Test fixture

Abstract

The utility model discloses a test fixture, include: first grating plate group and second grating plate group, first grating plate group includes two parallel fixed first grating plate, second grating plate group includes two parallel fixed second grating plate, between two first grating plate for placing first to be pricked fabric, between two second grating plate for placing second to be pricked fabric, two second grating plate clamps second to be pricked fabric, two first grating plate clamps first to be pricked fabric, and first grating plate group is located the top of second grating plate group, first grating plate group can be placed on second grating plate group or be hung vertically upwards. The utility model discloses a test fixture through adjusting the layer number or the proportion of laying of first to be pricked fabric and second to be pricked fabric respectively, can flexibly control the interlayer delamination position of three -dimensional needle -punched fabric, can obtain the interlayer connecting performance of three -dimensional needle -punched fabric.

Description

Technical Field

[0001] This utility model belongs to the field of needle penetration technology, specifically relating to a test fixture. Background Technology

[0002] Needle punching is an advanced and efficient fabric forming technology. Compared with traditional three-dimensional fabric forming technologies, needle punching offers advantages such as strong design flexibility, low cost, and short manufacturing cycle. Needle punching can be used to prepare large-size, complex-shaped fiber-reinforced materials, which have significant application potential in the field of composite materials. Three-dimensional needle-punched composites, with their excellent mechanical properties, have been widely used in aerospace, automotive engineering, and defense. The mechanical properties of three-dimensional needle-punched composites are highly dependent on the fiber structure of the preform, especially its interlaminar properties. Studies have shown that needle punching, by introducing Z-axis fiber bundles in the thickness direction, can significantly improve the interlaminar bond strength of the preform. However, insufficient interlaminar bonding can lead to delamination failure, which will seriously affect the load-bearing capacity of the composite material. Therefore, studying the interlaminar properties of three-dimensional needle-punched preforms (such as delamination behavior and bond strength) and establishing corresponding testing and characterization methods are crucial for optimizing the needle punching process and improving the mechanical properties of composite materials.

[0003] Current research primarily determines the interlayer mechanical properties of needle-punched fabrics by testing their interlayer peel force, as illustrated in invention patent "A Test Method and Application for Peel Strength of Needle-Punched Nonwoven Geotextile (CN104614312A)" and literature "Significantly Improve the Interlayer and In-Plane Properties of Needled Fabrics by Novel None-Felt Needling Technology." This test method involves applying peel force to the unbonded ends of the sample, causing interlayer peeling. During peeling, the untested portions of the fabric deform and wrinkle under the influence of the peel force, affecting the accuracy of subsequent test results. Furthermore, to ensure test effectiveness, this method has strict dimensional requirements, necessitating the preparation of fabric samples conforming to testing standards before each test, which incurs significant experimental costs. Therefore, optimizing the test method for the interlayer properties of three-dimensional needle-punched fabrics, saving experimental costs, and accurately obtaining the interlayer bonding force of three-dimensional needle-punched fabrics are problems that need to be addressed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a testing fixture. This fixture has a simple structure, facilitates the installation of fabric samples (hereinafter referred to as the first and second fabrics to be needled), offers flexible operation, and effectively saves experimental costs. This fixture can test the interlayer bonding force of three-dimensional needle-punched fabrics of different specifications and needle-punching parameters. By adjusting the number of layers or weight of the first and second fabrics to be needled, the interlayer delamination position of the three-dimensional needle-punched fabric can be flexibly controlled, thereby achieving the directional design of the prefabricated delamination behavior.

[0005] Another objective of this invention is to provide a method for testing the interlayer properties of three-dimensional needle-punched fabrics.

[0006] The objective of this utility model is achieved through the following technical solution.

[0007] A test fixture includes: a first grid plate group and a second grid plate group. The first grid plate group includes two parallel fixed first grid plates, and the second grid plate group includes two parallel fixed second grid plates. A first fabric to be punctured is placed between the two first grid plates, and a second fabric to be punctured is placed between the two second grid plates. The two second grid plates clamp the second fabric to be punctured, and the two first grid plates clamp the first fabric to be punctured. The first grid plate group is located above the second grid plate group.

