A fiber composite interlaminar toughening structure with self-repairing function and a preparation method thereof

Abstract

The application discloses a kind of interlaminar toughening structure of fiber composite with self-repairing function and preparation method thereof, the structure includes fiber reinforcement layer and resin matrix layer, multiple levels of interlaminar toughening self-repairing layer are arranged between adjacent fiber reinforcement layer, the interlaminar toughening self-repairing layer includes interface enhancement layer, energy dissipation layer and repair layer in turn from bottom to top.The interlaminar toughening structure of fiber composite of the application realizes multiple repairs in the same crack area using Diels-Alder reversible reaction, prolongs material life.At the same time, self-repairing and toughening function are integrated in the same functional layer, avoiding the interface complexity and performance decline caused by adding separately in traditional scheme.The slurry spraying / coating method used in the application is fully compatible with the existing prepreg-heat press tank process, without major equipment modification.The repair temperature of the application does not overlap with the use temperature, and is lower than the resin decomposition temperature, and the repair efficiency can reach more than 85%.

Description

Technical Field

[0001] This invention belongs to the field of fiber-reinforced composite materials technology, and particularly relates to an interlayer toughening structure of fiber composite materials with self-healing function and its preparation method. Background Technology

[0002] Fiber-reinforced composites (FRPs) are widely used due to their advantages such as high specific strength and high specific modulus. However, they have poor interlaminar toughness and are prone to delamination failure under impact or fatigue loads. At the same time, internal microcracks are difficult to detect and repair, threatening structural safety.

[0003] Existing technologies mainly improve upon existing methods through the following approaches: 1. Interlayer toughening: Introducing thermoplastic particles, carbon nanotubes, etc., but the toughening effect is singular and does not solve the crack repair problem. 2. Self-healing: Using microcapsules to encapsulate repair agents, but this has problems such as the capsule reducing the original mechanical properties, irreversible repair (failure after one repair), and poor interfacial compatibility. For example, the patent document with publication number CN115838981B mainly addresses the antibacterial function and does not involve interlayer toughening and self-healing; the patent document with publication number CN224012764U focuses on the production of high-grammage prepregs and does not address microcrack repair.

[0004] Therefore, there is an urgent need for an integrated interlayer structure that combines high toughness with multiple repair capabilities. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a self-healing fiber composite interlaminar toughening structure and its preparation method.

[0006] The present invention is achieved through the following technical solutions.

[0007] The present invention provides a fiber composite material interlayer toughening structure with self-healing function, comprising a fiber reinforcement layer and a resin matrix layer, wherein a multi-level interlayer toughening self-healing layer is provided between adjacent fiber reinforcement layers, wherein the interlayer toughening self-healing layer comprises, from bottom to top: an interface reinforcement layer, an energy dissipation layer and a repair layer.

[0008] Preferably, the interface reinforcement layer comprises the following components in parts by weight: 30-50 parts of nano-toughening filler, 5-15 parts of interface coupling agent, and 40-60 parts of thermosetting resin prepolymer. The energy dissipation layer comprises, by weight, the following components: 25-45 parts of thermoplastic resin, 30-50 parts of thermosetting resin prepolymer, 10-25 parts of nano-conductive filler, and 1-5 parts of curing accelerator.

[0009] Preferably, the repair layer comprises, by weight, the following components: 20-40 parts of first thermally reversible cross-linked polymer microspheres, 20-40 parts of second thermally reversible cross-linked polymer microspheres, 2-8 parts of interfacial coupling agent KH550, and 5-15 parts of thermoplastic resin; The first thermally reversible cross-linked polymer microspheres have a particle size distribution between 50 and 200 nm, and the Diels-Alder reversible reaction equilibrium temperature is 100 to 120 °C; the second thermally reversible cross-linked polymer microspheres have a particle size distribution between 200 and 500 nm, and the Diels-Alder reversible reaction equilibrium temperature is 130 to 150 °C.

[0010] Preferably, the nano-toughening filler is selected from one or more of carbon nanotubes, graphene nanosheets, and nano-silica; and the surface of the nano-toughening filler is grafted with at least one functional group selected from amino, carboxyl, epoxy, or hydroxyl groups. The interface coupling agent is a silane coupling agent containing amino, epoxy, or vinyl functional groups.

