A hydraulic shearing fixture and testing machine for composite material testing

Abstract

This invention discloses a hydraulic shearing fixture and testing machine for composite material testing, comprising at least an upper fixture and a lower fixture, both connected to the testing machine at their joints. The upper and lower fixtures clamp a composite material sample. Both the upper and lower fixtures are equipped with clamping parts for holding the composite material sample to complete the shear test. This design provides clamping power through a hydraulic cylinder and amplifies the clamping force through a two-stage lever structure, ensuring sufficient clamping force for shear force testing of thicker samples, effectively completing the shear force test. The two-stage lever structure ensures synchronous movement of the clamping jaws while maintaining uniform force distribution, better achieving consistency in clamping during sample testing and ensuring test accuracy. A positioning block ensures the testing accuracy of the positioned composite material sample. This design can meet the testing requirements of samples of different thicknesses, and is simple and fast.

Description

Technical Field

[0001] This invention relates to a testing device, and more particularly to a hydraulic shearing fixture and testing machine for testing the shear properties of composite materials. Background Technology

[0002] With the continuous advancement of science and technology, composite materials (carbon fiber, glass fiber, aramid fiber, etc.) are being used more and more widely (for example, in fields such as aviation, aerospace, energy, transportation, construction, machinery, information, biology, medicine, and sports). Composite materials have fundamental mechanical properties that differ from those of metallic materials. For example, the shear properties of composite laminates are one of the most important material characteristics of composite materials. Although the testing methods for the fundamental mechanical properties of metallic materials are relatively mature, the testing methods for the fundamental mechanical properties of composite materials are not yet perfect.

[0003] The primary equipment for determining the basic mechanical properties of materials is the universal testing machine. For compression specimens of metallic materials, the universal testing machine has corresponding standard fixtures; however, for V-groove composite shear specimens, traditional testing fixtures cannot meet the testing requirements. Fixtures designed using the ASTM D7078 (Standard Method for Testing V-groove Shear Properties of Composite Materials) standard method suffer from drawbacks such as complex operation, high spare parts consumption, and large dispersion of test results, which are pain points in the composite materials industry. Furthermore, for test samples with a thickness greater than 2.5 mm, current testing fixtures are inadequate in terms of clamping force and cannot meet the testing requirements.

[0004] Therefore, to address the aforementioned shortcomings, improvements to the existing technology are necessary. Summary of the Invention

[0005] To address the above problems, this invention proposes a hydraulic shearing fixture and testing machine for composite material testing. This fixture is characterized by convenient operation and good clamping consistency, and can meet the testing requirements of test samples of different thicknesses, thereby solving the defects in the aforementioned background technology.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A hydraulic shearing fixture for testing composite materials includes at least an upper fixture and a lower fixture. The upper fixture and the lower fixture have the same structure, and their joints are connected to a testing machine. The upper fixture and the lower fixture clamp a composite material sample. Both the upper fixture and the lower fixture are provided with clamping parts for clamping the composite material sample to complete the shearing test of the composite material sample.

[0007] Furthermore, the two clamping portions of the upper clamp and the lower clamp are arranged horizontally, and the composite material sample is clamped between the two clamping portions.

[0008] Furthermore, the upper clamp and the lower clamp are also provided with support parts connected to the clamping parts. The two support parts are arranged vertically and on the same vertical line. The two vertically arranged support parts and the two horizontally arranged clamping parts form a rectangular space between them. The composite material sample is clamped in the rectangular space and subjected to shear test.

[0009] Furthermore, a positioning block is installed on the rectangular space formed on the support portion of the lower clamp. The positioning block is provided with a V-shaped protrusion, which matches the V-shaped groove in the composite material sample. When the composite material sample is placed on the lower clamp, it is positioned with the positioning block as the reference.

[0010] Furthermore, the clamping part includes at least a hydraulic cylinder, a lever, and jaws. The hydraulic cylinder is located outside the clamping part and is connected to an external pressure control device to supply pressure for the clamping part to clamp the composite material sample. One end of the lever is connected to the hydraulic cylinder, and the other end is connected to the jaws, serving as a pressure transmission structure for the hydraulic cylinder to transmit pressure to the jaws. The jaws are located within the rectangular space formed by the upper clamp and the lower clamp and are used to clamp the composite material sample.

[0011] Furthermore, the lever includes at least a primary lever and a secondary lever, each of which has two lever plate structures. The two lever plate structures of the primary lever are movably connected to the two lever plate structures of the secondary lever. The other ends of the two lever plate structures of the primary lever are fixedly connected to the same position of the hydraulic cylinder via a connector, and the two lever plate structures can rotate around the connector. The other ends of the two lever plate structures of the secondary lever are respectively connected to the jaws.

