A test device and method for detecting bending and shearing performance of composite materials across span

Abstract

The application discloses a test device and a detection method for detecting the bending and shearing performance of a composite material with a span, and belongs to the technical field of composite material mechanics detection. The test device comprises a base, left and right pressure receiving tables with pressure rods are symmetrically arranged on the base, an upper pressure table with an upper pressure rod is arranged above the base, and three pressure rods form a three-point detection structure. The left and right pressure receiving tables are driven by screw transmission shafts with adjusting knobs, stepless adjustment of a supporting span can be realized, and a digital caliper is used to realize accurate reading of the span. Each pressure rod is installed in a floating mode through a spring, can adapt to small deflection of sample deformation, and prevents the pressure rod from being stuck. A limiting component is arranged on a pressure receiving surface, and accurate centering and positioning of the sample can be realized. The application solves the problems of complicated span adjustment, large measurement error and large discreteness of test data of a traditional tooling, can be compatible with bending and shearing dual working condition detection, has high positioning accuracy and good repeatability, and is suitable for accurate detection of the mechanical properties of various composite materials.

Description

Technical Field

[0001] This invention belongs to the field of mechanical property testing technology for composite material parts, and specifically relates to a test device and testing method for testing the bending and shear properties of composite materials over a span. Background Technology

[0002] Composite materials, with their superior properties such as high specific strength, high specific modulus, corrosion resistance, and fatigue resistance, are widely used in aerospace, rail transportation, new energy, and military equipment. Bending performance and interlaminar shear performance are core mechanical indicators for measuring the load-bearing capacity and structural stability of composite materials, and are also essential testing items for composite material factory inspection, selection and application, and performance iteration research and development.

[0003] Currently, the industry mostly uses traditional three-point bending test fixtures for bending and shearing tests of composite materials. The existing traditional fixtures have a fixed span for supporting the specimen. If it is necessary to test the bending and shearing performance under different span-to-thickness ratios, it is necessary to manually disassemble and replace pads of different thicknesses. The span adjustment operation is cumbersome, time-consuming and labor-intensive, and cannot achieve continuous stepless adjustment of the span, resulting in poor test versatility. Furthermore, the span size mostly relies on manual measurement with tape measures and calipers, and the manual alignment and reading errors are relatively large, which directly affects the accuracy of the test data.

[0004] Traditional tooling rollers are mostly rigidly fixed. During the loading and deformation of the specimen, the rollers cannot adaptively adjust, which can easily lead to problems such as roller jamming and force skew, resulting in uneven stress on the specimen, non-standard failure modes, and large dispersion of test data.

[0005] In summary, existing composite material bending and shear testing fixtures suffer from technical problems such as inconvenient span adjustment, low measurement accuracy, and easy jamming of the pressure bar, making it difficult to meet the requirements of high-precision, multi-condition, and high-efficiency testing of composite material mechanical properties. Therefore, there is an urgent need to design an integrated testing device and testing method that can accurately adjust the span, adaptively load, and accurately position the material. Summary of the Invention

[0006] The purpose of this invention is to provide a test device and method for testing the bending and shear properties of composite materials by span, which solves the technical problems of existing test fixtures such as non-adjustable span, large measurement error, and clamping of pressure bars, thereby realizing high-precision, multi-condition, and high-efficiency integrated testing of the bending and shear properties of composite materials.

[0007] To address the aforementioned technical problems, this invention provides a test apparatus for span-based testing of the bending and shear properties of composite materials, comprising a base,

[0008] A left pressure platform and a right pressure platform are symmetrically arranged on the base; a left pressure rod is movably installed on the left pressure platform, and a right pressure rod is movably installed on the right pressure platform; the left pressure rod and the right pressure rod respectively support the two ends of the composite material sample;

[0009] An upper pressure platform is provided above the base, and an upper pressure rod is movably installed on the upper pressure platform. The left pressure rod, the right pressure rod, and the upper pressure rod are arranged in a three-point manner to test the composite material sample.

[0010] The left and right pressure platforms are mounted on the same drive shaft. Under the action of the drive shaft, the left and right pressure platforms drive the left and right pressure rods to move closer or further apart, respectively, so as to realize the span detection of composite material samples.

[0011] Preferably, the drive shaft is a lead screw, and the left and right pressure plates are respectively connected to the lead screw via lead screw nuts. An adjustment knob is provided at one end of the drive shaft. By rotating the drive shaft through the adjustment knob, the left and right pressure rods are respectively driven to move closer or further apart, so as to realize the span detection of composite material samples.

