Method for testing normal tensile strength of T-shaped joint based on ceramic matrix composite material

Abstract

The invention discloses a method for testing normal tensile strength of a T-shaped joint based on a ceramic matrix composite material. The method comprises the following steps: acquiring the geometric dimension of a T-shaped sample; t-shaped components with the same geometric size as the T-shaped sample are obtained; the T-shaped sample and the T-shaped component are connected in a sleeving mode through a hoop, and the hoop is fixed through a limiting bolt; clamping the web part of the T-shaped sample by using a wedge-shaped clamp, and carrying out a tensile test to obtain the maximum loading force in the test process; and calculating the normal tensile strength of the T-shaped sample by using a formula. According to the invention, the problems of difficulty in clamping and inaccurate test result in the prior art are solved, and the accuracy of measuring the normal tensile strength of the T-shaped joint made of the ceramic matrix composite material is remarkably improved.

Description

Technical Field

[0001] The present invention relates to a tensile strength testing method for a T-joint, in particular to a normal tensile strength testing method for a T-joint based on a ceramic-based composite material, and belongs to the technical field of new aerospace materials. Background Art

[0002] Ceramic Matrix Composites (CMCs) are a new type of structural material with a ceramic matrix and fiber reinforcement. They offer significant advantages, including excellent high-temperature mechanical properties, wear resistance, corrosion resistance, thermal shock resistance, and low density. They hold broad application prospects in high-end equipment manufacturing, including aerospace, energy and power, and rail transportation. Compared to traditional single ceramic materials, CMCs significantly enhance toughness and crack resistance while maintaining high-temperature performance, making them a research hotspot for high-temperature structural materials.

[0003] With the continuous expansion of the application scope of ceramic-based composites, the connection and assembly technology of complex configuration structures has gradually become a key technical issue in engineering applications. Among them, T-joints, as a typical connection structure, are widely used in structures such as aircraft engine casings, fuselage frames, and connections between composite skins and reinforced components. T-joints can effectively transfer multi-directional loads and are important nodes in the design of high-performance composite structures. Especially in the integrated manufacturing of large-scale components, T-joints not only meet the strength requirements of structural connections, but also take into account the integrity and stiffness control of the components. Therefore, they are increasingly used in actual engineering.

[0004] In actual service conditions, T-joints are often subjected to complex loads, including shear, tension, compression and other stress states. Among them, normal tensile load is a typical and important form of failure, which is commonly seen in scenarios such as local tensile stress concentration caused by manufacturing defects of components, cracking tendency caused by structural deformation, and connection failure under installation load or extreme load conditions. Normal tensile conditions are the key basis for evaluating the reliability and failure mode of T-joint connections. Accurate measurement of their strength characteristics directly affects the design margin and safety performance of ceramic matrix composite structures.

[0005] Currently, the testing methods for the normal tensile properties of T-joints are mainly focused on resin-based composite systems, such as a metal-based composite interface normal bonding strength testing device and method disclosed in publication number CN109883947A. This method is used to stretch the test specimen and is suitable for measuring the normal bonding strength of the interface of continuous fiber-reinforced metal-based composites. These methods often rely on the material properties of low stiffness and good processability and are difficult to directly apply to high-stiffness, low-ductility ceramic-based composites. Specifically, when applied to ceramic-based composites, existing testing methods have problems such as difficult clamping, uneven loading, and early specimen damage, resulting in unstable test results, poor repeatability, and inaccurate strength measurements, making it difficult to meet the requirements of high-precision performance evaluation. Summary of the Invention

[0006] The purpose of the present invention is to provide a normal tensile strength testing method for T-joints based on ceramic-based composite materials in order to solve at least one of the above-mentioned technical problems. The method can overcome the limitations of the existing technology, realize reliable measurement of the mechanical properties of the ceramic-based composite material T-joint structure, and promote its engineering application in key structural components.