[0012] Furthermore, the lever plate structure of the secondary lever is provided with a fulcrum, which is located between the connection point of the secondary lever and the primary lever and the jaws, serving as a support structure for the lever movement.

[0013] Furthermore, the two levers of the upper clamp and the lower clamp are symmetrically distributed to ensure that the jaws on both sides of the composite material sample are pressed synchronously.

[0014] Furthermore, the two rod plate structures of the secondary lever are connected to the jaws via push rods, and each rod plate structure is provided with at least two push rods arranged vertically to ensure that the jaws are subjected to uniform force.

[0015] Based on the two-stage structure of the lever, when the hydraulic cylinder applies pressure, the force is transmitted to the first-stage lever. The first-stage lever uses the connector at one end as a fulcrum, and the other end pulls one end of the second-stage lever to move. The second-stage lever uses the fulcrum as support, and drives the end of the second-stage lever connected to the jaws to generate pressure in the direction of the composite material sample, thereby causing the jaws on both sides of the composite material sample to clamp the composite material sample.

[0016] Based on the aforementioned shearing clamp, this invention also claims a testing machine equipped with the aforementioned shearing clamp. Specifically, the joints of the upper clamp and the lower clamp are both connected to the testing machine, and the external of the hydraulic cylinder is connected to the pressure control device of the testing machine. Based on this structure, when the composite material sample is tested, the testing machine applies a pressure load to the hydraulic cylinder to clamp the composite material sample. The testing machine drives the upper clamp to move downward, so that the jaws apply a vertical shear force to the sample, thereby collecting the shear data of the composite material sample and calculating the characteristic values ​​of the composite material sample.

[0017] By implementing the above-mentioned hydraulic shearing fixture for composite material testing, the following beneficial effects are achieved: (1) The technical solution of this application provides clamping power through a hydraulic cylinder and amplifies the clamping force through a two-stage lever structure, which fully guarantees the clamping force required when performing shear force testing on thick sample products and effectively completes the shear force testing operation. (2) The technical solution of this application adopts a symmetrical two-stage lever layout and is equipped with a top rod. While ensuring that the clamping jaws can move synchronously, it also ensures that the clamping jaws are subjected to uniform force, thereby better achieving the coordination and consistency of clamping during the test of the sample product and ensuring the accuracy of the test. (3) The technical solution of this application is equipped with a positioning structure, and the positioning block is set according to the shape of the test product, which effectively ensures the test accuracy of the composite material sample after positioning; (4) The technical solution of this application uses an upper clamp and a lower clamp with the same structure, forming a clamping space between the upper clamp and the lower clamp, which can accommodate samples of different thicknesses for testing, and has a wide range of applications; (5) The clamping structure of the technical solution of this application is convenient to operate and has good clamping consistency. Furthermore, a set of compression clamps can meet the test requirements of samples of different thicknesses, which is simple and quick. Attached Figure Description

[0018] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein: Figure 1 This is a schematic diagram of the main structure of the compression clamp in a specific embodiment of the present invention; Figure 2This is a side view of the compression clamp structure in a specific embodiment of the present invention; Figure 3 This is a top view of the compression clamp structure in a specific embodiment of the present invention.

[0019] Figure label: 1. Upper clamp; 10. Connector I; 11. Locking nut; 12. Clamping part I; 120. Hydraulic cylinder; 121. First-stage lever; 122. Second-stage lever; 123. Jaws; 124. Pipe connector; 125. Connecting piece; 126. Push rod; 127. Fulcrum; 13. Support part I; 2. Lower clamp; 20. Connector II; 21. Clamping part II; 22. Supporting part II; 3. Composite material sample; 30. V-groove; 4. Positioning block; 40. V-shaped protrusion. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] The following is combined Figure 1-3 An example is given to illustrate the structure of a hydraulic shearing fixture for composite material testing.

[0022] like Figure 1-3 The diagram shows a hydraulic shearing fixture for testing composite materials, comprising at least an upper fixture 1 and a lower fixture 2. The upper fixture 1 and the lower fixture 2 have identical structures, and their joints I10 and I20 are connected to the testing machine and locked by a locking nut 11. The upper fixture 1 and the lower fixture 2 clamp a composite material sample 3. The upper fixture 1 and the lower fixture 2 are provided with clamping parts I12 and II21, which are used to clamp the composite material sample 3 to complete the shearing test of the composite material sample 3.

[0023] It should be noted that the composite material sample in this embodiment is a composite material sample with a V-groove.

