Two-degree-of-freedom clamp connecting piece

Abstract

The utility model discloses a two-degree-of-freedom clamp connecting piece which comprises a main body. The top wing plates extend from the top edge of the main body in the direction away from the main body in the mode that the top wing plates are opposite to each other and parallel to each other, top through holes are formed in the top wing plates, and the top through holes are aligned with each other and are constructed to allow the top pivot shafts to penetrate through; therefore, the two-degree-of-freedom clamp connecting piece is rotatably connected to a pull rod of the tensile machine; the bottom wing plates extend from the bottom edge of the main body in the direction away from the main body in a mutually opposite and mutually parallel mode, each bottom wing plate is provided with a bottom through hole, and the bottom through holes are aligned with each other and are configured to allow the bottom pivot shaft to penetrate through, so that the two-degree-of-freedom clamp connecting piece is rotationally connected to the test piece; each top wing plate is arranged in the mode that the extending direction of the top wing plate is different from the extending direction of each bottom plate wing plate, and therefore the axis of the top through hole is perpendicular to the axis of the bottom through hole in a non-coplanar mode.

Description

Technical Field

[0001] This utility model relates to a two-degree-of-freedom fixture connector, specifically to a two-degree-of-freedom fixture connector for a pull rod of a tensile testing machine. This two-degree-of-freedom fixture connector can connect a sample assembly of a composite sandwich structure plate to the pull rod of a tensile testing machine for mechanical testing. Background Technology

[0002] Typically, shear and planar tensile tests for composite sandwich panels are conducted using ASTM standards. Specifically, the standard for shear testing of composite sandwich panels is ASTM C 273, which describes the test principles, equipment, specimens, test conditions, and procedures for shear testing of the core material of composite sandwich structures, including the testing of shear strength and shear modulus parallel to the plane of the sandwich structure. The standard for planar tensile testing of composite sandwich structures is ASTM C 297, which similarly describes the test principles, equipment, specimens, test conditions, and procedures for planar tensile testing of composite sandwich structures, and includes testing of the planar tensile strength of the core material, the bond between the core material and the panel, and the panel layer of the sandwich structure.

[0003] In composite material mechanical testing, poor specimen alignment and parallelism will lead to inaccurate test results. The main reasons for poor specimen alignment and parallelism stem from three aspects: first, the fixtures of the testing equipment; second, the specimen installation process; and third, deviations in fiber orientation during specimen preparation and large end-point errors during processing. Therefore, in composite material mechanical testing, once the installation process of the testing equipment and the specimen preparation process are confirmed to be without problems, in order to eliminate the adverse effects of poor specimen alignment and parallelism, one should try to change the placement of the specimen in the fixture or modify the fixture to obtain better alignment or parallelism.

[0004] When performing shear tests on composite sandwich panel structures according to ASTM C 273, existing general-purpose fixtures primarily use unidirectional bolts to connect the fixture to the tensile testing machine. Since the specimen is fixed by only one set of bolts, the alignment of the specimen cannot be guaranteed, thus reducing the accuracy of the test results. Furthermore, when performing planar tensile tests on composite sandwich structures according to ASTM C 297, in order to obtain effective failure modes, in addition to the aforementioned alignment issue, the parallelism of the specimen is also crucial.

[0005] Therefore, a simple and reliable clamping connector is needed to ensure the centering and parallelism of specimens in composite mechanical tests. Utility Model Content

[0006] Therefore, the technical problem to be solved by this utility model is to overcome the fact that existing composite sandwich structure shear or planar tension fixtures cannot fix bolts in two directions at the same time, which makes it difficult to guarantee the centering and parallelism of the sample assembly, thereby reducing the test efficiency and the accuracy of the test results.

[0007] To address the aforementioned technical problems, this utility model provides a two-degree-of-freedom clamp connector. The two-degree-of-freedom clamp connector is configured to connect a composite sandwich panel specimen to the tie rod of a tensile testing machine for mechanical testing, and includes: a main body; a pair of top flanges extending parallel to each other from the top edge of the main body in a direction away from the main body, each top flange having a top through-hole aligned with each other and configured to allow a top pivot shaft to pass through it, thereby rotatably connecting the two-degree-of-freedom clamp connector to the tensile testing machine. A tie rod; a pair of bottom wing plates extending from the bottom edge of the body opposite to each other and parallel to each other in a direction away from the body, each bottom wing plate having a bottom through hole formed therein, the bottom through holes being aligned with each other and configured to allow a bottom pivot shaft to pass through therethrough, thereby rotatably connecting the two-degree-of-freedom fixture connector to the specimen; wherein each of the pair of top wing plates is configured such that its extension direction is different from the extension direction of each of the pair of bottom wing plates, such that the axis of the top through hole is perpendicular to the axis of the bottom through hole.