[0007] The present invention achieves the above-mentioned object through the following technical solutions: a method for testing the normal tensile strength of a T-joint based on a ceramic matrix composite material, comprising a test assembly for performing a tensile strength test on a T-joint specimen; The test assembly includes a T-shaped member, a hoop, and a wedge-shaped fixture. The T-shaped member and the T-shaped specimen are symmetrically placed together, and hoop is placed on both ends of the T-shaped member and the T-shaped specimen. The web of the T-shaped member and the T-shaped specimen are clamped with a wedge-shaped fixture. The normal tensile strength test method comprises the following steps: S1. Obtain the geometric dimensions of the T-type specimen; S2. Obtain a T-shaped member with the same geometric dimensions as the T-shaped specimen; S3. Use a ferrule to connect the T-shaped specimen to the T-shaped member, and fix the ferrule with a limit bolt; S4. Use a wedge-shaped fixture to clamp the web of the T-type specimen and perform a tensile strength test. S5. Obtain the maximum load during the test; S6. Calculate the normal tensile strength of the T-type specimen using the formula.

[0008] As a further solution of the present invention: threaded holes are provided on both ends of the T-shaped member and the body of the hoop, and the threaded holes are threadedly connected to limit bolts.

[0009] As a further solution of the present invention: in S1, the T-type specimen is a T-shaped structure, the T-type specimen consists of a web and a flange, and the web and the flange are connected by two symmetrically arranged arc segments.

[0010] As a further solution of the present invention: the geometric dimensions of the T-shaped specimen include the overall thickness of the T-shaped specimen, the length and width of the web, the length and width of the flange, and the radius of the arc segment.

[0011] As a further solution of the present invention: in S3, the ferrule is a rectangular structure made of aluminum alloy, and is provided with a threaded hole for connecting with the T-shaped member by bolts to fix the position of the ferrule.

[0012] As a further solution of the present invention: In S4, wedge-shaped clamps are used to clamp the web of the T-shaped specimen and the T-shaped member, respectively. If experimental conditions permit, as much of the web area as possible can be clamped to avoid clamping the arc area where the web and flange meet.

[0013] As a further solution of the present invention: a load-displacement curve is obtained by a testing machine, and the maximum load value generated during the test is extracted from the load-displacement curve for subsequent calculation of the normal tensile strength of the T-type specimen.

[0014] As a further solution of the present invention: the destructive strength of the T-type specimen (test specimen) is calculated using the stress expression formula, which is:

[0015] in, is the maximum load during the test, is the width of the web, is the thickness of the T-type specimen.

[0016] The beneficial effects of the present invention are: 1) The present invention achieves effective clamping and precise positioning of the specimen during the tensile test by combining a T-shaped specimen with a T-shaped member. The normal tensile loading is completed by combining a wedge-shaped fixture. Finally, the normal tensile strength of the ceramic matrix composite T-joint is calculated using a formula. 2) This test method effectively overcomes the problems of clamping difficulties and inaccurate test results in existing technologies, and significantly improves the reliability and accuracy of the normal tensile strength test of ceramic matrix composite T-joints. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Flowchart of the present invention; Figure 2 It is a schematic structural diagram of the T-type specimen of the present invention; Figure 3It is a structural schematic diagram of the T-shaped member of the present invention; Figure 4 It is a structural schematic diagram of the ferrule of the present invention; Figure 5 This is a schematic diagram of sample loading in the present invention; Figure 6 The load-displacement response image of the sample during the loading process recorded by the testing machine of the present invention; In the figure: 1. T-shaped member; 2. T-shaped specimen; 3. Hoop; 4. Limit bolt; 5. Wedge-shaped clamp; 6. Threaded hole. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] Example 1, as Figures 1 to 6 As shown, this embodiment provides a method for testing the normal tensile strength of a T-joint based on a ceramic matrix composite material. The test assembly required for performing a tensile strength test on the T-joint of the ceramic matrix composite material is a test device specially designed for the T-joint.

[0020] like Figure 5 As shown, the test device includes a T-shaped member 1 (as Figure 3 ), ferrule 3 (such as Figure 4 ) and a wedge-shaped clamp 5; wherein, the T-shaped member 1 and the T-shaped specimen 2 are symmetrically fitted together, that is, the web of the T-shaped member 1 and the web of the T-shaped specimen 2 are symmetrically fitted and contacted, and both ends of the T-shaped member 1 and the T-shaped specimen 2 where they are fitted together are sleeved with hoops 3, that is, the ends where the flanges of the T-shaped member 1 and the flanges of the T-shaped specimen 2 are fitted and contacted are sleeved with hoops 3; the webs of the T-shaped member 1 and the T-shaped specimen 2 are both clamped by a wedge-shaped clamp 5.

