Gradient distribution self-repairing carbon fiber-polymer composite material and preparation method thereof

Abstract

The invention discloses a gradient distribution self-repairing carbon fiber-polymer composite material and a preparation method thereof, and belongs to the technical field of polymer composite materials. The material is composed of three functional gradient areas of a lower layer surface, a middle transition area and an upper layer surface, the performance optimization of each region is realized through the differentiated ratio of the carbon fiber, the epoxy Vitrimer resin, the dynamic disulfide bond siloxane hybrid compound, the supramolecular hydrogen bond metal coordination bifunctional polymer and the catalyst. The preparation method comprises the following steps: carrying out oxidation and interface functionalization pretreatment on the carbon fiber fabric, respectively preparing slurry in different areas, realizing component gradient distribution by adopting a centrifugal forming technology, and shaping the material by adopting a segmented curing process. Through the unique gradient distribution design and the synergistic effect of the two novel self-repairing compounds, the contradiction between the mechanical property and the self-repairing efficiency of the material is effectively solved, the material is endowed with excellent multi-time self-repairing capacity and high strength and toughness, and the material has outstanding advantages in manufacturing of key parts such as badminton racket frames and badminton racket rods and has wide application prospects. The method has wide application prospects in the fields of aerospace, intelligent structures and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a gradient-distributed self-healing carbon fiber-polymer composite material and its preparation method. Background Technology

[0002] Carbon fiber reinforced polymer composites, due to their superior specific strength and specific modulus, have become indispensable key structural materials in badminton racket frames, shafts, and other fields. However, under harsh conditions such as complex alternating loads, extreme environments, or accidental impacts, these materials are highly susceptible to irreversible damage such as internal microcracks and interfacial debonding. This damage is characterized by its insidious nature, difficulty in detection and repair, and not only significantly reduces the mechanical properties and service life of the material but may also lead to catastrophic structural failures, seriously threatening the safety and reliability of the overall equipment. Traditional external repair techniques are often complex, costly, and difficult to apply internally. Therefore, developing intelligent composite materials with inherent self-healing capabilities, enabling them to mimic the wound healing mechanisms of living organisms, autonomously sense and repair damage, and thus restore their mechanical properties and functional integrity, has become a cutting-edge direction urgently needing breakthroughs in the field of new materials.

[0003] Currently, self-healing material systems mainly fall into three categories: microcapsule-based, vascular-based, and intrinsic self-healing. Microcapsule and vascular-based self-healing systems rely on pre-embedded repair agents to be released and solidified upon damage to achieve repair. While these methods can achieve some repair effects, they have inherent limitations such as easy depletion of the repair agent, typically only single-use repair capabilities, and complex encapsulation processes. Intrinsic self-healing materials, based on reversible chemical bonds or supramolecular interactions within the material, can achieve multiple damage repairs without external repair agents, showing greater application potential. However, existing intrinsic self-healing systems generally face a core contradiction: while high-density dynamic bonds can improve repair efficiency, they often lead to a significant decrease in mechanical properties such as material stiffness and strength; conversely, pursuing high mechanical properties usually comes at the cost of repair efficiency. Furthermore, in fiber-reinforced composites, the interface region between the fiber and the resin matrix is ​​a critical link in stress transfer and often the source of microcrack initiation, yet existing technologies rarely offer effective strategies to simultaneously achieve matrix self-healing and interface self-healing. Although the design concept of graded functional materials provides the possibility of synergistic optimization of different properties by spatially controlling the composition and structure of materials, there is still a lack of research on combining it with multi-mode self-healing mechanisms, especially in constructing self-healing networks with gradient distribution characteristics in carbon fiber composites, and the technical challenges are enormous.

[0004] In summary, existing self-healing carbon fiber composite technologies have significant shortcomings: firstly, it is difficult to simultaneously achieve both mechanical properties and self-healing efficiency; secondly, there is a lack of effective self-healing strategies for the weak fiber-matrix interface; and thirdly, uniformly distributed self-healing designs cannot meet the differentiated requirements for mechanical load-bearing and damage repair in different regions of the material. Therefore, there is an urgent need to develop a novel material design and preparation method that deeply integrates the gradient distribution concept with a multi-level self-healing mechanism, thereby endowing the material with efficient, controllable, and durable self-healing capabilities while maintaining high mechanical properties. This invention aims to fundamentally solve these technical challenges by designing novel self-healing compounds and innovating preparation processes to achieve precise spatial control and synergistic improvement of material properties, laying a solid technical foundation for the development of next-generation high-performance, long-life intelligent composite materials. Summary of the Invention

[0005] The purpose of this invention is to provide a gradient-distributed self-healing carbon fiber-polymer composite material and its preparation method, which solves the technical problems of existing self-healing materials, such as the difficulty in balancing mechanical properties and repair efficiency, insufficient self-healing ability of the fiber-matrix interface, and the inability of traditional uniform distribution design to achieve performance space optimization.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing a gradient-distributed self-healing carbon fiber-polymer composite material, comprising the following steps: S1. The carbon fiber fabric is ultrasonically cleaned in acetone, refluxed and oxidized in a concentrated nitric acid / concentrated sulfuric acid mixture at 78-82℃, and then impregnated in an ethanol solution of a dynamic disulfide bond-siloxane hybrid compound in a lifting device and cured at 118-122℃ to form a functionalized interface with dynamic disulfide bonds, thus obtaining the pretreated carbon fiber fabric; Vitrimer resin, dynamic disulfide bond-siloxane hybrid compound, supramolecular hydrogen bond-metal coordination bifunctional polymer, and stannous octoate are used to prepare slurries for the lower layer region, the intermediate transition region, and the upper layer region, respectively; wherein, the supramolecular hydrogen bond-metal coordination bifunctional polymer is first dissolved in N,N-dimethylformamide to form a solution, and then the solution is mixed with epoxy Vitrimer resin; S2. Fix the pretreated carbon fiber fabric to the bottom of the mold, and pour the slurry for the lower layer, the middle transition area, and the upper layer in the order of lower layer, middle layer, and upper layer. Centrifuge after each layer of slurry is poured. After all the slurry is poured, adjust the centrifuge speed. Then gel and cure at 64-66℃. Then, gradually increase the temperature to 84-86℃ for curing. Finally, cure at 118-122℃.

