Device and method for testing stress relaxation of winding forming fiber reinforced composite material

Abstract

The invention belongs to the technical field of mechanical property testing of resin-based fiber reinforced composites, and particularly discloses a stress relaxation testing device and method for a winding forming fiber reinforced composite, and the device comprises a special test sample, a strain measurement system, a load loading device and an environment box; according to the device and the method for testing the stress relaxation of the wound fiber reinforced composite material, through the innovative method and device, the stress relaxation behavior of the wound fiber reinforced composite material under the action of an external environment can be more comprehensively captured and analyzed; therefore, the stress relaxation characteristic of the fiber reinforced composite material prestressed winding structure in the long-term service process can be measured, and the problem of stress relaxation measurement of the winding forming fiber reinforced composite material prestressed structure can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical property testing of resin-based fiber-reinforced composite materials, and in particular relates to a stress relaxation testing device and method for a winding-molded fiber-reinforced composite material. Background Art

[0002] The high specific strength and high specific modulus of polymer-based composite materials make them play an indispensable role in aerospace, energy, sports, automotive industry and various infrastructures. The winding molding process is an important way to form the rotating structure of fiber-reinforced composite materials. In recent years, it has been used to form typical prestressed structures such as carbon fiber sheaths of high-speed motor rotors and high-pressure composite gas cylinders. The prestress of the winding structure provides positive pressure for the internal components, playing an important role in protecting the internal structure.

[0003] During the long-term use of fiber-reinforced composite materials, the viscoelasticity of the polymer matrix will cause changes in the long-term mechanical properties of fiber-reinforced composite materials, creep and stress relaxation, which will cause the prestress of the component to decay below the safety threshold. The deterioration of the prestressing force not only affects the reliability of the parts, but may also pose a threat to the safety of the entire system. Therefore, by measuring the changes in the long-term mechanical properties of fiber-reinforced composite materials under various complex service environments, obtaining the residual prestressing force of polymer-based composite materials during use is the key to evaluating the life of prestressed materials or structures. This is of great significance for improving the overall performance and economic benefits of the product, and also provides a scientific basis for further research and development of more advanced composite materials.

[0004] Chinese invention patent CN106568650A provides a stress relaxation test method for carbon fiber composite tendons, and Chinese invention patent CN111766164A provides a combined fatigue-stress relaxation test device for prestressed tendons. The above patents are mainly for pultruded composite tendons, and the test sample structure is a plate / strip shape. The stress relaxation test needs to ensure that the deformation of the sample during the test is a constant value. In the actual long-term test process, the deformation caused by the slip of the clamping end of the tested sample is very difficult to control, which leads to difficulties in measuring the stress relaxation performance of fiber-reinforced composite materials. Therefore, the above patents fail to clarify how to improve and control the influence of end changes. Chinese invention patent CN108801768A provides a stress relaxation test method for fiber-type flexible materials, Chinese invention patent CN113654779A discloses a stress relaxation test method suitable for conical structures, and Chinese invention patents CN102353588A and CN102650581A disclose equipment and methods for stress relaxation tests for rubber and leaf springs, respectively. However, the above devices and methods are difficult to apply to wound fiber-reinforced composite structures.

[0005] At present, there is a lack of testing devices and testing methods for stress relaxation characteristics of prestressed fiber reinforced composite materials for winding molding. At the same time, in the existing general fiber reinforced composite material testing methods, the end clamping position slips during the stress relaxation measurement of plate and strip specimens, which makes it difficult to accurately capture the strain. Therefore, the field needs to develop a stress relaxation testing device and method for winding molding fiber reinforced composite materials, which can effectively solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a stress relaxation testing device and method for a wound fiber reinforced composite material. Through this innovative method and device, the stress relaxation behavior of a wound fiber reinforced composite material under the action of an external environment can be more comprehensively captured and analyzed, and then the stress relaxation characteristics of a prestressed wound structure of a fiber reinforced composite material during long-term service can be measured, which can solve the problem of measuring stress relaxation of a prestressed structure of a wound fiber reinforced composite material.