[0008] The first grid panel assembly can be placed on the second grid panel assembly or lifted upwards in a vertical direction.

[0009] In the above technical solution, each first grid plate includes: a frame and a grid formed within the frame.

[0010] In the above technical solution, each second grid plate includes: a frame and a grid formed within the frame.

[0011] In the above technical solution, a lifting beam is fixedly installed on the upper first grid plate in the first grid plate group, and a lifting ring is fixedly installed in the middle of the lifting beam for lifting the first grid plate group.

[0012] A method for testing the interlayer properties of three-dimensional needle-punched fabrics includes the following steps:

[0013] Step 1: Place the first fabric to be punctured between the two first grid plates of the test fixture and clamp the first fabric to be punctured between the two first grid plates; place the second fabric to be punctured between the two second grid plates and clamp the second fabric to be punctured between the two second grid plates.

[0014] Step 2: Place the first grid plate group on the second grid plate group and perform needle punching on the first and second fabrics to be needled. The needles drive the Z-direction fiber bundles through the thickness direction of the first and second fabrics to be needled, forming interlayer fiber bridging.

[0015] Step 3: After the needle piercing is completed, keep the second grid plate group stationary and lift the first grid plate group so that the first grid plate group moves vertically upward at a speed V. Test the value of the force required to lift the first grid plate group.

[0016] In the above technical solution, the maximum value of Ft-m is the maximum load, and m is the value of Ft when the first puncture fabric and the second puncture fabric are no longer connected by any Z-direction fiber bundle after the first grid plate group is lifted.

[0017] In the above technical solution, the maximum load divided by the number of needle punches is the average connection force of a single Z-axis fiber bundle.

[0018] The above-mentioned test fixture is used to obtain the interlayer bonding properties of three-dimensional needle-punched fabrics.

[0019] The beneficial effects of this utility model are as follows:

[0020] 1. The present invention provides a method for testing the interlayer performance of three-dimensional needle-punched fabrics. It can freely test the interlayer bonding force of needle-punched fabrics per unit needle density or number of needles. There are no strict requirements on the size of the test fabric. It does not require the preparation of a needle-punched preform (three-dimensional needle-punched fabric) in advance. The test can be completed by manual needle punching. It effectively saves test costs and improves test efficiency. It is easy to operate and has good designability and accuracy.

[0021] 2. The test fixture of this utility model has a simple structure and is easy to install. By adjusting the number of layers or the layup ratio of the first and second fabrics to be needled, the interlayer separation position of the three-dimensional needle-punched fabric can be flexibly controlled, thereby realizing the directional design of the layering behavior of the needle-punched preform. The square holes of the grid holding the fabric facilitate the penetration of the needle into the fabric, forming a Z-direction fiber bundle (fiber bundle introduced in the thickness direction) connecting the fabric layers. The ribs of the grid help to hold the fabric around the Z-direction fiber bundle and pull it out vertically. The load and displacement measured by the universal testing machine are the pull-out force and displacement of the Z-direction fiber bundle of the sample (three-dimensional needle-punched fabric). The efficiency, designability, repeatability and accuracy of the entire experiment are greatly improved. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the test fixture.

[0023] Figure 2 A schematic diagram of the rotating hook of the test fixture (showing the connecting rod);

[0024] Figure 3 This is a schematic diagram of the structure of the first grid plate assembly;

[0025] Figure 4 This is a schematic diagram of the structure of the second grid plate assembly;

[0026] Figure 5 A schematic diagram of the process for testing the interlayer properties of three-dimensional needle-punched fabrics;

[0027] Figure 6 This is a schematic diagram of the load-displacement curve obtained by the three-dimensional needle-punched fabric interlayer performance testing method.