[0007] According to a preferred embodiment of the present invention, the preparation steps of the slurry in the lower layer region are as follows: 35g of epoxy Vitrimer resin is accurately weighed and placed in a 150mL mixing container. After preheating in a constant temperature water bath at 65℃ for 15min, 4g of dynamic disulfide bond-siloxane hybrid compound is added, and the mixture is mechanically stirred at 500r / min for 20min to ensure thorough dispersion. 1.5g of supramolecular hydrogen bond-metal coordination bifunctional polymer is dissolved in 15mL of N,N-dimethylformamide, filtered through a 0.45μm filter membrane, and slowly added dropwise to the resin system, controlling the dropwise addition rate at 2mL / min and maintaining a stirring rate of 800r / min during the dropwise addition. Finally, 0.2g of stannous octoate is added, and the stirring speed is increased to 1200r / min and stirred continuously for 40min until a homogeneous slurry is formed. The entire process is carried out under a nitrogen atmosphere.

[0008] According to a preferred embodiment of the present invention, the intermediate transition zone slurry preparation steps are as follows: 45g of epoxy Vitrimer resin is accurately weighed and placed in a 150mL mixing container. Under constant temperature water bath conditions of 60℃, 2.5g of dynamic disulfide bond-siloxane hybrid compound and 2.5g of supramolecular hydrogen bond-metal coordination bifunctional polymer are added sequentially (this polymer needs to be pre-dissolved in 12mL of N,N-dimethylformamide and sonicated for 10min). After mixing for 25min at an initial speed of 600r / min using an anchor-type stirring paddle, 0.2g of stannous octoate is added and the stirring speed is gradually increased to 1000r / min and stirring is continued for 35min. Throughout the process, the temperature is maintained within the range of 60±1℃ using a constant temperature water bath control system.

[0009] According to a preferred embodiment of the present invention, the upper layer slurry preparation steps are as follows: 55g of epoxy Vitrimer resin is accurately weighed and placed in a 200mL Teflon container. Under a water bath at 55°C, 1.5g of dynamic disulfide-siloxane hybrid compound and 4g of supramolecular hydrogen-metal coordination bifunctional polymer are added sequentially (this polymer needs to be pre-dissolved in 18mL of N,N-dimethylformamide and filtered through a 0.22μm microporous membrane). After primary emulsification at 1500r / min using a high-shear disperser for 15min, 0.2g of stannous octoate is added and the stirring speed is adjusted to 1200r / min and stirring is continued for 45min. The entire preparation process is carried out in a clean environment with a relative humidity of less than 30%.

[0010] In this invention, the molding mechanism of the gradient-distributed self-healing composite material integrates interfacial chemical modification, component gradient distribution, and multi-level curing kinetics. After mixed acid oxidation treatment, carbon fiber fabric generates active groups such as carboxyl and hydroxyl groups on its surface. These groups undergo condensation reactions with the silanol ends of dynamic disulfide bond-siloxane hybrid compounds, constructing a coupling layer containing dynamic disulfide bonds at the fiber-resin interface. This interfacial layer enhances the interfacial bonding strength through covalent bonding and utilizes the thermally reversible exchange properties of disulfide bonds to repair interfacial damage. During the gradient construction stage, driven by a centrifugal force field, differences in density and molecular structure lead to a redistribution of functional components along the thickness direction: high-density carbon fibers are enriched in the lower layer, providing mechanical support; while supramolecular polymers and dynamic compounds migrate to the middle and upper layers due to differences in molecular configuration and interactions. This spontaneous phase separation process forms a continuous gradient structure from high fiber content to high repair component content. During the curing process, stannous octoate first catalyzes the ring-opening polymerization of the epoxy group, forming a preliminary cross-linked network. Subsequent temperature increases activate the exchange activity of dynamic bonds: at moderate temperatures, hydrogen bonds and coordination bonds in the supramolecular polymer recombine, achieving low-temperature repair; at high temperatures, disulfide bonds and transesterification trigger covalent network reconstruction, completing deep repair. This spatiotemporal synergy of multi-scale dynamic interactions enables the material to achieve full-range self-healing capabilities from the interface to the matrix while maintaining high mechanical properties.

[0011] According to a preferred embodiment of the present invention, in step S1, the reflux oxidation treatment time at 78-82℃ is 2-4h; the curing time at 118-122℃ is 1-2h.

[0012] According to a preferred embodiment of the present invention, in step S2, the gel curing time at 64-66°C is 2-4 hours.

