CN119321956A - Device and method for testing stress relaxation of winding-formed fiber reinforced composite material - Google Patents
Device and method for testing stress relaxation of winding-formed fiber reinforced composite material Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/18—Performing tests at high or low temperatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0017—Tensile
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
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- G01N2203/0226—High temperature; Heating means
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
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Abstract
本发明属于树脂基纤维增强复合材料力学性能测试技术领域，具体公开了一种缠绕成型纤维增强复合材料应力松弛测试装置及方法，该装置包括特制测试样、应变测量系统、载荷加载装置、环境箱；本发明采用上述一种缠绕成型纤维增强复合材料应力松弛测试装置及方法，通过该创新性方法和装置，能够更全面地捕捉和分析外部环境作用下缠绕纤维增强复合材料的应力松弛行为，进而对纤维增强复合材料预应力缠绕结构在长期服役过程中的应力松弛特性进行测量，可解决缠绕成型纤维增强复合材料预应力结构的应力松弛的测量问题。
The present invention belongs to the technical field of mechanical property testing of resin-based fiber-reinforced composite materials, and specifically discloses a stress relaxation testing device and method for a filament-wound fiber-reinforced composite material, the device comprising a specially made test specimen, a strain measurement system, a load loading device, and an environmental chamber; the present invention adopts the above-mentioned stress relaxation testing device and method for a filament-wound fiber-reinforced composite material, and through the innovative method and device, it is possible to more comprehensively capture and analyze the stress relaxation behavior of the filament-wound fiber-reinforced composite material under the action of an external environment, and then measure the stress relaxation characteristics of a prestressed filament-wound structure of the fiber-reinforced composite material during long-term service, which can solve the problem of measuring the stress relaxation of the prestressed structure of the filament-wound fiber-reinforced composite material.
Description
Technical Field
The invention belongs to the technical field of mechanical property testing of resin-based fiber-reinforced composite materials, and particularly relates to a stress relaxation testing device and method for a winding-forming fiber-reinforced composite material.
Background
The high specific strength, high specific modulus properties of polymer matrix composites make them an indispensable role in aerospace, energy, sports, automotive industry and various infrastructures. The winding forming process is an important mode for forming the fiber reinforced composite material rotary structure, and is used for forming typical prestress structures such as a carbon fiber sheath of a high-speed motor rotor, a high-pressure composite gas cylinder and the like in recent years. The prestress of the winding structure provides positive pressure for the internal components, playing an important role in protecting the internal structure.
In the long-term use process of the fiber-reinforced composite material, the viscoelasticity of the polymer matrix can cause the long-term mechanical property of the fiber-reinforced composite material to change, creep and stress relaxation occur, and the prestress of the component is further attenuated to be lower than a safety threshold value. The deterioration of the preload force not only affects the reliability of the parts, but may also pose a threat to the safety of the overall system. Therefore, the residual pretightening force of the polymer matrix composite in the use process is obtained by measuring the change of the long-term mechanical property of the fiber reinforced composite in various complex service environments, and is the key for evaluating the service life of the prestressed material or the structure. The method has important significance for improving the overall performance and economic benefit of the product, and provides scientific basis for further research and development of more advanced composite materials.
Chinese patent No. CN106568650a provides a method for testing stress relaxation of carbon fiber composite material ribs, chinese patent No. CN111766164A provides a combined testing device for fatigue-stress relaxation of prestressed ribs. The above patent is mainly oriented to composite material ribs formed by pultrusion, the structure of a test sample is in a plate/strip shape, the deformation of the test sample in the test process needs to be ensured to be a fixed value in the stress relaxation test, and the deformation caused by the slip influence of the clamping end of the tested sample in the actual long-term test process is very difficult to control, so that the measurement of the stress relaxation performance of the fiber reinforced composite material is difficult, and therefore, the above patent fails to clearly improve and control the influence of the end change. Chinese invention patent CN108801768A provides a testing method for stress relaxation of fiber-oriented flexible material, chinese invention patent CN113654779a discloses a testing method for stress relaxation suitable for taper structure, chinese invention patent CN102353588A and chinese invention patent CN102650581a respectively disclose a testing device and a testing method for stress relaxation of rubber and sheet spring. The above-described apparatus and method are difficult to apply to wound fiber reinforced composite structures.