[0008] The dual-degree-of-freedom fixture connector described in this utility model has a bidirectional free connection method. Therefore, when installing the sample assembly, two bolts can be connected to ensure the centering or parallelism of the sample assembly, avoid premature failure of the sample due to stress concentration during the test, and improve the test efficiency and the accuracy of the test results.

[0009] According to one embodiment of the present invention, each of the pair of top wing plates has an arc-shaped outer contour, and the top through hole is opened on the longitudinal center line of the top wing plate away from the main body.

[0010] The dual-degree-of-freedom fixture connector described in this invention has an arc-shaped design at one end connecting to the tension testing machine's pull rod. Therefore, the dual-degree-of-freedom fixture connector can rotate a large range around the connecting end of the pull rod. This significantly shortens the displacement of the tension testing machine's crossbeam when disassembling the dual-degree-of-freedom fixture connector, thus significantly improving testing efficiency. Furthermore, the top through-hole design eliminates the need for an additional adapter block, resulting in a shorter fixture loading chain for the entire test.

[0011] According to one embodiment of the present invention, the arc-shaped outer contour is parabolic.

[0012] By adopting a parabolic profile for the top wing plate of the two-degree-of-freedom clamp connector, the range of rotation of the two-degree-of-freedom clamp connector around the connecting end of the tie rod can be further increased, and the difficulty of connecting the two-degree-of-freedom clamp connector to the tie rod of the tensioning machine can be reduced.

[0013] According to one embodiment of the present invention, each of the pair of bottom wing plates is rectangular, and the bottom through hole is opened at the center of the bottom wing plate away from the main body.

[0014] The dual-degree-of-freedom fixture connector according to this utility model can be rotatably connected to the sample assembly through its bottom wing plate, and by setting its bottom wing plate into a rectangular shape, it can facilitate the manufacturing, storage, transportation, and placement of the dual-degree-of-freedom fixture connector.

[0015] According to one embodiment of the present invention, the top pivot shaft or the bottom pivot shaft is a bolt.

[0016] According to one embodiment of the present invention, the dual-degree-of-freedom clamp connector is made of CrWMn steel.

[0017] According to one embodiment of the present invention, the dual-degree-of-freedom fixture connector is configured such that when the axes of the bottom through holes of the two dual-degree-of-freedom fixture connectors, which are respectively connected to the upper and lower pull rods of the tensile testing machine, are parallel to each other, it can be used for shear tests of composite sandwich structures.

[0018] According to one embodiment of the present invention, the dual-degree-of-freedom fixture connector is configured such that when the axes of the bottom through holes of the two dual-degree-of-freedom fixture connectors, which are respectively connected to the upper and lower pull rods of the tensile testing machine, are perpendicular to each other, it can be used for planar tensile testing of composite material sandwich structures.

[0019] The dual-degree-of-freedom clamp connector according to this invention can be used for shear and tensile tests of composite sandwich structures by adjusting the relative orientation between the dual-degree-of-freedom clamp connectors.

[0020] According to one embodiment of the present invention, the main body is made into a cuboid, and the pair of top wing plates and the pair of bottom wing plates extend from the top edge and bottom edge of the cuboid respectively, opposite to each other and parallel to each other, in a direction away from the cuboid, wherein the pair of top wing plates and the pair of bottom wing plates are respectively located on different sides of the cuboid.

[0021] By setting the main body of the two-degree-of-freedom fixture connector as a cuboid, the design and manufacturing process of the two-degree-of-freedom fixture connector can be simplified and its cost reduced.

[0022] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this utility model.

[0023] The positive and progressive effects of the above-described embodiments of this utility model are as follows:

[0024] 1. The dual-degree-of-freedom fixture connector of this utility model can significantly reduce the centering and parallelism errors caused by the installation of the specimen, and ensure that the load is applied horizontally to both ends of the specimen assembly, avoiding premature failure of the specimen due to local stress concentration, improving the accuracy of the test results and the effective failure success rate of 100%.