[0007] To achieve the above-mentioned purpose, the present invention provides a stress relaxation test device for a wound fiber reinforced composite material, comprising a special test sample, a strain measurement system, a load loading device, and an environmental chamber; the special test sample has an overall ring-shaped structure, which is composed of straight lines and transition arcs; the strain measurement system is composed of a flexible strain sensor embedded in the special test sample and an external measuring device; the load loading device is composed of a stretching fixture, a stretching screw, an axial force gauge, a hollow jack, a reaction force bracket, a tensioning nut, a locking nut, and a device base; a heating plate and a temperature control system are provided inside the environmental chamber, and a sensor connecting line lead-out hole is provided at the bottom of the outside of the environmental chamber; the environmental chamber is arranged on the top of the device base.

[0008] Preferably, the special test sample has an X and Y axis symmetrical structure, and the material of the special test sample is a fiber reinforced resin-based composite material, and the fiber reinforced resin-based composite material includes glass fiber, carbon fiber and many different types of fiber materials; the preparation process of the special test sample is fiber winding molding, and it is prepared by a unidirectional plate mold with an edge arc transition.

[0009] Preferably, the flexible strain sensor is provided with sensor lead wires, and the sensor lead wires include lower lead wires and upper lead wires; The flexible strain sensors are distributed in the middle layer or surface layer of the multi-layer winding in the thickness direction of the special test sample and are located in the middle of the width direction of the special test sample; two flexible strain sensors are symmetrically embedded on both sides of the center line of the annular structure of the special test sample; The flexible strain sensors are distributed on the straight section of the special test sample, and the embedded portion of the flexible strain sensor is greater than 70% of the length of the straight section of the special test sample.

[0010] Preferably, the stretching clamp is divided into a fixed stretching clamp and a movable stretching clamp, and both the fixed stretching clamp and the movable stretching clamp are composed of a clamp body and a roller pin inserted into a hole of the clamp body, and the clamp body is provided with a first bottom hole.

[0011] Preferably, the diameter of the roller pin of the stretching fixture is smaller than the inner arc size of the special test sample, and the width of the special test sample is smaller than the reserved width of the fixture body.

[0012] Preferably, the fixed stretching clamp and the movable stretching clamp are arranged inside the environmental chamber; the fixed stretching clamp is fixedly connected to the bottom of the environmental chamber, and the movable stretching clamp is connected to the stretching screw assembly through a connecting cap.

[0013] Preferably, the stretching screw is a hollow structure with a threaded structure on its outer surface; the upper part of the environmental chamber is provided with a hole-shaped slideway that matches the outer circle of the clamping base of the movable stretching clamp, and the top of the hole-shaped slideway is provided with an axial force meter base for installing the axial force meter, and the axial force meter is connected to the lower steel plate of the reaction force bracket; the reaction force bracket is composed of an upper steel plate, a lower steel plate, and studs with threads at both ends.

[0014] Preferably, a locking nut is provided on the lower steel plate of the reaction support, and the upper steel plate of the reaction support is connected to the bottom of the hollow jack; the tensioning screw passes through the middle hole of the axial force meter, the reaction support and the hollow jack, and the upper end of the tensioning screw is connected to the movable part of the hollow jack through the tensioning nut.

[0015] Preferably, the device base includes a bottom plate, and a second bottom hole matching the sensor connection line lead-out hole is provided at the contact point between the bottom plate and the sensor connection line lead-out hole; a wire outlet groove is provided at the bottom of the bottom plate, and one end of the wire outlet groove is connected to and penetrates the second bottom hole.