[0011] Preferably, the thermoplastic resin includes one or more of polyethersulfone, polyimide, and polyetherimide, and its glass transition temperature is higher than 150°C. The thermosetting resin prepolymer includes one or more of epoxy resin, bismaleimide resin, and cyanate ester resin; The nano-conductive filler is selected from one or more of carbon nanotubes, graphene nanosheets, and silver nanowires. The curing accelerator is one or more of triphenylphosphine, diisopropylbenzene peroxide, and cobalt acetylacetonate.

[0012] A method for preparing a fiber composite interlaminar toughening structure with self-healing function includes the following steps: A1: Preparation of the first thermally reversible cross-linked polymer microspheres and the second thermally reversible cross-linked polymer microspheres; A2: Preparation of interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry; A3: Preparation of fiber reinforcement layer, the steps include: impregnating the reinforcing fiber in a resin matrix to obtain fiber prepreg; A4: Construction of a multi-layered interlayer toughening self-healing layer: The fiber prepreg obtained in A3 is laid layer by layer, and the interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry are sequentially coated or sprayed between adjacent prepreg layers to form a three-layer interlayer toughening self-healing layer, thus obtaining a composite material layer. A5: Curing and molding: The composite material laminate structure is heated and pressurized to form a stable multi-level interlayer toughened self-healing structure. A6: Post-treatment: After curing, allow to cool naturally to room temperature and demold to obtain the interlayer toughened structure of fiber composite material.

[0013] Preferably, the method for preparing the first thermally reversible crosslinked polymer microspheres includes the following steps: B1: Furan-functionalized monomers and maleimide-functionalized monomers are dissolved in dioxane at a molar ratio of 1:0.8~1.2, and initiator AIBN is added. Free radical polymerization is carried out at 60~80℃ for 4~8 hours under nitrogen protection to obtain the first linear polymer containing furan and maleimide side groups. B2: Polymer microspheres with a particle size of 50~200nm were prepared using a first linear polymer via a fine emulsion-solvent evaporation method; the microspheres were then heat-treated at 100~110℃ for 2~4 hours to induce a Diels-Alder cycloaddition reaction between the furan groups and the maleimide groups, forming a cross-linked structure, thus obtaining the first thermally reversible cross-linked polymer microspheres with an equilibrium temperature of 100~120℃.

[0014] Preferably, the method for preparing the second thermally reversible crosslinked polymer microspheres includes the following steps: C1: Furan-functionalized monomers containing electron-donating substituents and maleimide-functionalized monomers are dissolved in dioxane at a molar ratio of 1:0.8~1.2, and initiator AIBN is added. The free radical polymerization reaction is carried out at 60~80℃ for 4~8 hours under nitrogen protection to obtain a second linear polymer containing furan and maleimide side groups. C2: Microspheres with a particle size of 200~500nm were prepared using a second linear polymer via a fine emulsion-solvent evaporation method, and then heat-treated at 130~140℃ for 2~4 hours to obtain second thermally reversible crosslinked polymer microspheres with an equilibrium temperature of 130~150℃.

[0015] Preferably, the preparation of the interface reinforcement layer slurry includes the following steps: adding nano-toughening filler, interface coupling agent, and thermosetting resin prepolymer to an organic solvent, and dispersing them evenly at a high speed of 7000~9000 rpm for 20~40 minutes to obtain a bottom layer slurry with a solid content of 10~30wt%. The preparation of the energy dissipation layer slurry includes the following steps: adding thermoplastic resin, thermosetting resin prepolymer, nano-conductive filler, and curing accelerator to an organic solvent, and dispersing them evenly at a high speed of 7000~9000rpm for 20~40 minutes to obtain a middle layer slurry with a solid content of 15~35wt%. The preparation of the repair layer slurry includes the following steps: adding the first thermally reversible cross-linked polymer microspheres, the second thermally reversible cross-linked polymer microspheres, the interfacial coupling agent, and the thermoplastic resin to an organic solvent, and dispersing them evenly at a high speed of 7000~9000 rpm for 20~40 minutes to obtain an upper layer slurry with a solid content of 10~25wt%.