[0025] 2. The top arc-shaped wing plate of the dual-degree-of-freedom fixture connector of this utility model has a through hole size that is close to the tension test rod, so there is no need to use an additional adapter block for connection, which makes the fixture loading chain of the whole test shorter, improves the load accuracy of mechanical test, and can also be adapted to environmental chambers of more sizes to carry out high and low temperature tests of composite material sandwich structures.

[0026] 3. The dual-degree-of-freedom fixture connector described in this utility model can be applied to both shear tests and planar tensile tests of composite sandwich structure plates;

[0027] 4. The dual-degree-of-freedom fixture connector of this utility model has a simple structure, good stability, high wear resistance, low cost and convenient installation, and is suitable for fixing in planar tensile or shear tests of various composite material sandwich structures;

[0028] 5. The dual-degree-of-freedom clamp connector described in this utility model can be used to fix composite sandwich structure samples of different thicknesses;

[0029] 6. The dual-degree-of-freedom fixture connector described in this utility model can save time and costs, reduce repetitive labor, and improve the accuracy and efficiency of testing. Attached Figure Description

[0030] Figure 1 This is an isometric view of a dual-degree-of-freedom clamp connector according to a preferred embodiment of the present invention.

[0031] Figure 2 This is a front view of a two-degree-of-freedom clamp connector according to a preferred embodiment of the present invention.

[0032] Figure 3 This is a side view of a dual-degree-of-freedom clamp connector according to a preferred embodiment of the present invention.

[0033] Figure 4 This is a top view of a dual-degree-of-freedom clamp connector according to a preferred embodiment of the present invention.

[0034] Figure 5 This is a bottom view of a dual-degree-of-freedom clamp connector according to a preferred embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram of a two-degree-of-freedom fixture connector according to a preferred embodiment of the present invention used for shear tests on composite sandwich structures.

[0036] Figure 7 This is a schematic diagram of a two-degree-of-freedom fixture connector according to a preferred embodiment of the present invention used for a planar tensile test of a composite sandwich structure.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1: Dual-degree-of-freedom fixture connector

[0039] 2: Top wing plate

[0040] 3: Main body

[0041] 4: Bottom wing plate

[0042] 5: Top through hole

[0043] 6: Bottom through hole

[0044] 7: Bolts

[0045] 8: Tensile testing machine tie rod

[0046] 9: Shear specimen assembly

[0047] 10: Planar tensile specimen assembly

[0048] 11: Sample loading block Detailed Implementation

[0049] The preferred embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The following description is exemplary and not intended to limit the present invention. Any other similar situations also fall within the protection scope of the present invention.

[0050] In the following detailed description, directional terms such as "left," "right," "up," "down," "front," and "back" are used with reference to the directions described in the accompanying drawings. Components of embodiments of this invention can be positioned in a variety of different orientations; the directional terms are for illustrative purposes and not restrictive.

[0051] Traditional fixtures used for shear and planar tensile testing of composite sandwich structures have only one degree of freedom in one direction. Therefore, it is difficult to ensure the centering and parallelism of the specimen after the fixture and specimen are installed. During the test, as the load increases, stress concentration may occur in the composite sandwich structure, which usually leads to a decrease in the strength of the composite sandwich structure, inaccurate test data, or abnormal failure modes.

[0052] Furthermore, traditional clamps are typically square at the end of the tension rod near the tensile testing machine, which limits the clamp's movement space. Therefore, after shear and planar tensile tests on composite sandwich structures, operators need to move the tensile testing machine's crossbeam a considerable distance to remove the specimen. Additionally, traditional clamps require additional connecting blocks at both ends, resulting in a longer loading chain, a larger required testing space, and consequently, reduced testing accuracy.

[0053] This utility model provides a two-degree-of-freedom fixture connector, which is configured to connect a composite sandwich panel sample assembly, i.e., a specimen, to the tie rod of a tensile testing machine for mechanical testing. Figure 1 As shown, the dual-degree-of-freedom fixture connector 1 includes a pair of top wing plates 2, a main body 3, and a pair of bottom wing plates 4.