[0013] According to a preferred embodiment of the present invention, the preparation method of the dynamic disulfide-siloxane hybrid compound includes: A1, under nitrogen protection, dissolving 2,2'-dipyridine disulfide in tetrahydrofuran, adding sodium borohydride and reacting at room temperature; subsequently adding 2-mercaptoethanol and continuing the reaction to form a hydroxyl-terminated disulfide intermediate; A2, reacting the hydroxyl-terminated disulfide intermediate with 3-isocyanate propyltriethoxysilane in the presence of dibutyltin dilaurate at 60-70°C; after the reaction is completed, rotary evaporation and purification by silica gel column chromatography.

[0014] In this invention, the preparation of dynamic disulfide-siloxane hybrid compounds is based on a two-step reaction process. Its core mechanism is the integration of dynamic disulfide bond construction and siloxane coupling function, achieving synergistic interfacial bonding and self-healing capabilities. In the first step, dipyridine disulfide undergoes homolytic cleavage under the reduction of sodium borohydride, generating a mercaptopyridine intermediate. This reduction process forms an active sulfur radical through the breaking of sulfur-sulfide bonds, which then undergoes an asymmetric disulfide bond exchange reaction with added mercaptoethanol, generating a disulfide intermediate terminated with a hydroxyl group. The key to this step lies in the mild reducing environment provided by sodium borohydride, which avoids sulfur bond destruction due to excessive reduction while ensuring the preservation of the dynamic exchange activity of the disulfide bonds. In the second step, the hydroxyl-terminated disulfide intermediate undergoes a nucleophilic addition reaction with isocyanate propyltriethoxysilane in the presence of a tin catalyst. The isocyanate group and hydroxyl group form an urethane bond through nucleophilic attack, while the ethoxy group at the siloxane terminus can hydrolyze to form silanol during the reaction, laying the foundation for subsequent condensation with hydroxyl groups on the carbon fiber surface. The entire reaction pathway fully utilizes the exchange properties of dynamic disulfide bonds and the coupling function of siloxanes. Under thermal excitation, the disulfide bonds can achieve interfacial self-repair through reversible cleavage and recombination, while the siloxane terminus ensures a strong bond with the reinforcement through covalent condensation.

[0015] According to a preferred embodiment of the present invention, in step A1, the reaction time at room temperature is 0.5-1 h.

[0016] According to a preferred embodiment of the present invention, in step A2, the reaction time at 60-70°C is 6-8 hours.

[0017] According to a preferred embodiment of the present invention, the method for preparing the supramolecular hydrogen-bonded-metal coordination bifunctional polymer includes: B1, reacting 2,4-dihydroxybenzaldehyde with 2-aminoethylpyridine in ethanol at 70-80°C to form an amino-terminated Schiff base ligand; B2, reacting the amino-terminated Schiff base ligand with zinc acetate dihydrate under reflux in methanol; subsequently adding polyethylene glycol diglycidyl ether and tetrabutylammonium bromide, and reacting at 88-92°C.

[0018] In this invention, the construction of a supramolecular hydrogen-bonded-metal-coordination bifunctional polymer relies on the synergistic effect of multi-level dynamic interactions, encompassing three key stages: Schiff base condensation, metal coordination, and epoxy ring-opening crosslinking. First, hydroxybenzaldehyde and aminoethylpyridine undergo a condensation reaction in ethanol solution, where the aldehyde group and amino group dehydrate to form an imine bond. Simultaneously, the phenolic hydroxyl group and pyridine nitrogen atom provide multiple hydrogen bonding sites, constituting a Schiff base ligand with both coordination and hydrogen bonding capabilities. Subsequently, this ligand undergoes metal coordination with zinc acetate under reflux conditions. The zinc ion forms a stable tetrahedral coordination structure with the imine nitrogen atom and pyridine nitrogen atom, while the phenolic hydroxyl group and amino group in the ligand further strengthen the supramolecular network through intermolecular hydrogen bonds. Based on this supramolecular framework, the epoxy groups of polyethylene glycol diglycidyl ether undergo a ring-opening reaction with the amino groups at the ends of the Schiff base ligand under ammonium salt catalysis, forming a crosslinked polyether network. This design achieves a gradient distribution of dynamic interactions: multiple hydrogen bonds provide rapid and reversible physical cross-linking at room temperature, endowing the material with immediate self-healing capabilities; metal coordination bonds contribute energy dissipation through coordination dissociation at moderate temperatures; and the covalent cross-linked network ensures the material's macroscopic stability and mechanical strength. This hydrogen-coordination-covalent triple recombination mechanism enables the polymer to possess efficient damage repair capabilities across different temperature ranges.

[0019] According to a preferred embodiment of the present invention, in step B1, the reaction time at 70-80°C is 4-6 hours.

[0020] According to a preferred embodiment of the present invention, in step B2, the reaction time at 88-92°C is 6-8 hours.

[0021] The present invention also provides a method for preparing the gradient distribution self-healing carbon fiber-polymer composite material, wherein the gradient distribution self-healing carbon fiber-polymer composite material is composed of a lower layer region, an intermediate transition region and an upper layer region. The lower layer region comprises the following raw materials in parts by weight: 60-70 parts by weight of carbon fiber fabric; 30-40 parts by weight of epoxy Vitrimer resin; 3-5 parts by weight of dynamic disulfide bond-siloxane hybrid compound; 1-2 parts by weight of supramolecular hydrogen bond-metal coordination bifunctional polymer; and 0.1-0.3 parts by weight of stannous octoate. The intermediate transition region comprises the following raw materials in parts by weight: 50-60 parts carbon fiber fabric; 40-50 parts epoxy Vitrimer resin; 2-3 parts dynamic disulfide bond-siloxane hybrid compound; 2-3 parts supramolecular hydrogen bond-metal coordination bifunctional polymer; and 0.1-0.3 parts stannous octoate. The upper layer region comprises the following raw materials in parts by weight: 40-50 parts by weight of carbon fiber fabric; 50-60 parts by weight of epoxy Vitrimer resin; 1-2 parts by weight of dynamic disulfide bond-siloxane hybrid compound; 3-5 parts by weight of supramolecular hydrogen bond-metal coordination bifunctional polymer; and 0.1-0.3 parts by weight of stannous octoate.

