A composite material three-point bending test fixture

Abstract

The utility model discloses a kind of composite material three-point bending test fixture, including the support base plate being installed on testing machine, the both sides of support base plate are connected with positioning frame, the top of positioning frame is connected with air floating guide rail, air floating guide rail's both sides are slidably installed with air floating slide block, one side of air floating slide block is installed with ball bearing, driven shaft is rotatably installed in the inside of ball bearing, one end of driven shaft is equipped with clamping mechanism, the surface one side of support base plate is equipped with centering mechanism, one side of clamping mechanism is equipped with bending pressure head. The utility model has following effect: by clamping mechanism, two ends of sample are firmly clamped, ensure that sample is always effectively constrained in whole loading process, effectively prevent sample slippage or suddenly break out in bending experiment process, ensure that experimental process is stable and controllable.

Description

Technical Field

[0001] This utility model relates to the field of material bending performance testing technology, specifically to a composite material three-point bending test fixture. Background Technology

[0002] Composite materials, due to their excellent specific strength, specific modulus, and high designability, have been widely used in aerospace, rail transportation, automobile manufacturing, and construction engineering. When evaluating the mechanical properties of composite materials, bending performance is a key indicator, directly reflecting the material's bending strength and stiffness under bending loads. Currently, the three-point bending test method is commonly used to test the bending performance of composite materials. This method involves placing the specimen horizontally on two fixed support points, applying a concentrated load at the mid-span position using a loading head located directly above the specimen. This causes the specimen to bend under continuous pressure until it fractures, thus obtaining key parameters such as the material's bending strength and elastic modulus.

[0003] However, in actual testing, as the load continues to increase, composite material specimens may suddenly fracture when they reach their ultimate load-bearing capacity. Especially for some composite materials with large mass and high hardness, the elastic strain energy released at the moment of fracture causes fragments or blocks of the specimen to rapidly detach from the support point under inertia, flying downwards or laterally. This fracture spatter phenomenon can not only damage the testing equipment, but more seriously, it poses significant safety hazards, potentially causing impact injuries to operators and affecting the safety of the testing environment. Existing three-point bending test fixtures mostly focus on the centering of the load and the stability of the support, lacking effective constraints and protection for the specimen after fracture, making it difficult to effectively prevent the specimen from flying out during fracture. Utility Model Content

[0004] In view of the problems in the related technologies, this utility model proposes a composite material three-point bending test fixture to overcome the above-mentioned technical problems existing in the existing related technologies.

[0005] Therefore, the specific technical solution adopted by this utility model is as follows:

[0006] A composite material three-point bending test fixture includes a support base plate mounted on a testing machine. Positioning frames are connected to both sides of the support base plate. An air-bearing guide rail is connected to the top of the positioning frames. Air-bearing sliders are slidably mounted on both sides of the air-bearing guide rail. A ball bearing is mounted on one side of the air-bearing slider. A driven shaft is rotatably mounted inside the ball bearing. A clamping mechanism is provided at one end of the driven shaft. A centering mechanism is provided on one side of the surface of the support base plate. A bending pressure head is provided on one side of the clamping mechanism.

[0007] Furthermore, in order to achieve a stable clamping of the composite material that needs to be bent, the clamping mechanism includes a support frame connected to the end of the driven shaft, a lifting screw threaded to one side of the surface of the support frame, a clamping plate rotatably connected to one end of the lifting screw, and a screwing head connected to the other end.

[0008] Furthermore, in order to achieve the centering effect during the installation of composite materials, the centering mechanism includes a transmission groove on the surface of the support base plate, a bidirectional screw is rotatably installed inside the transmission groove, and a centering plate is threadedly connected to both sides of the surface of the bidirectional screw.

[0009] Furthermore, in order to ensure that the two air-bearing sliders are at the same distance from the midpoint, a lifting rod is slidably installed inside the center plate, a limit groove is opened at the bottom of the support frame, one end of the lifting rod is matched with the limit groove, and a clamping bolt is threadedly connected to one side of the center plate.

[0010] Furthermore, in order to increase the friction when clamping the two sides of the composite material, anti-slip textures are provided on one side of the surface of the support frame and the clamping plate.

[0011] Furthermore, to facilitate the twisting and rotation of the bidirectional screw, one end of the bidirectional screw rotates through the support base plate and is connected to a twisting ring.

[0012] Furthermore, in order to limit the adjustment of the air-float slider, a limit frame is connected to one side of the air-float slider, and the surface of the limit frame is threaded with positioning bolts.

[0013] The beneficial effects of this utility model are as follows:

[0014] 1. By setting up a clamping mechanism consisting of a support frame, clamping plate, and lifting screw, the two ends of the specimen are firmly clamped before the test, ensuring that the specimen is effectively constrained throughout the entire loading process. Even if the specimen breaks, its fragments are still limited within a certain range by the clamping mechanism, greatly suppressing the phenomenon of fragmentation and effectively protecting operators and surrounding equipment, fundamentally solving the safety risks existing in the prior art.

