Test method and test system

Abstract

Provided are a test method and a test system. The test method is configured to test the tensile property of a prepreg (51). The test method comprises: performing film applying, i.e., covering each of two side surfaces of the prepreg (51) with a film (52); performing sealing, i.e., sealing a composite body formed by the prepreg (51) and films (52) on two sides of the prepreg (51); performing vacuumizing, i.e., vacuumizing covered spaces formed by the films (52) on the two sides of the prepreg (51), such that the prepreg (51) is attached to the films (52) on the two sides; performing stretching, i.e., applying a stretching force to the composite body at a preset temperature and a preset pressure; and performing measurement, i.e., measuring a shearing angle and a shearing force during a stretching process.

Description

Test method and test system

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on March 15, 2024, with application number 202410296850.4. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of material performance testing, for example, to a testing method and a testing system. Background Art

[0003] In-plane shear performance is generally considered to be the main deformation mechanism of prepregs. Good shear performance prevents the material from wrinkling or buckling during the process of changing from a flat structure to a three-dimensional structure (for example, in the molding process of a double-curvature structural part).

[0004] The shear performance data of prepregs is a necessary input for simulating the prepreg preforming process using simulation methods. In addition, testing the forming performance of prepregs is also beneficial for understanding the deformation behavior of the material during the forming process and making reasonable selection based on the deformation performance of the material, thereby improving the quality of the formed structural parts.

[0005] At present, the shear performance of prepregs under a certain molding temperature and a certain pressure is relatively different from the shear performance under room temperature and normal pressure mode. Moreover, the data measured at room temperature and normal pressure does not have sufficient reference value for the simulation analysis of the preforming process and the analysis of the deformation mechanism of the preforming process. In addition, the viscosity of the prepreg resin is low at high temperature, and the thickness of the clamping end of the prepreg is easily changed under the action of pressure, which causes the sample to slip. Summary of the Invention

[0006] The present application provides a testing method and a testing system for realizing the tensile performance test of prepreg under the dual action of a certain temperature and a certain pressure, while ensuring that the prepreg is stably clamped during the stretching process, thereby improving the accuracy of the prepreg tensile test.

[0007] The present application provides a test method for performing tensile property testing on prepreg, including:

[0008] Laminating, covering the surfaces of both sides of the prepreg with membranes;

[0009] Sealing: sealing the prepreg and the composite formed by the membranes on both sides of the prepreg;

[0010] Vacuuming the covering space formed by the membranes on both sides of the prepreg to make the prepreg fit the membranes on both sides;

[0011] stretching, applying a stretching force to the composite at a preset temperature and a preset pressure;

[0012] Measure the shear angle and shear force during stretching.

[0013] As an optional solution of a testing method, before the vacuuming, the method further includes: pre-pressing the composite body at a first preset temperature for a first preset time.

[0014] The present application also provides a testing system, based on the testing method described in any of the above schemes, the testing system comprising a prepreg, a double-layer diaphragm, a sealing strip, an upper fixture, a lower fixture, an environmental chamber, and a vacuum tube;

[0015] The double-layer membrane covers both sides of the prepreg, and the prepreg and the membranes on both sides form a composite body;

[0016] The sealing strip is configured to seal the composite body along the periphery of the double-layer membrane;

[0017] The upper clamp is configured to clamp the first end of the composite body;

[0018] The lower clamp is configured to clamp the second end of the composite body;

[0019] The upper fixture, the lower fixture and the composite body are all placed in the environmental box, and the temperature in the environmental box is variable;

[0020] The vacuum tube is configured such that a first end is inserted into the interior of the composite body and a second end is connected to a vacuum pump.

[0021] As an optional solution for a testing system, the upper clamp includes a first clamping plate and a second clamping plate; the first clamping plate and the second clamping plate are respectively provided with a plurality of first mounting holes, the first end of the complex is placed between the first clamping plate and the second clamping plate, and the first clamping plate and the second clamping plate are configured to clamp the first end of the complex by means of threaded fasteners passing through the first mounting holes.

[0022] As an optional solution of the testing system, the first clamping plate or the second clamping plate is configured to connect to a first end of a traction rod, and a second end of the traction rod is connected to a traction end of a mechanical testing machine.

[0023] As an optional solution for the testing system, a through hole is provided on the complex at a position corresponding to the first mounting hole, and the first clamping plate and the second clamping plate are configured to pass through the first mounting hole and the through hole through threaded fasteners to clamp the first end of the complex.