[0024] In addition to clamping parts I12 and II21, the upper clamp 1 and the lower clamp 2 are also provided with supporting parts I13 and II22 connected to the clamping parts I12 and II21. The clamping parts I12 and II21 are horizontally arranged and located on the same horizontal line, while the supporting parts I13 and II22 are vertically arranged and located on the same vertical line. A rectangular space is formed between the vertically arranged clamping parts I12 and II21 and the horizontally arranged supporting parts I13 and II22. The composite material sample 3 is clamped in the rectangular space for shear testing.

[0025] A positioning block 4 is installed on the rectangular space formed on the support part II22 of the lower clamp 2. A V-shaped protrusion 40 is provided on the positioning block 4. The V-shaped protrusion 40 matches the V-shaped groove 30 in the composite material sample 3. When the composite material sample 3 is placed on the lower clamp 2, it is positioned with the positioning block 4 as the reference.

[0026] In the aforementioned structure, since the upper clamp 1 and the lower clamp 2 have the same structure, the structure of the upper clamp 1 will be specifically described here. The clamping part I12 of the upper clamp 1 includes at least a hydraulic cylinder 120, a lever, and jaws 123. The hydraulic cylinder 120 is a hydraulic cylinder located inside the housing of the upper clamp 1 and outside the clamping part I12. It has a hydraulic pipe connector 124 that protrudes from the housing of the upper clamp 1 and is connected to the pressure control device of the external testing machine to supply pressure for the clamping part I12 to clamp the composite material sample 3. The lever includes at least a primary lever 121 and a secondary lever 122, as shown in the figure. Both the primary lever 121 and the secondary lever 122 have two rod plate structures, and the two rod plate structures of each stage are positioned relative to the composite material sample 3. The levers 121 and 122 are symmetrically distributed in a plane and are movably connected at one end. The other ends of the two levers 121 are fixedly connected to the middle position of the cylinder 120 via a connector 125. The two levers can rotate around the connector 125. The other ends of the two levers 122 are respectively connected to a push rod 126. The push rod 126 is connected to the jaws 123. As shown in the figure, the push rods 126 on each side are arranged vertically, and there are two push rods 126 arranged vertically to ensure that the jaws 123 are subjected to uniform force. The jaws 123 are located in a rectangular space and are symmetrically arranged on both sides with the composite material sample 3 as the center. They are used to clamp the composite material sample 3.

[0027] The lever plate structure of the secondary lever 122 is provided with a fulcrum 127, which is located between the connection point of the secondary lever 122 and the primary lever 121 and the top rod 126, and serves as a support structure for the lever movement.

[0028] The two lever structures of the upper clamp 1 and the lower clamp 2 are symmetrically distributed to ensure that the jaws 123 on both sides of the composite material sample 3 apply pressure synchronously.

[0029] Based on the two-stage lever structure, when the hydraulic cylinder 120 applies pressure, the force is transmitted to the first-stage lever 121. The first-stage lever 121 uses the connector 125 at one end as a fulcrum, and the other end pulls one end of the second-stage lever 122 to move. The second-stage lever 122 uses the fulcrum 127 as a support, and drives the end of the second-stage lever 122 connected to the jaws 123 to generate pressure in the direction of the composite material sample 3, thereby causing the jaws 123 on both sides of the composite material sample 3 to clamp the composite material sample.

[0030] In the actual testing process, the aforementioned shearing fixtures are installed on the testing machine. Specifically, the joints I10 and I20 of the upper fixture 1 and the lower fixture 2 are connected to the testing machine and locked by the locking nut 11; and the external hydraulic cylinder 120 is connected to the pressure control device of the testing machine. Based on this structure, the operating steps for testing composite material samples are as follows: (1) Install the positioning block 4 onto the lower clamp 2, making it fit tightly against the lower clamp 2, with one side of the V-shaped protrusion 40 facing the side of the composite material sample 3; (2) Insert the composite material sample 3 into the jaws 123 within the rectangular space formed by the upper clamp 1 and the lower clamp 2, and fit the V-groove 30 of the composite material sample 3 tightly with the V-protrusion 40 of the positioning block 4. (3) Pressure is supplied to the cylinder 120 of the lower clamp 2 by the testing machine to drive the first-stage lever 121, the second-stage lever 122 and the jaws 123 to clamp the composite material sample 3; (4) The upper clamp 1 is driven down by the testing machine and stops when the composite material sample 3 is located in the middle of the jaws 123; (5) Pressure is supplied to the cylinder 120 of the upper clamp 1 by the testing machine to drive the first-stage lever 121, the second-stage lever 122 and the jaws 123 to clamp the composite material sample 3. (6) Loosen and remove the positioning block 4. At this point, the composite material sample 3 is installed and the upper clamp 1, lower clamp 2 and composite material sample 3 are clamped together as a whole. (7) Connect the deformation measurement accessories, adjust the test software, and start the test; during the test, the test machine drives the upper clamp 1 to move down, and applies a vertical shear force to the composite material sample 3 through the jaws 123; by collecting the test force value and sample deformation data, calculate the sample's strength, elastic modulus and other characteristic values; (8) After the test is completed, the cylinders 120 of the upper clamp 1 and the lower clamp 2 are depressurized, the jaws 123 loosen the composite material sample 3, the upper clamp 1 moves up and the sample is taken out.