[0016] Preferably, in the process of sequentially coating or spraying the interface reinforcement layer slurry, energy dissipation layer slurry, and repair layer slurry between adjacent prepreg layers, the dry film thickness of the interface reinforcement layer slurry is controlled to be 5~15μm, the dry film thickness of the energy dissipation layer is 10~25μm, the dry film thickness of the repair layer is 10~20μm, and the total dry film thickness of the three-layer interlayer toughening self-repairing layer is 25~60μm. The resin matrix is ​​one or more of epoxy resin, bismaleimide resin, or cyanate ester resin; The reinforcing fiber is carbon fiber; The coating or spraying method is one of spraying, scraping, or screen printing; The process parameters for curing in A5 include: heating rate of 1~3℃ / min, curing temperature of 120~200℃, curing pressure of 0.3~0.8MPa, and holding time of 2~6 hours.

[0017] The beneficial effects of this invention are as follows: 1. Temperature gradient graded self-healing: Two types of thermally reversible cross-linked polymer microspheres with different Diels-Alder reversible reaction equilibrium temperatures are used to selectively and precisely repair cracks of different depths through graded heating. The repair efficiency can still be maintained above 85% after multiple repairs, overcoming the defect of traditional microcapsules that fail after a single repair.

[0018] 2. Multi-layered structural design: A three-layer functional structure is constructed sequentially between adjacent fiber layers: an interlayer toughening self-healing layer (upper layer), an energy dissipation layer (middle layer), and an interface reinforcement layer (bottom layer). The interlayer toughening self-healing layer is responsible for crack filling and self-repair; the energy dissipation layer absorbs impact energy through the plastic deformation of the thermoplastic elastomer; and the interface reinforcement layer enhances the interlayer bonding strength through the bridging and pull-out effect of nanofillers. The synergistic effect of the three layers increases the interlayer fracture toughness (GIC) by more than 50%.

[0019] 3. Integrated self-healing and self-reporting functions: Nano-conductive fillers are introduced into the energy dissipation layer to construct an interlayer conductive network. When microcracks occur between the layers, the conductive network is damaged, leading to a significant increase in resistance (up to 100%~200%). After thermal stimulation repair, the conductive network partially recovers, and the resistance decreases synchronously. Through an external resistance monitoring device, the occurrence of damage and the effectiveness of repair can be determined in real time.

[0020] 4. Strong process compatibility: The three-layer structure of this invention is constructed layer by layer by spraying or coating, which is fully compatible with the existing prepreg-autoclave molding process, requires no major equipment modification, and is easy to promote industrially.

[0021] The present invention aims to solve the technical problems of insufficient interlaminar toughness and difficulty in repairing microcracks in existing fiber composite materials. It provides a composite material structure that can achieve efficient self-repair of interlaminar interfaces multiple times and significantly improve interlaminar fracture toughness. It is suitable for applications with high requirements for material safety and durability, such as aerospace, wind power generation, and automotive lightweighting. Detailed Implementation

[0022] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0023] Example 1: A fiber composite interlayer toughening structure with self-healing function includes a fiber reinforcement layer and a resin matrix layer. A multi-level biomimetic interlayer toughening self-healing layer is provided between adjacent fiber reinforcement layers. The interlayer toughening self-healing layer includes, from bottom to top, an interface reinforcement layer, an energy dissipation layer and a repair layer.

[0024] The interface reinforcement layer comprises the following components in parts by weight: 30 parts of nano-toughening filler, 5 parts of interface coupling agent, and 40 parts of thermosetting resin prepolymer. The energy dissipation layer comprises the following components in parts by weight: 25 parts thermoplastic resin, 30 parts thermosetting resin prepolymer, 10 parts nano-conductive filler, and 1 part curing accelerator.

[0025] The repair layer comprises the following components in parts by weight: 20 parts of first thermally reversible cross-linked polymer microspheres, 20 parts of second thermally reversible cross-linked polymer microspheres, 2 parts of interfacial coupling agent KH550, and 5 parts of thermoplastic resin. The first thermally reversible cross-linked polymer microspheres have a particle size distribution between 50 and 200 nm, and the Diels-Alder reversible reaction equilibrium temperature is 100 to 120 °C; the second thermally reversible cross-linked polymer microspheres have a particle size distribution between 200 and 500 nm, and the Diels-Alder reversible reaction equilibrium temperature is 130 to 150 °C.