At present, a testing device and a testing method for stress relaxation characteristics of a winding-forming pre-stress fiber reinforced composite material are lacked, and meanwhile, the problem that strain is difficult to accurately capture due to end clamping position sliding in stress relaxation measurement of a plate and strip sample in the conventional general fiber reinforced composite material testing method is solved. Therefore, a device and a method for testing stress relaxation of a winding fiber reinforced composite material have to be developed in the art, and the problems can be effectively solved.
Disclosure of Invention
The invention aims to provide a stress relaxation testing device and method for a winding fiber reinforced composite material, and by the innovative method and device, the stress relaxation behavior of the winding fiber reinforced composite material under the action of an external environment can be more comprehensively captured and analyzed, so that the stress relaxation characteristic of a prestress winding structure of the fiber reinforced composite material in a long-term service process is measured, and the problem of measuring the stress relaxation of the prestress structure of the winding fiber reinforced composite material can be solved.
The invention provides a stress relaxation testing device for a winding-forming fiber reinforced composite material, which comprises a special testing sample, a strain measuring system, a load loading device and an environment box, wherein the whole special testing sample structure is annular and consists of a straight line and an excessive arc, the strain measuring system consists of a flexible strain sensor embedded with the special testing sample and an external measuring device, the load loading device consists of a stretching clamp, a stretching screw, a shaft force meter, a hollow jack, a counter-force bracket, a stretching nut, a locking nut and a device base, a heating plate and a temperature control system are arranged in the environment box, a sensor connecting wire leading-out hole is formed in the bottom end of the outer part of the environment box, and the environment box is arranged at the top of the device base.
Preferably, the special test sample is in an X-axis and Y-axis symmetrical structure, the special test sample material is a fiber reinforced resin matrix composite material, the fiber reinforced resin matrix composite material comprises glass fibers and carbon fibers of various different types, and the preparation process of the special test sample is fiber winding molding and is prepared by a unidirectional plate die with edge arc transition.
Preferably, the flexible strain sensor is provided with a sensor lead-out wire, and the sensor lead-out wire comprises a lower lead-out wire and an upper lead-out wire;
The flexible strain sensors are distributed in the thickness direction of the special test sample and are positioned in the middle of the width direction of the special test sample, and two flexible strain sensors are symmetrically embedded in two sides of the central line of the annular structure of the special test sample;
The flexible strain sensor is distributed on the straight line part of the special test sample, and the embedded part of the flexible strain sensor is more than 70% of the length of the straight line section of the special test sample.
Preferably, the stretching clamp is divided into a fixed stretching clamp and a movable stretching clamp, wherein the fixed stretching clamp and the movable stretching clamp are respectively 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.
Preferably, the diameter size of the roller pin of the stretching clamp is smaller than the inner circular arc size of the special test sample, and the width of the special test sample is smaller than the reserved width of the clamp body.
The fixed stretching clamp and the movable stretching clamp are arranged in the environment box, the fixed stretching clamp is fixedly connected with the bottom of the environment box, and the movable stretching clamp is connected with the stretching screw rod in a combined mode through the connecting cap.
The stretching screw is of a hollow structure, the outer surface of the stretching screw is provided with a thread structure, the upper part of the environment box is provided with a hole-type slideway matched with the outer circle of the clamp body base of the movable stretching clamp, the top of the hole-type slideway is provided with a shaft force gauge base for installing a shaft force gauge, the shaft force gauge is connected with a lower steel plate of a counterforce support, and the counterforce support consists of an upper steel plate, a lower steel plate and studs with threads at two ends.
Preferably, a lock nut is arranged on the lower steel plate of the counter-force support, the upper steel plate of the counter-force support is connected with the bottom of the hollow jack, a stretching screw rod penetrates through the axial force meter, the counter-force support and the middle hole of the hollow jack, and the upper end part of the stretching screw rod is connected with the movable part of the hollow jack through the stretching nut.