[0024] As an optional solution for the testing system, the lower clamp includes a third clamping plate and a fourth clamping plate; the third clamping plate and the fourth clamping plate are respectively provided with a plurality of second mounting holes, the second end of the complex is placed between the third clamping plate and the fourth clamping plate, and the third clamping plate and the fourth clamping plate are configured to pass through the second mounting holes by threaded fasteners to clamp the second end of the complex.

[0025] As an optional solution of the testing system, the third clamping plate or the fourth clamping plate is configured to connect to a first end of a mounting rod, and a second end of the mounting rod is connected to a fixed end of a mechanical testing machine.

[0026] As an optional solution of the testing system, an observation window is provided on the door of the environmental chamber, and the observation window is configured so that a camera can photograph the tensile state of the composite through the observation window.

[0027] As an optional solution of a test system, the diaphragm is a silicone rubber membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a flow chart of a testing method provided in an embodiment of the present application;

[0029] FIG2 is a schematic structural diagram of an upper clamp provided in an embodiment of the present application;

[0030] FIG3 is a schematic structural diagram of a lower clamp provided in an embodiment of the present application;

[0031] FIG4 is a schematic diagram of structural parameters of a prepreg before deformation provided in an embodiment of the present application;

[0032] FIG5 is a schematic diagram of structural parameters of a prepreg after deformation provided in an embodiment of the present application;

[0033] FIG6 is a schematic diagram of a tracking line for marking a prepreg provided in an embodiment of the present application;

[0034] FIG7 is a schematic diagram of a test system provided in an embodiment of the present application;

[0035] FIG8 is a schematic diagram of a composite formed by a prepreg and membranes on both sides of the prepreg provided in an embodiment of the present application;

[0036] FIG9 is a schematic diagram of a clamp holding a complex body provided in an embodiment of the present application;

[0037] FIG10 is a schematic diagram of an upper clamp connected to a traction rod and a lower clamp connected to a mounting rod provided in an embodiment of the present application.

[0038] In the figure: 1. Upper clamp; 11. First clamping plate; 12. Second clamping plate; 2. Lower clamp; 21. Third clamping plate; 22. Fourth clamping plate; 3. Pull rod; 4. Mounting rod; 51. Prepreg; 52. Diaphragm; 53. Sealing strip; 54. Environmental chamber; 55. Observation window; 56. Vacuum tube; 57. Vacuum pump; 58. Camera; 61. First mounting hole; 62. Second mounting hole; 63. Through hole; 64. Threaded fastener. DETAILED DESCRIPTION

[0039] The present application will be described below with reference to the accompanying drawings and embodiments. It will be understood that the specific embodiments described herein are intended only to illustrate the present application and are not intended to limit the present application. In addition, for ease of description, only some or all of the structures relevant to the present application are shown in the accompanying drawings.

[0040] In the description of this application, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0041] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first feature being in direct contact with the second feature, or may include the first feature being in contact with the second feature through another feature between them instead of being in direct contact. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0042] In the description of this embodiment, terms such as "upper," "lower," "right," and "left" are used to refer to positions or locations based on those shown in the accompanying drawings. These terms are intended solely to facilitate description and simplify operation, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0043] Referring to FIG. 1 , this embodiment relates to a testing method for testing the tensile properties of prepregs. Specifically, the method includes the following steps:

[0044] S1, laminating, covering the surfaces of both sides of the prepreg with a film;

[0045] S2. Sealing: sealing the prepreg and the membranes on both sides of the prepreg;

[0046] S3, vacuuming the covering space formed by the membranes on both sides of the prepreg to make the prepreg fit the membranes on both sides;

[0047] S4, stretching, applying a tensile force to the composite formed by the prepreg and the membranes on both sides of the prepreg at a preset temperature and a preset pressure;

[0048] S5. Measure the shear angle and shear force.

[0049] Prepregs are a composite of continuous fibers or fabrics impregnated with a resin matrix under strictly controlled temperature conditions. They serve as an intermediate material in the preparation of composite materials. Because prepreg resin has low viscosity at high temperatures, the thickness of the prepreg clamping end can easily change under pressure, causing specimen slippage during tensile testing.