[0016] A stress relaxation test method for a wound fiber reinforced composite material comprises the following steps: Step S1, loosen the locking nut, unload the hollow jack, unscrew the tensioning nut, and adjust the upper and lower positions of the tensioning screw according to the length of the special test sample; Step S2, extract the roller pins of the fixed tensile fixture and the movable tensile fixture, pass through the ring structure of the test sample and then insert into the hole of the fixture body; first complete the installation of the special test sample at the end of the fixed tensile fixture, and then move the movable tensile fixture to fix the movable tensile fixture and the test sample; Step S3, the lower lead wire of the sensor is led out through the first bottom hole of the clamp body, the sensor connection wire lead hole at the bottom of the environmental chamber, the second bottom hole of the device base, and the lead groove; the upper lead wire is led out to the external measuring device through the center hole of the stretching screw to determine the strain data of the sample; Step S4, tighten the tensioning nut, adjust the upper and lower positions of the tensioning screw, ensure that the movable tensioning fixture enters the upper slideway of the environmental chamber, and at the same time ensure that the roller pins of the movable tensioning fixture and the fixed tensioning fixture are in the same direction; Step S5, after tightening the tension nut, preload it through the hollow jack, the movable part of the hollow jack moves upward to drive the tension screw to move, so that the movable tension fixture moves upward, and the test sample is tensioned; Step S6, the tensile load on the specially made test sample is transmitted to the axial force meter in the form of reaction force through the hollow jack and the reaction force bracket, and the current tensile load is read out through the axial force meter; the tensile load is fine-tuned to zero under given load conditions using the tension nut; Step S7, determine the prestress and test environment temperature to be applied to the special test sample according to the test requirements, use the hollow jack to continue loading to the required load, and then use the locking nut to firmly lock the tensile screw and the steel plate under the reaction support; Step S8, fix the total strain of the test sample, record the current readings of the axial force gauge and the strain measurement system, and realize the stress change monitoring of the special test sample under given strain conditions.

[0017] The present invention adopts the above-mentioned device and method for testing stress relaxation of wound fiber reinforced composite materials, and the beneficial effects are as follows: (1) The present invention utilizes the characteristics of the fiber winding process, adopts a closed annular test sample structure consisting of a straight line and an end transition arc, and cooperates with a tensile fixture consisting of a roller pin and a clamp body, so that the clamping end can be clamped without slipping during the measurement process; (2) The present invention designs a loading device for closed ring structure test samples. When unloading, the movable clamp can move up and down along the slide rail, and the special test sample can be quickly installed and removed. The hollow tensile screw is used to reasonably arrange the internal sensor wiring under the premise of ensuring the loading path. The reaction force bracket is used to accurately measure the tensile load using the reaction force. The environmental chamber is integrated in structure and function. The upper slide provides precise radial positioning for the movable clamp, tensile screw, etc. The box itself is also regarded as part of the reaction force bracket. At the same time, the environmental chamber has a high temperature function, which can realize the response of the stress relaxation characteristics of the special test sample to temperature. The locking nut firmly locks the movable tensile clamp and the reaction force bracket to achieve long-term stability of the total strain of the test sample; (3) In order to achieve accurate measurement of the strain of the test sample, the present invention embeds a flexible strain sensor into the winding layer during the winding molding process of the test sample, thereby achieving in-situ measurement of the strain; (4) The present invention, through the innovative method and device, helps to optimize the composite winding molding process, and will also improve the reliability and service life of composite materials in various engineering applications, and can provide assistance for the application of composite winding molding in high-speed motor rotors, high-pressure gas cylinders, etc.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of a stress relaxation testing device and method embodiment of a winding fiber reinforced composite material of the present invention; Figure 2 It is a schematic structural diagram of a tensile fixture of an embodiment of a stress relaxation testing device and method for a wound fiber reinforced composite material according to the present invention; Figure 3 It is a schematic structural diagram of a roller pin in an embodiment of a stress relaxation testing device and method for a wound fiber reinforced composite material according to the present invention; Figure 4 A cross-sectional view of an environmental chamber of an embodiment of a device and method for testing stress relaxation of a wound fiber-reinforced composite material according to the present invention; Figure 5 It is a structural schematic diagram of a device base of an embodiment of a device and method for testing stress relaxation of a wound fiber reinforced composite material according to the present invention; Figure 6 It is a schematic structural diagram of a test sample of an embodiment of a device and method for testing stress relaxation of a wound fiber-reinforced composite material according to the present invention; Figure 7 It is a schematic diagram of the connection between a tensile screw and a movable tensile clamp in an embodiment of a device and method for testing stress relaxation of a wound fiber reinforced composite material according to the present invention.