Preferably, the device base comprises a bottom plate, a second bottom hole matched with the sensor connecting wire leading-out hole is formed in the contact position of the bottom plate and the sensor connecting wire leading-out hole, a wire outlet groove is formed in the bottom of the bottom plate, and one end of the wire outlet groove is connected and communicated with the second bottom hole.
A stress relaxation test method for a winding formed fiber reinforced composite material comprises the following steps:
Step S1, loosening a lock nut, unloading a hollow jack, unscrewing a tensioning nut, and adjusting the upper and lower positions of a tensioning screw according to the length of a special test sample;
S2, extracting roller pins of the fixed stretching clamp and the movable stretching clamp, inserting the roller pins into a clamp body hole site after penetrating through the annular structure of the test sample;
S3, leading out a lower leading-out wire of the sensor to an external measuring device through a first bottom hole of the clamp body, a leading-out hole of a sensor connecting wire at the bottom of the environment box, a second bottom hole of the device base and a wire outlet groove, and leading out an upper leading-out wire to the external measuring device through a central hole of the stretching screw for determining strain data of a sample;
s4, screwing a tensioning nut, adjusting the upper and lower positions of a tensioning screw, ensuring that the movable tensioning clamp enters an upper slideway of the environment box, and simultaneously ensuring that the roller pin directions of the movable tensioning clamp and the fixed tensioning clamp are consistent;
s5, pre-loading is carried out through a hollow jack after the tensioning nut is screwed, and a movable part of the hollow jack moves upwards to drive the tensioning screw rod to move so that the movable tensioning clamp moves upwards, and the test sample is tensioned;
S6, transmitting the tensile load received by the special test sample to the axial force meter in a counterforce mode through the hollow jack and the counterforce bracket, and reading the current tensile load through the axial force meter;
S7, determining the prestress and the test environment temperature required to be applied by the special test sample according to the test requirement, and firmly locking the stretching screw with the lower steel plate of the counter-force bracket by using the locking nut after the special test sample is continuously loaded to the required load by using the hollow jack;
And S8, fixing the total strain of the test sample, recording the indication number of the current axial force meter and the strain measurement system, and realizing the stress change monitoring of the special test sample under the given strain condition.
The device and the method for testing the stress relaxation of the winding fiber reinforced composite material have the beneficial effects that:
(1) The invention utilizes the fiber winding process characteristics, adopts a closed ring-shaped test sample structure consisting of a straight line and an end transitional circular arc, and is matched with a stretching clamp consisting of a roller pin and a clamp body, so that the clamping end part can not slide in the measuring process;
(2) The invention designs a loading device for a test sample with a closed annular structure, a movable clamp can move up and down along a slide rail under the unloading condition, a special test sample is quickly installed and removed, an internal sensor wiring is reasonably arranged on the premise of ensuring a loading path by using a hollow stretching screw, a reaction force bracket is used for accurately measuring the stretching load by using a reaction force, an environment box is integrated in structure and function, an upper slideway provides accurate radial positioning for the movable clamp, the stretching screw and the like, the box body is also regarded as a part of the reaction force bracket, and meanwhile, the environment box has a high-temperature function and can realize the response of the stress relaxation characteristic of the special test sample to temperature. The locking nut firmly locks the movable stretching clamp and the counter-force bracket, so that the long-term stability of the total strain of the test sample is realized;
(3) In order to realize accurate measurement of the strain of the test sample, the invention is embedded into the flexible strain sensor channel winding layer in the process of winding and forming the test sample, and can realize in-situ measurement of the strain;
(4) The invention is helpful to optimize the winding forming process of the composite material through the innovative method and the device, and can also improve the reliability and the service life of the composite material in various engineering applications, thereby providing assistance for the application of the winding forming of the composite material in high-speed motor rotors, high-pressure gas cylinders and the like.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a test device for stress relaxation of a wound fiber reinforced composite material and an embodiment of the method of the present invention;
FIG. 2 is a schematic diagram of a device and method for testing stress relaxation of a fiber reinforced composite material according to an embodiment of the present invention;
FIG. 3 is a schematic view of a roll pin structure of an embodiment of a device and method for testing stress relaxation of a wound fiber reinforced composite material according to the present invention;
FIG. 4 is 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 in accordance with the present invention;
FIG. 5 is a schematic view of a device base structure of an apparatus for testing stress relaxation of a wound fiber reinforced composite material according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a device and method for testing stress relaxation of a fiber reinforced composite material according to an embodiment of the present invention;
FIG. 7 is a schematic diagram showing the connection of a stretching screw and a movable stretching clamp in an embodiment of a device and a method for testing stress relaxation of a winding fiber reinforced composite material according to the present invention.