[0054] A pair of top flanges 2 extend from the top edge of the body 3 opposite to each other and parallel to each other in a direction away from the body 3. Each top flange has a top through hole 5 formed therein, which are aligned and configured to allow a top pivot shaft to pass through, thereby rotatably connecting the two-degree-of-freedom fixture connector 1 to the tensile testing machine pull rod 8. A pair of bottom flanges 4 extend from the bottom edge of the body 3 opposite to each other and parallel to each other in a direction away from the body 3. Each bottom flange has a bottom through hole 6 formed therein, which are aligned and configured to allow a bottom pivot shaft to pass through, thereby rotatably connecting the two-degree-of-freedom fixture connector 1 to the sample assembly.

[0055] In this pair of top wing plates 2, each top wing plate is configured such that its extension direction is different from the extension direction of each bottom wing plate in the pair of bottom wing plates 4, so that the axis of the top through hole 5 is perpendicular to the axis of the bottom through hole 6.

[0056] The dual-degree-of-freedom fixture connector provided by this invention can rotate relative to the tension rod and specimen assembly of the tensile testing machine, thus possessing two degrees of freedom and ensuring the centering and parallelism of the specimen. During the test, the specimen assembly can adaptively adjust its centering and parallelism, thereby reducing stress concentration in the composite sandwich structure and improving the accuracy of the test data.

[0057] like Figures 2-5As shown, each top wing plate 2 of the dual-degree-of-freedom fixture connector 1 includes an arc-shaped outer contour extending away from the main body 3, and a top through hole 5 is located away from the main body 3 and is opened on the longitudinal centerline of the top wing plate 2.

[0058] The end of the two-degree-of-freedom fixture connector connected to the tie rod is constructed in an arc shape, which significantly increases the range of rotational motion of the two-degree-of-freedom fixture connector around the connecting end of the tie rod. For example, after the mechanical test of the composite sandwich structure, because the two-degree-of-freedom fixture connector can rotate a large distance around the connecting end of the tie rod, the operator can easily disassemble the sample assembly without adjusting the crossbeam of the tensile testing machine, significantly improving the testing efficiency.

[0059] Furthermore, by placing the top through-hole 5 on the side of the top wing plate 2 away from the main body 3, it can be connected to the pull rod 8 of the tensile testing machine without an additional adapter block, thus shortening the loading chain of the tensile force and improving the accuracy of the test data. Moreover, the shorter loading chain of the tensile force allows the test space of the tensile testing machine, i.e., the space between the upper and lower pull rods of the tensile testing machine, to meet the size requirements of the environmental chamber. Therefore, the dual-degree-of-freedom clamp connector described in this invention can also be used for high-temperature environmental chamber tests of shear and planar tensile composite sandwich structures.

[0060] Preferably, the arc-shaped outer contour of the top wing plate 2 of the dual-degree-of-freedom fixture connector 1 is parabolic.

[0061] The top wing plate 2 of the dual-degree-of-freedom clamp connector 1 has an arc-shaped outer contour with a parabolic design, which can further increase the range of rotation of the dual-degree-of-freedom clamp connector around the connecting end of the tie rod and reduce the difficulty of connecting the dual-degree-of-freedom clamp connector with the tie rod of the tensioning machine.

[0062] As shown in the figure, each bottom wing plate 4 of the dual-degree-of-freedom fixture connector 1 is rectangular, and the bottom through hole 6 is far away from the main body 3 and is opened in the center of the bottom wing plate 4.

[0063] The bottom of the two-degree-of-freedom fixture connector 1 is constructed in an inverted U-shape, which allows the two-degree-of-freedom fixture connector to be easily connected to the sample assembly, and the two-degree-of-freedom fixture connector and the sample assembly can rotate relative to each other.

[0064] The rectangular shape of the bottom wing plate 4 of the two-degree-of-freedom clamp connector 1 allows for stable placement of the two-degree-of-freedom clamp connector. However, the shape of the bottom wing plate of the two-degree-of-freedom clamp connector is not limited to this.

[0065] The top or bottom pivot of the two-degree-of-freedom clamp connector 1 can be a bolt. That is, Figure 6 and Figure 7As shown, the top wing plate 2 is connected to the tie rod 8 by bolts 7, and the bottom wing plate is also connected to the sample assembly by bolts 7.

[0066] The dual-degree-of-freedom fixture connector may be made of materials that are resistant to high temperature, have good stability, high strength, and high wear resistance. Preferably, the dual-degree-of-freedom fixture connector is made of CrWMn steel.

