shortcomings, that is, the larger the fiber braiding angle, the lower the axial tensile strength, while the corresponding ultimate tensile strain is large. Summary of the invention

[0004] The purpose of the present invention is to provide a high-strength and high-toughness ceramic-based composite cladding tube gradient structure and a design method thereof, aiming to improve the axial tensile strength and ultimate tensile strength of the ceramic-based composite cladding tube and shorten the design cycle of the ceramic-based composite cladding tube structure.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A high-strength and high-toughness ceramic-based composite cladding tube gradient structure is composed of 3 to 5 layers of SiC fiber preforms and a ceramic matrix coating the SiC fiber preforms. The braiding angle of each layer of SiC fiber preforms is different, ranging from 30° to 60°. The braiding angles of two adjacent layers of SiC fiber preforms vary in a gradient, and the braiding angle is the angle between the axis of a single SiC fiber and the axis of the heterogeneous cladding tube.

[0007] Furthermore, the ceramic matrix is ​​one of silicon carbide, silicon nitride and zirconium oxide.

[0008] Furthermore, the weaving angle of the two adjacent layers of preforms changes in a gradient manner, uniformly reducing or increasing the weaving angle along the radial direction of the composite cladding tube. The inner diameter of the gradient structure of the composite cladding tube is 10.0mm~11.0mm, the outer diameter is 11.8mm~13.4mm, the thickness of the ceramic matrix is ​​0.3~0.4mm, the axial tensile strength of the gradient structure of the composite cladding tube is not less than 225MPa, and the ultimate tensile strain is not less than 0.5%.

[0009] The present invention also provides a method for designing a high-strength and high-toughness ceramic-based composite cladding tube gradient structure, comprising the following steps:

[0010] a. Establishing single-layer preform models with different inner diameters and different braiding angles: According to the actual geometric dimensions of SiC fiber and ceramic matrix, three groups of single-layer preform models with different inner diameters and different braiding angles are constructed in finite element software;

[0011] b. Establishing a multilayer composite cladding tube model with a gradient braided structure: The three groups of single-layer preform models established in step a are combined into three multilayer composite cladding tube models with a gradient braided structure in an arrangement from small to large inner diameter. The braiding angle of each group of single-layer preform models is 30° to 60°, and the relative tolerance value of the multilayer composite cladding tube model is used to remove overlaps and gaps in the model;

[0012] c. Performing solid meshing on the multilayer composite cladding tube model: Based on the multilayer composite cladding tube model established in step b, the ceramic matrix and SiC fiber preform in the model are divided into hexahedral meshes;

[0013] d. Define the damage criteria of SiC fiber preform and ceramic matrix: SiC fiber preform is tough and adopts Hashin criterion, while ceramic matrix is ​​brittle material and adopts first strength theory criterion;

[0014] e. Setting the boundary conditions of the multi-layer composite cladding tube model: setting an increasing displacement series on the specified surface of the multi-layer composite cladding tube model to simulate the process of the composite cladding tube being subjected to axial tension;

[0015] f. Determine the structural design of the multi-layer composite cladding tube with high strength and high toughness: Based on the boundary conditions set in step e, select the Newton iteration method to calculate the stress-strain curve of the composite cladding tube, draw the axial stress-strain curve of the composite cladding tube, and find the stress value corresponding to the highest point in the axial stress-strain curve. The stress value is the axial tensile strength of the multi-layer composite cladding tube, and the tensile strain corresponding to the axial tensile strength is the ultimate tensile strain. At this time, the model structure corresponding to the axial tensile strength and the ultimate tensile strain is the designed gradient structure of the ceramic-based composite cladding tube with high strength and high toughness.

[0016] Furthermore, the actual geometric dimensions of the ceramic matrix and SiC fiber include thicknesses of 0.30-0.40 mm and 0.21-0.27 mm respectively; the composite cladding tube gradient structure height is 31.5-32 mm, the inner diameter is 10.0-11.0 mm, and the outer diameter is 11.8-13.4 mm.

[0017] Furthermore, the multilayer composite cladding tube model with a gradient weaving structure is a single-layer preform model with different weaving angles, which is respectively arranged in three ways: inner layer 30°, middle layer 45°, outer layer 60°, inner layer 30°, middle layer 60°, outer layer 45°, inner layer 60°, middle layer 45°, outer layer 30°, to form three multilayer composite cladding tube models.