Reference numerals
1. The special test sample comprises a special test sample, an environment box, a 3, a stretching screw rod, a 4, an axial force meter, a 5, a hollow jack, a 6, a counterforce support, a 7, a stretching nut, a 8, a locking nut, a 9, a device base, a 10, a heating plate, a 11, a sensor connecting wire leading-out hole, a 12, a lower leading-out wire, a 13, an upper leading-out wire, a 14, a fixed stretching clamp, a 15, a movable stretching clamp, a 16, a clamp body, a 17, a roller pin, a 18, a first bottom hole, a 19, a connecting cap, a 20, a hole-type slideway, a 21, an axial force meter base, a 22, a bottom plate, a 23, a second bottom hole, a 24, a wire outlet groove and a 25, and a flexible strain sensor.
Detailed Description
The technical scheme of the invention is further described below through the attached drawings and the embodiments.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.
As shown in fig. 1, a device for testing stress relaxation of a winding-forming fiber reinforced composite material comprises a special test sample 1, a strain measurement system, a load loading device and an environment box 2.
As shown in fig. 6, the whole structure of the special test sample is annular and consists of a straight line and an excessive arc, and the special test sample 1 is in an X-axis and Y-axis symmetrical structure. The special test sample 1 is made of fiber reinforced resin matrix composite materials, wherein the fiber reinforced resin matrix composite materials comprise glass fibers and carbon fibers and are of various different types of fiber materials. The preparation process of the special test sample 1 is fiber winding molding, and the special test sample is prepared by a unidirectional plate die with edge arc transition.
The strain measurement system consists of a flexible strain sensor 25 embedded with a special test sample 1 and an external measurement device, and monitors 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.
The flexible strain sensors 25 are distributed in the thickness direction of the special test sample 1 in the multi-layer winding middle layer or surface layer and are positioned in the middle of the width direction of the special test sample 1. Two flexible strain sensors 25 are symmetrically embedded at two sides of the central line of the annular structure of the special test sample 1.
The flexible strain sensors 25 are distributed on the straight line part of the special test sample 1, and the embedded part of the flexible strain sensors 25 is larger than 70% of the length of the straight line section of the special test sample 1. The type, the measuring range and the sensitivity of the sensor can be selected according to different application scenes, and the external measuring device is matched with the type of the sensor.
The load loading device consists of a stretching clamp, a stretching screw 3, a shaft force meter 4, a hollow jack 5, a counter-force bracket 6, a stretching nut 7, a locking nut 8 and a device base 9, and provides a given stretching force for a test sample and measures the pulling force. The environmental chamber 2 provides a variable high temperature environment for the test samples, and some of the components are part of the loading device.
As shown in fig. 2 to 3, the stretching jigs are divided into a fixed stretching jig 14 and a movable stretching jig 15, the fixed stretching jig 14 and the movable stretching jig 15 are each composed of a jig body 16 and a roller pin 17 inserted into a hole of the jig body 16, and the jig body 16 is provided with a first bottom hole 18.
The diameter of the roller pin 17 of the stretching clamp is slightly smaller than the inner circular arc 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. Ensuring that no offset occurs when mounted on the stretching clamp.
The fixed stretching jig 14 and the movable stretching jig 15 are provided inside the environmental chamber 2. The fixed stretching clamp 14 is fixedly connected with the bottom of the environment box 2, and the movable stretching clamp 15 is combined and connected with the stretching screw 3 through the connecting cap 19.