[0022] The beneficial effects of this invention are as follows: This invention successfully resolves the inherent contradiction between mechanical properties and repair efficiency that has long existed in the field of self-healing materials through a unique gradient distribution design. The material exhibits a precisely controlled component distribution along its thickness: the lower layer is rich in carbon fiber fabric, providing excellent structural strength and rigidity, ensuring superior load-bearing capacity; the upper layer is rich in two functional repair compounds, endowing the material with outstanding damage repair properties; the intermediate transition region achieves a smooth transition of performance, avoiding abrupt interface changes. This innovative gradient configuration allows the high-fiber-content lower layer to bear the main mechanical function under mechanical loads, while the high-repair-component upper layer specifically addresses damage such as microcracks, thus achieving both high mechanical performance and high-efficiency self-healing. Compared to traditional homogeneous composite materials, this material significantly improves repair efficiency while maintaining the same strength level, breaking through the inherent bottleneck of material performance.

[0023] This invention constructs a multi-layered, wide-temperature-range self-healing network system through the synergistic effect of two innovative repair compounds. The dynamic disulfide-bonded siloxane hybrid compound ingeniously integrates dynamic covalent chemistry and interfacial coupling functionality, forming strong chemical bonds with the carbon fiber surface and achieving interfacial damage repair through reversible disulfide bond exchange under moderate temperatures, significantly improving stress transfer efficiency between the fiber and matrix. The supramolecular hydrogen-bonded metal-coordination bifunctional polymer innovatively integrates two dynamic reversible interactions: multiple hydrogen bonds and metal coordination bonds. Multiple hydrogen bonds rapidly and reversibly bind at room temperature, providing immediate self-healing capability; while metal coordination bonds contribute additional repair efficiency in the moderate-temperature range. These two repair mechanisms effectively complement each other in temperature response, enabling the material to possess excellent damage repair capabilities across a wide temperature range from room temperature to medium-high temperatures, and allowing for repeated repair.

[0024] This invention innovatively combines centrifugal molding technology with gel casting technology, achieving precise control and efficient preparation of gradient structures in complex-shaped components. By adjusting centrifugation parameters and slurry formulation, the concentration gradient of each functional component along the material thickness direction can be precisely controlled, ensuring the stability and repeatability of the gradient structure. The segmented curing process effectively guarantees the integrity of the material structure and the reliability of its performance: firstly, the slurry is gel-cured at a lower temperature to stabilize the initially formed gradient distribution; then, the resin matrix is ​​fully cross-linked through staged heating, activating the network reconstruction capability of dynamic covalent bonds. This material has outstanding advantages in the manufacture of key components such as badminton racket frames and shafts. Simultaneously, it shows broad application prospects in aerospace, transportation, and high-end equipment fields, not only significantly extending the service life of structural components and reducing maintenance costs, but also improving the reliability and safety of equipment, providing a new technical route for the development of next-generation intelligent structural materials. Detailed Implementation

[0025] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0026] The main suppliers of related equipment and materials are as follows: The carbon fiber fabric was purchased from Zhongfu Shenying Carbon Fiber Co., Ltd.

[0027] The Vitrimer resin was purchased from Bluestar Chemical Co., Ltd.

[0028] The stannous octoate was purchased from Beijing Huawirui Chemical Co., Ltd.

[0029] The 2,2'-dipyridine disulfide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0030] The sodium borohydride was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0031] The 3-isocyanate propyltriethoxysilane was purchased from Hubei Xinlantian New Materials Co., Ltd.

[0032] The dibutyltin dilaurate was purchased from Beijing Huawirui Chemical Co., Ltd.

[0033] The 2,4-dihydroxybenzaldehyde was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0034] The 2-aminoethylpyridine was purchased from Shanghai Dipo Chemical Technology Co., Ltd.

[0035] The zinc acetate dihydrate was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0036] The polyethylene glycol diglycidyl ether was purchased from Hubei Zhenhua Chemical Co., Ltd.

[0037] The tetrabutylammonium bromide was purchased from Sinopharm Chemical Reagent Co., Ltd. Example 1

[0038] Preparation of dynamic disulfide-siloxane hybrid compounds: Under nitrogen protection, 5.00 g of 2,2'-dipyridine disulfide was dissolved in 50 mL of anhydrous tetrahydrofuran solvent. 1.20 g of sodium borohydride powder was slowly added under magnetic stirring at 400 rpm, and the reaction was carried out at 25 °C for 0.8 h. Subsequently, 2.50 g of 2-mercaptoethanol was added dropwise through a constant-pressure dropping funnel at a rate of 1 mL / min. After the addition was complete, the reaction was continued for 13 h to obtain a hydroxyl-terminated disulfide intermediate solution. The obtained intermediate solution was concentrated under reduced pressure and then reacted with 6.00 g of 3-isocyanate propyltriethoxysilane in an oil bath at 65 °C for 7 h under the catalysis of 0.10 g dibutyltin dilaurate, with nitrogen protection during the reaction. After the reaction was completed, the mixture was concentrated by rotary evaporator at 45℃ and -0.09MPa, and purified by silica gel column chromatography with 200-300 mesh, using petroleum ether / ethyl acetate at a volume ratio of 3:1 as the eluent. The target component was collected and dried in a vacuum drying oven at 40℃ for 12 hours to obtain a pale yellow transparent oily product.

