Vacuum-assisted preparation device and method for preparing thermosetting resin microdroplet debonding sample

Abstract

The invention discloses a preparation device and method for vacuum-assisted preparation of a thermosetting resin microdroplet debonding sample, the preparation device for vacuum-assisted preparation of the thermosetting resin microdroplet debonding sample comprises an upper mold, a clamping assembly and a lower mold, the end face of one side of the upper mold is provided with a glue injection port, the lower mold is matched with the upper mold, and the clamping assembly is matched with the upper mold. The clamping assembly is located on the end face of the bottom of the upper die and fixedly connected to a pair of opposite end faces of the lower die, the clamping assembly comprises multiple sets of clamping blocks, limiting grooves are formed in the multiple sets of clamping blocks, springs are arranged in the limiting grooves, and matched die cavities are formed in the upper die and the lower die. The sample preparation stability is good. The mold is adopted for preparing the sample, the surface performance of the sample can be improved, surface defects can be reduced, meanwhile, the size of the microdroplet can be accurately controlled, the roundness meeting the requirement can be prepared according to the method even if the models of the carbon fibers are different, the sample preparation stability is good, and the sample preparation efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-droplet debonding sample preparation, and particularly relates to a preparation device and method for vacuum-assisted preparation of thermosetting resin micro-droplet debonding samples. Background Art

[0002] The micro-droplet debonding method is a commonly used method for testing the interfacial strength of single fibers of thermosetting resins. The specific operation is to apply a matrix solution or sol on a single fiber filament, and after curing, micro-droplets are formed. By applying a pair of scrapers on both sides of the micro-droplets and loading along the fiber axis, a shearing force is generated to detach the micro-droplets from the fiber filament, and the maximum load during the process is recorded. Combining the micro-droplet length and fiber diameter, the interfacial shear strength is obtained using a formula.

[0003] The axisymmetry of the specimen morphology and the resin uniformity are the most direct influencing factors on the interfacial micro-mechanical properties, directly affecting the measurement of the interfacial shear strength. The "sphere" shape is the most ideal model, so that when the micro-droplet sphere contacts the blade, the forces on both sides are balanced, and the value of the measured maximum load is more accurate. Usually, due to the characteristics of the material itself and the influence of artificial sample preparation, semi-circular regions will be formed at both ends of the resin microsphere after the resin matrix infiltrates the fiber, and the ideal "sphere" shape cannot be achieved. An overly large semi-circular region will affect the measurement of the embedding length, resulting in errors in the measurement of the embedding length and directly affecting the measurement of the shear strength. In addition, the phenomenon of uneven resin distribution during the sample preparation process, where the resin matrix around the fiber is larger on one side and smaller on the other side, and the "burr" phenomenon on the surface of the resin microsphere will directly affect the final test results, with large data discreteness. Therefore, the preparation quality of the micro-droplet sample directly affects the accuracy of the test.

[0004] Patent Invention CN 117804871 B discloses a curing device for basalt fiber micro-droplet debonding samples. By driving the micro-droplet mold to rotate using a driving mechanism, the photosensitive resin located in the micro-droplet mold is evenly distributed in the micro-droplet cavity under the action of centrifugal force. At the same time, a photosensitive light source is used to continuously and evenly irradiate the photosensitive resin in the rotating micro-droplet mold to improve the roundness of the micro-droplet sphere of the micro-droplet sample after curing. Although this method can prepare micro-droplets with a relatively high roundness, the operation is relatively complex, and the relationship between the transverse diameter of the micro-droplet sphere, the fiber diameter, and the embedding length of the fiber in the micro-droplet is not clear. If the embedding length of the fiber in the micro-droplet is too large, the debonding force required for the test will be greater than the tensile strength of the fiber, resulting in the fiber being broken before the micro-sphere is debonded. At the same time, it cannot be too small, and it is necessary to ensure that the volume fraction of the resin matrix is above 98%. Otherwise, the micro-droplet will be dissimilated and contrary to the spherical shape and fail, bringing certain uncertainties to the curing molding. At the same time, through rotation and centrifugal action, it is impossible to ensure a tight combination between the fiber and the resin interface, and small air bubbles are likely to be generated at the fiber and resin, affecting the result of the interfacial shear strength.