[0021] In addition, the T-shaped member 1 is made of aluminum alloy, and threaded holes 6 are provided on both ends (flanges) of the T-shaped member 1 and the body of the hoop, and the threaded holes 6 are internally threadedly connected to the limit bolts 4.

[0022] It should be noted that the T-shaped member 1 made of aluminum alloy should have a sufficiently high strength to ensure that the T-shaped member 1 does not fail before the T-shaped specimen 2 of the ceramic-based composite material fails, thereby ensuring that the measured maximum failure load truly reflects the normal tensile strength of the T-shaped specimen 2 of the ceramic-based composite material.

[0023] A method for testing the normal tensile strength of a ceramic matrix composite T-joint comprises the following steps: First: obtain the geometric dimensions of T-type specimen 2.

[0024] like Figure 2 As shown, the T-type specimen 2 is a T-shaped structure. The T-type specimen 2 consists of a web and a flange, and the web and the flange are connected by two symmetrically arranged arc segments.

[0025] like Figure 2 As shown, the geometric dimensions of the T-shaped specimen 2 include the overall thickness of the T-shaped specimen 2, the length and width of the web, the length and width of the flange, and the radius of the arc segment.

[0026] Second: obtain a T-shaped component 1 made of aluminum alloy with the same geometric dimensions (similar geometric dimensions) as the T-shaped specimen 2.

[0027] The T-shaped member 1 made of aluminum alloy should have similar (identical) geometric dimensions to the T-shaped specimen 2 made of ceramic matrix composite material, and two bolt holes 6 should be machined on its flange at symmetrical positions relative to the web, which are used to subsequently fix the position of the hoop 4 through the limit bolts 4 to ensure the stability of the specimen during loading.

[0028] Third: Use the hoop 3 to connect the T-shaped specimen 2 and the T-shaped component 1, and fix the hoop 3 with the limiting bolt 4.

[0029] The ferrule 3 is a rectangular structure made of aluminum alloy and is provided with threaded holes 6 for bolting to the T-shaped member 1. This secures the ferrule 3 in place and prevents loosening during loading. This ferrule structure tightly couples the T-shaped specimen 2 to the T-shaped member 1, facilitating clamping and loading operations during subsequent tensile testing.

[0030] Fourth: Use the wedge-shaped fixture 5 to perform tensile strength tests on the plate parts of the T-shaped specimen 2 and the T-shaped component 1 respectively.

[0031] Use wedge-shaped grips 5 to clamp the web of T-shaped specimen 2 and T-shaped member 1. If experimental conditions permit, clamp as much of the web area as possible to prevent specimen slippage during testing. However, avoid clamping the circular arc section where the web meets the flange to prevent affecting stress distribution. After clamping, perform a tensile test, applying a normal tensile load.

[0032] Fifth: Obtain the maximum load force during the test.

[0033] The load-displacement curve is obtained by the testing machine, and the maximum load value generated during the test is extracted from the load-displacement curve for the subsequent calculation of the normal tensile strength of the T-type specimen 2.

[0034] Sixth: Use the formula to calculate the normal tensile strength of T-type specimen 2.

[0035] The stress expression formula is used to calculate the destructive strength of T-type specimen 2 (i.e., the normal tensile strength of the ceramic matrix composite T-type joint), and the formula is:

[0036] in, is the maximum load during the test, is the width of the web, is the thickness of the T-type specimen.

[0037] Example 2: This example provides a method for testing the normal tensile strength of a T-joint based on a ceramic matrix composite material. The normal tensile strength testing method specifically includes: First, a batch of T-shaped specimens of ceramic matrix composite materials are obtained (i.e., the plane is composed of a web and a flange connected by two 90° circular rings, and has a certain thickness in the direction perpendicular to the plane), such as Figure 2 As shown, the specific geometric parameters of the measured specimen include the overall thickness of the T-type specimen , the length of the web , the width of the web , flange length , flange width , the radius of the arc segment The specific parameters of the samples are shown in Table 1.