[0020] Reference numerals 1. Special test sample; 2. Environmental chamber; 3. Tensile screw; 4. Axial force meter; 5. Hollow jack; 6. Reaction bracket; 7. Tension nut; 8. Lock nut; 9. Device base; 10. Heating plate; 11. Sensor connection wire lead-out hole; 12. Lower lead-out wire; 13. Upper lead-out wire; 14. Fixed tensile fixture; 15. Movable tensile fixture; 16. Clamp body; 17. Roller pin; 18. First bottom hole; 19. Connecting cap; 20. Hole slideway; 21. Axial force meter base; 22. Bottom plate; 23. Second bottom hole; 24. Wire outlet slot; 25. Flexible strain sensor. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0022] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0023] like Figure 1 As shown, a stress relaxation test device for a wound fiber reinforced composite material includes a special test sample 1, a strain measurement system, a load loading device, and an environmental chamber 2.

[0024] like Figure 6As shown, the structure of the special test sample is annular as a whole, consisting of straight lines and transition arcs, and the special test sample 1 is a symmetrical structure of the X and Y axes. The material of the special test sample 1 is a fiber-reinforced resin-based composite material, and the fiber-reinforced resin-based composite material includes glass fiber, carbon fiber and many different types of fiber materials. The preparation process of the special test sample 1 is fiber winding molding, and it is prepared by a unidirectional plate mold with edge arc transition.

[0025] The strain measurement system is composed of a flexible strain sensor 25 embedded in a special test sample 1 and an external measuring device to monitor the strain data of the test sample. The flexible strain sensor 25 is provided with sensor lead wires, including a lower lead wire 12 and an upper lead wire 13.

[0026] The flexible strain sensors 25 are distributed in the multi-layer winding middle layer or surface layer in the thickness direction of the special test sample 1 and are located in the middle of the width direction of the special test sample 1. Two flexible strain sensors 25 are symmetrically embedded on both sides of the center line of the annular structure of the special test sample 1.

[0027] The flexible strain sensor 25 is distributed in the straight section of the special test sample 1, and the embedded portion of the flexible strain sensor 25 is greater than 70% of the length of the straight section of the special test sample 1. The type, range and sensitivity of the sensor can be selected according to different application scenarios, and the external measuring device matches the sensor type.

[0028] The load loading device is composed of a tensile fixture, a tensile screw 3, an axial force meter 4, a hollow jack 5, a reaction support 6, a tension nut 7, a locking nut 8, and a device base 9, which provides a given tensile force for the test sample and measures the magnitude of the tensile force. The environmental chamber 2 provides a variable high temperature environment for the test sample, and some components are part of the loading device.

[0029] like Figure 2-Figure 3 As shown, the stretching clamp is divided into a fixed stretching clamp 14 and a movable stretching clamp 15 . Both the fixed stretching clamp 14 and the movable stretching clamp 15 are composed of a clamp body 16 and a roller pin 17 inserted into a hole of the clamp body 16 . The clamp body 16 is provided with a first bottom hole 18 .

[0030] The diameter of the roller pin 17 of the tensile fixture is slightly smaller than the internal arc size of the special test sample 1, and the width of the special test sample 1 is slightly smaller than the reserved width of the clamp body 16. It is ensured that the installation on the tensile fixture does not deviate.

[0031] The fixed stretching fixture 14 and the movable stretching fixture 15 are arranged inside the environmental chamber 2. The fixed stretching fixture 14 is fixedly connected to the bottom of the environmental chamber 2, and the movable stretching fixture 15 is combined and connected with the stretching screw 3 through a connecting cap 19.