[0005] The information disclosed in this background section is only intended to enhance the overall understanding of the background of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0006] The object of the present invention is to provide a preparation device and method for vacuum-assisted preparation of thermosetting resin microdroplet debonding samples, which can solve the above problems.

[0007] To achieve the above object, the technical solutions provided by a specific embodiment of the present invention are as follows:

[0008] The preparation device for vacuum-assisted preparation of thermosetting resin microdroplet debonding samples includes an upper mold, a clamping assembly, and a lower mold. A glue injection port is provided on one end face of the upper mold. The lower mold is matched with the upper mold and is located at the bottom end face of the upper mold. The clamping assembly is fixedly connected to a pair of opposite end faces of the lower mold. The clamping assembly includes multiple groups of clamping blocks, and limiting grooves are provided in each of the multiple groups of clamping blocks, and springs are provided inside the limiting grooves.

[0009] In one or more embodiments of the present invention, the glue injection port is a threaded hole.

[0010] In one or more embodiments of the present invention, matching mold cavities are provided on both the upper mold and the lower mold, and the mold cavities are cylindrical linear structures.

[0011] In one or more embodiments of the present invention, a plurality of positioning bosses are evenly distributed on one end face of the upper mold, and positioning holes matching the positioning bosses are provided on the lower mold.

[0012] In one or more embodiments of the present invention, glue injection pipes matching the glue injection port are provided on both the upper mold and the lower mold. Microdroplet holes matching the glue injection port are provided on the end face where the upper mold and the lower mold are in contact. A vacuum pump connected to the glue injection pipe is installed on the bottom end face of the lower mold, and the glue injection port, the microdroplet holes, and the glue injection pipes are connected and communicated.

[0013] In one or more embodiments of the present invention, a plurality of first bolt holes are provided on the clamping assembly, and second threaded holes matching the first bolt holes are provided on the lower mold. The clamping assembly is fixed to one end face of the lower mold by screwing bolts through the first bolt holes and the second threaded holes.

[0014] In one or more embodiments of the present invention, the size of the microdroplet holes depends on the fiber embedding length L and the microdroplet diameter d. The fiber embedding length L and the microdroplet diameter d can be determined according to the following formula:

[0015] Wherein, d is the droplet diameter, df is the fiber diameter, L is the fiber embedding length, Fmax is the maximum tensile force value at which droplet debonding occurs under the tensile action of the specimen, P is the single-filament strength of the fiber, π is the pi, and the values of the droplet diameter d and the fiber embedding length L are approximately equal. is the ceiling function, is the floor function.

[0016] In one or more embodiments of the present invention, a semicircular tubular rubber sleeve is adhesively bonded to the inner end face of the mold cavity, and the inner diameter of the rubber sleeve is smaller than the fiber diameter.

[0017] In one or more embodiments of the present invention, the size of the glue injection pipe is larger than the size of the mold cavity.

[0018] A preparation method for vacuum-assisted preparation of a thermosetting resin droplet debonding sample includes the following steps:

[0019] S1. Preparation of fiber single filaments:

[0020] Select a carbon fiber model and measure the fiber diameter df;

[0021] Cut a carbon fiber tow that is longer than the length of the sample preparation mold, and then separate the single filaments.

[0022] S2. Determination of the single-filament strength of the fiber:

[0023] Measure the single-filament strength of the fiber as P.

[0024] S3. Determine the specific parameters of the sample preparation mold

[0025] Using a sample preparation device, confirm the size of the droplet hole:

[0026] S4. Preparation of droplet samples

[0027] Using a sample preparation device, fix the clamping assembly on both end faces of the lower mold, apply a release agent to the droplet holes of the upper mold and the lower mold respectively, then take a carbon fiber single filament and place it in the mold cavity, fix both ends of the lower mold through the clamping assembly, perform mold clamping through the positioning holes and positioning bosses, open the vacuum pump and the glue injection port, start pouring the resin, the resin flows to the droplet hole through the glue injection pipe, after the resin completely infiltrates the droplet hole, close the glue injection port, keep the vacuum for a period of time and then close the vacuum pump, cure according to the resin curing conditions, and finally demold to take out the carbon fiber droplet sample for testing.