[0050] In this method, a diaphragm is covered on both sides of the prepreg. The diaphragm can be a thin silicone rubber diaphragm. Since the prepreg needs to be completely covered by the diaphragm, the area of ​​the diaphragm actually used is larger than the surface area of ​​the prepreg. When the diaphragm is bonded to the prepreg, the outer periphery of the diaphragm can completely cover the outer periphery of the prepreg. The gap formed by the double-layer diaphragm is sealed at the outer periphery of the diaphragm to completely wrap the prepreg. At this time, there is not enough bonding pressure between the prepreg and the diaphragm. The coating space formed by the double-layer diaphragm is vacuumed and the double-layer diaphragm is tightly bonded to the prepreg using air pressure. The test temperature and pressure are adjusted to the preset temperature and preset pressure respectively, and a tensile test is performed on both ends of the composite formed by the prepreg and the double-layer diaphragm. The shear force and shear angle of the prepreg stretching process and the change process are obtained through the test.

[0051] In this embodiment, since the friction coefficient between the surfaces of the diaphragm and the prepreg is very small, during the tensile test, the effect of the friction force introduced into the diaphragm on the tensile force value of the prepreg is also relatively small. Therefore, the tensile test of the composite can relatively truly reflect the tensile properties of the prepreg itself. On the other hand, the clamping end acts on the diaphragm, and the diaphragm and the prepreg have become a complete composite, which avoids the situation where the viscosity of the prepreg decreases under high temperature and the thickness changes under pressure. It can effectively prevent the entire composite from slipping when clamped, thereby ensuring the stable progress of the tensile test.

[0052] In summary, this test method can realize the tensile performance test of prepreg under the dual action of a certain temperature and a certain pressure. Compared with the data measured at room temperature and normal pressure, the test data obtained by this method has more sufficient reference value for the simulation analysis of the preforming process and the analysis of the deformation mechanism of the preforming process. At the same time, the composite can ensure that the prepreg is stably clamped during the stretching process, thereby improving the accuracy and stability of the prepreg tensile test.

[0053] Optionally, before the vacuuming step, the composite body is pre-pressed at a first preset temperature for a first preset time.

[0054] In this embodiment, when the vacuum degree reaches 1 atmosphere, the pressure is maintained at 40° C. for 10 minutes to pre-compact the prepreg laminate, which can improve the overall stiffness of the prepreg laminate and facilitate subsequent operations.

[0055] Referring to Figures 2, 3, and 7, this embodiment also relates to a testing system comprising a prepreg 51, a double-layer diaphragm 52, a sealing strip 53, an upper fixture 1, a lower fixture 2, an environmental chamber 54, and a vacuum tube 56. The double-layer diaphragm 52 covers both sides of the prepreg 51, forming a composite body with the prepreg 51 and the diaphragms 52 on both sides. The sealing strip 53 seals the composite body along the outer periphery of the double-layer diaphragm 52, as shown in Figure 8. The upper fixture 1 clamps a first end of the composite body; the lower fixture 2 clamps a second end of the composite body opposite to the first end of the composite body. The upper fixture 1, the lower fixture 2, and the composite body are all located in the environmental chamber 54, where the temperature inside the environmental chamber 54 is variable. The first end of the vacuum tube 56 is inserted into the composite body, and the second end of the vacuum tube 56, opposite to the first end of the vacuum tube 56, is connected to a vacuum pump 57.

[0056] In this embodiment, the prepreg 51 is cut to the required size; space for sealant is reserved on both sides of the diaphragm 52. The ends of the composite of the diaphragm 52 and prepreg 51 are clamped by an upper clamp 1 and a lower clamp 2, respectively. The upper clamp 1 is the stretching end, and the lower clamp 2 is the fixed end. The upper clamp 1 pulls the composite upward. The upper clamp 1, the lower clamp 2, and the composite are completely placed inside an environmental chamber 54, which is set to the temperature and pressure of the composite's stretching environment. At the same time, vacuum tubes 56 are introduced on both sides of the composite, and a vacuum pump 57 is used to evacuate the interior of the composite. After reaching the predetermined pressure, the vacuum pump 57 is turned off and the pressure is maintained for 15 minutes without leakage to ensure the sealing between the diaphragms 52.

[0057] Based on the above test method, this system can ensure that the tensile test of the prepreg 51 is stably completed under a certain temperature and a certain pressure. At the same time, the composition structure of this test system is relatively simple, which saves test costs.