[0032] like Figure 4As shown, a heating plate 10 and a temperature control system are provided inside the environmental box 2, and a sensor connection line lead-out hole 11 is provided at the bottom of the external part of the environmental box 2. The stretching screw 3 has a hollow structure, and its outer surface has a threaded structure. It can rotate freely without affecting the direction of the roller pin 17.

[0033] The upper part of the environmental chamber 2 is provided with a hole-shaped slideway 20 matching the outer circle of the base of the clamp body 16 of the movable tensile clamp 15. The movable tensile clamp 15 can move in the hole-shaped slideway 20 on the upper part of the environmental chamber 2 driven by the tensile screw 3. The top of the hole-shaped slideway 20 is provided with an axial force meter base 21 to install the axial force meter 4, and the axial force meter 4 is connected to the lower steel plate of the reaction force bracket 6. The reaction force bracket 6 is composed of an upper steel plate, a lower steel plate, and a stud with threads at both ends.

[0034] A locking nut 8 is provided on the lower steel plate of the reaction support 6 to lock the relative position of the lower bottom plate 22 of the reaction support 6 and the tensile screw 3, thereby fixing the total strain of the test sample. The upper steel plate of the reaction support 6 is connected to the bottom of the hollow jack 5. Figure 7 As shown, the tension screw 3 passes through the middle hole of the axial force meter 4, the reaction force bracket 6 and the hollow jack 5, and the upper end of the tension screw 3 is connected to the movable part of the hollow jack 5 through the tension nut 7. When the hollow jack 5 is loaded, the tension screw 3 is driven to move upward through the tension nut 7, and at the same time, the movable tension clamp 15 is driven to move to achieve the application of the tension load. The tension load is transmitted to the axial force meter 4 through the bottom of the jack and the reaction force bracket 6, and the tension load is obtained by testing the reaction force. The tension nut 7 at the end of the tension screw 3 can fine-tune the tension load.

[0035] The environmental chamber 2 is arranged on the top of the device base 9. Figure 5 As shown, the device base 9 includes a bottom plate 22, and a second bottom hole 23 matching the sensor connection line lead-out hole 11 is provided at the bottom of the bottom plate 22. A wire outlet groove 24 is provided at the bottom of the bottom plate 22, and one end of the wire outlet groove 24 is connected to the second bottom hole 23.

[0036] Example In this embodiment, the test sample is wound on a one-way plate mold with an arc transition at the edge by tension winding. Wet and dry winding can be used. When the test sample is wound to half of the total number of layers, the optical fiber sensor is embedded, and the lead wire is reserved and then wound to the full thickness, demolded and polished to the appropriate size.

[0037] A stress relaxation test method for a winding-molded carbon fiber reinforced epoxy resin composite material for a high-speed motor sheath comprises the following steps: Step S1, loosen the locking nut 8, unload the hollow jack 5, unscrew the tensioning nut 7, and adjust the upper and lower positions of the tensioning screw 3 according to the length of the test sample.

[0038] Step S2, pull out the roller pin 17 of the fixed tensile clamp 14 and the movable tensile clamp 15, pass through the ring structure of the test sample and then insert into the hole of the clamp body 16. First complete the installation of the test sample at the end of the fixed tensile clamp 14, and then move the movable tensile clamp 15 to achieve the fixation of the movable tensile clamp 15 and the test sample.

[0039] Step S3, the lower lead wire 12 of the sensor is led out through the first bottom hole 18 of the clamp body 16, the sensor connection wire lead-out hole 11 at the bottom of the environmental chamber 2, the second bottom hole 23 of the device base 9, and the wire outlet groove 24, and the upper lead wire 13 is led out to the external measuring device through the center hole of the stretching screw 3 to determine the sample strain data.

[0040] Step S4, tighten the tensioning nut 7, adjust the upper and lower positions of the stretching screw 3, ensure that the movable stretching fixture enters the upper slideway of the environmental chamber 2, and at the same time ensure that the roller pins 17 of the movable stretching fixture and the fixed stretching fixture 14 are in the same direction.