[0015] 2. By driving the two centering plates on both sides synchronously with a bidirectional screw, and by utilizing the cooperation between the lifting rod and the limiting groove of the support frame, the two support frames can be initially aligned to ensure that their distances to the midpoint are equal. Subsequently, after the sample is loaded, the centering plates are finely adjusted to achieve secondary precise positioning of both ends of the sample, ensuring that the line of action of the loading force strictly passes through the center of the sample, avoiding eccentric force, thereby obtaining more realistic and reliable bending strength and elastic modulus data. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the surface structure of a composite material three-point bending test fixture according to an embodiment of the present utility model;

[0018] Figure 2 This is a side view of a composite material three-point bending test fixture according to an embodiment of the present utility model;

[0019] Figure 3 This is a rear view of a composite material three-point bending test fixture according to an embodiment of the present utility model;

[0020] Figure 4 This is a bottom view of a composite material three-point bending test fixture according to an embodiment of the present utility model;

[0021] Figure 5 This is a schematic diagram of the surface structure of a composite material three-point bending test fixture after the sample is installed, according to an embodiment of the present invention.

[0022] In the picture:

[0023] 1. Support base plate; 2. Positioning frame; 3. Air-bearing guide rail; 4. Air-bearing slider; 5. Ball bearing; 6. Driven shaft; 7. Clamping mechanism; 701. Support frame; 702. Lifting screw; 703. Clamping plate; 704. Tightening head; 8. Centering mechanism; 801. Transmission groove; 802. Bidirectional screw; 803. Centering plate; 804. Lifting rod; 805. Limiting groove; 806. Clamping bolt; 9. Bending pressure head; 10. Anti-slip texture; 11. Tightening ring; 12. Limiting frame; 13. Positioning bolt. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] like Figures 1-5As shown, a composite material three-point bending test fixture according to an embodiment of the present invention includes a support base plate 1 mounted on a testing machine, which is a universal material testing machine capable of applying pressure to the bending test of composite materials; a pair of positioning frames 2 are connected to both sides of the support base plate 1, and air-bearing guide rails 3 are connected to the top of the two positioning frames 2; a pair of air-bearing sliders 4 are slidably mounted on both sides of the air-bearing guide rails 3; clean compressed air that has been filtered and pressure-regulated is input into the throttling orifices on the air-bearing guide rails 3 and air-bearing sliders 4 through an external air source (such as an air compressor), forming an extremely thin air film between the sliders and the guide rail surface, thereby achieving frictionless sliding of the air-bearing sliders 4 on the air-bearing guide rails 3; a pair of air-bearing sliders 4 are mounted on one side. The ball bearing 5 has a driven shaft 6 rotatably mounted inside it. One end of the driven shaft 6 is equipped with a clamping mechanism 7, which is used to firmly clamp both sides of the composite material to be bent. One side of the surface of the support base plate 1 is equipped with a centering mechanism 8, which is used to achieve the centering effect when the composite material is installed. One side of the clamping mechanism 7 is equipped with a bending pressure head 9. The universal material testing machine applies pressure to the midpoint of the composite material after centering and clamping through the bending pressure head 9, so that the composite material gradually bends and deforms until it breaks or reaches the predetermined deformation amount. During the bending process, the ball bearing 5 can rotate freely to adapt to the angle change of the sample end. The air float slider 4 moves on the air float guide rail 3 to adapt to the displacement change of the composite material during bending.

[0026] like Figures 1-5As shown, the clamping mechanism 7 includes a support frame 701 connected to the end of the driven shaft 6. A lifting screw 702 is threadedly connected to one side of the surface of the support frame 701. One end of the lifting screw 702 is rotatably connected to a clamping plate 703, and the other end is connected to a turning head 704. After the composite material is centered and placed inside the two support frames 701, the lifting screw 702 is rotated to drive the clamping plate 703 to move downward by rotating the turning head 704, thereby firmly clamping the composite material inside the support frame 701. The centering mechanism 8 includes a transmission groove 801 opened on the surface of the support base plate 1. A double-acting screw 802 is rotatably mounted inside 801. The threads on both sides of the double-acting screw 802 are opposite, and a centering plate 803 is threadedly connected to both sides of the double-acting screw 802. A lifting rod 804 is slidably mounted inside the centering plate 803. A limit groove 805 is opened at the bottom of the support frame 701. One end of the lifting rod 804 cooperates with the limit groove 805. A clamping bolt 806 is threadedly connected to one side of the centering plate 803. After adjusting the height of the lifting rod 804 inside the centering plate 803, the adjusted height is fixed by the clamping bolt 806. Then, the double-acting screw 802 is turned to fix the height. Rod 802 causes relative movement between centering plate 803 and clamping plate 703, thereby pressing and centering both ends of the composite material to be tested. After adjusting the height of lifting rod 804, the top of lifting rod 804 is fitted into the limiting groove 805 at the bottom of support frame 701, thus enabling synchronous movement of the two support frames 701, ensuring that the distances from the midpoint to both support frames 701 are the same. Anti-slip textures 10 are provided on one side of both support frame 701 and clamping plate 703 to increase friction when clamping the composite material and prevent it from falling off during pressure application. A bidirectional screw 8... One end of 02 rotates through the support base plate 1 and is connected to a screwing ring 11, which is used to facilitate the screwing and rotation of the bidirectional screw 802; one side of the air float slider 4 is connected to a limit frame 12, and the surface of the limit frame 12 is threaded with a positioning bolt 13, which is used to fix the air float slider 4 in the adjusted position by screwing the positioning bolt 13 after adjusting the position of the two support frames 701, so as to prevent the air float slider 4 and the support frame 701 from sliding freely when the composite material is installed and clamped. After the composite material is clamped and installed, the positioning bolt 13 is rotated to contact the limit, which facilitates subsequent bending tests.

