Self-repairing carbon fiber composite material and repairing method thereof

Abstract

The invention discloses a self-repairing carbon fiber composite material, which is characterized in that the self-repairing carbon fiber composite material comprises a plurality of carbon fiber bundles, the outer layers of the carbon fiber bundles are coated with silver coatings, composite material filling matrixes are filled among the carbon fiber bundles, and hot melting microcapsules are uniformly distributed in the composite material filling matrixes. According to the method, a large amount of manual operation is not needed, the repairing process is simplified, and the technical requirements for operators are reduced; the repair cost and complexity are obviously reduced, and inconvenience caused by repeated manual repair is also avoided; the reliability and the service life of the material are improved; the reliability and convenience of repairing are improved, and the performance stability and safety of the material in various complex environments are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of materials science, and particularly to a self-healing carbon fiber composite material and a repair method thereof. Background Art

[0002] Carbon fiber composite materials have the advantages of high specific strength, high specific modulus, and excellent designability, and are widely used in many cutting-edge fields such as aerospace, shipbuilding, consumer electronics, construction engineering, and robot manufacturing. However, during long-term service, carbon fiber composite materials are inevitably subject to structural damage and aging. This not only seriously threatens the structural stability of the composite materials, but also increases the maintenance cost of the materials. Therefore, there is an urgent need to develop a technical measure for intelligently repairing internal damage of carbon fiber composite materials.

[0003] Patent CN202110434907.9 discloses a device and method for repairing delamination damage of a carbon fiber reinforced thermosetting resin matrix composite material. This invention provides an efficient method for repairing delamination damage of a carbon fiber reinforced thermosetting resin matrix composite material. Compared with traditional repair methods such as patching, adhesive bonding patching, and mechanical connection patching, this method simplifies the repair process and reduces the repair cost. However, this method requires a large amount of manual operations, including ablation treatment, CT scan positioning, filling with thermoplastic resin, etc., which is relatively cumbersome and cannot achieve automated multiple repairs.

[0004] Patent CN201810768112.X discloses a method for repairing damaged areas of aircraft composite materials. This repair method improves the flatness and strength of the repair area by introducing heat-expandable sheets and is applicable to the repair of aircraft composite materials. However, this method also has some limitations, such as high equipment requirements, complex operation steps, and long curing time, etc.

[0005] Patent CN202410153026.3 discloses a method for repairing carbon fiber composite materials. This method ensures high-quality repair of damaged areas of carbon fiber composite materials through refined operations and strict tests. However, this method is relatively complex in operation, has high technical requirements for operators, requires a long curing time and high material costs. The entire repair process requires certain technical experience and professional knowledge, and it is difficult to implement for operators without relevant skills.

[0006] The existing patented technologies have the following deficiencies:

[0007] 1. Require complex manual operations: This method requires multiple steps of manual operations, such as ablation treatment, CT scan positioning, filling with thermoplastic resin, etc. The operation process is relatively cumbersome, increasing the operation difficulty and time cost.

[0008] 2. High equipment dependence: Specific equipment support is required, such as CT scanners, external power supplies, indenter components, etc., which increases the cost and complexity of repair.

[0009] 3. Certain technical threshold: The entire repair process requires certain technical experience and professional knowledge, which is difficult to implement for operators without relevant skills.

[0010] 4. Most techniques are methods for repairing obvious damages (i.e., damages that have been clearly discovered and visualized). However, for potential damages (i.e., damages that have not yet appeared or been discovered), there are certain limitations in these technical solutions. Summary of the Invention

[0011] In view of the deficiencies in the prior art, the present invention provides a self-healing carbon fiber composite material and a repair method thereof to solve the technical problems such as complex operation, high dependence, high technical threshold in the repair process, and limitations in the repair of potential damages in the prior art.

[0012] The present invention provides a self-healing carbon fiber composite material, including: several carbon fiber bundles, the outer layer of the carbon fiber bundles is wrapped with a silver-plated layer, a composite material filling matrix is filled between the carbon fiber bundles, and heat-melt microcapsules are uniformly distributed in the composite material filling matrix.

