Mechanical properties testing device, equipment and method

Abstract

The present invention discloses a mechanical property testing device, equipment and method, wherein the testing device comprises an upper beam and a lower beam; the testing device further comprises two guide posts and a slider; the two guide posts are arranged on the lower beam and are slidably connected with the upper beam; the guide posts are made of a carbon fiber reinforced polyimide composite material; the two sliders are relatively slidably arranged on the upper end of the lower beam, and the slider is provided with a lower pressure roller that rotates with the slider; the lower end of the middle part of the upper beam is detachably provided with an upper pressure block, and the lower end of the upper pressure block is provided with an upper pressure roller that rotates with the slider. Under the action of the guide post made of the carbon fiber reinforced polyimide composite material, the present invention effectively solves the problem of reduced test accuracy caused by sliding blockage of the traditional metal guide post due to thermal expansion.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical property testing of high temperature resistant resin-based composite materials, and in particular to a mechanical property testing device, equipment and method. Background Art

[0002] Fiber-reinforced resin-based composite materials have high specific strength, high specific modulus, and excellent fatigue resistance. They are widely used in aviation, aerospace, automotive and other fields. However, as the flight speed continues to increase, the surface temperature of the aircraft also increases. In supersonic and hypersonic aircraft (Ma>3), the surface temperature of the aircraft can reach 400°C or even higher. Traditional epoxy resin-based composite materials can no longer meet the design requirements, and more and more high-temperature resistant resin-based composite materials are used in aerospace load-bearing structures. In the design process of aircraft structures, the testing and characterization of the mechanical properties of materials are necessary conditions for structural design optimization and strength verification.

[0003] In order to further expand the application of high-temperature resistant resin-based composite systems, the testing and characterization of its mechanical properties under normal and high temperature environments are necessary. However, there is currently no reliable experimental equipment for the mechanical properties of high-temperature resin-based composite materials in high-temperature environments. If traditional experimental equipment is used to test the mechanical properties of materials under high temperature conditions, the guide column in the experimental equipment will expand due to heat, the shaft-hole clearance will become smaller, and the sliding will be blocked, and it will not be able to effectively play a guiding role. The friction generated by thermal expansion will greatly affect the experimental accuracy. In addition, the guide column made of traditional stainless steel materials will be affected by the high temperature of the environment, and its stiffness and strength will also decrease significantly, and it will not be able to play the role of positioning, guiding, and enhancing stiffness. In a hot and humid environment, the guide column will rust due to the presence of water vapor, and the experimental equipment will often be damaged. Summary of the invention

[0004] The present invention provides a mechanical property testing device, equipment and method, which fills the gap in high-temperature mechanical property testing of high-temperature resistant resin-based composite materials, solves the difficulty of using normal temperature experimental equipment under high temperature conditions, greatly improves the accuracy and reliability of high-temperature experiments, and provides necessary support for the application of high-temperature resin-based structural composite materials.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a mechanical property testing device, comprising an upper beam and a lower beam; the testing device also comprises:

[0006] Two guide columns, which are arranged on the lower beam and are slidably connected to the upper beam; the guide columns are made of carbon fiber reinforced polyimide composite material;

[0007] Two sliders, which are relatively slidably arranged on the upper end of the lower beam, and the sliders are provided with lower pressing rollers that rotate with them;

[0008] An upper pressing block is detachably provided at the lower end of the middle part of the upper beam, and an upper pressing roller rotatably matched with the upper pressing block is provided at the lower end of the upper pressing block.

[0009] As a further description of the above technical solution:

[0010] The carbon fiber reinforced polyimide guide column is formed by winding and curing carbon fiber monofilaments after dipping them into polyimide resin; the carbon fiber monofilaments are T700, T800, T1000, M40J or M55J carbon fiber monofilaments; and the polyimide resin is a thermosetting polyimide resin with a glass transition temperature above 450°C.

[0011] As a further description of the above technical solution:

[0012] The carbon fiber reinforced polyimide guide column is sprayed with a 0.5 mm ceramic nano coating.

[0013] As a further description of the above technical solution:

[0014] The lower beam is provided with a sliding groove, and the two sliding blocks are provided with a first bolt passing through the sliding groove and locked on the lower beam.

[0015] As a further description of the above technical solution:

[0016] A semicircular groove cooperating with the lower pressure roller is provided on the upper part of the slider, and the lower pressure roller is rotatably fixed on the slider through a bracket; a positioning plate is provided on the side of the slider, the positioning plate is higher than the slider, and a long hole is provided on the positioning plate. The positioning plate and the slider are slidably connected by a second screw passing through the long hole.