[0028] Among them, 1: connecting rod, 2: rotating hook, 3: lifting beam, 4: first grid plate, 5: second grid plate, 6: double-ended stud, 7: base, 8: cross countersunk screw, 9: nut, 10: lifting ring, 11: first through hole, 12: bolt, 13: second through hole, 14: third through hole, 15: external thread, 16: fastening nut, 17-1: first fabric to be punctured, 17-2: second fabric to be punctured, 18: puncture needle, 19: needle hole. Detailed Implementation

[0029] The following is a detailed description of the three-dimensional needle-punched fabric interlayer performance testing method of this utility model with reference to the accompanying drawings.

[0030] Example 1

[0031] like Figures 1-4 As shown, a test fixture includes: a first grid plate group and a second grid plate group. The first grid plate group includes two parallel fixed first grid plates 4. Each first grid plate 4 includes: a square frame and a grid formed within the frame (the grid has square grids, 4×4 grids).

[0032] The second grid plate assembly includes two parallel fixed second grid plates 5. Each second grid plate 5 includes a square frame and a grid formed within the frame (the grid has square cells, a 4×4 grid). The grid structure of the second grid plate 5 is the same as that of the first grid plate 4 and is symmetrically arranged along the horizontal plane (i.e., the grids of the second grid plate 5 and the grids of the first grid plate 4 are symmetrically arranged along the horizontal plane).

[0033] The two first grid plates 4 are fixed together by a cross countersunk screw 8 and a nut 9 that mates with the cross countersunk screw 8. The space between the two first grid plates 4 is used to place the first fabric to be punctured 17-1 (the first fabric to be punctured 17-1 has a larger area than the first grid plate 4). After the two first grid plates 4 are fixed, the first fabric to be punctured 17-1 is clamped in place.

[0034] The space between the two second grid plates 5 is used to place the second fabric to be punctured 17-2 (the second fabric to be punctured 17-2 has a larger area than the second grid plate 5), and the two second grid plates 5 are fixed to clamp the second fabric to be punctured 17-2. Figure 4As shown, the second grating plate assembly is fixedly mounted on a base 7. The two second grating plates 5 are secured to the base 7 by four double-ended studs 6, clamping the second fabric to be pierced 17-2. The first grating plate assembly is located above the second grating plate assembly.

[0035] like Figure 3 As shown, a lifting beam 3 is fixedly installed on the first grid plate 4 at the top of the first grid plate group, and a lifting ring 10 is fixedly installed in the middle of the lifting beam 3 for lifting the first grid plate group.

[0036] The first grid plate assembly can be placed on the second grid plate assembly or suspended vertically upwards. After the test fixture is assembled, ensure that the first fabric to be pierced 17-1 and the second fabric to be pierced 17-2 inside the grid are in close contact, so that the needle can penetrate the first fabric to be pierced 17-1 and the second fabric to be pierced 17-2 through the mesh of the grid.

[0037] Example 2

[0038] like Figure 2 As shown, in Embodiment 1, the test fixture is lifted by rotating the hook 2. The bottom of the rotating hook 2 is the hook body, and the top of the rotating hook 2 is fixed to the bottom of the connecting rod 1. The top of the connecting rod 1 has a first through hole 11, and the top of the connecting rod 1 is connected to the universal testing machine through the first through hole 11.

[0039] like Figure 2 As shown, a third through hole 14 is formed on the top of the rotating hook 2, and a groove is formed on the bottom of the connecting rod 1. A second through hole 13 is formed on the side wall of the groove. The top of the rotating hook 2 extends into the groove, and the third through hole 14 and the second through hole 13 are opposite each other. A bolt 12 is inserted into the third through hole 14 and the second through hole 13. An external thread 15 is formed on the bolt 12, and the bolt 12 is fastened by engaging with a fastening nut 16 through its external thread 15, thereby fixing the top of the rotating hook 2 to the bottom of the connecting rod 1. The rotating hook 2 can rotate around the bolt 12 through the third through hole 14, which facilitates connection with the lifting ring 10 on the lifting beam 3.