[0028] Compared with the prior art, the preparation device and method for vacuum-assisted preparation of a thermosetting resin droplet debonding sample of the present invention have the following benefits:

[0029] 1) Good sample preparation stability: Using a mold to prepare samples can improve the surface properties of the samples, reduce surface defects, and accurately control the size of microdroplets. Even if different types of carbon fibers are used, circularity that meets the requirements can be prepared according to the method in the present invention. The sample preparation has good stability and high efficiency.

[0030] 2) High test repeatability: The vacuum condition can greatly eliminate interface defects and resin matrix defects. The method is fixed and the operation is simple. When the test personnel master this method proficiently, even if different test personnel operate, samples can be prepared in batches, and the discreteness of test data BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is a schematic structural diagram of a device for preparing a debonded sample of thermosetting resin microdroplets by vacuum assistance in an embodiment of the present invention;

[0033] Figure 2 It is a sectional view of a device for preparing a debonded sample of thermosetting resin microdroplets by vacuum assistance in an embodiment of the present invention;

[0034] Figure 3 For Figure 2 Schematic structural diagram of part A;

[0035] Figure 4 It is a schematic structural diagram of the upper mold in an embodiment of the present invention;

[0036] Figure 5 It is a schematic structural diagram of the lower mold in an embodiment of the present invention;

[0037] Figure 6 It is a schematic structural diagram of the clamping assembly in an embodiment of the present invention;

[0038] Figure 7 It is a schematic structural diagram of the sample in an embodiment of the present invention;

[0039] Figure 8 It is a comparison table of the sample preparation effects of debonded microdroplet samples.

[0040] Main reference numeral description:

[0041] 1. Upper mold; 2. Lower mold; 3. Clamping assembly; 4. Glue injection port; 5. First bolt hole; 6. Second threaded hole; 7. Microdroplet hole; 8. Mold cavity; 9. Positioning hole; 10. Positioning boss; 11. Clamping block; 12. Limiting groove; 13. Vacuum pump; 14. Glue injection pipeline; 15. Sample. Detailed implementation manners

[0042] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] As Figure 1 shown, the preparation device and method for vacuum-assisted preparation of thermosetting resin microdroplet debonding samples in an embodiment of the present invention can improve the surface performance of the samples, reduce surface defects, and at the same time can accurately control the microdroplet size. Even if the carbon fiber models are different, circularity that meets the requirements can be prepared according to the method in the present invention, and the sample preparation has good stability and high efficiency. The vacuum condition can greatly eliminate interface defects and resin matrix defects. With a fixed method, when the test personnel master this method proficiently, even if different test personnel operate, samples can be prepared in batches, and the discreteness of the test data is small.

[0044] As Figure 1 shown, the preparation device for vacuum-assisted preparation of thermosetting resin microdroplet debonding samples includes an upper mold 1, a lower mold 2 and a clamping assembly 3. A glue injection port 4 is provided on one end face of the upper mold 1, and the glue injection port 4 is located on the middle end face of the upper mold 1.

[0045] The glue injection port 4 is a threaded hole, which is convenient for quick connection with the glue injection joint.

[0046] The lower mold 2 is matched with the upper mold 1 and is located on the bottom end face of the upper mold 1. Matching mold cavities 8 are provided on both the upper mold 1 and the lower mold 2, and the mold cavity 8 is a cylindrical linear structure.

[0047] Furthermore, a rubber sleeve in the shape of a semi-cylindrical tube is bonded to the inner end face of the mold cavity 8, and the inner diameter of the rubber sleeve is smaller than the fiber diameter

[0048] The size of the glue injection pipeline 14 is larger than the size of the mold cavity 8

[0049] As Figures 2 - 5 shown, both the upper mold 1 and the lower mold 2 are provided with glue injection pipelines 14 that are matched with the glue injection port 4, and the diameter of the glue injection pipeline 14 is smaller than the diameter of the glue injection port 4.

[0050] The end faces where the upper mold 1 and the lower mold 2 are fitted are provided with micro-droplet holes 7 that match the injection ports 4. A vacuum pump 13 connected to the injection pipeline 14 is installed at the bottom end face of the lower mold 2, and the injection ports 4, the micro-droplet holes 7, and the injection pipeline 14 are connected and communicated with each other.