[0017] As a further description of the above technical solution:

[0018] A semicircular groove cooperating with the upper pressing roller is provided at the lower part of the upper pressing block. The upper pressing roller is rotatably fixed on the upper pressing block through a mounting frame. The radius R of the upper pressing roller is 3mm, 25mm, and 50mm respectively. A conversion section is detachably provided at the upper end of the upper beam.

[0019] As a further description of the above technical solution:

[0020] A stopper is provided at the upper end of the guide column to prevent the upper beam from sliding out of the guide column, and the stopper is a bolt.

[0021] A mechanical property testing device comprises a testing machine and the mechanical property testing device as described above.

[0022] As a further description of the above technical solution: the testing machine includes a push-down pier, a temperature control box, a controller and a centering anti-rotation device.

[0023] A testing method according to the above mechanical properties testing device comprises the following steps:

[0024] In the first step, the sample size, the span between the two lower pressing rollers and the diameter of the upper pressing roller are selected according to the experimental requirements.

[0025] The second step is to place the sample in the mechanical property testing device, place the entire testing device on the testing machine, and adjust the testing device to ensure that the base is level.

[0026] The third step is to install the centering anti-rotation device on the push-down pier, and then adjust the center of the sample to achieve the centering of the test device in the testing machine.

[0027] The fourth step is to operate the controller to prepare for the mechanical properties test experiment.

[0028] The fifth step is to operate the temperature control box and set the heating curve, heating rate and insulation time as required.

[0029] Step 6. When the ambient temperature reaches the preset requirement, start the testing machine to start loading, enable displacement control, and record the loading time, displacement, and force value.

[0030] Step 7. After loading is completed, operate the temperature control box, wait for the temperature to drop to room temperature, then take out the test device, record the sample damage and complete data processing.

[0031] The present invention has the following beneficial effects:

[0032] (1) The present invention effectively solves the problem of reduced test accuracy caused by sliding blockage due to thermal expansion of traditional metal guide columns under the action of the guide column made of carbon fiber reinforced polyimide composite material.

[0033] (2) The present invention can carry out high-temperature three-point bending tests, high-temperature short-beam shear tests, wet-heat three-point bending tests, and wet-heat short-beam shear tests on different materials and at different temperatures, and can be used in conjunction with different testing machines to complete a variety of mechanical experiments, thus forming a multifunctional experimental device.

[0034] (3) The present invention can adjust the radius of the upper pressure roller by replacing the upper pressure block, and can adjust the span between the two lower pressure rollers by sliding the two sliders. It can also select a suitable radius and span according to different material properties, thereby reducing the impact of the experimental device on the experimental accuracy and effectively obtaining the failure behavior of the material.

[0035] (4) The parts of the present invention are removable and replaceable, and the heating equipment adopts a temperature control box for heating, which requires little equipment investment and has low manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1It is a structural schematic diagram of a mechanical properties testing device;

[0037] Figure 2 is a structural schematic diagram of a positioning plate;

[0038] Figure 3 It is a structural schematic diagram of the mechanical properties testing equipment;

[0039] Figure 4 This is a partial enlarged view of the mechanical properties testing equipment;

[0040] Figure 5 This is the working principle diagram of mechanical properties test;

[0041] Figure 6 This is the centering adjustment diagram for the specimen span direction;

[0042] Figure 7 This is the centering adjustment diagram of the specimen in the thickness direction.

[0043] In the figure: 1-lower beam; 2-second screw; 3-bracket; 4-lower pressure roller; 5-upper pressure roller; 6-upper beam; 7-mounting frame; 8-upper pressure block; 9-conversion section; 10-long hole; 11-stop block; 13-guide column; 14-sample; 15-positioning plate; 16-slider; 17-first bolt; 30-testing machine; 31-pushing pier; 32-middle anti-rotation device; 33-temperature control box. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Reference Figure 1-2 , an embodiment provided by the present invention: a mechanical property testing device, comprising an upper beam 6 and a lower beam 1; the testing device also comprises two guide columns 13, which are arranged on the lower beam 1 and are slidably connected with the upper beam 6; preferably, the lower beam 1 has a groove facing downward, and two positioning holes are provided at the upper end of the lower beam 1, and the guide columns 13 are pressed into the positioning holes of the lower beam 1 with a tightness of 0.01mm-0.039mm, and are punched at four points around the positioning holes to prevent loosening; then the upper beam 6 is provided with two guide holes, and the guide holes are aligned with the two guide columns 13 assembled on the lower beam 1, and are mounted on the guide columns 13 from top to bottom to form a square frame structure, which greatly increases the rigidity. In order to prevent the upper beam 6 from sliding off the guide columns 13, a stopper 11 is provided at the upper end of the guide column 13, and the stopper 11 is a bolt. Specifically, a threaded hole is provided at the upper end of the guide column 13, and the bolt 11 is fixed to the threaded hole at the upper end of the guide column 13.