[0039] Preparation of supramolecular hydrogen-bonded metal-coordination bifunctional polymers: 8.00 g of 2,4-dihydroxybenzaldehyde and 6.50 g of 2-aminoethylpyridine were dissolved in 80 mL of anhydrous ethanol and reacted in a reflux condenser at 75 °C for 5 h. During the reaction, the solution color gradually changed from light yellow to orange-red. After cooling the obtained amino-terminated Schiff base ligand solution to room temperature, 7.20 g of zinc acetate dihydrate was added, and the mixture was refluxed in methanol solution at 65 °C for 3 h, turning the solution into a deep red transparent liquid. Subsequently, 12.00 g of polyethylene glycol diglycidyl ether and 0.30 g of tetrabutylammonium bromide were added to the system, and the temperature was raised to 90 °C for another 7 h. During the reaction, the viscosity of the system increased significantly. After the reaction, the product was poured into a polytetrafluoroethylene mold and aged in a vacuum drying oven at 50 °C for 24 h to obtain a brownish-red elastic solid product.

[0040] Preparation of gradient-distributed self-healing carbon fiber-polymer composite: A 200mm × 200mm three-dimensional four-way woven carbon fiber fabric was ultrasonically cleaned three times in acetone for 30 minutes each time; then refluxed and oxidized in a 1:3 volume ratio of concentrated nitric acid and concentrated sulfuric acid at 80℃ for 3 hours, washed with deionized water until neutral, and dried. The oxidized carbon fiber fabric was then immersed in an ethanol solution (5% by mass) containing 4.00g of dynamic disulfide bond-siloxane hybrid compound at a speed of 2mm / s in a lifting device, and cured in a 120℃ forced-air drying oven for 1.5 hours to obtain the pretreated carbon fiber fabric. Three layers of slurry were prepared: the lower layer slurry consisted of 65.0g carbon fiber fabric, 35.0g epoxy Vitrimer resin, 4.00g dynamic disulfide-siloxane hybrid compound, 1.50g supramolecular hydrogen-bonded metal coordination bifunctional polymer, and 0.20g stannous octoate; the middle layer slurry consisted of 55.0g carbon fiber fabric, 45.0g epoxy Vitrimer resin, 2.50g dynamic disulfide-siloxane hybrid compound, 2.50g supramolecular hydrogen-bonded metal coordination bifunctional polymer, and 0.20g stannous octoate; and the upper layer slurry consisted of 45.0g carbon fiber fabric, 55.0g epoxy Vitrimer resin, 1.50g dynamic disulfide-siloxane hybrid compound, 4.00g supramolecular hydrogen-bonded metal coordination bifunctional polymer, and 0.20g stannous octoate. Pretreated carbon fiber fabric was fixed at the bottom of the mold, and three layers of slurry were poured in sequentially from bottom to top. After each layer was injected, the mixture was centrifuged at 1000 r / min for 5 min. After all the slurry was injected, the mixture was centrifuged at 1500 r / min for 10 min. The mixture was then gelled at 65℃ for 3 h, then gradually heated to 85℃ for 4 h, and finally cured at 120℃ for 2 h to obtain a gradient distribution self-healing carbon fiber-polymer composite material with a thickness of 2.0 mm. Example 2

[0041] The specific implementation method is the same as in Example 1, except that the preparation of the dynamic disulfide-siloxane hybrid compound is as follows: Under nitrogen protection, 5.20 g of 2,2'-dipyridine disulfide was dissolved in 50 mL of tetrahydrofuran, and 1.30 g of sodium borohydride was added. The reaction was carried out at room temperature for 0.5 h; then 2.60 g of 2-mercaptoethanol was added, and the reaction was continued for 12 h. The hydroxyl-terminated disulfide intermediate was reacted with 6.20 g of 3-isocyanate propyltriethoxysilane at 60 °C for 8 h in the presence of 0.10 g of dibutyltin dilaurate. The mixture was purified by rotary evaporation and silica gel column chromatography. Preparation of supramolecular hydrogen-bonded metal-coordinated bifunctional polymers: 8.50 g of 2,4-dihydroxybenzaldehyde and 6.80 g of 2-aminoethylpyridine were reacted in 80 mL of ethanol at 70 °C for 6 h; the ligand was then reacted with 7.50 g of zinc acetate dihydrate in methanol under reflux for 4 h, followed by the addition of 13.00 g of polyethylene glycol diglycidyl ether and 0.30 g of tetrabutylammonium bromide, and the reaction was carried out at 88 °C for 8 h. Preparation of gradient-distributed self-healing carbon fiber-polymer composites: Carbon fiber fabrics were ultrasonically cleaned in acetone, then refluxed in a 1:3 mixture of concentrated nitric acid and concentrated sulfuric acid at 78 °C for 4 h, followed by impregnation in an ethanol solution containing 3.00 g of a dynamically disulfide-siloxane hybrid compound, and cured at 118 °C for 2 h. Three layers of slurry were prepared: the lower layer slurry contained 60.0g carbon fiber fabric, 40.0g epoxy Vitrimer resin, 3.00g dynamic disulfide-siloxane hybrid compound, 2.00g supramolecular hydrogen-metal coordination bifunctional polymer, and 0.10g stannous octoate; the middle layer slurry contained 50.0g carbon fiber fabric, 50.0g epoxy Vitrimer resin, 2.00g dynamic disulfide-siloxane hybrid compound, 3.00g supramolecular hydrogen-metal coordination bifunctional polymer, and 0.10g stannous octoate; and the upper layer slurry contained 40.0g carbon fiber fabric, 60.0g epoxy Vitrimer resin, 1.00g dynamic disulfide-siloxane hybrid compound, 5.00g supramolecular hydrogen-metal coordination bifunctional polymer, and 0.10g stannous octoate. The pretreated carbon fiber fabric was fixed at the bottom of the mold, and three layers of slurry were poured in sequentially from bottom to top. Each layer was centrifuged at 1000 r / min for 5 min. After all the slurry was poured in, the centrifugation was adjusted to 1500 r / min for 10 min. The slurry was then gelled and cured at 64℃ for 4 h, then gradually heated to 84℃ for 4 h, and finally cured at 118℃ for 2 h. Example 3