[0013] Further, the heat-melt microcapsule includes: a heat-melt film, a repair agent is wrapped inside the heat-melt film, and heat-expandable microspheres are uniformly distributed in the repair agent.

[0014] Further, two kinds of heat-melt microcapsules are uniformly distributed in the composite material filling matrix. Among them, the repair agent in one kind of heat-melt microcapsule is: medium-temperature thermosetting epoxy resin; the repair agent in the other kind of heat-melt microcapsule is: thiol.

[0015] Further, the mass ratio of the two heat-melt microcapsules is: 1:1.

[0016] Further, the diameter range of the heat-melt microcapsule is: 30 - 300 microns.

[0017] Further, the melting point range of the heat-melt film is: 65 - 110 °C.

[0018] Further, the excitation temperature range of the heat-expandable microspheres is: 80 - 200 °C.

[0019] The present invention also provides a repair method for the self-healing carbon fiber composite material, including the following steps:

[0020] Step 1: Cover the two end faces of the carbon fiber bundles in the self-healing carbon fiber composite with a conductive layer, and cover the remaining parts of the two end faces of the self-healing carbon fiber composite with an insulating layer;

[0021] Step 2: Connect an external constant power supply between the conductive layers at both ends of the self-healing carbon fiber composite;

[0022] Step 3: Linearly increase the current of the constant power supply within 1 - 2 minutes until the preset current value is reached for preheating the carbon fiber bundles;

[0023] Step 4: Maintain the current of the constant power supply at the preset current value for 20 - 60 minutes for repairing the carbon fiber bundles;

[0024] Step 5: Turn off the constant power supply, and after the self-healing carbon fiber composite cools down, the repair of the carbon fiber bundles is completed.

[0025] Further, the setting method of the preset current value is as follows:

[0026] According to the material of the carbon fiber bundles, through Joule's law, during the process of heating the carbon fiber bundles by energization, obtain the current corresponding to the carbon fiber bundles when the temperature reaches 80 - 90% of the melting point temperature of the hot-melt microcapsules as the preset current value.

[0027] Further, a flexible conductive material is provided between the interface of the conductive layer and the carbon fiber bundles.

[0028] Further, the flexible conductive material is gold foil.

[0029] Advantages of the present invention:

[0030] The present invention does not require a large amount of manual operations, simplifies the repair process, and reduces the technical requirements for operators; the equipment required by the present invention is simple and easy to operate, significantly reducing the repair cost and complexity; the present invention can achieve multiple automated repairs, not only improving the repair efficiency but also avoiding the inconvenience brought by repeated manual repairs; the present invention adopts a non-destructive repair technology, which can effectively repair potential damages that are not easily observable without damaging the original structure of the material, improving the reliability and service life of the material; the present invention can be automatically repaired, further enhancing the reliability and convenience of the repair, ensuring the performance stability and safety of the material in various complex environments. The present invention can improve the sustainable usability of the carbon fiber composite, reduce resource consumption, not only extend the service life of the material but also reduce the maintenance cost. Description of the Drawings

[0031] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as imposing any limitation on the present invention. In the drawings:

[0032] Figure 1It is a schematic diagram during repair in a specific embodiment of the present invention;

[0033] Figure 2 It is a schematic longitudinal sectional view of a self-healing carbon fiber composite material in a specific embodiment of the present invention;

[0034] Figure 3 It is a schematic internal structure view of a hot-melt microcapsule in a specific embodiment of the present invention. Specific Embodiments

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0036] The present invention will be further clarified below with specific embodiments. Those skilled in the art should understand that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Modifications to various equivalent forms of the present invention all fall within the scope defined by the appended claims of this application.

[0037] As Figure 2 shown, the present invention provides a self-healing carbon fiber composite material, including: several carbon fiber bundles 4. The distribution of the carbon fiber bundles 4 in the self-healing carbon fiber composite material can be arranged in an array manner as Figure 2 shown, or in any distribution manner that meets the design requirements; the outer layer of the carbon fiber bundle 4 is wrapped with a silver-plated layer 3, the composite material filling matrix 1 is filled between the carbon fiber bundles 4, and hot-melt microcapsules 2 are evenly distributed in the composite material filling matrix 1. The composite material filling matrix 1 generally remains solid within a temperature range of 500°C. The silver element in the silver-plated layer 3 will react with thiol to form a coordination bond when the fiber interface is damaged, and to a certain extent, repair the interface damage.

