Clamping device for out-of-plane uniaxial tension and fatigue test of fiber reinforced composite material

Abstract

The invention discloses a fiber reinforced composite material out-of-plane uniaxial tension and fatigue test clamping device, and belongs to the technical field of material mechanical property testing equipment.The device comprises a fixing assembly connected with a testing machine and a self-centering assembly connected with a test piece, and the fixing assembly is movably connected with the self-centering assembly; the self-centering device is used for self-centering of direct loading of the test piece. By adopting the clamping device for the out-of-plane uniaxial tension and fatigue test of the fiber reinforced composite material, self-centering of direct loading of a test piece is realized, the accuracy and reliability of a test result are improved, and the test cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material mechanical property testing equipment, in particular to a fiber-reinforced composite material out-of-plane uniaxial tensile and fatigue test clamping device. BACKGROUND

[0002] Fiber-reinforced composite materials have been widely used in aerospace, high-end manufacturing and other high-tech fields due to their excellent properties such as high strength, high modulus and low density. The structural design and safe application of the material depend on the accurate testing of its mechanical properties in all directions, such as strength and fatigue.

[0003] Current research on the in-plane mechanical properties of fiber-reinforced composite materials is relatively complete, but there is a lack of research on the out-of-plane mechanical properties of the material. Due to the anisotropic structure of fiber-reinforced composite materials, the size in the out-of-plane direction is much smaller than the cross-sectional size perpendicular to the out-of-plane direction, and it is usually difficult to meet the requirement of sufficient length for out-of-plane loading, which puts higher requirements on the clamping method for out-of-plane loading of fiber-reinforced composite materials, making it difficult for conventional tensile-fatigue testing machines to meet the out-of-plane loading requirements of fiber-reinforced composite materials.

[0004] In the prior art, a completely fixed clamping and loading scheme and a non-completely fixed clamping and loading scheme have been given in a NASA report. Both clamping schemes have defects: the completely fixed scheme not only requires high accuracy of the testing machine, but also easily introduces multi-axial effects and causes initial damage during the pre-tightening process, and it is difficult to adapt to different sizes of test pieces, resulting in waste; the non-completely fixed scheme has some improvements, but it still easily introduces initial bending moments in some degrees of freedom, affecting the experimental results, and it is still difficult to adapt to different sizes of test pieces, and the complexity of the mechanism compared to the completely fixed scheme increases the cost. Therefore, a special clamping device is needed to solve the above technical problems. SUMMARY

[0005] The purpose of the present application is to provide a fiber-reinforced composite material out-of-plane uniaxial tensile and fatigue test clamping device, which realizes self-centering of the test piece direct loading system, improves the accuracy and reliability of the test results, and reduces the test cost.

[0006] To achieve the above purpose, the present application provides a fiber-reinforced composite material out-of-plane uniaxial tensile and fatigue test clamping device, which comprises a fixed component connected with a testing machine, and a self-centering component connected with a test piece, the fixed component and the self-centering component are movably connected, realizing self-centering of the test piece direct loading.

[0007] Preferably, the fixing assembly comprises a clamping rod and a hinged unit, the self-centering assembly comprises a universal joint and a bonding unit, the clamping rod is rigidly connected with the hinged unit, the universal joint is movably connected with the hinged unit and rigidly connected with the bonding unit.

[0008] Preferably, the clamping rod is a straight rod with equal cross sections, one end of which is provided with a short threaded segment for fixing with the hinged unit, and the other end of which is matched with the clamping head of the testing machine.

[0009] Preferably, the hinged unit comprises a connecting head, a short rod, a nut and a washer; the connecting head is in U-shaped structure, and a pair of through holes coaxial with and perpendicular to the central axis of the connecting head are arranged on the side wall of the open end of the connecting head, which are respectively a left through hole of the connecting head and a right through hole of the connecting head.

[0010] Preferably, the non-open end of the connecting head is provided with a connecting head threaded hole coaxial with the central axis of the connecting head; the short rod is a straight rod with equal cross sections, both ends of which are provided with short threaded segments.

[0011] Preferably, one end of the universal joint is provided with a variable cross-section through hole perpendicular to the central axis of the component, and the other end is provided with a universal joint threaded hole coaxial with the central axis of the component; the variable cross-section through hole is a smooth double-horn type through hole formed by concave circular arc rotation, the hole diameter first decreases and then increases, and the minimum hole diameter is greater than the diameter of the short rod.

[0012] Further, the double-horn type through hole can release the degrees of freedom in XZ direction, XY direction, YZ direction and Y direction, allowing the test piece to produce displacement in the corresponding direction when directly loaded, while ensuring that the tangent point of the universal joint and the short rod is in contact.