[0031] It should be further noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "connected" or "linked" and similar terms used in this patent application specification and claims are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "end," and "side" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0032] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This application is intended to cover any uses or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0033] It should be understood that the present invention is not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A hydraulic shearing fixture for testing composite materials, comprising at least an upper fixture and a lower fixture, wherein the upper fixture and the lower fixture have identical structures, and their joints are both connected to a testing machine, wherein a composite material sample is clamped between the upper fixture and the lower fixture; characterized in that, Both the upper clamp and the lower clamp are provided with clamping parts, which are used to clamp the composite material sample to complete the shear test of the composite material sample; The clamping part includes at least a lever and jaws. The lever includes at least a primary lever and a secondary lever. Each primary lever has two rod plate structures. The two rod plate structures of the primary lever are movably connected to the two rod plate structures of the secondary lever. The other ends of the two rod plate structures of the secondary lever are respectively connected to the jaws. A fulcrum is provided on the rod plate structure of the secondary lever. The fulcrum is located between the connection point of the secondary lever, the primary lever, and the jaws, serving as a support structure for the lever movement. The two rod plate structures of the secondary lever are connected to the jaws via push rods. At least two push rods are provided between each rod plate structure and the jaws, arranged vertically, to ensure uniform force distribution on the jaws. The jaws are located between the upper clamp and the lower clamp and are used to clamp the composite material sample.

2. The hydraulic shearing fixture for composite material testing as described in claim 1, characterized in that, The two clamping parts of the upper clamp and the lower clamp are arranged horizontally, and the composite material sample is clamped between the two clamping parts.

3. The hydraulic shearing fixture for composite material testing as described in claim 2, characterized in that, The upper clamp and the lower clamp are also provided with support parts connected to the clamping parts. The two support parts are arranged vertically and on the same vertical line. The two vertically arranged support parts and the two horizontally arranged clamping parts form a rectangular space. The composite material sample is clamped in the rectangular space and subjected to shear test.

4. The hydraulic shearing fixture for composite material testing as described in claim 3, characterized in that, A positioning block is installed on the rectangular space formed on the support portion of the lower clamp. The positioning block is provided with a V-shaped protrusion, which matches the V-shaped groove in the composite material sample. When the composite material sample is placed on the lower clamp, it is positioned with the positioning block as the reference.

5. The hydraulic shearing fixture for composite material testing as described in claim 3, characterized in that, The clamping part includes at least a hydraulic cylinder; wherein the hydraulic cylinder is located outside the clamping part and is connected to an external pressure control device to supply pressure for the clamping part to clamp the composite material sample; one end of the lever is connected to the hydraulic cylinder and the other end is connected to the jaws, serving as a pressure transmission structure for the hydraulic cylinder to transmit pressure to the jaws; the jaws are located within the rectangular space formed by the upper clamp and the lower clamp and are used to clamp the composite material sample.

6. The hydraulic shearing fixture for composite material testing as described in claim 5, characterized in that, The other ends of the two rod plate structures of the primary lever are fixedly connected to the same position of the oil cylinder by a connector, and the two rod plate structures can rotate around the connector.

7. The hydraulic shearing fixture for composite material testing as described in claim 6, characterized in that, The two levers of the upper clamp and the lower clamp are symmetrically distributed to ensure that the jaws on both sides of the composite material sample are pressed synchronously.

8. A testing machine, characterized in that, The testing machine is equipped with a hydraulic shearing fixture for testing composite materials as described in any one of claims 5-7. The joints of the upper and lower fixtures are connected to the testing machine, and the external of the hydraulic cylinder is connected to the pressure control device of the testing machine. Based on this structure, when the composite material sample is tested, the testing machine applies a pressure load to the hydraulic cylinder to clamp the composite material sample. The testing machine drives the upper fixture to move downward, so that the jaws apply a vertical shear force to the sample, thereby collecting the shear data of the composite material sample and calculating the characteristic value of the composite material sample.

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