[0012] Preferably, a digital caliper is detachably mounted on the base, and the span between the left pressure bar and the right pressure bar is read through the digital caliper.

[0013] Preferably, the left pressure rod is horizontally installed in the arc-shaped groove of the left pressure plate, and its two ends are movably connected by a left spring. Under the pre-tightening force of the left spring, the left pressure rod is fitted into the arc-shaped groove of the left pressure plate.

[0014] Preferably, the right pressure rod is horizontally installed in the arc-shaped groove of the right pressure plate, and its two ends are movably connected by a right spring. Under the pre-tightening force of the left spring, the right pressure rod is fitted into the arc-shaped groove of the right pressure plate.

[0015] The right pressure bar and the left pressure bar are arranged parallel to each other on the same plane.

[0016] Preferably, the tops of the left and right pressure-bearing platforms are pressure-bearing surfaces for placing composite material samples, and a limiting component is slidably installed on the pressure-bearing surfaces. The limiting component abuts against the side wall of the composite material sample, thereby adjusting the horizontal position of the composite material sample.

[0017] Preferably, the limiting component includes a limiting plate and a set bolt, wherein the limiting plate moves horizontally along the bearing surface and is locked in position by the set bolt.

[0018] Preferably, the upper pressing table is mounted on the upper sliding seat, and the upper sliding seat slides via the guide sleeve along the guide post vertically mounted on the base.

[0019] Preferably, the upper pressing rod is horizontally installed in the arc-shaped groove of the upper pressing table, with both ends movably connected via upper springs respectively. Under the pre-tightening force of the upper springs, the upper pressing rod is fitted and installed in the arc-shaped groove of the upper pressing table.

[0020] The present invention further provides a detection method for a test device for detecting bending and shear properties of composite materials with adjustable span, comprising the following steps:

[0021] S1. Fixture installation: Fix the base of the test device in the positioning hole at the bottom of the mechanical property testing machine, and connect and fix the upper pressing table of the test device to the upper pressure sensor on the crossbeam of the mechanical property testing machine; the upper pressing table realizes vertical sliding guidance through the upper sliding seat cooperating with the guide post and the guide sleeve, and provides precise loading power for composite material shear and bending detection by adjusting the crossbeam displacement of the mechanical property testing machine.

[0022] S2. Sample installation and span adjustment: Place the composite material test sample on the bearing surfaces of the left bearing table and the right bearing table, and make line contact with the supporting surfaces of the left pressing rod and the right pressing rod, manually rotate the adjusting knob to drive the transmission shaft of the screw structure to rotate, drive the left bearing table and the right bearing table to move relatively and horizontally through the screw nut transmission, synchronously drive the left pressing rod and the right pressing rod to move and adjust to the preset test span; accurately read and confirm the actual span value between the two pressing rods through the digitally caliper detachably mounted on the base, so as to complete the precise calibration of the span.

[0023] S3. Sample centering and position adjustment: Relying on the bearing surfaces at the tops of the left bearing table and the right bearing table, the limit plates of the limit assembly abut against the two side walls of the test sample, and the horizontal position of the test sample is finely adjusted to keep the center of the test sample coaxially aligned with the center of the upper pressing rod; after the position calibration is completed, the position of the limit plate is locked by the set bolt to limit the horizontal offset of the sample; then adjust the crossbeam of the mechanical property testing machine to drive the upper pressing rod to move down to be close to the upper surface of the test sample, set the initial force value of the testing machine, and complete the pre-positioning of the sample.

[0024] S4. Mechanical strength detection: Enter the composite material test standard parameters into the supporting test software of the mechanical testing machine, and complete the calibration of the testing machine equipment and the zeroing operation of load and displacement; after confirming that the states of the equipment and the sample are correct, start the compression test, and control the mechanical testing machine to perform downward compression loading at a preset constant rate; during the test, the left pressing rod realizes adaptive floating fit through the left spring, the right pressing rod through the right spring, and the upper pressing rod through the upper spring respectively, and rotates slightly with the deformation of the sample to avoid the jamming of the pressing rods; the testing machine continuously collects test load and displacement data until the structure of the test sample is damaged or the test load drops sharply by 20%, and the single test is automatically terminated.

[0025] S5. Single Sample Analysis: After the test, raise the crossbeam of the testing machine, take out the tested sample, visually observe and record the failure mode of the sample, simultaneously organize the original test data, analyze the test load parameters, and determine whether the single test data meets the test standard requirements.