[0047] The guide column 13 combines the functions of positioning, guiding and enhancing rigidity. Therefore, it is necessary and essential to set a dual-axis guide structure for the three-point bending test device.

[0048] The upper beam 6 and the lower beam 1 are relatively wide and thick, ensuring sufficient rigidity to avoid distortion during loading.

[0049] In some embodiments, the present invention aims to solve the problem that the metal guide column 13 loses its guiding and supporting functions due to thermal expansion. The guide column 13 is prepared using a carbon fiber reinforced polyimide composite material. The carbon fiber reinforced polyimide guide column 13 is formed by impregnating a carbon fiber monofilament into a polyimide resin and then winding and curing it. The selected polyimide resin has a high glass transition temperature, and has a low strength and modulus loss rate below 500°C, which can effectively provide support for the test device. After curing, a layer of ceramic nano-coating of about 0.5 mm is sprayed on the outer surface of the guide column 13, which can effectively play a heat-insulating role and can greatly reduce the thermal expansion coefficient of the guide column 13, effectively solving the problem of the guide column being unable to guide and be blocked due to thermal expansion. In addition, the composite material has good moisture and heat properties, and the surface nano-coating can effectively block water vapor, greatly improving the life of the guide column.

[0050] In some embodiments, in order to improve the stiffness of the guide column 13 at high temperatures, the present invention selects carbon fiber with moderate strength and modulus as a reinforcing material. T700, T800, T1000, M40J, M55J carbon fiber, etc. can be selected according to different stiffness and strength requirements. Under the same conditions, M40J carbon fiber is preferably used as a reinforcing material. The T1000 carbon fiber guide column has the highest strength, and the M55J carbon fiber has the best stiffness, but its cost is relatively high, and the performance improvement of the composite material made of M40J carbon fiber is not much, and the M40J fiber has a strong bonding force with the resin, and the composite material is simple to form.

[0051] In some embodiments, the present invention has no special requirements for the selected polyimide resin, but in order to maintain better material performance under high temperature conditions, a thermosetting polyimide resin with a glass transition temperature above 450° C. is preferred. Below 450° C., the thermal shock test under a long-term high temperature environment cannot be met, and the life of the guide column is greatly reduced.

[0052] In some embodiments, in order to improve the anti-corrosion and heat-insulating properties of the guide post 13, the present invention sprays a 0.5 mm ceramic nano coating on the surface of the guide post 13. Experiments show that when the coating thickness is less than 0.5 mm, the heat-insulating property is insufficient, and the guide post 13 is easily bent by thermal shock. When the coating thickness is greater than 0.5 mm, the straightness and coaxiality of the guide post cannot be met, and problems arise in the fit with the hole. Preferably, a coating thickness of 0.5 mm is optimal.

[0053] In some embodiments, in order to reduce the thermal expansion problem of the guide column 13 at high temperature, the fiber angle of the present invention adopts (+45 / 0 / -45 / 90)2s. Experimental evaluation has proved that such a winding angle has the lowest thermal expansion rate.

[0054] The testing device also includes two sliders 16, which are relatively slidably arranged on the upper end of the lower beam 1, and the sliders 16 are provided with a lower pressing roller 4 that rotates with the lower beam 6. An upper pressing block 8 is detachably provided at the lower end of the middle part of the upper beam 6, and an upper pressing roller 5 that rotates with the upper pressing block 8 is provided at the lower end. A semicircular groove that cooperates with the upper pressing roller 5 is provided at the lower part of the upper pressing block 8. A semicircular groove that cooperates with the lower pressing roller 4 is provided at the upper part of the slider 16.

[0055] The upper pressing block 8 is bolted to the groove in the center below the upper beam with the small end facing downward. The left and right position deviation of the groove is ±0.025mm to ensure the centering. The quenched upper pressing roller 5 is fixed to the semicircular groove at the bottom of the upper pressing block 8 by screws through the mounting frame 7. The radius of the upper pressing roller 5 R = 3mm is relatively small and is only suitable for the three-point bending test of small specimens. For large specimens, the upper pressing roller 5 with R = 25mm or R = 50mm can be replaced.