[0026] Both the first thermally reversible crosslinked polymer microsphere and the second thermally reversible crosslinked polymer microsphere are furan-maleimide type thermally reversible crosslinked polymer microspheres based on the Diels-Alder reversible reaction, and the equilibrium temperatures of the two Diels-Alder reversible reactions are different.

[0027] The nano-toughening filler is a carbon nanotube with an aspect ratio greater than 50; and the surface of the nano-toughening filler is grafted with amino active functional groups.

[0028] The thermoplastic resin is polyethersulfone, and its glass transition temperature is higher than 150°C. The thermosetting resin prepolymer is epoxy resin E51; The nano-conductive filler includes carbon nanotubes, which are used to realize the interlayer resistance monitoring function. The curing accelerator is triphenylphosphine.

[0029] A method for preparing a fiber composite interlaminar toughening structure with self-healing function includes the following steps: A1: Preparation of the first thermally reversible cross-linked polymer microspheres and the second thermally reversible cross-linked polymer microspheres; A2: Preparation of interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry; A3: Preparation of fiber-reinforced layer, the steps include: impregnating reinforcing fibers in a resin matrix solution to obtain fiber prepreg; the reinforcing fibers are T700-12K carbon fibers, and the resin matrix content is controlled at 35±2wt%; A4: Construction of a multi-layered interlayer toughening self-healing layer: The fiber prepreg obtained in A3 is cut into 300mm×300mm pieces and then laid layer by layer. An interface reinforcement layer slurry, an energy dissipation layer slurry, and a repair layer slurry are applied or sprayed between adjacent prepreg layers in sequence to form a three-layer structure interlayer toughening self-healing layer, thus obtaining a composite material layer. A5: Curing and molding: The composite material laminate structure after 16 layers is placed in a vacuum bag. During the curing process, each layer and the resin matrix undergo a co-curing reaction to form a stable multi-level interlayer toughened self-healing structure. A6: Post-treatment: After curing, allow to cool naturally to room temperature and demold to obtain the interlayer toughened structure of fiber composite material.

[0030] The preparation method of the first thermally reversible crosslinked polymer microspheres includes the following steps: B1: 0.1 mol of furanyl functionalized monomer and 0.1 mol of maleimide functionalized monomer were dissolved in 200 mL of dioxane at a molar ratio of 1:0.8. 0.5 g of initiator AIBN was added, and the free radical polymerization reaction was carried out at 60 °C for 4 hours under nitrogen protection to obtain the first linear polymer containing furanyl and maleimide side groups. The furanyl functionalized monomer was furfuryl methacrylate, and the maleimide functionalized monomer was N-(4-hydroxyphenyl)maleimide methacrylate. B2: The first linear copolymer is dissolved in dichloromethane, and polymer microspheres with a particle size of 50~200nm are prepared by the first linear copolymer through a fine emulsion-solvent evaporation method; the microspheres are then heat-treated at 100℃ for 2 hours to induce a Diels-Alder cycloaddition reaction between the furan group and the maleimide group to form a cross-linked structure, thereby obtaining the first thermally reversible cross-linked polymer microspheres with an equilibrium temperature of 100℃.

[0031] The steps for preparing polymer microspheres with a particle size of 50~200nm using a first linear polymer via a fine emulsion-solvent evaporation method are as follows: B3: Dissolve the first linear polymer mentioned above in dichloromethane to prepare a 5 wt% polymer solution as the oil phase; add hexadecane to the oil phase as a co-stabilizer at an amount of 0.5% of the oil phase volume; B4: Dissolve polyvinyl alcohol (PVA, molecular weight 17000, degree of alcoholysis 88%) in deionized water to prepare a 1.5wt% aqueous solution as the aqueous phase; B5: Mix the oil phase and water phase at a volume ratio of 1:8, and emulsify for 8 minutes at 7000 rpm using a high-shear emulsifier under ice-water bath conditions to form a stable oil-in-water (O / W) fine emulsion. B6: The resulting fine emulsion was stirred at 400 rpm for 12 hours at room temperature to allow the dichloromethane to slowly evaporate and the polymer microspheres to gradually solidify and precipitate. B7: The solidified microsphere suspension was centrifuged at 5000 rpm, the supernatant was discarded, and the microspheres were washed three times with deionized water and then twice with ethanol. The microspheres were then dried in a vacuum drying oven at 40℃ for 24 hours to obtain polymer microspheres with a particle size distribution between 50 and 200 nm.