[0026] S6. Strength Limit Repeat Test: After the data of a single test is qualified, repeat the operation of steps S2, S3 and S4, replace the new sample to be tested or adjust the test span by adjusting the knob, and complete multiple sets of parallel tests or gradient span tests until all preset test conditions are completed.

[0027] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0028] 1. This invention uses a lead screw drive shaft in conjunction with an adjustment knob to achieve stepless continuous adjustment of the support span of the left and right pressure rods. It can adapt to bending and shear test conditions with different span-to-thickness ratios without replacing the pads. It is compatible with composite material three-point bending tests and short beam shear tests, making the equipment highly versatile, greatly simplifying the test operation process and improving test efficiency. In addition, a detachable digital caliper is set on the base, which can read the test span value in real time and accurately, replacing the traditional manual measurement method, completely eliminating manual measurement errors, and controlling the span adjustment accuracy within a high precision range, effectively improving the accuracy and reliability of test data.

[0029] 2. The left pressure bar, right pressure bar, and upper pressure bar of this invention all adopt a spring-floating movable installation structure. Under the action of spring preload, they are installed in close contact with the arc-shaped groove. During the test, they can adaptively deflect slightly with the bending and shear deformation of the sample, which completely solves the problems of easy jamming and uneven force distribution of traditional rigid pressure bars. At the same time, pressure bars of different diameters can be replaced by springs to adapt to different test standard requirements, ensuring that the stress state of the sample conforms to the standard test conditions and reducing the dispersion of test data.

[0030] 3. The present invention is equipped with a sliding limiting component, which can quickly complete the centering and positioning of the sample by means of the limiting plate and the set bolt, effectively avoiding sample offset and misalignment during the test, ensuring the coincidence of the loading axis, and greatly improving the sample positioning accuracy and test repeatability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the experimental device provided by the present invention;

[0032] Figure 2 A front view of the experimental apparatus provided by the present invention;

[0033] Figure 3 This is a schematic diagram of the installation of the pressure platform provided by the present invention;

[0034] Figure 4 This is a schematic diagram of the installation of the limiting component provided by the present invention on the pressure plate.

[0035] The meanings of the markings in the attached diagram are as follows:

[0036] In the diagram: 1. Base; 2. Left pressure plate; 3. Right pressure plate; 4. Left pressure rod; 5. Right pressure rod; 6. Upper pressure plate; 7. Upper pressure rod; 8. Drive shaft; 9. Adjustment knob; 10. Left spring; 11. Right spring; 12. Limiting assembly; 121. Limiting plate; 122. Set bolt; 13. Pressure surface, upper slide; 14. Guide post; 15. Upper spring. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0038] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Example

[0041] This invention provides a test apparatus for span-based testing of the bending and shear properties of composite materials. Please refer to [link / reference]. Figure 1-4 The base 1 of the entire test device is precisely positioned and locked in the special positioning hole at the bottom of the electronic universal testing machine to ensure that the base 1 is horizontal and without deviation; the upper pressure platform 6 is fixedly installed on the upper pressure sensor detection end of the crossbeam of the testing machine to realize the real-time and accurate acquisition of the loading force value.

[0042] Specifically, the upper pressing platen 6 forms a sliding pair with the guide posts 14 and guide sleeves vertically arranged on the base 1 by relying on the upper sliding seat 13, and can slide vertically and smoothly along the guide posts 14 without jamming or lateral shaking, so as to ensure the straightness and stability of subsequent bending loading and complete the standardized clamping of the entire set of fixtures; a standard composite material bending specimen is selected and stably placed on the pressure-bearing surfaces 13 of the left pressure-bearing table 2 and the right pressure-bearing table 3, so that the lower surface of the specimen is in complete line contact with the rod body supporting surfaces of the left pressing rod 4 and the right pressing rod 5, which conforms to the test force bearing standard.

[0043] According to the requirements of the specimen thickness and the standard span-thickness ratio of the test, the adjusting knob 9 is manually rotated to drive the transmission shaft 8 of the lead screw structure to rotate synchronously; the transmission shaft 8 drives the left pressure-bearing table 2 and the right pressure-bearing table 3 to move horizontally and relatively on the base 1 through the lead screw nut transmission pair, and synchronously drives the left pressing rod 4 and the right pressing rod 5 to approach or move away, so as to realize stepless fine adjustment of the support span. During the adjustment process, the center distance between the two pressing rods is read in real time through a digital caliper detachably mounted on the base 1, and accurately calibrated to the preset standard span of the test, so as to eliminate the error of manual estimation.