[0058] Optionally, as shown in Figure 9, the upper clamp 1 includes a first clamping plate 11 and a second clamping plate 12; a plurality of first mounting holes 61 are respectively provided on the first clamping plate 11 and the second clamping plate 12, the first end of the complex is placed between the first clamping plate 11 and the second clamping plate 12, and the threaded fastener 64 passes through the first mounting hole 61 so that the first clamping plate 11 and the second clamping plate 12 clamp the first end of the complex.

[0059] As shown in Figure 9, the lower clamp 2 includes a third clamping plate 21 and a fourth clamping plate 22; a plurality of second mounting holes 62 are respectively provided on the third clamping plate 21 and the fourth clamping plate 22, and the second end of the complex is placed between the third clamping plate 21 and the fourth clamping plate 22, and the threaded fastener 64 passes through the second mounting hole 62 so that the third clamping plate 21 and the fourth clamping plate 22 clamp the second end of the complex.

[0060] In this embodiment, the structures of the upper clamp 1 and the lower clamp 2 are basically the same, and the two ends of the complex are stably clamped by double-plate pressure clamping. The structures of the upper clamp 1 and the lower clamp 2 are simple, and the locking method using multiple sets of threaded fasteners 64 is simple and easy to operate.

[0061] As shown in Figure 10, one end of the upper clamp 1 holds the composite body, and the other end is connected to a traction rod 3. Optionally, one of the first clamping plate 11 and the second clamping plate 12 is connected to the first end of the traction rod 3, and the second end of the traction rod 3, opposite the first end of the traction rod 3, is connected to the traction end of the mechanical testing machine.

[0062] In this embodiment, the traction end of the mechanical testing machine acts on the traction rod 3, which is screwed to the first clamping plate 11 or the second clamping plate 12, so that the traction rod 3 drives the entire upper clamp 1 to pull the complex upward.

[0063] As shown in Figure 10, one end of the lower clamp 2 holds the composite body, and the other end is connected to a mounting rod 4. Optionally, one of the third clamping plate 21 and the fourth clamping plate 22 is connected to the first end of the mounting rod 4, and the second end of the mounting rod 4, opposite the first end, is connected to the fixed end of the mechanical testing machine.

[0064] In this embodiment, the fixed end of the mechanical testing machine is connected to the mounting rod 4 , and the mounting rod 4 is configured to fix the lower clamp 2 .

[0065] Optionally, a through hole 63 is provided on the composite body at a position corresponding to the first mounting hole 61 , and a threaded fastener 64 can pass through the through hole 63 and the first mounting hole 61 to enable the first clamping plate and the second clamping plate to clamp the first end of the composite body.

[0066] In this embodiment, by providing a through hole 63 at a position of the composite body corresponding to the first mounting hole 61 and allowing the threaded fastener 64 to pass through the through hole 63 , the composite body can be stably positioned relative to the upper fixture 1 , thereby improving operability.

[0067] Optionally, an observation window 55 is provided on the door of the environmental chamber 54 , and a camera 58 can be used to photograph the stretched state of the composite through the observation window 55 .

[0068] To monitor the changes in the prepreg fibers during the test, a camera 58 mounted outside the environmental chamber 54 records the entire stretching process of the prepreg stack. The camera 58 is connected to a processor signal and uses the relevant software of the computing platform to process and record the data.

[0069] The following content is used to introduce the calculation principle of the prepreg tensile performance test model.

[0070] In the case of double diaphragm pressure, the diaphragm material and prepreg deform together during the test without sliding against each other. Therefore, the friction between the two is not considered. The force to stretch the prepreg stack can be calculated using the following formula: F be =F t -F d (1)

[0071] Where F t is the force value recorded by the mechanical testing machine, F d F is the force value obtained by stretching the diaphragm material under the same conditions; be is the force to stretch the prepreg laminate.

[0072] For fabric materials, according to the Pin-Jointed Net (PJN) theory, the specimen can be divided into three regions: A, B, and C, as shown in Figures 4 and 5. If there is no intra-layer slip in the specimen, region C is a pure shear region, and the shear angle can be extracted from this region. The shear angle in region B is always half of that in region C, while the shear angle in region A remains unchanged during deformation. In Figure 4, Lc is the side length of the square in region C and remains unchanged during deformation. Assuming that the fiber angle of the prepreg is ±45° before deformation, the fiber angle during deformation can be calculated using formula (2).