[0018] Furthermore, the displacement sequence of increasing value is set on the specified surface of the multilayer composite cladding tube model as follows: along the axial direction of the composite cladding tube, the displacement sequence of increasing value is set on the upper surface with 0 mm as the starting value, 1×10 -3 mm~4×10 -3 mm is the step length, and 0.3mm~0.5mm is the increasing series of the end value.

[0019] Furthermore, the termination judgment method of the Newton iteration method is that the maximum number of iterations is 20 to 25 times, and the maximum relative error is 0.001 to 0.005.

[0020] By adopting the above technical solution, the advantages and beneficial effects of the present invention are:

[0021] The multilayer ceramic-based composite cladding tube with a gradient structure of the present invention is composed of 3 to 5 layers of SiC fiber preforms and a ceramic matrix coating the SiC fiber preforms. The braiding angle of each layer of the preform is different, ranging from 30° to 60°, and the braiding angles of two adjacent layers of the preforms vary in a gradient. The inner diameter of the composite cladding tube is 10.0 mm to 11.0 mm, the outer diameter is 11.8 mm to 13.4 mm, and the thickness of the ceramic matrix is ​​0.3 to 0.4 mm. The axial tensile strength of the multilayer composite cladding tube with the structure can reach 225 MPa. Compared with other two-dimensionally woven multilayer ceramic-based composite cladding tubes, the axial tensile strength is increased by 20% to 25%. At the same time, the ultimate tensile strain of the multilayer composite cladding tube with the structure is not less than 0.5%, indicating that the structure exhibits higher toughness.

[0022] By numerically calculating the stress-strain curve of the composite cladding tube with a gradient weaving angle structure, analyzing and comparing the axial tensile strength and ultimate strain of cladding tubes with different structures, and then screening out the design method of the composite cladding tube structure with high strength and high toughness, it not only reduces the cost of material development and testing, but also shortens the material design cycle, which is of great significance to promoting the development of accident-tolerant fuel cladding materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of the structure design of an embodiment of the present invention;

[0024] Figure 2 The SiC f / SiC composite cladding tube, the inner layer braiding angle is 30°, the middle layer braiding angle is 45°, and the outer layer braiding angle is 60°;

[0025] Figure 3 The SiC f / SiC composite cladding tube, the inner layer braiding angle is 30°, the middle layer braiding angle is 60°, and the outer layer braiding angle is 45°;

[0026] Figure 4 The SiC f / SiC composite cladding tube, the inner layer braiding angle is 60°, the middle layer braiding angle is 45°, and the outer layer braiding angle is 30°;

[0027] Figure 5 This is a stress-strain curve diagram calculated for an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0029] The high-strength and high-toughness ceramic-based composite cladding tube gradient structure in the embodiment of the present invention is composed of three layers of SiC fiber preforms and a ceramic matrix coating the SiC fiber preforms. The braiding angle of each layer of SiC fiber preforms is different, ranging from 30° to 60°. The braiding angles of two adjacent layers of SiC fiber preforms vary in a gradient. The braiding angle is the angle between the axis of a single SiC fiber and the axis of the heterogeneous cladding tube. The design method is shown in Figure 1 .

[0030] Example 1

[0031] In this embodiment, the ceramic substrate is a SiC substrate. f The inner layer braiding angle of the SiC composite cladding tube is 30°, the middle layer braiding angle is 60°, and the outer layer braiding angle is 45°. Figure 3 As shown;

[0032] The specific design method is:

[0033] Step 1: Establish a single-layer preform model with different inner diameters and different braiding angles: According to the SiC fiber SiC f The actual geometric dimensions of the SiC matrix include the thickness of the SiC matrix and SiC fiber, which are 0.30 mm and 0.21 mm respectively, the height of the composite cladding tube gradient structure is 31.5 mm, the inner diameter is 10.0 mm, and the outer diameter is 11.8 mm. Three groups of single-layer preform models with different inner diameters and different braiding angles are constructed in the finite element software, wherein the braiding angles and inner diameters of the first group of single-layer preform models are 30°, 10.0 mm, 45°, 10.6 mm, 60°, 11.2 mm respectively, the braiding angles and inner diameters of the second group of single-layer preform models are 30°, 10.0 mm, 60°, 10.6 mm, 45°, 11.2 mm respectively, and the braiding angles and inner diameters of the third group of single-layer preform models are 60°, 10.0 mm, 45°, 10.6 mm, 30°, 11.2 mm respectively;