[0041] Step S5, after tightening the tension nut 7, preload is performed through the hollow jack 5, and the movable part of the hollow jack 5 moves upward to drive the tension screw 3 to move, so that the movable tension fixture 15 moves upward, and the test sample is tensioned. The preload ensures that the special test sample 1 is subjected to uniform and controllable force in subsequent tests.

[0042] Step S6: The tensile load on the test sample is transmitted to the axial force meter 4 in the form of reaction force through the hollow jack 5 and the reaction force bracket 6, and the current tensile load is read out through the axial force meter 4. The tensile load is fine-tuned to zero under given load conditions using the tension nut 7.

[0043] Step S7, determine the prestress and test environment temperature to be applied to the special test sample 1 according to the test requirements, use the hollow jack 5 to continue loading to the required load, and then use the locking nut 8 to firmly lock the tension screw 3 and the lower steel plate of the reaction support 6.

[0044] Step S8, fix the total strain of the test sample, record the current readings of the axial force gauge 4 and the strain measurement system, and realize the stress change monitoring of the test sample under given strain conditions.

[0045] The method used in this embodiment is a test method for a special test sample at room temperature. If the stress relaxation characteristics are tested at high temperature, first fill the first bottom hole 18 of the fixed tensile fixture 14 and the movable tensile fixture 15 with heat insulation material. Set the test temperature through the temperature control system of the environmental box 2 to ensure that the environmental box 2 is preloaded after reaching the predetermined temperature. The remaining steps are the same as the method for testing the special test sample 1 at room temperature.

[0046] Therefore, the present invention adopts the above-mentioned stress relaxation testing device and method for winding fiber-reinforced composite materials. Through this innovative method and device, it is possible to more comprehensively capture and analyze the stress relaxation behavior of the wound fiber-reinforced composite materials under the action of the external environment, and then measure the stress relaxation characteristics of the prestressed wound structure of the fiber-reinforced composite materials during long-term service, which can solve the problem of measuring the stress relaxation of the prestressed structure of the wound fiber-reinforced composite materials.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A stress relaxation test device for winding fiber reinforced composite materials, characterized in that: It includes a special test specimen, a strain measurement system, a load loading device, and an environmental chamber; the special test specimen has an overall ring-shaped structure, which is composed of straight lines and transition arcs; the strain measurement system is composed of a flexible strain sensor embedded in the special test specimen and an external measuring device; the load loading device is composed of a stretching fixture, a stretching screw, an axial force gauge, a hollow jack, a reaction support, a tensioning nut, a locking nut, and a device base; a heating plate and a temperature control system are provided inside the environmental chamber, and a sensor connecting line lead-out hole is provided at the bottom of the outside of the environmental chamber; the environmental chamber is arranged on the top of the device base.

2. A stress relaxation testing device for a wound fiber reinforced composite material according to claim 1, characterized in that: The special test sample has an X- and Y-axis symmetrical structure. The material of the special test sample is a fiber-reinforced resin-based composite material. The fiber-reinforced resin-based composite material includes glass fiber, carbon fiber and many other different types of fiber materials. The special test specimens were prepared by filament winding using a unidirectional plate mould with rounded edge transitions.

3. The stress relaxation testing device for a wound fiber reinforced composite material according to claim 1, characterized in that: The flexible strain sensor is provided with sensor lead wires, which include lower lead wires and upper lead wires; The flexible strain sensors are distributed in the middle layer or surface layer of the multi-layer winding in the thickness direction of the special test sample and are located in the middle of the width direction of the special test sample; two flexible strain sensors are symmetrically embedded on both sides of the center line of the annular structure of the special test sample; The flexible strain sensors are distributed on the straight section of the special test sample, and the embedded portion of the flexible strain sensor is greater than 70% of the length of the straight section of the special test sample.

4. The stress relaxation testing device for a wound fiber reinforced composite material according to claim 1, characterized in that: The stretching clamp is divided into a fixed stretching clamp and a movable stretching clamp. Both the fixed stretching clamp and the movable stretching clamp are composed of a clamp body and a roller pin inserted into a hole of the clamp body. The clamp body is provided with a first bottom hole.