[0051] It should be noted that the size of the micro-droplet hole 7 depends on the fiber embedding length L and the micro-droplet diameter d. If the fiber embedding length L in the micro-droplet is too large, the debonding force required for testing will be greater than the strength P of the fiber, resulting in the fiber being broken before the microsphere debonds. At the same time, it cannot be too small, and it must ensure that the volume fraction of the resin matrix is above 98%. Otherwise, the micro-droplet will be dissimilated and fail contrary to the spherical shape. Therefore, the fiber embedding length L and the micro-droplet diameter d can be determined according to the following formula:

[0052] Among them, d is the micro-droplet diameter, df is the fiber diameter, L is the fiber embedding length, Fmax is the maximum tensile force value when the micro-droplet debonds under tensile action of the specimen, P is the single-filament strength of the fiber, and π is the pi. The values of the micro-droplet diameter d and the fiber embedding length L are approximately equal. is the ceiling function, is the floor function.

[0053] As Figures 2 - 6 shown, the clamping assembly 3 is fixedly connected to a pair of opposite end faces of the lower mold 2. The clamping assembly 3 includes multiple groups of clamping blocks 11. Limiting grooves 12 are provided inside the multiple groups of clamping blocks 11, and springs are provided inside the limiting grooves 12. The clamping blocks 11 are made of rubber material. Under the push of the springs in the limiting grooves 12, the clamping blocks 11 clamp and fix the two ends of the straightened carbon fiber tow, thereby preventing the carbon fiber tow from being coiled and loosened in the mold cavity 8.

[0054] Furthermore, multiple first bolt holes 5 are provided on the clamping assembly 3, and second threaded holes 6 that match the multiple first bolt holes 5 are provided on the lower mold 2. Bolts are threadedly connected to the first bolt holes 5 and the second threaded holes 6. The clamping assembly 3 is fixed to a pair of opposite end faces of the lower mold 2 by threadedly connecting bolts to the first bolt holes 5 and the second threaded holes 6.

[0055] Specifically, it is fixed to both ends of the lower mold 2 through the clamping assembly 3, and the mold is closed by the cooperation of the positioning holes 9 and the positioning bosses 10.

[0056] Multiple positioning bosses 10 are evenly distributed on one side end face of the upper mold 1. Positioning holes 9 that match the positioning bosses 10 are provided on the lower mold 2, and the injection ports 4 are clamped to the inner wall end face of the positioning holes 9.

[0057] As Figures 1 - 5 shown, a preparation method for a vacuum-assisted preparation of a thermosetting resin micro-droplet debonding sample includes the following steps:

[0058] S1. Preparation of single fiber filaments:

[0059] Select the carbon fiber type and measure the fiber diameter df;

[0060] Cut a carbon fiber bundle longer than the length of the sample preparation mold, and then separate the single filaments.

[0061] S2. Determination of the strength of single fiber filaments:

[0062] Measure the strength of the single fiber filament as P.

[0063] S3. Determine the specific parameters of the sample preparation mold

[0064] Use the sample preparation device to confirm the size of the microdroplet hole 7:

[0065] S4. Preparation of microdroplet samples

[0066] Use the sample preparation device to fix the clamping assembly 3 on both end faces of the lower mold 2. Apply a release agent to the microdroplet holes 7 of the upper mold 1 and the lower mold 2 respectively. Then take a carbon fiber single filament and place it in the mold cavity 8. Fix both ends of the lower mold 2 through the clamping assembly 3. Through the mutual clamping and matching of the positioning holes 9 and the positioning bosses 10 on the upper mold 1 and the lower mold 2, close the mold. Open the vacuum pump 13 and the injection port 4, and start pouring the resin. The resin flows through the injection pipeline 14 to the microdroplet hole 7. After the resin completely infiltrates the microdroplet hole 7, close the injection port 4. Keep the vacuum for a period of time and then close the vacuum pump 13. Cure according to the resin curing conditions. Finally, demold and take out the carbon fiber microdroplet sample for testing.

[0067] Example 1

[0068] S1. Preparation of carbon fiber single filaments:

[0069] Select T300 carbon fiber and measure the carbon fiber diameter df = 6.75 μm;

[0070] Cut a carbon fiber bundle about 13 cm long, and then ultrasonically separate the single filaments with an ethanol aqueous solution.

[0071] S2. Determination of the strength of single fiber filaments:

[0072] Measure the strength of the single fiber filament as P = 0.66 MPa.