As shown in fig. 4, a heating plate 10 and a temperature control system are arranged inside the environment box 2, and a sensor connecting wire leading-out hole 11 is arranged at the bottom end outside the environment box 2. The stretching screw 3 has a hollow structure, and an outer surface thereof has a screw thread structure. Can freely rotate without affecting the orientation of the roller pin 17.
The upper part of the environment box 2 is provided with a hole-type slideway 20 matched with the outer circle of the base of the clamp body 16 of the movable stretching clamp 15, and the movable stretching clamp 15 can move in the hole-type slideway 20 at the upper part of the environment box 2 under the drive of the stretching screw 3. The top of the hole-type slideway 20 is provided with an axial force meter base 21 for installing an axial force meter 4, and the axial force meter 4 is connected with a lower steel plate of the counter-force bracket 6. The reaction bracket 6 consists of an upper steel plate, a lower steel plate and studs with threads at two ends.
And a locking nut 8 is arranged on the lower steel plate of the counter-force bracket 6, the relative position of the lower bottom plate 22 of the counter-force bracket 6 and the stretching screw 3 is locked, and the total strain of the test sample is fixed. The steel plate on the counter-force bracket 6 is connected with the bottom of the hollow jack 5. As shown in fig. 7, the tension screw 3 passes through the intermediate holes of the thrust meter 4, the reaction bracket 6 and the hollow jack 5, and the upper end portion of the tension screw 3 is connected to the movable portion of the hollow jack 5 by the tension nut 7. When the hollow jack 5 is loaded, the stretching screw rod 3 is driven to move upwards through the stretching nut 7, and meanwhile, the movable stretching clamp 15 is driven to move, so that the stretching load is applied. The tensile load is transmitted to the axial force meter 4 through the jack bottom and the counter-force bracket 6, and the tensile load is obtained by testing the counter-force. The tension nut 7 at the end of the tension screw 3 can finely adjust the tension load.
The environmental chamber 2 is provided on top of the device base 9. As shown in fig. 5, the device base 9 includes a bottom plate 22, and a second bottom hole 23 matching the sensor connection wire extraction hole 11 is provided at a contact position of the bottom plate 22 and the sensor connection wire extraction hole 11. The bottom of the bottom plate 22 is provided with a wire outlet groove 24, and one end of the wire outlet groove 24 is connected and communicated with the second bottom hole 23.
Examples
In this embodiment, the test sample is wound on the unidirectional plate mold with excessive edge arc by adopting a tension winding mode, and can be wound by adopting a wet method and a dry method, the optical fiber sensor is embedded after the test sample is wound to half of the total layer number, the outgoing line is reserved, then the test sample is wound to the complete thickness, and the test sample is demoulded and polished to a proper size.
A stress relaxation test method of a winding molding carbon fiber reinforced epoxy resin composite material for a high-speed motor sheath comprises the following steps:
Step S1, loosening the locking nut 8, unloading the hollow jack 5, unscrewing the tensioning nut 7, and adjusting the upper and lower positions of the tensioning screw rod 3 according to the length of the test sample.
Step S2, the roller pins 17 of the fixed stretching clamp 14 and the movable stretching clamp 15 are pulled out, pass through the annular structure of the test sample and then are inserted into the holes of the clamp body 16. The test sample is mounted at the end of the fixed stretching clamp 14, and then the movable stretching clamp 15 is moved to fix the movable stretching clamp 15 and the test sample.
Step S3, the lower outgoing line 12 of the sensor is led out through the first bottom hole 18 of the clamp body 16, the sensor connecting line leading-out hole 11 at the bottom of the environment box 2, the second bottom hole 23 of the device base 9 and the line outlet groove 24, and the upper outgoing line 13 is led out to an external measuring device through the central hole of the stretching screw 3 for determining the strain data of the sample.