[0067] As shown in the figure, the main body 3 of the two-degree-of-freedom clamp connector 1 is made into a cuboid. However, the shape of the main body 3 is not limited to this. A pair of top wing plates 2 and a pair of bottom wing plates 4 extend from the top edge and bottom edge of the cuboid respectively, opposite to each other and parallel to each other, in a direction away from the cuboid, and the pair of top wing plates 2 and the pair of bottom wing plates 4 are located on different sides of the cuboid.

[0068] like Figure 6 and Figure 7 As shown, by changing the relative orientation of the two-degree-of-freedom fixture connector 1, the two-degree-of-freedom fixture connector 1 can be used for shear and tensile tests of composite sandwich structures.

[0069] Figure 6 This diagram illustrates the application of the dual-degree-of-freedom clamp connector of this invention in shear testing of composite sandwich structures. During the test, a shear specimen assembly 9, including a specimen and a specimen loading block 11, is first prepared as shown. Then, the two ends of the shear specimen assembly 9 are connected to the bottom through holes of two dual-degree-of-freedom clamp connectors via, for example, a bottom pivot shaft using a bolt. The top flange of one dual-degree-of-freedom clamp connector is then connected to the connecting end of the upper pull rod 8 of the tensile testing machine via, for example, a top pivot shaft using a bolt. It should be noted that when the two ends of the shear specimen assembly 9 are connected to the bottom through holes of the two dual-degree-of-freedom clamp connectors, as shown in the diagram, the axes of the bottom through holes of the two dual-degree-of-freedom clamp connectors are parallel to each other. Next, the load zero point of the tensile testing machine is adjusted, and the crossbeam of the tensile testing machine is adjusted so that the top flange of the other dual-degree-of-freedom clamp connector can be connected to the connecting end of the lower pull rod 8 of the tensile testing machine via a top pivot shaft. Finally, the crossbeam of the tensile testing machine is moved upward to apply a certain preload to the shear specimen assembly 9. The alignment and parallelism of the shear specimen assembly 9 are ensured through adaptive adjustment of the two degrees of freedom of the two-degree-of-freedom clamp connectors. This ensures that the plane defined by the axes of the bottom through holes of the two-degree-of-freedom clamp connectors passes through the diagonal surface of the specimen in the shear specimen assembly 9, and the load lines defined by the upper and lower tie rods 8 pass through this diagonal surface, thus guaranteeing the accuracy of the test results. When determining the planar shear strength, a uniform and continuous load is applied until failure or a significant decrease or stagnation of the load. The maximum load is read and the failure mode is recorded.

[0070] Figure 7This diagram illustrates the use of the dual-degree-of-freedom clamp connector of this invention for planar tensile testing of composite sandwich structures. During the test, a planar tensile specimen assembly 10, including a specimen and a specimen loading block 11, is first prepared as shown. Then, the two ends of the planar tensile specimen assembly 10 are connected to the bottom through holes 6 of two dual-degree-of-freedom clamp connectors 1 via a top pivot shaft, for example, a bolt 7. The top flange 5 of one dual-degree-of-freedom clamp connector 1 is connected to the connecting end of the upper pull rod 8 of the tensile testing machine via a top pivot shaft. It should be noted that when the two ends of the planar tensile specimen assembly 10 are connected to the bottom flanges 4 of the two dual-degree-of-freedom clamp connectors 1, as shown, the axes of the bottom through holes of the two dual-degree-of-freedom clamp connectors are perpendicular to each other. Next, the load zero point of the tensile testing machine is adjusted, and the crossbeam of the tensile testing machine is adjusted so that the top flange 2 of the other dual-degree-of-freedom clamp connector 1 can be connected to the connecting end of the lower pull rod 8 of the tensile testing machine via a top pivot shaft, for example, a bolt. Finally, the crossbeam of the tensile testing machine is moved upward to apply a certain preload to the planar tensile specimen assembly 10. The alignment and parallelism of the planar tensile specimen assembly 10 are ensured by adaptive adjustment of the two degrees of freedom of the two-degree-of-freedom clamp connectors 1. This ensures that the bottom surfaces of the main bodies of the two-degree-of-freedom clamp connectors 1 are parallel to each other and parallel to the upper and lower surfaces of the specimen. Furthermore, the load lines determined by the upper and lower tie rods 8 pass through the center of the upper and lower surfaces of the specimen and are perpendicular to them, thus ensuring the accuracy of the test results. When determining the planar tensile strength, a uniform and continuous load is applied until failure. The failure load value is read and the failure mode is recorded.