[0073] S3. Determine the specific parameters of the sample preparation mold

[0074] The sample preparation mold includes an upper mold 1, a lower mold 2, a clamping assembly 3 and an injection port 4. The upper mold 1 and the lower mold 2 are symmetric structures, and are internally provided with microdroplet holes 7 and a mold cavity 8. The size of the microdroplet hole 7 mainly depends on the carbon fiber embedding length L and the microdroplet diameter d, and can be determined according to the following formula:

[0075] Therefore, the diameter of the micro-droplet holes in the sample preparation mold is 60 μm, the diameter of the mold cavity is 8 μm, and the diameter of the resin injection pipe 14 is 9 μm.

[0076] S4. Preparation of micro-droplet samples

[0077] First, fix the clamping assembly 3 on both sides of the lower mold 2 with bolts, and apply a mold release agent to the micro-droplet holes 7 of the upper mold 1 and the lower mold 2 respectively. Then, take a single carbon fiber filament and pass it through both ends of the clamping assembly 3 and straighten it. At this time, under the push of the spring in the limiting groove 12, the clamping blocks 11 clamp and fix both ends of the straightened carbon fiber bundle, thus preventing the carbon fiber bundle from winding and loosening in the mold cavity 8. Select a rubber sleeve with an inner diameter of 6 μm and paste it on the mold cavity 8. Then, achieve the mold closing of the mold through the cooperation of the positioning holes 9 and the positioning bosses 10. Then, perform vacuum degassing on the required resin, and then turn on the vacuum pump 13 and the resin injection port 4 to start pouring the resin. The resin flows through the resin injection pipe 14 to the micro-droplet holes 7. Wait until the resin completely infiltrates the micro-droplet holes 7, close the resin injection port 4, keep the vacuum for a period of time, and then turn off the vacuum pump 13. Cure according to the resin curing conditions, and finally demold. Take out the first bolt hole 5 [i.e., as Figure 6 shown] for testing, and repeat the sample preparation 10 times.

[0078] Comparative Example 1:

[0079] Select T300 carbon fiber, cut a carbon fiber bundle about 13 cm long, then ultrasonically separate the single filaments with an ethanol aqueous solution and fix them on a hollow rack. Then, dip a small amount of resin with a glass rod and drop it on the carbon fiber single filaments. Finally, place the rack in an oven for curing. After completion, take out the carbon fiber micro-droplet samples for testing, and repeat the sample preparation 10 times.

[0080] Compare the sample preparation effects of the micro-droplet debonding samples in Example 1 of the present invention and Comparative Example 1, and the obtained results are as Figure 8 shown. By observing the test results of the examples and the comparative examples, it is found that although the existing sample preparation method is easy to operate, the sample preparation effect is poor, the repeatability is low, the requirements for personnel operation are high, and it is very difficult to prepare samples with high roundness and good interfaces. The present invention uses a sample preparation mold for sample preparation, and can obtain samples with regular shapes and high roundness. At the same time, through vacuum-assisted resin perfusion, samples with good fiber and resin interfaces can be obtained, which are uniform and bubble-free, with good sample preparation stability and high efficiency. Even if different experimental personnel operate, samples can be prepared in batches.

[0081] As can be seen from the above technical solutions, a method for vacuum-assisted preparation of a thermosetting resin fiber microdroplet debonding sample provided by the present invention has the following advantages: it provides a sample preparation method with controllable and reliable process. The sample preparation mold has a simple structure and is easy to operate. It can produce samples with regular shapes and high vacuum degrees. At the same time, according to the different diameters of fiber types, the mold parameter microdroplet hole size is changed, that is, the fiber embedding length and microdroplet diameter are adjusted, and then the microdroplet roundness is adjusted. This not only solves the problem of microdroplet roundness, but also clarifies the relationship between the microdroplet diameter, fiber diameter and fiber embedding length in the microdroplet. At the same time, the problem of the interface combination between the fiber and the resin is solved by vacuum-assisted resin perfusion. The repeatability is relatively high, greatly reducing the operation requirements for the test personnel, improving the sample preparation efficiency, and at the same time improving the stability of sample preparation, making the test data less discrete. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0082] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0083] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A vacuum-assisted preparation device for preparing thermosetting resin droplet debonding samples, characterized in that: Included are: The upper mold has a glue injection port on one end surface; The lower mold is matched with the upper mold and is located at the bottom end surface of the upper mold; The clamping assembly is fixedly connected to a pair of opposite end surfaces of the lower mold. The clamping assembly includes multiple groups of clamping blocks. Limiting grooves are arranged in the multiple groups of clamping blocks. Springs are arranged inside the limiting grooves.