[0038] Then, the T-type specimen and the aluminum alloy T-type member are sleeved together with a hoop and fixed with a limit bolt. A wedge-shaped fixture is used to clamp the web of the T-type specimen and the T-type member respectively, and then a tensile test is carried out to apply a normal tensile load. Figure 6 As shown, get the load P -Displacement D The maximum load value generated during the test is extracted from the curve .

[0039] Finally, the destructive strength of the test sample (i.e., the normal tensile strength of the ceramic matrix composite T-joint) is calculated using the formula:

[0040] Working process: obtain the geometric dimensions of the T-type specimen; obtain a T-type component with the same geometric dimensions as the T-type specimen; use a hoop structure to connect the T-type specimen and the T-type component, and fix the hoop with a limit bolt; use a wedge-shaped fixture to clamp the web part of the T-type joint and perform a tensile test; obtain the maximum load force during the test; use the formula to calculate the normal tensile strength of the T-type specimen.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0042] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for testing the normal tensile strength of a T-joint of a ceramic matrix composite material, characterized by: A test assembly comprising a test assembly for performing a tensile strength test on a T-type test specimen (2); The test assembly comprises a T-shaped member (1), a hoop (3) and a wedge-shaped clamp (5); the T-shaped member (1) and the T-shaped specimen (2) are symmetrically fitted together, and both ends of the T-shaped member (1) and the T-shaped specimen (2) are sleeved with a hoop (3); the webs of the T-shaped member (1) and the T-shaped specimen (2) are clamped with a wedge-shaped clamp (5); The normal tensile strength testing method comprises the following steps: S1. Obtain the geometric dimensions of the T-type specimen (2); S2, obtaining a T-shaped component (1) having the same geometric dimensions as the T-shaped specimen (2); S3, using a hoop (3) to connect the T-shaped specimen (2) and the T-shaped member (1), and fixing the hoop (3) by a limit bolt (4); S4. Clamp the web of the T-type specimen (2) using a wedge-shaped fixture (5) and perform a tensile strength test; S5. Obtain the maximum load during the test; S6. Calculate the normal tensile strength of the T-type specimen (2) using the formula.

2. The normal tensile strength testing method according to claim 1, wherein: Threaded holes (6) are provided on both ends of the T-shaped member (1) and the body of the hoop (3), and the threaded holes (6) are internally threadedly connected to limit bolts (4).

3. The normal tensile strength testing method according to claim 1, wherein: In S1, the T-shaped specimen (2) is a T-shaped structure, the T-shaped specimen (2) is composed of a web and a flange, and the web and the flange are connected by two symmetrically arranged circular arc segments.

4. The normal tensile strength testing method according to claim 2, wherein: In said S1, the geometrical dimensions of the T-shaped specimen (2) include the overall thickness of the T-shaped specimen (2), the length and width of the web, the length and width of the flange, and the radius of the arc segment.

5. The normal tensile strength testing method according to claim 1, wherein: In the S3, the hoop (3) is a rectangular structure made of aluminum alloy, and a threaded hole (6) is provided on the hoop (3) for connecting with the T-shaped member (1) by bolts to achieve fixing of the position of the hoop (3).

6. The normal tensile strength testing method according to claim 1, wherein: In the above-mentioned S4, a wedge-shaped clamp (5) is used to clamp the web portion of the T-shaped specimen (2) and the T-shaped member (1) respectively.

7. The normal tensile strength testing method according to claim 1, wherein: In the above-mentioned S5, a load-displacement curve is obtained by a testing machine, and the maximum load value generated during the test is extracted from the load-displacement curve for subsequent calculation of the normal tensile strength of the T-type specimen (2).

8. The method for testing the normal tensile strength of a joint according to claim 1, wherein: In S6, the stress expression formula is used to calculate the breaking strength of the T-type specimen (2), which is: ； in, is the maximum load during the test, is the width of the web, is the thickness of the T-type specimen.

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