[0042] The specific implementation method is the same as in Example 1, except that the preparation of the dynamic disulfide-siloxane hybrid compound is as follows: Under nitrogen protection, 4.80 g of 2,2'-dipyridine disulfide was dissolved in 50 mL of tetrahydrofuran, and 1.10 g of sodium borohydride was added. The reaction was carried out at room temperature for 1 h; then 2.40 g of 2-mercaptoethanol was added, and the reaction was continued for 14 h. The hydroxyl-terminated disulfide intermediate was reacted with 5.80 g of 3-isocyanate propyltriethoxysilane at 70 °C for 6 h in the presence of 0.10 g of dibutyltin dilaurate. The mixture was purified by rotary evaporation and silica gel column chromatography. Preparation of supramolecular hydrogen-bonded metal-coordinated bifunctional polymers: 7.50 g of 2,4-dihydroxybenzaldehyde and 6.20 g of 2-aminoethylpyridine were reacted in 80 mL of ethanol at 80 °C for 4 h; the ligand was then refluxed with 7.00 g of zinc acetate dihydrate in methanol for 2 h, followed by the addition of 11.00 g of polyethylene glycol diglycidyl ether and 0.30 g of tetrabutylammonium bromide, and the reaction was carried out at 92 °C for 6 h. Preparation of gradient-distributed self-healing carbon fiber-polymer composites: Carbon fiber fabrics were ultrasonically cleaned in acetone, then refluxed in a 1:3 mixture of concentrated nitric acid and concentrated sulfuric acid at 82 °C for 2 h, followed by impregnation in an ethanol solution containing 5.00 g of a dynamically disulfide-siloxane hybrid compound, and cured at 122 °C for 1 h. Three layers of slurry were prepared: the lower layer slurry contained 70.0g carbon fiber fabric, 30.0g epoxy Vitrimer resin, 5.00g dynamic disulfide-siloxane hybrid compound, 1.00g supramolecular hydrogen-metal coordination bifunctional polymer, and 0.30g stannous octoate; the middle layer slurry contained 60.0g carbon fiber fabric, 40.0g epoxy Vitrimer resin, 3.00g dynamic disulfide-siloxane hybrid compound, 2.00g supramolecular hydrogen-metal coordination bifunctional polymer, and 0.30g stannous octoate; and the upper layer slurry contained 50.0g carbon fiber fabric, 50.0g epoxy Vitrimer resin, 2.00g dynamic disulfide-siloxane hybrid compound, 3.00g supramolecular hydrogen-metal coordination bifunctional polymer, and 0.30g stannous octoate. The pretreated carbon fiber fabric was fixed at the bottom of the mold, and three layers of slurry were poured in sequentially from bottom to top. Each layer was centrifuged at 1000 r / min for 5 min. After all the slurry was poured in, the centrifugation was adjusted to 1500 r / min for 10 min. The slurry was then gelled and cured at 66℃ for 2 h, then gradually heated to 86℃ for 4 h, and finally cured at 122℃ for 2 h.

[0043] Comparative Example 1 The specific implementation method is the same as in Example 1, except that the carbon fiber fabric is ultrasonically cleaned in acetone and then refluxed at 80°C for 3 hours in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 1:3), without interface functionalization. A uniform slurry containing 55.0g carbon fiber fabric, 45.0g epoxy Vitrimer resin, and 0.20g stannous octoate is prepared. The carbon fiber fabric is fixed at the bottom of the mold, the slurry is poured in, and the mixture is centrifuged at 1000r / min for 5min. It is then gel-cured at 65°C for 3 hours, gradually increased to 85°C for 4 hours, and finally cured at 120°C for 2 hours.

[0044] Comparative Example 2 The specific implementation method is the same as in Example 1, except that after ultrasonically cleaning the carbon fiber fabric in acetone, it is refluxed and oxidized at 80°C for 3 hours in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 1:3). Subsequently, it is impregnated with an ethanol solution containing 4.00 g of a dynamic disulfide-siloxane hybrid compound and cured at 120°C for 1.5 hours. A uniform slurry containing 55.0 g of carbon fiber fabric, 45.0 g of epoxy Vitrimer resin, 4.00 g of the dynamic disulfide-siloxane hybrid compound, and 0.20 g of stannous octoate is prepared. The pretreated carbon fiber fabric is fixed at the bottom of a mold, the slurry is poured in, and it is centrifuged at 1000 r / min for 5 minutes. It is then gel-cured at 65°C for 3 hours, gradually increased to 85°C for 4 hours, and finally cured at 120°C for 2 hours.