[0044] By means of the slidable limiting assembly 12 on the pressure-bearing surface 13, the limiting plates 121 are manually pushed to slide horizontally along the pressure-bearing surface 13, so that the limiting plates 121 on both sides are in close contact with the side wall of the composite specimen to be tested, and the horizontal position of the specimen is accurately fine-tuned to ensure that the length center of the specimen is completely coaxially aligned with the pressing center of the upper pressing rod 7, so as to completely avoid the eccentric loading problem. After the alignment is completed, the tightening bolt 122 of the limiting assembly 12 is tightened to lock the position of the limiting plate 121, so as to prevent the specimen from horizontal slipping, shifting and misalignment during the test. Then the crossbeam of the testing machine is controlled to move down slowly, driving the upper pressing platen 6 and the upper pressing rod 7 to move down, so that the upper pressing rod 7 is close to the upper surface of the specimen, the initial preload value of the testing machine is set to eliminate the mechanism clearance, and the pre-positioning of the specimen is completed.

[0045] Further, standard test parameters such as the width, thickness, span and test rate of the specimen are accurately entered into the supporting test software of the testing machine, the calibration and zero clearing operations of the load and displacement channels of the testing machine are completed, and the test is started after confirming that the states of the equipment, fixture and specimen are correct. The testing machine is controlled to perform downward compression loading at a constant rate of 2mm / min to carry out a three-point bending test. During the test loading process, the left pressing rod 4 is fitted to the arc-shaped groove of the left pressure-bearing table 2 under the preload action of the left spring 10, the right pressing rod 5 is fitted to the arc-shaped groove of the right pressure-bearing table 3 under the preload action of the right spring 11, and the upper pressing rod 7 is fitted to the arc-shaped groove of the upper pressing platen 6 under the preload action of the upper spring 15. All three pressing rods can adaptively rotate slightly and fit with the bending deformation of the specimen, completely avoiding the problems of jamming and local stress concentration of the traditional rigid pressing rod.

[0046] After a single test is completed, the crossbeam of the testing machine is raised, the specimen is taken out stably, the bending failure mode of the specimen is visually observed and recorded, the original test data are statistically analyzed, abnormal data are eliminated, and the single test is confirmed to be valid.

[0047] After the test is completed, all valid test data are summarized, and the core mechanical parameters such as bending strength, bending modulus, and bending fracture load of the composite material specimens are calculated. The variation law of bending performance under different span conditions is analyzed. At the same time, the test results are determined to meet the industry testing standards by combining the specimen failure mode.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A test apparatus for span-based testing of the bending and shear properties of composite materials, characterized in that, Including the base (1) A left pressure platform (2) and a right pressure platform (3) are symmetrically arranged on the base (1); a left pressure rod (4) is movably installed on the left pressure platform (2), and a right pressure rod (5) is movably installed on the right pressure platform (3); the left pressure rod (4) and the right pressure rod (5) respectively support the two ends of the composite material sample; An upper pressure platform (6) is provided above the base (1), and an upper pressure rod (7) is movably installed on the upper pressure platform (6). The left pressure rod (4), the right pressure rod (5) and the upper pressure rod (7) are used to test the composite material sample in a three-point manner. The left pressure plate (2) and the right pressure plate (3) are mounted on the same drive shaft (8). Under the action of the drive shaft (8), the left pressure plate (2) and the right pressure plate (3) drive the left pressure rod (4) and the right pressure rod (5) to move closer to each other or further away from each other, so as to realize the span detection of composite material samples.

2. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 1, characterized in that, The drive shaft (8) is a lead screw, and the left pressure plate (2) and the right pressure plate (3) are connected to the lead screw through the lead screw nut. An adjustment knob (9) is provided at one end of the drive shaft (8). By rotating the drive shaft (8) through the adjustment knob (9), the left pressure rod (4) and the right pressure rod (5) are driven to move closer or further away from each other, so as to realize the span detection of composite material samples.

3. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 2, characterized in that, A digital caliper is detachably mounted on the base (1) to read the span between the left pressure bar (4) and the right pressure bar (5).

4. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 1, characterized in that, The left pressure rod (4) is horizontally installed in the arc-shaped groove of the left pressure plate (2), and its two ends are movably connected by the left spring (10). Under the pre-tightening force of the left spring (10), the left pressure rod (4) is fitted into the arc-shaped groove of the left pressure plate (2).

5. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 4, characterized in that, The right pressure rod (5) is horizontally installed in the arc groove of the right pressure plate (3), and its two ends are movably connected by the right spring (11). Under the pre-tightening force of the left spring (11), the right pressure rod (5) is fitted into the arc groove of the right pressure plate (3). The right pressure bar (5) and the left pressure bar (4) are arranged parallel to each other on the same plane.

6. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 5, characterized in that, The top of the left pressure plate (2) and the right pressure plate (3) are pressure-bearing surfaces (13) for placing composite material samples. A limiting component (12) is slidably installed on the pressure-bearing surface (13). The limiting component (12) abuts against the side wall of the composite material sample, thereby adjusting the horizontal position of the composite material sample.

7. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 6, characterized in that, The limiting component (12) includes a limiting plate (121) and a set bolt (122). The limiting plate (121) moves horizontally along the bearing surface (13) and is locked in position by the set bolt (122).

8. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 1, characterized in that, The upper pressure plate (6) is mounted on the upper slide (13), and the upper slide (13) slides along the guide post (14) which is vertically mounted on the base (1) via the guide sleeve.

9. The test apparatus for span-based testing of the bending and shear properties of composite materials according to claim 8, characterized in that, The upper pressure rod (7) is horizontally installed in the arc-shaped groove of the upper pressure table (6), and its two ends are movably connected by upper springs (15). Under the pre-tightening force of the upper springs (15), the upper pressure rod (7) is fitted into the arc-shaped groove of the upper pressure table (6).

10. A testing method using the test apparatus for span testing of the bending and shear properties of composite materials according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Fixture installation: Fix the base (1) of the test device in the positioning hole at the bottom of the mechanical performance testing machine, and connect and fix the upper pressure platform (6) of the test device to the upper pressure sensor of the crossbeam of the mechanical performance testing machine; the upper pressure platform (6) achieves vertical sliding guidance through the upper slide (13) in conjunction with the guide column (14) and guide sleeve, and provides precise loading power for composite material shearing and bending detection by adjusting the displacement of the crossbeam of the mechanical performance testing machine; S2. Sample installation and span adjustment: Place the composite material sample to be tested on the bearing surfaces (13) of the left bearing platform (2) and the right bearing platform (3), and make contact with the support surfaces of the left pressure rod (4) and the right pressure rod (5). Manually rotate the adjustment knob (9) to drive the transmission shaft (8) of the screw structure to rotate. Drive the left bearing platform (2) and the right bearing platform (3) to move horizontally relative to each other through the screw nut transmission, and simultaneously drive the left pressure rod (4) and the right pressure rod (5) to move and adjust to the test preset span. Accurately read and confirm the actual span value between the two pressure rods through the digital caliper that can be detachably installed on the base (1), and complete the accurate span calibration. S3. Sample centering and position adjustment: Relying on the bearing surfaces (13) at the top of the left bearing platform (2) and the right bearing platform (3), the limiting plate (121) of the limiting component (12) abuts against the two side walls of the sample to be tested, and the horizontal position of the sample to be tested is finely adjusted so that the center of the sample to be tested is coaxially aligned with the center of the upper pressure rod (7); After the position calibration is completed, the position of the limiting plate (121) is locked by the set bolt (122) to limit the horizontal displacement of the sample; Then, the crossbeam of the mechanical property testing machine is adjusted to drive the upper pressure rod (7) down to near the upper surface of the sample to be tested, the initial force value of the testing machine is set, and the sample pre-positioning is completed; S4. Mechanical strength test: Input the standard parameters of composite material test into the test software of the mechanical testing machine, and complete the calibration of the testing machine and zeroing of load and displacement. After confirming that the equipment and sample are in the correct condition, start the compression test and control the mechanical testing machine to compress downward at a preset constant rate. During the test, the left pressure bar (4) achieves adaptive floating fit through the left spring (10), the right pressure bar (5) through the right spring (11), and the upper pressure bar (7) through the upper spring (15), and rotates slightly with the deformation of the sample to avoid the pressure bar jamming. The testing machine continuously collects test load and displacement data until the sample under test is structurally damaged or the test load drops by 20%, and automatically terminates the single test. S5. Single Sample Analysis: After the test, raise the crossbeam of the testing machine, take out the tested sample, visually observe and record the failure mode of the sample, simultaneously organize the original test data, analyze the test load parameters, and determine whether the single test data meets the test standard requirements. S6. Strength limit repeated test: After the single test data is qualified, repeat the operation of steps S2, S3 and S4, replace the new test sample or adjust the test span by adjusting the knob (9) to complete multiple sets of parallel tests or gradient span tests until all preset test conditions are completed.

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