[0056] The slider 16 is mounted on the lower beam 1 with its small end facing upwards through a first bolt 17, wherein the bolt is installed in a hidden groove below the lower beam 1 to prevent it from protruding from the surface of the lower beam 1; both sliders 16 have a first bolt 17 passing through a slide groove and locked on the lower beam 1, so that the first bolt 17 can move the slider 16 left and right along the hidden groove to meet the requirements of different lengths of the specimens, and the test span can be freely adjusted between 10mm and 76mm.

[0057] The lower pressure roller 4 is fixed in the semicircular groove at the upper end of the slider 16 by screws through the bracket 3. A positioning plate 15 is provided on the side of the slider 16. The positioning plate 15 is higher than the slider 16. A long hole 10 is opened on the positioning plate 15. The positioning plate 15 and the slider 16 are slidably connected through the long hole by the second screw 2. The second screw 2 can slide with the long hole 10, so that the sample 14 to be selected is centered, and then the second screw 2 is fixed, so as to ensure that the test results of the samples 14 in the same batch are not affected by the inconsistency in centering. Finally, the conversion section 9 is fixed on the middle part of the upper beam 6 by bolts to prevent the guide column from being crushed during the test.

[0058] The radius R of the upper pressure roller 5 is divided into three groups, namely 3mm, 25mm, and 50mm. During the test, the assembly can be selected according to actual needs.

[0059] Working principle of the experimental device (such as Figure 5 As shown in Figure 2), P is the bending force applied by the upper pressure head of the test device, and L is the span. The bending strength σ is calculated by recording the value of P during the experiment through the force sensor. f (i.e. the maximum stress on the outer surface corresponding to the maximum load):

[0060]

[0061] Where:

[0062] σ f —— flexural strength, in MPa;

[0063] P max ——The maximum load that the specimen can bear, in Newton;

[0064] L——span, in millimeters:

[0065] h——specimen thickness, in millimeters;

[0066] ω——specimen width, in millimeters.

[0067] In another embodiment, if Figure 3-4As shown, a mechanical property testing device includes a testing machine 30 and a mechanical property testing device as described in the above embodiment; the testing machine 30 includes a push-down pier 31, a temperature control box 33, a force sensor, a controller and a centering anti-rotation device 32. When performing a fatigue test, due to the high vibration frequency and large amplitude, a lateral force will be generated during the fatigue test, causing the push-down pier 31 to rotate. After the centering anti-rotation device 32 is installed on the push-down pier 31, the torque generated by the vibration can be offset, greatly improving the accuracy and reliability of the fatigue test. Before performing a three-point bending test, first place the sample stably on the test device, use the positioning plate 15 to adjust the angle of the sample 14, and ensure that the sample 14 and the test device are consistent in centering. Then place the entire experimental device on the push-down pier 31, and adjust the test device to ensure that the base is level. Install the centering anti-rotation device 32 on the push-down pier 31, and then adjust the centering again to achieve the centering of the test device to the testing machine 30. After the adjustment is completed, the experiment can be started.

[0068] A testing method of the mechanical property testing device according to the above embodiment comprises the following steps:

[0069] In the first step, the size of the sample 14, the span between the two lower pressing rollers 4 and the diameter of the upper pressing roller 5 are selected according to the experimental requirements.

[0070] In the second step, the sample 14 is placed in the mechanical property testing device, and the entire testing device is placed on the testing machine 30, and the testing device is adjusted to ensure that the base is level.

[0071] In the third step, the centering anti-rotation device 32 is installed on the push-down pier 31 , and then the sample 14 is centered and adjusted to realize the centering of the test device in the testing machine 30 .

[0072] In order to meet the different span requirements of the specimens, each batch of specimens must be aligned and adjusted, such as Figure 6-7 As shown, the specimen is first centered in the span direction according to the formula: A = 180 / 2-L / 2-13 = B. Where L is the deviation of the specimen span A and B values ​​± 0.05 mm, and then the first bolt 17 is fixed.

[0073] Next, the specimen is centered in the thickness direction using the formula C = 64 / 2-D / 2, where D is the specimen thickness. The C value deviation is ±0.05 mm, and then the second screw 2 is fixed.