[0045] Comparative Example 3 The specific implementation method is the same as in Example 1, except that after ultrasonically cleaning the carbon fiber fabric in acetone, it is refluxed and oxidized at 80°C for 3 hours in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 1:3). Subsequently, it is impregnated with an ethanol solution containing 4.00 g of a dynamic disulfide-siloxane hybrid compound and cured at 120°C for 1.5 hours. A uniform slurry is prepared containing 55.0 g of carbon fiber fabric, 45.0 g of epoxy Vitrimer resin, 4.00 g of the dynamic disulfide-siloxane hybrid compound, 4.00 g of a supramolecular hydrogen-bonded metal-coordinating bifunctional polymer, and 0.20 g of stannous octoate. The pretreated carbon fiber fabric is fixed to the bottom of a mold, the slurry is poured in, and it is centrifuged at 1000 r / min for 5 minutes. It is then gel-cured at 65°C for 3 hours, gradually increased to 85°C for 4 hours, and finally cured at 120°C for 2 hours.

[0046] Performance testing According to national and industry standard testing specifications, the gradient distribution self-healing carbon fiber-polymer composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were systematically evaluated using the following performance testing methods. Performance testing methods: Before testing, the samples were conditioned for 48 hours in an environment with a temperature of 23℃ and humidity of 50%. Bending performance testing was conducted using a universal testing machine with a span-to-thickness ratio set to 32:1, a loading head radius of 5mm, a support radius of 2mm, and a loading speed of 2mm / min. Five samples were tested in each group, and the average value was taken. Interlaminar shear strength testing was performed using the short beam shear method, with a span-to-thickness ratio adjusted to 4:1 and a loading speed of 1mm / min. The strength value was calculated by recording the first peak load. Fracture toughness testing was conducted using a single-sided notched bending sample with a pre-crack length to sample width ratio of 0.5 and a loading speed of 10mm / min. The stress intensity factor was calculated using the load-displacement curve. The self-healing efficiency assessment employed an impact-repair-retest scheme. First, a drop hammer impact tester applied 10J of impact energy to the specimen to induce damage. Then, the damaged specimen was placed in a hot air circulating oven and heat-treated at 120℃ for 2 hours to complete the repair. Finally, the repair efficiency was calculated by comparing the flexural strength values ​​before and after repair. The repair efficiency calculation formula is: (Flexural strength after repair / Initial flexural strength) × 100%. Microscopic morphology analysis was performed using a scanning electron microscope. The impact-damaged area and the repaired fracture surface were sputter-coated with gold, and crack closure and interface bonding were observed under an accelerating voltage of 15kV. Dynamic thermomechanical analysis was conducted using a dynamic mechanical analyzer, with a test temperature range of 30-150℃, a heating rate of 3℃ / min, and a frequency of 1Hz. Storage modulus, loss modulus, and glass transition temperature were measured. Multiple repair capability testing involved repeating the impact-repair cycle 5 times, and the flexural strength retention rate was measured after each cycle.

[0047] Performance test results: Table 1 Performance Test Results Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Bending strength (MPa) 298 235 285 275 260 268 Interlaminar shear strength (MPa) 42.5 38.7 41.2 34.8 39.5 40.1 <![CDATA[Fracture toughness (MPa·m 1 / 2 )]]> 5.76 4.85 5.35 4.25 4.68 4.92 Initial bending strength (MPa) 298 235 285 275 260 268 Bending strength after repair (MPa) 274 209 256 159 208 230 Repair efficiency (%) 92.0 89.0 89.8 57.8 80.0 85.8 Glass transition temperature (°C) 125 118 122 130 126 124 Energy storage modulus (30℃, GPa) 8.5 7.2 8.1 7.8 8.0 8.2 Strength retention rate (%) after 5 repairs 82.5 78.3 80.1 45.2 65.7 72.4 As shown in Table 1, Examples 1-3 systematically solved the three major technical challenges of existing self-healing materials through innovative material design and structural construction. Examples 1-3 demonstrated significant advantages in the synergistic improvement of mechanical properties and repair efficiency. Example 1 achieved a flexural strength of 298 MPa and a repair efficiency of 92.0%, significantly better than all comparative examples. Comparative Example 3, although containing two functional compounds, adopted a uniform distribution design, and its repair efficiency was only 85.8%, fully demonstrating the crucial role of gradient distribution design in breaking through the performance balance bottleneck. Regarding the insufficient self-healing ability of the fiber-matrix interface, Example 1 achieved an interlaminar shear strength of 42.5 MPa, far exceeding the 34.8 MPa of Comparative Example 1. This is attributed to the reversible covalent bond network constructed at the interface by the dynamic disulfide-siloxane hybrid compound. Comparative data showed that while Comparative Example 2, using only this compound, showed improved interface strength, its overall repair efficiency remained limited. In overcoming the limitations of traditional uniform distribution designs, Example 1 maintained an 82.5% strength retention rate after 5 repair cycles, while Comparative Example 3 only achieved a 72.4% strength retention rate under the same conditions. This difference clearly demonstrates the unique value of gradient distribution structures in achieving performance space optimization, enabling the material to specifically perform structural support or damage repair functions in different regions, thereby maximizing overall performance. The test results fully demonstrate that this invention, through the organic combination of gradient distribution design and multi-level self-healing mechanisms, successfully overcomes the long-standing technical bottleneck in the field of self-healing materials.