[0032] The method for preparing the second thermally reversible crosslinked polymer microspheres includes the following steps: C1: 0.1 mol of a furanyl-functionalized monomer containing electron-donating substituents and 0.1 mol of a maleimide-functionalized monomer were dissolved in 200 mL of dioxane at a molar ratio of 1:0.8. 0.5 g of initiator AIBN was added, and the mixture was subjected to free radical polymerization at 60 °C for 4 hours under nitrogen protection to obtain a second linear polymer containing furanyl and maleimide side groups. The furanyl-functionalized monomer containing electron-donating substituents was 5-methylfurfuryl methacrylate; the maleimide-functionalized monomer was N-(4-hydroxyphenyl)maleimide methacrylate. C2: Microspheres with a particle size of 200~500nm were prepared using a second linear polymer via a fine emulsion-solvent evaporation method. After heat treatment at 130℃ for 2 hours, microspheres of the second thermally reversible crosslinked polymer with an equilibrium temperature of 130℃ were obtained.

[0033] The steps for preparing microspheres with a particle size of 200~500 nm using a second linear polymer via a fine emulsion-solvent evaporation method are as follows: C3: Dissolve the above-mentioned second linear polymer in dichloromethane to prepare a 10wt% polymer solution as the oil phase; add no or only a very small amount (≤0.2%) of hexadecane as a stabilizer; C4: Polyvinyl alcohol (PVA, molecular weight 17000, degree of alcoholysis 88%) is dissolved in deionized water to prepare a 0.5wt% aqueous solution as the aqueous phase; C5: Mix the oil phase and water phase at a volume ratio of 1:5, and emulsify at 6000 rpm for 5 minutes at room temperature using a high-shear emulsifier to form an oil-in-water (O / W) fine emulsion. C6: The resulting fine emulsion was stirred at 300 rpm for 12 hours at room temperature to allow the dichloromethane to slowly evaporate and the polymer microspheres to gradually solidify and precipitate. C7: The solidified microsphere suspension was centrifuged at 4000 rpm, the supernatant was discarded, and the microspheres were washed three times with deionized water and then twice with ethanol. The microspheres were then dried in a vacuum drying oven at 40℃ for 24 hours to obtain polymer microspheres with a particle size distribution between 200 and 500 nm.

[0034] The preparation of the interface reinforcement layer slurry includes the following steps: adding nano toughening filler, interface coupling agent, and thermosetting resin prepolymer to the organic solvent acetone, and dispersing them evenly at high speed of 7000 rpm for 20 minutes to obtain a bottom layer slurry with a solid content of 10 wt%. The preparation of the energy dissipation layer slurry includes the following steps: adding thermoplastic resin, thermosetting resin prepolymer, nano-conductive filler and curing accelerator to an organic solvent, and dispersing them evenly at a high speed of 7000 rpm for 20 minutes to obtain a middle layer slurry with a solid content of 15 wt%. The preparation of the repair layer slurry includes the following steps: adding the first thermally reversible cross-linked polymer microspheres, the second thermally reversible cross-linked polymer microspheres, the interfacial coupling agent, and the thermoplastic resin to the organic solvent acetone, and dispersing them evenly at a high speed of 7000 rpm for 20 minutes to obtain an upper layer slurry with a solid content of 10 wt%; the interfacial coupling agent is coupling agent KH550.