[0074] Finally, align and adjust with the testing machine. To ensure that the three-point bending fixture is well aligned when installed on the MTS machine, Figure 3As shown, a centering anti-rotation device 32 must be added. Specifically, the centering anti-rotation device 32 is installed on the MTS machine push-down pier 31 with the inner diameter facing downward, and then the three-point bend of the above-mentioned sample is adjusted and the lower beam 1 is installed in the groove opened on the centering anti-rotation device 32 (such as Figure 4 As shown), the three-point bending fixture is aligned with the testing machine.

[0075] The fourth step is to operate the controller to prepare for the mechanical properties test experiment.

[0076] The fifth step is to operate the temperature control box 33 and set the heating curve, heating rate and insulation time according to requirements.

[0077] Step 6. When the ambient temperature reaches the preset requirement, start the testing machine to start loading, enable displacement control, and record the loading time, displacement, and force value.

[0078] Step 7: After loading is completed, operate the temperature control box 33, wait for the temperature to drop to room temperature, then take out the test device, record the sample damage and complete data processing.

[0079] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A testing method for mechanical properties testing equipment, characterized in that: The mechanical property testing equipment comprises a testing machine and a mechanical property testing device, wherein the mechanical property testing device comprises an upper beam and a lower beam; the mechanical property testing device further comprises: two guide columns, which are arranged on the lower beam and are slidably connected with the upper beam; the guide columns are made of carbon fiber reinforced polyimide composite materials; two sliders, which are relatively slidably arranged on the upper end of the lower beam, and the sliders are provided with a lower pressure roller that rotates with the sliders; an upper pressure block is detachably provided at the lower end of the middle part of the upper beam, and an upper pressure roller that rotates with the sliders is provided at the lower end of the upper pressure block; the testing machine comprises a push-down pier, a temperature control box, a controller and a centering anti-rotation device; The method comprises the following steps: S1: selecting the sample size, the span between the two lower pressing rollers and the diameter of the upper pressing roller according to the experimental requirements; S2: placing the sample in the mechanical properties testing device, placing the entire mechanical properties testing device on the testing machine, and adjusting the mechanical properties testing device to ensure that the base is level; S3: Install the centering anti-rotation device on the push-down pier, and then adjust the center of the sample to achieve the centering of the mechanical property testing device in the testing machine; S4: operating the controller to prepare for the mechanical properties test experiment; S5: Operate the temperature control box and set the heating curve, heating rate and insulation time as required; S6: When the ambient temperature reaches the preset requirement, start the testing machine to start loading, enable displacement control, and record the loading time, displacement and force value; S7: After loading, operate the temperature control box, wait for the temperature to drop to room temperature, then take out the test device, record the sample damage and complete data processing.

2. The testing method of the mechanical properties testing equipment according to claim 1, characterized in that: The guide column is formed by winding and curing carbon fiber monofilaments immersed in polyimide resin; The carbon fiber monofilament is T700, T800, T1000, M40J or M55J carbon fiber monofilament; the polyimide resin is a thermosetting polyimide resin with a glass transition temperature above 450°C.

3. The testing method of the mechanical properties testing equipment according to claim 2, characterized in that: The guide column of the carbon fiber reinforced polyimide composite material is sprayed with a 0.5 mm ceramic nano coating.

4. The testing method of the mechanical properties testing equipment according to claim 1, characterized in that: The lower beam is provided with a sliding groove, and the two sliding blocks are provided with a first bolt passing through the sliding groove and locked on the lower beam.

5. The testing method of the mechanical properties testing equipment according to claim 1, characterized in that: A semicircular groove cooperating with the lower pressure roller is provided on the upper part of the slider, and the lower pressure roller is rotatably fixed on the slider through a bracket; a positioning plate is provided on the side of the slider, the positioning plate is higher than the slider, and a long hole is provided on the positioning plate. The positioning plate and the slider are slidably connected by a second screw passing through the long hole.

6. The testing method of the mechanical properties testing equipment according to claim 1, characterized in that: A semicircular groove cooperating with the upper pressing roller is provided at the lower part of the upper pressing block. The upper pressing roller is rotatably fixed on the upper pressing block through a mounting frame. The radius R of the upper pressing roller is 3mm, 25mm, and 50mm respectively. A conversion section is detachably provided at the upper end of the upper beam.

7. The testing method of the mechanical properties testing equipment according to claim 1, characterized in that: A stopper is provided at the upper end of the guide column to prevent the upper beam from sliding out of the guide column, and the stopper is a bolt.

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