[0073] Where H0 is the initial effective length, W0 is the initial width of the specimen, and d is the displacement during the test.

[0074] The shear angle γ during the eccentric tensile test can be calculated using formula (3).

[0075] Since there is no shear limit restriction of fabric material during the shearing process of unidirectional prepreg, its shearing behavior is quite different from that of fabric, that is, formula (2) does not hold. At the same time, in the actual material forming process, the shearing behavior of the prepreg laminate is affected by pressure, temperature and stretching rate. Therefore, this application proposes an improved off-axis stretching shear angle analysis model. The calculation formula for the off-axis stretching shear angle of unidirectional prepreg under pressure, temperature and stretching rate can be defined as: γ=90°-2θ=90°-2(K1d+K2d 2 ) (4)

[0076] Where K1 and K2 are model parameters. K1 and K2 are obtained by nonlinear fitting of the shear angle-displacement curve of the specimen at different temperatures, pressures, and stretching rates. K1 and K2 are functions related to temperature T (K), stretching rate V (mm / min), and pressure P (MPa): K1 = a1 + a2T + a3V + a4P (5) K2 = b1 + b2T + b3V + b4P (6)

[0077] Wherein a1, a2, a3, a4, b1, b2, b3 and b4 are model parameters, among which a1, a2, a3 and a4 can be obtained by linear fitting of K1 and temperature / stretching rate / pressure curve, and b1, b2, b3 and b4 can be obtained by linear fitting of K2 and temperature / stretching rate / pressure curve.

[0078] Since the data directly obtained from the test is axial force, not shear force, it is necessary to extract the shear force. From formula (4), we can know that:

[0079] Where, is the shear rate, is the stretching rate.

[0080] During the test, F be Acting on the specimen, it causes deformation in areas B and C. Therefore, the following formula can be obtained:

[0081] Where A γ is the initial area of ​​zone C, is the initial area of ​​area B, C s (γ) is the torque required to produce γ shear deformation per unit area. To produce per unit area The torque required for shear deformation. Substituting formula (9) and formula (10) into formula (8), we can obtain:

[0082] Unit area torque C s and shear force F nor The relationship is: C s (γ)=F nor (γ)·cos(γ) (12)

[0083] therefore,

[0084] It can be found from formula (13) that (13) depends on its own value at γ / 2, that is, In addition, the lack of a boundary condition makes it difficult to solve these equations. In order to obtain a more accurate shear force, an analytical expression for the relationship between shear force and shear angle is proposed, assuming that there is a power function relationship between the normalized shear force and shear angle: nor (γ)=Aγ B +C (15)

[0085] Substituting formula (15) into formula (14), we can obtain the following formula:

[0086] Because F nor (0) = 0, so the parameter C in formula (15) is 0. From formula (4)

[0087] You can get:

[0088] Therefore, formula (16) can be transformed into:

[0089] The shear angle γ obtained from the test is compared with its corresponding F be Substituting the values ​​into formula (18) can obtain the parameter values ​​of the model.

[0090] Shear stress F sh (γ) can be obtained by normalizing the shear force F nor (γ) divided by the initial thickness of the specimen (h) yields:

[0091] The shear modulus G(γ) is determined by the derivative of the shear stress with respect to the shear angle:

[0092] This application also provides a test method for performing tensile property testing on prepreg, including:

[0093] S11, cutting, cutting the prepreg and the membrane according to the actual required size;

[0094] The diaphragm size is adjusted based on the prepreg size. Its width should be larger than the width of the clamp at the end, and space should be reserved for sealant on both sides. In addition, this application requires the prepreg and clamp to be fixed with threaded fasteners, so the diaphragm needs to be punched according to the size of the threaded fasteners to facilitate subsequent installation.

[0095] S12, prepreg laying, completing the prepreg laying according to the designed layer to obtain a prepreg stack;

[0096] S13, pre-compacting the prepreg, placing the prepreg stack into a vacuum bag for pre-compacting;

[0097] Among them, when the vacuum degree reaches 1 atmosphere, the pressure is maintained at 40°C for 10 minutes to pre-compact the above-mentioned prepreg laminate to improve the overall stiffness of the prepreg laminate and facilitate subsequent operations.