[0035] In the process of sequentially coating the interface reinforcement layer slurry, the energy dissipation layer slurry, and the repair layer slurry between adjacent prepreg layers, the dry film thickness of the interface reinforcement layer slurry is controlled to be 5~15μm, the dry film thickness of the energy dissipation layer is 10~25μm, the dry film thickness of the repair layer is 10~20μm, and the total dry film thickness of the three-layer interlayer toughening self-repairing layer is 25~60μm. The resin matrix is ​​epoxy resin (epoxy resin E51 and curing agent sulfamic acid DDS are prepared at a mass ratio of 100:30). The reinforcing fiber is T700-12K carbon fiber; The process parameters for curing in A5 include: heating rate of 1℃ / min, curing temperature of 120℃, curing pressure of 0.3MPa, and holding time of 2 hours.

[0036] Example 2: A fiber composite interlayer toughening structure with self-healing function includes a fiber reinforcement layer and a resin matrix layer. A multi-level biomimetic interlayer toughening self-healing layer is provided between adjacent fiber reinforcement layers. The interlayer toughening self-healing layer includes, from bottom to top, an interface reinforcement layer, an energy dissipation layer and a repair layer.

[0037] The interface reinforcement layer comprises the following components in parts by weight: 50 parts of nano-toughening filler, 15 parts of interface coupling agent, and 60 parts of thermosetting resin prepolymer. The energy dissipation layer comprises the following components in parts by weight: 40 parts thermoplastic resin, 45 parts thermosetting resin prepolymer, 25 parts nano-conductive filler, and 5 parts curing accelerator.

[0038] The repair layer comprises the following components in parts by weight: 40 parts of first thermally reversible cross-linked polymer microspheres, 40 parts of second thermally reversible cross-linked polymer microspheres, 8 parts of interfacial coupling agent KH550, and 15 parts of thermoplastic resin. The first thermally reversible cross-linked polymer microspheres have a particle size distribution between 50 and 200 nm, and the Diels-Alder reversible reaction equilibrium temperature is 100 to 120 °C; the second thermally reversible cross-linked polymer microspheres have a particle size distribution between 200 and 500 nm, and the Diels-Alder reversible reaction equilibrium temperature is 130 to 150 °C.

[0039] Both the first thermally reversible crosslinked polymer microsphere and the second thermally reversible crosslinked polymer microsphere are furan-maleimide type thermally reversible crosslinked polymer microspheres based on the Diels-Alder reversible reaction, and the equilibrium temperatures of the two Diels-Alder reversible reactions are different.

[0040] The nano-toughening filler is graphene nanosheet, and the surface of the nano-toughening filler is grafted with carboxyl active functional groups.

[0041] The thermoplastic resin is polyimide, and its glass transition temperature is higher than 150°C. The thermosetting resin prepolymer is a bismaleimide resin; The nano-conductive filler is graphene nanosheet, used to realize the interlayer resistance monitoring function; The curing accelerator is dicumyl peroxide (DCP).

[0042] A method for preparing a fiber composite interlaminar toughening structure with self-healing function includes the following steps: A1: Preparation of the first thermally reversible cross-linked polymer microspheres and the second thermally reversible cross-linked polymer microspheres; A2: Preparation of interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry; A3: Preparation of fiber-reinforced layer, the steps include: impregnating reinforcing fibers in a resin matrix solution to obtain fiber prepreg; the reinforcing fibers are T700-12K carbon fibers, and the resin matrix content is controlled at 35±2wt%; A4: Construction of a multi-layered interlayer toughening self-healing layer: The fiber prepreg obtained in A3 is cut into 300mm×300mm pieces and then laid layer by layer. An interface reinforcement layer slurry, an energy dissipation layer slurry, and a repair layer slurry are applied or sprayed between adjacent prepreg layers in sequence to form a three-layer structure interlayer toughening self-healing layer, thus obtaining a composite material layer. A5: Curing and molding: The composite material laminate structure after 16 layers is placed in an autoclave. During the curing process, each layer and the resin matrix undergo a co-curing reaction to form a stable multi-level interlayer toughened self-healing structure. A6: Post-treatment: After curing, allow to cool naturally to room temperature and demold to obtain the interlayer toughened structure of fiber composite material.