[0038] As Figure 3 shown, the hot-melt microcapsule 2 includes: a hot-melt film 5, a repair agent 6 is wrapped inside the hot-melt film, and heat-expandable microspheres 7 are evenly distributed in the repair agent 6.

[0039] The melting point range of the hot-melt film 5 is: 65 - 110°C; the excitation temperature range of the heat-expandable microspheres 7 is: 80 - 200°C. The heat-expandable microspheres 7 include a thermoplastic polymer shell and an internal low-boiling hydrocarbon core, and can expand to dozens of times their original size and remain stable at a temperature of 80 - 200°C.

[0040] Two types of hot-melt microcapsules 2 are evenly distributed in the composite material-filled matrix 1. Among them, the repair agent 6 in one type of hot-melt microcapsule 2 is: medium-temperature thermosetting epoxy resin, and the curing temperature is about 100 - 150 °C; the repair agent 6 in the other type of hot-melt microcapsule 2 is: thiol, which belongs to a compound containing active thiol groups (-SH).

[0041] The present invention also provides a repair method for a self-healing carbon fiber composite material, including the following steps:

[0042] Step 1: As shown in Figure 1 , a conductive layer 8 is covered on the two end faces of the carbon fiber bundle in the self-healing carbon fiber composite material. A flexible conductive material 11 is provided between the interface of the conductive layer 8 and the carbon fiber bundle 4, and the flexible conductive material 11 is preferably gold foil; the remaining parts of the two end faces of the self-healing carbon fiber composite material are covered with an insulating layer 9;

[0043] Step 2: A constant power supply 12 is externally connected between the conductive layers at both ends of the self-healing carbon fiber composite material through a wire 10; during preliminary preparation, a microcurrent can be passed through the constant power supply 12 for 1 - 2 seconds to check and determine whether the circuit is normally powered on. When electrical signals are input in both cases, then proceed to the next step, otherwise check and improve the circuit connection;

[0044] Step 3: Linearly increase the current of the constant power supply within 1 - 2 minutes until the preset current value is reached to preheat the carbon fiber bundle;

[0045] For the setting of the preset current value, the method is to obtain the current corresponding to the carbon fiber bundle when the temperature reaches 80 - 90% of the melting point temperature of the hot-melt microcapsule according to the material of the carbon fiber bundle through Joule's law during the electrified heating process of the carbon fiber bundle as the preset current value. For example, when the melting point range of the hot-melt film 5 is: 65 - 110 °C, the electrified heating temperature range of the carbon fiber bundle is: 50 - 55 °C. Through Joule's law Q = I²Rt combined with the material of the carbon fiber bundle, the current intensity corresponding to this temperature range can be obtained as: 0.11 A / mm 2 , then 0.11 A / mm 2 is used as the preset current value;

[0046] Step 4: Maintain the current of the constant power supply at the preset current value for 20 - 60 minutes to repair the carbon fiber bundle;

[0047] During the repair process, for the damaged carbon fiber bundles, since some carbon fibers inside the carbon fiber bundle 4 are broken or irreversibly deformed, a corresponding contact resistance is generated or the cross-sectional area is reduced, and the resistance of the damaged part increases by several times or even dozens of times compared to the original. According to Joule's law Q = I²Rt, the heat generation in this damaged area increases accordingly, and a hot spot can be observed in the area through an infrared thermal imager. The temperature near this damaged area will gradually rise and first exceed the melting point of the hot melt film 5, which is 65 - 110°C. At this time, the hot melt film 5 gradually melts. Then the temperature exceeds the activation temperature of the thermally expandable microspheres 7, which is 80 - 200°C. At this time, the thermally expandable microspheres 7 expand in volume and extrude the repair agent 6 inside the hot melt microcapsule 2. For the thermosetting epoxy resin repair agent cured at medium temperature, the temperature will gradually cure in the range of 100 - 150°C. If the curing temperature is exceeded, the curing time will be correspondingly shortened, forming a cured product with certain heat resistance and high mechanical strength; for the thiol repair agent, the extruded thiol groups will react with the silver-plated layer 3 on the surface of the carbon fiber, forming a coordination bond with silver elements, thereby achieving the repair of the interface.