[0048] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a gradient distribution self-repairing carbon fiber-polymer composite material, characterized by the steps of Comprising: S1, ultrasonic cleaning of carbon fiber fabric in acetone, 78-82℃ reflux oxidation treatment in concentrated nitric acid / concentrated sulfuric acid mixture, followed by immersion in an ethanol solution of dynamic disulfide-siloxane hybrid compound in a puller device, curing at 118-122℃, forming a functionalized interface with dynamic disulfide bond, obtaining pretreated carbon fiber fabric; Vitrimer resin, dynamic disulfide-siloxane hybrid compound, supramolecular hydrogen bond-metal coordination bifunctional polymer and stannous octoate are respectively prepared into lower surface area slurry, middle transition area slurry and upper surface area slurry; wherein the supramolecular hydrogen bond-metal coordination bifunctional polymer is first dissolved in N,N-dimethylformamide to form a solution, and then the solution is mixed with the epoxy Vitrimer resin; S2, fix the pretreated carbon fiber fabric on the bottom of the mold, pour the lower surface area slurry, the middle transition area slurry and the upper surface area slurry in order of lower surface, middle layer and upper layer, and centrifuge after pouring each layer of slurry; adjust the centrifugal speed after all the slurry is injected; then gel and solidify at 64-66℃; Then stage heating to 84-86℃ for curing; finally post-curing at 118-122℃.

2. The method for preparing a gradient distribution self-repairing carbon fiber-polymer composite material according to claim 1, characterized in that, In step S1, the 78-82℃ reflux oxidation treatment time is 2-4h; the curing time at 118-122℃ is 1-2h.

3. The method for preparing gradient-distributed self-healing carbon fiber-polymer composite material according to claim 1, characterized in that, In step S2, the gel and solidification time at 64-66℃ is 2-4h.

4. The method for preparing gradient-distributed self-healing carbon fiber-polymer composite material according to claim 1, characterized in that, The preparation method of the dynamic disulfide-siloxane hybrid compound comprises: A1, under nitrogen protection, dissolve 2,2'-dipyridyl disulfide in tetrahydrofuran, add sodium borohydride and react at room temperature; then add 2-mercaptoethanol and continue to react to form a hydroxyl-terminated disulfide intermediate; A2, react the hydroxyl-terminated disulfide intermediate with 3-isocyanate propyl triethoxysilane in the presence of dibutyltin dilaurate at 60-70℃; after the reaction is completed, rotary evaporation and purification by silica gel column chromatography.

5. The method for preparing gradient-distributed self-healing carbon fiber-polymer composite material according to claim 4, characterized in that, In step A1, the reaction time at room temperature is 0.5-1h.

6. The method for preparing gradient-distributed self-healing carbon fiber-polymer composite material according to claim 4, characterized in that, In step A2, the reaction time at 60-70℃ is 6-8h.

7. The method for preparing gradient-distributed self-healing carbon fiber-polymer composite material according to claim 1, characterized in that, The preparation method of the supramolecular hydrogen bond-metal coordination bifunctional polymer comprises: B1, react 2,4-dihydroxybenzaldehyde with 2-aminoethylpyridine in ethanol at 70-80℃ to form an amino-terminated Schiff base ligand; B2, reflux reaction of the amino-terminated Schiff base ligand with zinc acetate dihydrate in methanol; then add polyethylene glycol diglycidyl ether and tetrabutylammonium bromide and react at 88-92℃.

8. The method for preparing gradient-distributed self-healing carbon fiber-polymer composite material according to claim 7, characterized in that, In step B1, the reaction time at 70-80℃ is 4-6h.

9. The method for preparing gradient-distributed self-healing carbon fiber-polymer composite material according to claim 7, characterized in that, In step B2, the reaction time at 88-92℃ is 6-8h.

10. A gradient distribution self-repairing carbon fiber-polymer composite material prepared by the method of any one of claims 1-9, consisting of a lower surface area, an intermediate transition area and an upper surface area, characterized in that, The lower surface area comprises the following raw materials by weight: carbon fiber fabric 60-70 parts by weight; epoxy Vitrimer resin 30-40 parts by weight; dynamic disulfide-siloxane hybrid compound 3-5 parts by weight; supramolecular hydrogen bond-metal coordination bifunctional polymer 1-2 parts by weight; stannous octoate 0.1-0.3 parts by weight; The intermediate transition region comprises the following raw materials by weight: carbon fiber fabric 50-60 parts by weight; epoxy Vitrimer resin 40-50 parts by weight; dynamic disulfide-siloxane hybrid compound 2-3 parts by weight; supramolecular hydrogen bond-metal coordination bifunctional polymer 2-3 parts by weight; stannous octoate 0.1-0.3 parts by weight; The upper layer region comprises the following raw materials by weight: carbon fiber fabric 40-50 parts by weight; epoxy Vitrimer resin 50-60 parts by weight; dynamic disulfide-siloxane hybrid compound 1-2 parts by weight; supramolecular hydrogen bond-metal coordination bifunctional polymer 3-5 parts by weight; stannous octoate 0.1-0.3 parts by weight.