[0027] In actual use, by rotating the turning ring 11 at one end of the bidirectional screw 802, the two centering plates 803 are driven to move synchronously towards or away from each other within the transmission groove 801 using the opposite threads on both sides. At this time, the lifting rod 804 on the centering plate 803 has been pre-adjusted to a suitable height and fixed by the clamping bolt 806. Its top end is embedded in the limiting groove 805 at the bottom of the support frame 701 on both sides, realizing the cooperative connection between the lifting rod 804 and the support frame 701. When the centering plate 803 moves, it drives the lifting rod 804 connected to it to push the support frame 701 to move synchronously, thereby precisely adjusting the relative position between the two support frames 701 so that the distances from the two to the center line are completely equal, achieving centering of the support position. Subsequently, by tightening the positioning bolt 13 on the limiting frame 12 on one side of the air float slider 4, the air float slider 4 is fixed on the air float guide rail 3 to prevent it from being displaced by external force in subsequent operations. The composite material sample to be tested is placed horizontally in the inner groove of the two support frames 701. At this time, the lifting rod 804 is taken out from the limiting groove 805 and its height is raised. The bidirectional screw 802 is rotated again to make the two centering plates 803 move relative to each other in the transmission groove 801, pushing the lifting rod 804 on its inner side to drive the composite material sample placed in the support frame 701 to perform end compression, achieving precise centering of the sample in the fixture, ensuring that the sample axis is perpendicular to the loading direction and the loading point is located at the mid-span position, thus improving the testing accuracy. After the composite material sample is clamped and aligned, the positioning bolts 13 on the limiting frame 12 are loosened to release the mechanical limit on the air-bearing slider 4. The universal testing machine is then started, causing the crossbeam to descend and drive the bending indenter 9 to act on the midpoint of the composite material sample, applying a concentrated load. The sample begins to bend and deform. During the bending process, the ball bearing 5 can rotate freely to adapt to the angle change at the end of the sample. The air-bearing slider 4 moves on the air-bearing guide rail 3 to adapt to the displacement change of the composite material during bending. Throughout the loading process until fracture, the clamping mechanism 7 firmly fixes both ends of the sample, significantly suppressing the risk of fragments flying at the moment of fracture and improving the safety and reliability of the test.

[0028] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A three-point bending test fixture for composite materials, characterized in that, The support base plate (1) is installed on the testing machine. Positioning frames (2) are connected to both sides of the support base plate (1). An air-bearing guide rail (3) is connected to the top of the positioning frame (2). Air-bearing sliders (4) are slidably installed on both sides of the air-bearing guide rail (3). A ball bearing (5) is installed on one side of the air-bearing slider (4). A driven shaft (6) is rotatably installed inside the ball bearing (5). A clamping mechanism (7) is provided at one end of the driven shaft (6). A centering mechanism (8) is provided on one side of the surface of the support base plate (1). A bending pressure head (9) is provided on one side of the clamping mechanism (7).

2. The composite material three-point bending test fixture according to claim 1, characterized in that, The clamping mechanism (7) includes a support frame (701) connected to the end of the driven shaft (6). A lifting screw (702) is threadedly connected to one side of the surface of the support frame (701). One end of the lifting screw (702) is rotatably connected to a clamping plate (703), and the other end is connected to a screwing head (704).

3. A composite material three-point bending test fixture according to claim 2, characterized in that, The centering mechanism (8) includes a transmission groove (801) on the surface of the support base plate (1), a bidirectional screw (802) is rotatably installed inside the transmission groove (801), and a centering plate (803) is threadedly connected to both sides of the surface of the bidirectional screw (802).

4. A composite material three-point bending test fixture according to claim 3, characterized in that, A lifting rod (804) is slidably installed inside the middle plate (803). A limit groove (805) is opened at the bottom of the support frame (701). One end of the lifting rod (804) is matched with the limit groove (805). A clamping bolt (806) is threadedly connected to one side of the middle plate (803).

5. A composite material three-point bending test fixture according to claim 2, characterized in that, The support frame (701) and the clamping plate (703) are provided with anti-slip texture (10) on one side of their surfaces.

6. A composite material three-point bending test fixture according to claim 3, characterized in that, One end of the double-ended screw (802) rotates through the support base plate (1) and is connected to a screwing ring (11).

7. A composite material three-point bending test fixture according to claim 1, characterized in that, One side of the air-bearing slider (4) is connected to a limit frame (12), and the surface of the limit frame (12) is threaded with a positioning bolt (13).

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