5. A stress relaxation testing device for a wound fiber reinforced composite material according to claim 4, characterized in that: The diameter of the roller pin of the tensile fixture is smaller than the inner arc size of the special test sample, and the width of the special test sample is smaller than the reserved width of the fixture body.

6. A stress relaxation testing device for a filament winding fiber reinforced composite material according to claim 5, characterized in that: The fixed stretching fixture and the movable stretching fixture are arranged inside the environmental chamber; the fixed stretching fixture is fixedly connected to the bottom of the environmental chamber, and the movable stretching fixture is combinedly connected to the stretching screw through a connecting cap.

7. A stress relaxation testing device for a filament winding fiber reinforced composite material according to claim 6, characterized in that: The stretching screw is a hollow structure with a threaded structure on its outer surface; the upper part of the environmental chamber is provided with a hole-shaped slideway that matches the outer circle of the clamp base of the movable stretching clamp, and the top of the hole-shaped slideway is provided with an axial force meter base for installing the axial force meter, and the axial force meter is connected to the lower steel plate of the reaction force bracket; the reaction force bracket is composed of an upper steel plate, a lower steel plate, and studs with threads at both ends.

8. The stress relaxation testing device for a wound fiber reinforced composite material according to claim 7, characterized in that: A locking nut is arranged on the lower steel plate of the reaction support, and the upper steel plate of the reaction support is connected to the bottom of the hollow jack; the tension screw passes through the middle hole of the axial force meter, the reaction support and the hollow jack, and the upper end of the tension screw is connected to the movable part of the hollow jack through the tension nut.

9. The stress relaxation testing device for a wound fiber reinforced composite material according to claim 1, characterized in that: The device base includes a bottom plate, and a second bottom hole matching the sensor connection line lead-out hole is provided at the contact point between the bottom plate and the sensor connection line lead-out hole; a wire outlet groove is provided at the bottom of the bottom plate, and one end of the wire outlet groove is connected and penetrated with the second bottom hole.

10. A stress relaxation test method for a wound fiber reinforced composite material as claimed in claims 1 to 9, characterized in that: The following steps are involved: Step S1, loosen the locking nut, unload the hollow jack, unscrew the tensioning nut, and adjust the upper and lower positions of the tensioning screw according to the length of the special test sample; Step S2, extract the roller pins of the fixed tensile fixture and the movable tensile fixture, pass through the ring structure of the test sample and then insert into the hole of the fixture body; first complete the installation of the special test sample at the end of the fixed tensile fixture, and then move the movable tensile fixture to fix the movable tensile fixture and the test sample; Step S3, the lower lead wire of the sensor is led out through the first bottom hole of the clamp body, the sensor connection wire lead hole at the bottom of the environmental chamber, the second bottom hole of the device base, and the lead groove; the upper lead wire is led out to the external measuring device through the center hole of the stretching screw to determine the strain data of the sample; Step S4, tighten the tensioning nut, adjust the upper and lower positions of the tensioning screw, ensure that the movable tensioning fixture enters the upper slideway of the environmental chamber, and at the same time ensure that the roller pins of the movable tensioning fixture and the fixed tensioning fixture are in the same direction; Step S5, after tightening the tension nut, preload it through the hollow jack, the movable part of the hollow jack moves upward to drive the tension screw to move, so that the movable tension fixture moves upward, and the test sample is tensioned; Step S6, the tensile load on the specially made test sample is transmitted to the axial force meter in the form of reaction force through the hollow jack and the reaction force bracket, and the current tensile load is read out by the axial force meter; Use the tension nut to fine-tune the tensile load to zero under given load conditions; Step S7, determine the prestress and test environment temperature to be applied to the special test sample according to the test requirements, use the hollow jack to continue loading to the required load, and then use the locking nut to firmly lock the tensile screw and the steel plate under the reaction support; Step S8, fix the total strain of the test sample, record the current readings of the axial force gauge and the strain measurement system, and realize the stress change monitoring of the special test sample under given strain conditions.

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