And S4, screwing a tensioning nut 7, adjusting the upper and lower positions of the tensioning screw rod 3, ensuring that the movable tensioning clamp enters an upper slideway of the environment box 2, and simultaneously ensuring that the directions of roller pins 17 of the movable tensioning clamp and the fixed tensioning clamp 14 are consistent.
Step S5, after tightening the tensioning nut 7, preloading is carried out through the hollow jack 5, the movable part of the hollow jack 5 moves upwards to drive the tensioning screw rod 3 to move, the movable tensioning clamp 15 moves upwards, the test sample is tensioned, and the preloading ensures that the stress of the special test sample 1 in the follow-up test is uniform and controllable.
In step S6, the tensile load applied to the test sample is transmitted to the axial force meter 4 through the hollow jack 5 and the reaction force bracket 6 in a reaction force manner, and the current tensile load is read out by the axial force meter 4. The tensile load is fine-tuned to zero under given load conditions using the tensioning nut 7.
And S7, determining the prestress and the test environment temperature required to be applied by the special test sample 1 according to the test requirement, and firmly locking the stretching screw 3 and the steel plate under the counter-force bracket 6 by using the locking nut 8 after the hollow jack 5 is continuously loaded to the required load.
And S8, fixing the total strain of the test sample, recording the indication number of the current axial force meter 4 and the strain measurement system, and realizing the stress change monitoring of the test sample under the given strain condition.
The method used in this example is a test method for a specific test sample at room temperature. If the stress relaxation property test is performed at a high temperature, the first bottom holes 18 of the fixed drawing jig 14 and the movable drawing jig 15 are filled with the heat insulating material. The temperature control system of the environment box 2 is used for setting the test temperature, so that the environment box 2 is preloaded after reaching the preset temperature, and the rest steps are the same as those of the method for testing the special test sample 1 at normal temperature.
Therefore, the stress relaxation testing device and the stress relaxation testing method for the winding fiber reinforced composite material can more comprehensively capture and analyze the stress relaxation behavior of the winding fiber reinforced composite material under the action of external environment, further measure the stress relaxation characteristic of the prestress winding structure of the fiber reinforced composite material in the long-term service process, and solve the problem of measuring the stress relaxation of the prestress structure of the winding fiber reinforced composite material.
It should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted by the same, and the modified or substituted technical solution may not deviate from the spirit and scope of the technical solution of the present invention.
Claims (10)
1. A stress relaxation testing device for a winding-forming fiber reinforced composite material is characterized by comprising a special testing sample, a strain measuring system, a load loading device and an environment box, wherein the whole special testing sample structure is annular and consists of a straight line and an excessive arc, the strain measuring system consists of a flexible strain sensor embedded with the special testing sample and an external measuring device, the load loading device consists of a stretching clamp, a stretching screw, a shaft force meter, a hollow jack, a counter-force support, a stretching nut, a locking nut and a device base, a heating plate and a temperature control system are arranged in the environment box, a sensor connecting wire leading-out hole is formed in the bottom end of the outer portion of the environment box, and the environment box is arranged at the top of the device base.
2. The device for testing stress relaxation of winding-formed fiber-reinforced composite materials according to claim 1, wherein the special test sample is of an X-axis and Y-axis symmetrical structure, the special test sample material is a fiber-reinforced resin-based composite material, the fiber-reinforced resin-based composite material comprises glass fibers and carbon fibers of various different types, and the special test sample is prepared by a fiber winding forming process and is prepared by a unidirectional plate die with an edge arc transition.
3. The stress relaxation testing device for the winding-formed fiber reinforced composite material according to claim 1, wherein the flexible strain sensor is provided with a sensor lead-out wire, and the sensor lead-out wire comprises a lower lead-out wire and an upper lead-out wire;
The flexible strain sensors are distributed in the thickness direction of the special test sample and are positioned in the middle of the width direction of the special test sample, and two flexible strain sensors are symmetrically embedded in two sides of the central line of the annular structure of the special test sample;
The flexible strain sensor is distributed on the straight line part of the special test sample, and the embedded part of the flexible strain sensor is more than 70% of the length of the straight line section of the special test sample.