[0034] Step 2, establish a multilayer composite cladding tube model with a gradient braiding structure: the three groups of single-layer preform models established in step 1 are combined into three multilayer composite cladding tube models with a gradient braiding structure according to the arrangement of inner diameter from small to large. The gradient braiding structures are 30° for the inner layer, 45° for the middle layer, and 60° for the outer layer. Figure 2 As shown; inner layer 30°, middle layer 60°, outer layer 45°, as Figure 3 As shown; inner layer 60°, middle layer 45°, outer layer 30°, as shown Figure 4 As shown; and the overlaps and gaps in the model are removed by modifying the relative tolerance value of the composite cladding tube;

[0035] Step 3, performing solid mesh division on the multilayer composite cladding tube model: based on the three multilayer composite cladding tube models established in step 2, performing hexahedral mesh division on the SiC matrix and SiC fiber in the model;

[0036] Step 4, defining the damage criteria of the SiC fiber preform and the SiC matrix: the SiC fiber preform is tough and adopts the Hashin criterion (Formula 1), and the SiC matrix is ​​a brittle material and adopts the first strength theory criterion (Formula 2);

[0037] Formula 1:

[0038]

[0039] In the formula, σ 11 is the tensile stress, is the tensile strength, α is the contribution coefficient of shear stress, τ 12 is the shear stress, is the shear strength.

[0040] Formula 2:

[0041] σ 11θ ≥σ t ,σ 11θ >0

[0042] In the formula, σ 11θ is the tensile stress, σ t For tensile strength.

[0043] Step 5: Set the boundary conditions of the multilayer composite cladding tube model: set the starting value of 0 mm and the boundary conditions of 1×10 -3 mm is the step length and 0.3 mm is the increasing series of the terminal value to simulate the process of the composite cladding tube undergoing axial tension;

[0044] Step 6, determine the structural design of the multi-layer composite cladding tube with high strength and high toughness: Based on the boundary conditions set in step 5, select the Newton iteration method to calculate the stress-strain curves of the three multi-layer composite cladding tubes respectively. The termination judgment method of the Newton iteration method is that the maximum number of iterations is 20 times, and the maximum relative error is 0.003. The calculation results are sorted out, and the axial stress-strain curves of the three multi-layer composite cladding tubes are drawn, such as Figure 5 As shown in the figure, it can be seen that: Figure 5 The curve No. Ⅲ corresponds to the SiC with a gradient structure of inner layer braiding angle of 30°, middle layer braiding angle of 45°, and outer layer braiding angle of 60°. f / SiC composite cladding tube, the highest point of the curve is the axial tensile strength of 200MPa, and the corresponding limit strain is 0.5%. Figure 5 The curve No. Ⅰ corresponds to the SiC with a gradient structure of inner layer braiding angle of 30°, middle layer braiding angle of 60°, and outer layer braiding angle of 45°. f / SiC composite cladding tube, the highest point of the curve is the axial tensile strength of 250MPa, and the corresponding limit strain is 0.5%. Figure 5 The curve No. Ⅱ corresponds to the SiC with a gradient structure of 60° inner layer braiding angle, 45° middle layer braiding angle and 30° outer layer braiding angle. f / SiC composite cladding tube, the highest point of the curve is the axial tensile strength of 225MPa, and the corresponding limit strain is 0.5%. By comparison, SiC with a gradient structure of inner layer braiding angle of 30°, middle layer braiding angle of 60°, and outer layer braiding angle of 45° can be screened out. f / SiC composite cladding tube exhibits the best axial strength and toughness, and the other two structures have good axial strength and toughness.

[0045] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A high-strength and high-toughness ceramic-based composite cladding tube gradient structure, characterized in that: The invention is composed of 3 to 5 layers of SiC fiber preforms and a ceramic matrix coating the SiC fiber preforms. The braiding angle of each layer of SiC fiber preforms is different, ranging from 30° to 60°. The braiding angles of two adjacent layers of SiC fiber preforms vary in a gradient. The braiding angle is the angle between the axis of a single SiC fiber and the axis of the heterogeneous cladding tube.