[0098] S14, marking the sample tracking line, dividing a preset number of deformation areas on the prepreg laminate;

[0099] As shown by the white line on the sample in Figure 6, it is convenient to track and record the changes in the fiber angle. The relationship between the effective length H0 of the sample and the width W0 of the sample is: H0>2×W0×tan(α) (21)

[0100] Where α is the fiber angle.

[0101] S15, laminating, covering both sides of the prepreg laminate with a film;

[0102] S16, sealing, sealing the composite formed by the prepreg laminate and the membranes on both sides of the prepreg;

[0103] S17, evacuating the space formed by the membranes on both sides of the prepreg laminate to laminate the prepreg laminate to the membranes on both sides;

[0104] S18, installing, installing the complex on a fixture;

[0105] S19, stretching, applying a stretching force to the composite at a preset temperature and a preset pressure;

[0106] S20. Measure the shear angle and shear force during the stretching process.

Claims

1. A test method for performing tensile property testing on a prepreg, comprising: Laminating, covering the surfaces of both sides of the prepreg with membranes; Sealing: sealing the prepreg and the composite formed by the membranes on both sides of the prepreg; Vacuuming the covering space formed by the membranes on both sides of the prepreg to make the prepreg and the membranes on both sides fit together; stretching, applying a stretching force to the composite at a preset temperature and a preset pressure; Measure the shear angle and shear force during stretching.

2. The testing method according to claim 1, further comprising, before the vacuuming: The composite is pre-extruded at a first preset temperature for a first preset time.

3. A test system, based on the test method according to any one of claims 1 and 2, comprising a prepreg (51), a double-layer diaphragm (52), a sealing strip (53), an upper fixture (1), a lower fixture (2), an environmental chamber (54), and a vacuum tube (56); The double-layer membrane (52) covers both sides of the prepreg (51), and the prepreg (51) and the membranes (52) on both sides form a composite body; The sealing strip (53) is configured to seal the composite body along the outer periphery of the double-layered membrane (52); The upper clamp (1) is configured to clamp the first end of the composite body; The lower clamp (2) is configured to clamp the second end of the composite body; The upper fixture (1), the lower fixture (2) and the composite body are all placed in the environmental box (54), and the temperature in the environmental box (54) is variable; The vacuum tube (56) is configured such that a first end is inserted into the interior of the composite body and a second end is connected to a vacuum pump (57).

4. The test system according to claim 3, wherein: The upper clamp (1) includes a first clamping plate (11) and a second clamping plate (12); a plurality of first mounting holes (61) are respectively provided on the first clamping plate (11) and the second clamping plate (12); the first end of the composite body is placed between the first clamping plate (11) and the second clamping plate (12); the first clamping plate (11) and the second clamping plate (12) are configured to clamp the first end of the composite body through a threaded fastener (64) passing through the first mounting hole (61).

5. The test system according to claim 4, wherein: The first clamping plate (11) or the second clamping plate (12) is configured to connect to the first end of the traction rod (3), and the second end of the traction rod (3) is connected to the traction end of the mechanical testing machine. The test system according to claim 4 , wherein: A through hole (63) is provided on the composite body at a position corresponding to the first mounting hole (61), and the first clamping plate (11) and the second clamping plate (12) are configured to pass through the first mounting hole (61) and the through hole (63) via a threaded fastener (64) to clamp the first end of the composite body.

7. The test system according to claim 3, wherein: The lower clamp (2) includes a third clamping plate (21) and a fourth clamping plate (22); a plurality of second mounting holes (62) are respectively provided on the third clamping plate (21) and the fourth clamping plate (22); the second end of the composite body is placed between the third clamping plate (21) and the fourth clamping plate (22); the third clamping plate (21) and the fourth clamping plate (22) are configured to pass through the second mounting holes (62) through threaded fasteners (64) to clamp the second end of the composite body.

8. The test system according to claim 7, wherein: The third clamping plate (21) or the fourth clamping plate (22) is configured to connect to the first end of the mounting rod (4), and the second end of the mounting rod (4) is connected to the fixed end of the mechanical testing machine.

9. The test system according to claim 3, wherein: An observation window (55) is provided on the door of the environmental box (54), and the observation window (55) is configured so that a camera (58) can photograph the stretched state of the complex through the observation window (55).

10. The test system according to claim 3, wherein: The diaphragm (52) is a silicone rubber membrane.

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