[0043] The preparation method of the first thermally reversible crosslinked polymer microspheres includes the following steps: B1: 0.1 mol of furanyl functionalized monomer and 0.1 mol of maleimide functionalized monomer were dissolved in 200 mL of dioxane at a molar ratio of 1:1.2. 0.5 g of initiator AIBN was added, and the mixture was subjected to free radical polymerization at 80 °C for 8 hours under nitrogen protection to obtain the first linear polymer containing furanyl and maleimide side groups. The furanyl functionalized monomer was furfuryl methacrylate, and the maleimide functionalized monomer was N-(4-hydroxyphenyl)maleimide methacrylate. B2: The first linear copolymer is dissolved in dichloromethane, and polymer microspheres with a particle size of 50~200nm are prepared by the first linear copolymer through a fine emulsion-solvent evaporation method; the microspheres are then heat-treated at 110℃ for 4 hours to induce a Diels-Alder cycloaddition reaction between the furan group and the maleimide group to form a cross-linked structure, thereby obtaining the first thermally reversible cross-linked polymer microspheres with an equilibrium temperature of 120℃.

[0044] The steps for preparing polymer microspheres with a particle size of 50~200nm using a first linear polymer via a fine emulsion-solvent evaporation method are as follows: B3: Dissolve the first linear polymer mentioned above in dichloromethane to prepare an 8 wt% polymer solution as the oil phase; add hexadecane as a co-stabilizer to the oil phase at an amount of 1.0% of the oil phase volume; B4: Dissolve polyvinyl alcohol (PVA, molecular weight 17000, degree of alcoholysis 88%) in deionized water to prepare a 2.0 wt% aqueous solution as the aqueous phase; B5: Mix the oil phase and water phase at a volume ratio of 1:12, and emulsify them for 12 minutes at a speed of 9000 rpm using a high-shear emulsifier under ice-water bath conditions to form a stable oil-in-water (O / W) fine emulsion. B6: The resulting fine emulsion was stirred at 600 rpm for 24 hours at room temperature to allow the dichloromethane to slowly evaporate and the polymer microspheres to gradually solidify and precipitate. B7: The solidified microsphere suspension was centrifuged at 7000 rpm, the supernatant was discarded, and the microspheres were washed three times with deionized water and then twice with ethanol. The microspheres were then dried in a vacuum drying oven at 40°C for 24 hours to obtain polymer microspheres with a particle size distribution between 50 and 200 nm.

[0045] The method for preparing the second thermally reversible crosslinked polymer microspheres includes the following steps: C1: 0.1 mol of a furanyl functionalized monomer containing electron-donating substituents and 0.1 mol of a maleimide functionalized monomer were dissolved in 200 mL of dioxane at a molar ratio of 1:1.2. 0.5 g of initiator AIBN was added, and the mixture was subjected to free radical polymerization at 80 °C for 8 hours under nitrogen protection to obtain a second linear polymer containing furanyl and maleimide side groups. The furanyl functionalized monomer containing electron-donating substituents was 5-methylfurfuryl methacrylate; the maleimide functionalized monomer was N-(4-hydroxyphenyl)maleimide methacrylate. C2: Microspheres with a particle size of 200~500nm were prepared using a second linear polymer via a fine emulsion-solvent evaporation method. After heat treatment at 140℃ for 4 hours, microspheres of the second thermally reversible crosslinked polymer with an equilibrium temperature of 150℃ were obtained.

[0046] The steps for preparing microspheres with a particle size of 200~500 nm using a second linear polymer via a fine emulsion-solvent evaporation method are as follows: C3: Dissolve the above-mentioned second linear polymer in dichloromethane to prepare a 15wt% polymer solution as the oil phase; add no or only a very small amount (≤0.2%) of hexadecane as a stabilizer; C4: Polyvinyl alcohol (PVA, molecular weight 17000, degree of alcoholysis 88%) is dissolved in deionized water to prepare a 1.0 wt% aqueous solution as the aqueous phase; C5: Mix the oil phase and water phase at a volume ratio of 1:8, and emulsify at 8000 rpm for 8 minutes at room temperature using a high-shear emulsifier to form an oil-in-water (O / W) fine emulsion. C6: The resulting fine emulsion was stirred at 500 rpm for 24 hours at room temperature to allow the dichloromethane to slowly evaporate and the polymer microspheres to gradually solidify and precipitate. C7: The solidified microsphere suspension was centrifuged at 6000 rpm, the supernatant was discarded, and the microspheres were washed three times with deionized water and then twice with ethanol. The microspheres were then dried in a vacuum drying oven at 40℃ for 24 hours to obtain polymer microspheres with a particle size distribution between 200 and 500 nm.