2. The high-strength and high-toughness ceramic-based composite cladding tube gradient structure according to claim 1 is characterized in that: The ceramic matrix is ​​one of silicon carbide, silicon nitride and zirconium oxide.

3. The high-strength and high-toughness ceramic-based composite cladding tube gradient structure according to claim 1 is characterized in that: The inner diameter of the composite cladding tube gradient structure is 10.0mm-11.0mm, the outer diameter is 11.8mm-13.4mm, the thickness of the ceramic matrix is ​​0.3-0.4mm, the axial tensile strength of the composite cladding tube gradient structure is not less than 225MPa, and the ultimate tensile strain is not less than 0.5%.

4. The method for designing a high-strength and high-toughness ceramic-based composite cladding tube gradient structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: a. Establishing single-layer preform models with different inner diameters and different braiding angles: According to the actual geometric dimensions of SiC fiber and ceramic matrix, three groups of single-layer preform models with different inner diameters and different braiding angles are constructed in finite element software; b. Establishing a multilayer composite cladding tube model with a gradient braided structure: The three groups of single-layer preform models established in step a are combined into three multilayer composite cladding tube models with a gradient braided structure according to the arrangement of the inner diameter from small to large. The braiding angle of each group of single-layer preform models is 30° to 60°, and the overlap and gap in the model are removed by modifying the relative tolerance value of the multilayer composite cladding tube model; c. Performing solid meshing on the multilayer composite cladding tube model: Based on the multilayer composite cladding tube model established in step b, the ceramic matrix and SiC fiber preform in the model are divided into hexahedral meshes; d. Define the damage criteria of SiC fiber preform and ceramic matrix: SiC fiber preform is tough and adopts Hashin criterion, while ceramic matrix is ​​brittle material and adopts first strength theory criterion; e. Setting the boundary conditions of the multi-layer composite cladding tube model: setting an increasing displacement series on the specified surface of the multi-layer composite cladding tube model to simulate the process of the composite cladding tube being subjected to axial tension; f. Determine the structural design of the multi-layer composite cladding tube with high strength and high toughness: Based on the boundary conditions set in step e, select the Newton iteration method to calculate the stress-strain curve of the composite cladding tube, draw the axial stress-strain curve of the composite cladding tube, and find the stress value corresponding to the highest point in the axial stress-strain curve. The stress value is the axial tensile strength of the multi-layer composite cladding tube, and the tensile strain corresponding to the axial tensile strength is the ultimate tensile strain. At this time, the model structure corresponding to the axial tensile strength and the ultimate tensile strain is the designed gradient structure of the ceramic-based composite cladding tube with high strength and high toughness.

5. The design method of a high-strength and high-toughness ceramic-based composite cladding tube gradient structure according to claim 4 is characterized in that: The actual geometric dimensions of the ceramic matrix and SiC fiber described in step a include thicknesses of 0.30-0.40 mm and 0.21-0.27 mm respectively; the gradient structure height of the composite cladding tube is 31.5-32 mm, the inner diameter is 10.0-11.0 mm, and the outer diameter is 11.8-13.4 mm.

6. The method for designing a high-strength and high-toughness ceramic-based composite cladding tube gradient structure according to claim 4, characterized in that: The multilayer composite cladding tube model with a gradient weaving structure described in step b is a single-layer preform model with different weaving angles, which is respectively arranged in three ways: inner layer 30°, middle layer 45°, outer layer 60°, inner layer 30°, middle layer 60°, outer layer 45°, inner layer 60°, middle layer 45°, outer layer 30°, to form three multilayer composite cladding tube models.

7. The method for designing a high-strength and high-toughness ceramic-based composite cladding tube gradient structure according to claim 4, characterized in that: The incremental displacement sequence set on the specified surface of the multilayer composite cladding tube model in step e is: along the axial direction of the composite cladding tube, the displacement sequence is set with 0 mm as the starting value, 1×10 -3 mm~4×10 -3 mm is the step length, and 0.3mm~0.5mm is the increasing series of the end value.

8. The method for designing a high-strength and high-toughness ceramic-based composite cladding tube gradient structure according to claim 4, characterized in that: The termination judgment method of the Newton iteration method described in step f is that the maximum number of iterations is 20 to 25 times, and the maximum relative error is 0.001 to 0.005.

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