[0071] The beneficial technical effects of the above-mentioned preferred embodiments of this utility model are as follows:

[0072] 1. The dual-degree-of-freedom fixture connector described in this utility model can significantly reduce the centering and parallelism errors caused by the installation of the specimen, and ensure that the load is applied horizontally and evenly at both ends of the specimen assembly, avoiding premature failure of the specimen due to local stress concentration, and improving the accuracy of the test results and the effective failure success rate of 100%.

[0073] 2. The top arc-shaped wing plate of the dual-degree-of-freedom fixture connector of this utility model has a through hole size that is close to the tension test rod, so there is no need to use an additional adapter block for connection, which makes the fixture loading chain of the whole test shorter, improves the load accuracy of mechanical test, and can also be adapted to environmental chambers of more sizes to carry out high and low temperature tests of composite material sandwich structures.

[0074] 3. The dual-degree-of-freedom fixture connector described in this utility model can be applied to both shear tests and planar tensile tests of composite sandwich structure plates;

[0075] 4. The dual-degree-of-freedom fixture connector of this utility model has a simple structure, good stability, high wear resistance, low cost and convenient installation, and is suitable for fixing in planar tensile or shear tests of various composite material sandwich structures;

[0076] 5. The dual-degree-of-freedom clamp connector described in this utility model can be used to fix composite sandwich structure samples of different thicknesses;

[0077] 6. The dual-degree-of-freedom fixture connector described in this utility model can save time and costs, reduce repetitive labor, and improve the accuracy and efficiency of testing.

[0078] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. A two degree of freedom fixture link configured to connect a test specimen of a composite sandwich structure panel to a pull rod of a tensile testing machine for mechanical testing, characterized by, The double-degree-of-freedom clamp connector comprises: a main body; a pair of top wings extending from a top edge of the main body in a direction away from the main body, each of the top wings being formed with a top through hole, the top through holes being aligned with each other and configured to allow a top pivot shaft to pass therethrough so as to rotatably connect the double-degree-of-freedom clamp connector to a pull rod of the tensile testing machine; a pair of bottom wings extending from a bottom edge of the main body in a direction away from the main body, each of the bottom wings being formed with a bottom through hole, the bottom through holes being aligned with each other and configured to allow a bottom pivot shaft to pass therethrough so as to rotatably connect the double-degree-of-freedom clamp connector to the test piece; wherein each of the top wings is arranged such that its extending direction is different from that of each of the bottom wings, so that the axis of the top through hole is perpendicular to that of the bottom through hole.

2. The dual degree-of-freedom clamp link of claim 1, wherein, Each of the top wings has an arc-shaped outer contour, and the top through hole is formed on a longitudinal center line of the top wing away from the main body.

3. The dual degree-of-freedom clamp link of claim 2, wherein, The arc-shaped outer contour is parabolic.

4. The dual degree-of-freedom clamp link of claim 1, wherein, Each of the bottom wings is rectangular, and the bottom through hole is formed in the center of the bottom wing away from the main body.

5. The dual degree-of-freedom clamp link of claim 1, wherein, The top pivot shaft or the bottom pivot shaft is a bolt.

6. The dual degree-of-freedom clamp link of claim 1, wherein, The double-degree-of-freedom clamp connector is made of CrWMn steel.

7. The dual degree-of-freedom clamp link of claim 1, wherein, The double-degree-of-freedom clamp connector is configured to be used for a shear test of a composite sandwich structure when the axes of the bottom through holes of two double-degree-of-freedom clamp connectors connected with the upper and lower pull rods of the tensile testing machine are parallel to each other.

8. The dual degree-of-freedom clamp link of claim 1, wherein, The double-degree-of-freedom clamp connector is configured to be used for a plane tensile test of a composite sandwich structure when the axes of the bottom through holes of two double-degree-of-freedom clamp connectors connected with the upper and lower pull rods of the tensile testing machine are perpendicular to each other.

9. The two-degree-of-freedom clamp link of any of claims 1-8, wherein, The main body is made into a cuboid, and the pair of top wings and the pair of bottom wings extend from the top edge and the bottom edge of the cuboid in a direction away from the cuboid, respectively, wherein the pair of top wings and the pair of bottom wings are on different sides of the cuboid, respectively.

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