[0048] For the carbon fiber bundles with no or almost no damage, the temperature of the carbon fiber bundles will be in the range of 50 - 55°C. Throughout the process, the temperature does not exceed the melting point of the hot melt film 5, which is 65 - 110°C, nor does it exceed the curing temperature of the thermosetting epoxy resin, which is 100 - 150°C, and the activation temperature of the thermally expandable microspheres 7, which is 80 - 200°C. Therefore, the hot melt microcapsule 2 nearby will not be damaged.

[0049] Step 5: Turn off the constant power supply and use air cooling for heat dissipation. As the temperature of the self-healing carbon fiber composite material drops to room temperature as a whole, the damaged areas of the carbon fibers inside it complete self-repair, and the carbon fiber bundles are repaired after the self-healing carbon fiber composite material cools down.

[0050] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A self-repairing carbon fiber composite material, characterized in that: include: A plurality of carbon fiber bundles, wherein the outer layers of the carbon fiber bundles are wrapped with a silver-plated layer, a composite material filling matrix is ​​filled between the carbon fiber bundles, and hot-melt microcapsules are evenly distributed in the composite material filling matrix.

2. The self-repairing carbon fiber composite material according to claim 1, characterized in that: The hot-melt microcapsule comprises a hot-melt film, a repair agent is wrapped in the hot-melt film, and heat-expandable microspheres are evenly distributed in the repair agent.

3. The self-repairing carbon fiber composite material according to claim 1 or 2, characterized in that: Two kinds of hot-melt microcapsules are evenly distributed in the composite material filling matrix, wherein the repairing agent in one hot-melt microcapsule is: medium-temperature thermosetting epoxy resin; and the repairing agent in the other hot-melt microcapsule is: thiol.

4. The self-repairing carbon fiber composite material according to claim 3, characterized in that: The mass ratio of the two hot-melt microcapsules is 1:

1.

5. The self-repairing carbon fiber composite material according to claim 1, characterized in that: The diameter of the hot-melt microcapsules ranges from 30 to 300 microns.

6. The self-repairing carbon fiber composite material according to claim 2, characterized in that: The melting point range of the hot-melt film is 65-110°C; the excitation temperature range of the heat-expandable microspheres is 80-200°C.

7. A method for repairing a self-repairing carbon fiber composite material according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Covering the two end surfaces of the carbon fiber bundle in the self-repairing carbon fiber composite material with a conductive layer, and covering the rest of the two end surfaces of the self-repairing carbon fiber composite material with an insulating layer; Step 2: Connect a constant power source between the conductive layers at both ends of the self-repairing carbon fiber composite material; Step 3: linearly increase the current of the constant power supply to a preset current value within 1-2 minutes to preheat the carbon fiber bundle; Step 4: Maintain the current of the constant power supply at a preset current value for 20-60 minutes to repair the carbon fiber bundle; Step 5: Turn off the constant power supply and complete the carbon fiber bundle repair after the self-repairing carbon fiber composite cools down.

8. The method for repairing a self-repairing carbon fiber composite material according to claim 7, characterized in that: The method for setting the preset current value is: According to the material of the carbon fiber bundle and Joule's law, during the heating process of the carbon fiber bundle, the current corresponding to when the temperature of the carbon fiber bundle reaches 80-90% of the melting point of the hot-melt microcapsule is obtained as the preset current value.

9. The method for repairing a self-repairing carbon fiber composite material according to claim 7, characterized in that: A flexible conductive material is provided between the conductive layer and the interface of the carbon fiber bundle.

10. The method for repairing a self-repairing carbon fiber composite material according to claim 9, characterized in that: The flexible conductive material is gold foil.

Images