2. The vacuum-assisted preparation device for thermosetting resin droplet debonding samples according to claim 1, characterized in that: The glue injection port is a threaded hole.

3. The vacuum-assisted preparation device for thermosetting resin droplet debonding samples according to claim 2, characterized in that: The upper mold and the lower mold are both provided with matching mold cavities, and the mold cavities are cylindrical linear structures.

4. The vacuum-assisted preparation device for thermosetting resin droplet debonding sample according to claim 3, characterized in that: A plurality of positioning bosses are evenly distributed on one end surface of the upper mold, and a positioning hole matching the positioning bosses is opened on the lower mold.

5. The vacuum-assisted preparation device for thermosetting resin droplet debonding sample according to claim 1 or 4, characterized in that: The upper mold and the lower mold are both provided with glue injection pipes matching the glue injection port, the end faces where the upper mold and the lower mold are in contact are provided with micro-drop holes matching the glue injection port, the bottom end face of the lower mold is equipped with a vacuum pump connected to the glue injection pipe, and the glue injection port, micro-drop holes and glue injection pipe are connected.

6. The vacuum-assisted preparation device for thermosetting resin droplet debonding samples according to claim 5, characterized in that: The clamping assembly is provided with a plurality of first bolt holes, the lower mold is provided with second threaded holes matching the first bolt holes, and the clamping assembly is fixed to one side end surface of the lower mold through threaded connection bolts of the first bolt holes and the second threaded holes.

7. The vacuum-assisted preparation device for thermosetting resin droplet debonding samples according to claim 6, characterized in that: The size of the microdroplet hole depends on the fiber embedding length L and the microdroplet diameter d, which can be determined according to the following formula: Where d is the droplet diameter, df is the fiber diameter, L is the fiber embedding length, Fmax is the maximum tensile force value of the droplet debonding under the tensile action of the sample, P is the single fiber strength of the fiber, π is the circumference, and the droplet diameter d and the fiber embedding length L are approximately equal. To round up, To round down.

8. The vacuum-assisted preparation device for thermosetting resin droplet debonding samples according to claim 7, characterized in that: A semi-circular rubber sleeve is bonded to the inner end surface of the mold cavity, and the inner diameter of the rubber sleeve is smaller than the fiber diameter.

9. The vacuum-assisted preparation device for thermosetting resin droplet debonding samples according to claim 7, characterized in that: The size of the glue injection pipeline is larger than the size of the mold cavity.

10. A method for preparing a sample of thermosetting resin droplet debonding by vacuum-assisted preparation, using the preparation device of the sample of thermosetting resin droplet debonding by vacuum-assisted preparation as claimed in claim 1, characterized in that: The steps include: S1. Preparation of fiber monofilament: Select the carbon fiber model and measure the fiber diameter df; Cutting carbon fiber bundles longer than the length of the sample preparation mold and then separating the single fibers; S2. Determination of fiber monofilament strength: The single-filament strength of the fiber is measured as P; S3. Determine the specific parameters of the sample making mold: Using the sample preparation device, confirm the size of the microdroplet hole: S4. Microdroplet sample preparation: The sample preparation device is used to fix the clamping assembly on the two side end faces of the lower mold, and the release agent is applied to the micro-droplet holes of the upper mold and the lower mold respectively. Then, a carbon fiber monofilament is put into the mold cavity, and the two ends of the lower mold are fixed by the clamping assembly. The mold is closed through the positioning holes and positioning bosses, and the vacuum pump and the injection port are turned on to start pouring resin. The resin flows to the micro-droplet holes through the injection pipe. After the resin completely infiltrates the micro-droplet holes, the injection port is closed. After maintaining the vacuum for a period of time, the vacuum pump is turned off, and the resin is cured according to the resin curing conditions. Finally, the mold is demolded and the carbon fiber micro-droplet sample is taken out for testing.

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