[0040] Example 3

[0041] The method for testing the interlayer properties of three-dimensional needle-punched fabrics using the test fixture in Example 2 includes the following steps:

[0042] Step 1: Place the first fabric to be pierced 17-1 between the two first grating plates 4, clamping the first fabric to be pierced 17-1 between the two first grating plates 4. Place the second fabric to be pierced 17-2 between the two second grating plates 5, clamping the second fabric to be pierced 17-2 between the two second grating plates 5. In this embodiment, both the first fabric to be pierced 17-1 and the second fabric to be pierced 17-2 are six layers of T-700 carbon fiber mesh with uniform thickness arranged in parallel. The areal density of a single layer of T-700 carbon fiber mesh is 30 g / m². 2 .

[0043] Step 2: Holding the needle 18, perform vertical needling from top to bottom on the first fabric to be needled 17-1 and the second fabric to be needled 17-2. This causes the barbs on the needle 18 to grasp and transfer fibers within the fabric along the thickness direction, forming a Z-direction fiber bundle that provides interlayer bonding. In this embodiment, the bundle is 2cm long. 2 Twenty needles were inserted into the fabric, with a needle depth of 12 mm.

[0044] Step 3: After needle punching, the needle holes 19 are left on the surface of the second fabric to be punched 17-2. Keeping the second grid plate group stationary, the universal testing machine lifts the first grid plate group, causing it to move vertically upwards at a rate of 100±10 mm / min until the first fabric to be punched 17-1 and the second fabric to be punched 17-2 separate, and the Z-direction fiber bundle is pulled out. Since the universal testing machine is equipped with sensors, the force required to lift the first grid plate group during its vertical upward movement at a speed of 100±10 mm / min can be obtained as Ft. In this embodiment, the experiment ends after the Z-direction fiber bundle is pulled out of the second fabric to be punched 17-2 (i.e., when the first and second fabrics are no longer connected by any Z-direction fiber bundle after lifting the first grid plate group). The load (Ft-m)-displacement curve is recorded, where m is the value of Ft when the first and second fabrics are no longer connected by any Z-direction fiber bundle after lifting the first grid plate group. Figure 6 As shown.

[0045] The above-described three-dimensional needle-punched fabric interlayer performance test method was repeated 5 times, and the maximum load F (unit: N, i.e. F is the maximum value of Ft-m) of the three-dimensional needle-punched fabric interlayer performance test method was recorded each time, as shown in Table 1. Since the number of needles n in this embodiment is 20, the average connection force of a single Z-direction fiber bundle in the sample (F / n, unit: N) can be calculated, and the test results are shown in Table 1.

[0046] Table 1

[0047]

[0048] The average connection force of a single Z-axis fiber bundle was calculated to be 0.01062 N and the standard deviation was 0.001191 for five tests of the interlayer performance of three-dimensional needle-punched fabrics. This shows that the interlayer performance testing method of three-dimensional needle-punched fabrics of this invention has good accuracy and stability.

[0049] The present invention has been described above by way of example. It should be noted that, without departing from the core of the present invention, any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort fall within the protection scope of the present invention.

Claims

1. A test fixture, comprising: include: A first grid plate group and a second grid plate group, wherein the first grid plate group includes two parallel fixed first grid plates and the second grid plate group includes two parallel fixed second grid plates. A first fabric to be punctured is placed between the two first grid plates and a second fabric to be punctured is placed between the two second grid plates. The two second grid plates clamp the second fabric to be punctured and the two first grid plates clamp the first fabric to be punctured. The first grid plate group is located above the second grid plate group. The first grid panel assembly can be placed on the second grid panel assembly or lifted upwards.

2. The test fixture of claim 1, wherein, Each first grid panel includes: a frame and a grid formed within the frame.

3. The test fixture of claim 1, wherein, Each second grid panel includes: a frame and a grid formed within the frame.

4. The test fixture of claim 1, wherein, A lifting beam is fixedly installed on the upper first grating plate in the first grating plate assembly, and a lifting ring is fixedly installed in the middle of the lifting beam for lifting the first grating plate assembly.

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