4. The device for testing stress relaxation of a winding-formed fiber reinforced composite material according to claim 1, wherein the stretching clamp is divided into a fixed stretching clamp and a movable stretching clamp, 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.
5. The device for testing stress relaxation of fiber reinforced plastic composite materials by winding according to claim 4, wherein the diameter of the roller pin of the stretching clamp is smaller than the inner circular arc of the special test sample, and the width of the special test sample is smaller than the reserved width of the clamp body.
6. The device for testing stress relaxation of winding formed fiber reinforced composite materials according to claim 5, wherein the fixed stretching clamp and the movable stretching clamp are arranged in the environment box, the fixed stretching clamp is fixedly connected with the bottom of the environment box, and the movable stretching clamp is combined and connected with the stretching screw rod through the connecting cap.
7. The stress relaxation testing device for the winding-forming fiber reinforced composite material is characterized in that a stretching screw is of a hollow structure, the outer surface of the stretching screw is provided with a threaded structure, a hole-type slide way matched with the outer circle of a clamp body base of a movable stretching clamp is arranged at the upper part of an environment box, a shaft force meter base is arranged at the top of the hole-type slide way, the shaft force meter is connected with a lower steel plate of a counterforce support, and the counterforce support consists of an upper steel plate, a lower steel plate and studs with threads at two ends.
8. The device for testing stress relaxation of winding-forming fiber reinforced composite materials according to claim 7, wherein a lock nut is arranged on a lower steel plate of the counter-force support, the upper steel plate of the counter-force support is connected with the bottom of the hollow jack, a stretching screw rod penetrates through a shaft force meter, the counter-force support and a middle hole of the hollow jack, and the upper end portion of the stretching screw rod is connected with a movable portion of the hollow jack through the tension nut.
9. The device for testing stress relaxation of winding-forming fiber reinforced composite materials according to claim 1, wherein the device base comprises a bottom plate, a second bottom hole matched with the sensor connecting wire leading-out hole is formed in the contact position of the bottom plate and the sensor connecting wire leading-out hole, a wire outlet groove is formed in the bottom of the bottom plate, and one end of the wire outlet groove is connected with the second bottom hole.
10. A method of testing the stress relaxation of a wound-formed fiber-reinforced composite material according to any one of claims 1-9, comprising the steps of:
Step S1, loosening a lock nut, unloading a hollow jack, unscrewing a tensioning nut, and adjusting the upper and lower positions of a tensioning screw according to the length of a special test sample;
S2, extracting roller pins of the fixed stretching clamp and the movable stretching clamp, inserting the roller pins into a clamp body hole site after penetrating through the annular structure of the test sample;
S3, leading out a lower leading-out wire of the sensor to an external measuring device through a first bottom hole of the clamp body, a leading-out hole of a sensor connecting wire at the bottom of the environment box, a second bottom hole of the device base and a wire outlet groove, and leading out an upper leading-out wire to the external measuring device through a central hole of the stretching screw for determining strain data of a sample;
s4, screwing a tensioning nut, adjusting the upper and lower positions of a tensioning screw, ensuring that the movable tensioning clamp enters an upper slideway of the environment box, and simultaneously ensuring that the roller pin directions of the movable tensioning clamp and the fixed tensioning clamp are consistent;
s5, pre-loading is carried out through a hollow jack after the tensioning nut is screwed, and a movable part of the hollow jack moves upwards to drive the tensioning screw rod to move so that the movable tensioning clamp moves upwards, and the test sample is tensioned;
S6, transmitting the tensile load received by the special test sample to the axial force meter in a counterforce mode through the hollow jack and the counterforce bracket, and reading the current tensile load through the axial force meter;
S7, determining the prestress and the test environment temperature required to be applied by the special test sample according to the test requirement, and firmly locking the stretching screw with the lower steel plate of the counter-force bracket by using the locking nut after the special test sample is continuously loaded to the required load by using the hollow jack;
And S8, fixing the total strain of the test sample, recording the indication number of the current axial force meter and the strain measurement system, and realizing the stress change monitoring of the special test sample under the given strain condition.
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