[0013] Preferably, the short rod passes through the left through hole of the connecting head, the variable cross-section through hole and the right through hole of the connecting head in sequence, and both ends of the short rod are fixedly connected with the washer and the nut for movably connecting the hinged unit with the universal joint.

[0014] Preferably, the threaded end of the clamping rod is rigidly connected with the threaded hole of the connecting head, and the two cannot move relative to each other.

[0015] Preferably, the bonding unit comprises end pieces on both sides of the test piece; one end of the end piece is a bonding surface, and the other end is provided with a threaded head.

[0016] Further, by replacing end pieces of different sizes, test pieces of different specifications can be adapted, and the device can be reused.

[0017] Preferably, the bonding surface of the end piece is bonded with the test piece by an adhesive, and the threaded head of the end piece is rigidly connected with the threaded hole of the universal joint.

[0018] Therefore, the application adopts the above-mentioned fiber reinforced composite out-of-plane uniaxial tension and fatigue test clamping device, and has the following technical effects: High test accuracy: the initial load in XZ, XY, YZ and Y directions can be released at the same time, mechanical errors and random errors are offset, self-centering during direct loading of the test piece is realized, multi-axial effect and initial damage are avoided, and the accuracy and reliability of the test results are greatly improved.

[0019] Strong adaptability: only different sizes of end pieces need to be replaced to match various specifications of test pieces, the device body can be reused, and the test cost is significantly reduced.

[0020] Simple structure: only one pair of rotating pairs is introduced to release multiple direction degrees of freedom, complex mechanism design is not needed, cost stacking and operation complication are avoided, and the practicability is strong.

[0021] The technical solutions of the application will be further described in detail below through the drawings and examples. DETAILED DESCRIPTION

[0022] Figure 1 is a device structure schematic diagram of an embodiment of the fiber reinforced composite out-of-plane uniaxial tension and fatigue test clamping device of the application; Figure 2 is a device structure partial exploded view and a cross-sectional view of the gimbal perpendicular to the X axis and passing through the center axis of the through hole of the device of the fiber reinforced composite out-of-plane uniaxial tension and fatigue test clamping device of the application.

[0023] Reference signs 1, clamping rod; 2, connecting head; 3, gasket; 4, nut; 5, short rod; 6, gimbal; 7, end piece; 8, test piece; 9, variable cross-section through hole; 10, left through hole of connecting head; 11, right through hole of connecting head. DETAILED DESCRIPTION

[0024] The technical solutions of the application will be further described in detail below through the drawings and examples.

[0025] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0026] Example 1 like Figure 1 , Figure 2 As shown, the present invention provides a clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials. The device includes a fixing component and a self-centering component. The two parts of the device located above and below the test piece 8 are symmetrically arranged about the test piece 8.

[0027] The fixing assembly includes a clamping rod 1 and a hinge unit, and the self-centering assembly includes a universal head 6 and an adhesive unit. The clamping rod 1 is rigidly connected to the hinge unit, the universal head 6 is movably connected to the hinge unit, and rigidly connected to the adhesive unit.

[0028] The clamping rod 1 is a straight rod with a short threaded section at one end, which is used to fix it to the hinge unit. The non-threaded end of the clamping rod 1 is matched and connected to the chuck of the testing machine.

[0029] The hinge unit includes a connector 2, a short rod 5, a nut 4, and a washer 3. The connector 2 has a U-shaped structure. The side wall of the open end of the connector 2 is provided with a pair of coaxial through holes that are perpendicular to the central axis of the connector, namely the left through hole 10 and the right through hole 11.

[0030] The non-open end of connector 2 is provided with a threaded hole coaxial with the central axis of connector 2, and the threaded hole of connector 2 is rigidly connected to the threaded end of clamping rod 1. Short rod 5 is a straight rod with a uniform cross-section and short threaded sections at both ends.

[0031] One end of the universal head 6 is provided with a variable cross-section through hole 9 perpendicular to the central axis of the component, and the other end is provided with a universal head threaded hole coaxial with the central axis of the component. The variable cross-section through hole 9 is a smooth double-flare-shaped through hole formed by rotating an inward concave arc. The hole diameter first decreases and then increases, and the minimum hole diameter is greater than the diameter of the short rod 5.

[0032] The double-horn type through hole can release the freedom degrees of XZ direction, XY direction, YZ direction and Y direction, allows the test piece 8 to produce displacement in the corresponding direction when directly loaded, and ensures the point contact of the universal joint 6 and the short rod 5.

[0033] During connection, the short rod 5 is sequentially threaded through the left through hole 10 of the connecting head, the variable cross-section through hole 9 and the right through hole 11 of the connecting head, and the two ends of the short rod 5 are fixedly connected with the gaskets 3 and the nuts 4, for the movable connection of the hinged unit and the universal joint 6.

[0034] The bonding unit comprises the end pieces 7 on both sides of the test piece 8, one end of the end piece 7 is a bonding surface, and the other end is provided with a threaded head, the bonding surface of the end piece 7 is bonded with the test piece 8 through an adhesive, and the threaded head of the end piece 7 is rigidly connected with the universal joint threaded hole, different sizes of the end piece 7 can be replaced to adapt to different specifications of the test piece 8, and the device can be reused.

[0035] The fixed assembly is installed: the non-threaded end of the clamping rod 1 is matched and connected with a testing machine clamp (not shown in the figure), the threaded end of the clamping rod 1 is screwed into the non-opening end connecting head threaded hole of the connecting head 2 to form a rigid connection; the short rod 5 is sequentially threaded through the left through hole 10 of the connecting head 2, the variable cross-section through hole 9 and the right through hole 11 of the connecting head, and the gaskets 3 are respectively sleeved on both sides of the connecting head 2, and then the nuts 4 are tightened to complete the movable connection of the fixed assembly and the universal joint 6.

[0036] The self-centering assembly is installed: the end pieces 7 of different sizes are selected according to the size of the test piece 8, the bonding surfaces of the two end pieces 7 are bonded with the two end surfaces of the test piece 8 through an adhesive to form an end piece-test piece-end piece rigid system; the threaded head of the end piece 7 is screwed into the universal joint threaded hole of the universal joint 6 to realize the complete connection of the self-centering assembly and the fixed assembly.

[0037] During the test, the testing machine transmits the load through the fixed assembly, the variable cross-section through hole 9 of the universal joint 6 allows the test piece direct loading system to produce a small displacement in the XZ, XY, YZ and Y directions, automatically offsets the initial load caused by various errors, and ensures the accurate loading of the out-of-plane single-axis tension and fatigue test.

[0038] Therefore, the above-mentioned fiber-reinforced composite out-of-plane single-axis tension and fatigue test clamping device is adopted, the self-centering of the test piece direct loading is realized, the accuracy and reliability of the test results are improved, and the test cost is reduced.

[0039] It should be noted that the drawings in the present application are only examples, not drawn according to the condition of the same proportion, and should not be taken as a limitation on the protection scope actually required by the present application. In addition, the transformation modes in different embodiments can be properly combined.

[0040] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials, characterized in that: It includes a fixed assembly connected to the testing machine and a self-aligning assembly connected to the test piece, wherein the fixed assembly and the self-aligning assembly are movably connected.

2. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 1, characterized in that: The fixing component includes a clamping rod and a hinge unit, and the self-centering component includes a universal head and an adhesive unit. The clamping rod is rigidly connected to the hinge unit, the universal head is movably connected to the hinge unit, and rigidly connected to the adhesive unit.

3. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 2, characterized in that: The clamping rod is a straight rod with a short threaded section at one end, which is used to fix it to the hinge unit. The non-threaded end of the clamping rod is matched and connected to the chuck of the testing machine.

4. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 3, characterized in that: The hinge unit includes a connector, a short rod, a nut, and a washer; the connector has a U-shaped structure, and the side wall of the open end of the connector has a pair of coaxial through holes that are perpendicular to the central axis of the connector, namely the left through hole and the right through hole of the connector.

5. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 4, characterized in that: The non-open end of the connector is provided with a threaded hole coaxial with the central axis of the connector; the short rod is a straight rod with a uniform cross-section and short threaded sections at both ends.

6. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 5, characterized in that: One end of the universal head is provided with a variable cross-section through hole perpendicular to the central axis of the universal head, and the other end is provided with a universal head threaded hole coaxial with the central axis of the universal head; the variable cross-section through hole is a smooth double-flare-shaped through hole formed by rotating an inward concave arc, with the hole diameter decreasing first and then increasing, and the minimum hole diameter being larger than the diameter of the short rod.

7. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 6, characterized in that: The short rod passes through the left through hole, the variable cross-section through hole, and the right through hole of the connector in sequence. Both ends of the short rod are fixedly connected with washers and nuts for the movable connection between the hinge unit and the universal joint.

8. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 7, characterized in that: The threaded end of the clamping rod is rigidly connected to the threaded hole of the connector, and the two do not move relative to each other.

9. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 8, characterized in that: The bonding unit includes end pieces on both sides of the test piece; one end of each end piece is a bonding surface, and the other end is provided with a threaded head.

10. The clamping device for out-of-plane uniaxial tensile and fatigue testing of fiber-reinforced composite materials according to claim 9, characterized in that: The bonding surface of the end piece is bonded to the test piece with adhesive, and the threaded head of the end piece is rigidly connected to the threaded hole of the universal head.

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