[0047] The preparation of the interface reinforcement layer slurry includes the following steps: adding nano toughening filler, interface coupling agent, and thermosetting resin prepolymer to the organic solvent acetone, and dispersing them evenly at a high speed of 9000 rpm for 40 minutes to obtain a bottom layer slurry with a solid content of 30 wt%. The preparation of the energy dissipation layer slurry includes the following steps: adding thermoplastic resin, thermosetting resin prepolymer, nano-conductive filler and curing accelerator to an organic solvent, and dispersing them evenly at a high speed of 9000 rpm for 40 minutes to obtain a middle layer slurry with a solid content of 35 wt%. The preparation of the repair layer slurry includes the following steps: adding the first thermally reversible cross-linked polymer microspheres, the second thermally reversible cross-linked polymer microspheres, the interfacial coupling agent, and the thermoplastic resin to the organic solvent acetone, and dispersing them evenly at a high speed of 9000 rpm for 40 minutes to obtain an upper layer slurry with a solid content of 25 wt%; the interfacial coupling agent is coupling agent KH550.

[0048] In the process of sequentially spraying interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry between adjacent prepreg layers, the dry film thickness of the interface reinforcement layer slurry is controlled to be 5~15μm, the dry film thickness of the energy dissipation layer is 10~25μm, the dry film thickness of the repair layer is 10~20μm, and the total dry film thickness of the three-layer interlayer toughening self-repairing layer is 25~60μm. The resin matrix is ​​a bismaleimide resin; The reinforcing fiber is T700-12K carbon fiber; The process parameters for curing in A5 include: heating rate of 3℃ / min, curing temperature of 200℃, curing pressure of 0.8MPa, and holding time of 6 hours.

[0049] Example 3: A fiber composite interlayer toughening structure with self-healing function includes a fiber reinforcement layer and a resin matrix layer. A multi-level biomimetic interlayer toughening self-healing layer is provided between adjacent fiber reinforcement layers. The interlayer toughening self-healing layer includes, from bottom to top, an interface reinforcement layer, an energy dissipation layer and a repair layer.

[0050] The interface reinforcement layer comprises the following components in parts by weight: 40 parts of nano-toughening filler, 10 parts of interface coupling agent, and 50 parts of thermosetting resin prepolymer. The energy dissipation layer comprises the following components in parts by weight: 30 parts thermoplastic resin, 40 parts thermosetting resin prepolymer, 15 parts nano-conductive filler, and 3 parts curing accelerator.

[0051] The repair layer comprises the following components in parts by weight: 30 parts of first thermally reversible cross-linked polymer microspheres, 30 parts of second thermally reversible cross-linked polymer microspheres, 5 parts of interfacial coupling agent KH550, and 10 parts of thermoplastic resin. The first thermally reversible cross-linked polymer microspheres have a particle size distribution between 50 and 200 nm, and the Diels-Alder reversible reaction equilibrium temperature is 100 to 120 °C; the second thermally reversible cross-linked polymer microspheres have a particle size distribution between 200 and 500 nm, and the Diels-Alder reversible reaction equilibrium temperature is 130 to 150 °C.

[0052] Both the first thermally reversible crosslinked polymer microsphere and the second thermally reversible crosslinked polymer microsphere are furan-maleimide type thermally reversible crosslinked polymer microspheres based on the Diels-Alder reversible reaction, and the equilibrium temperatures of the two Diels-Alder reversible reactions are different.

[0053] The nano-toughening filler is nano-silica, and the surface of the nano-toughening filler is grafted with epoxy-based active functional groups. The thermoplastic resin is polyetherimide, and its glass transition temperature is higher than 150°C. The thermosetting resin prepolymer is a cyanate ester resin; The nano-conductive filler is silver nanowire, used to realize the interlayer resistance monitoring function; The curing accelerator is cobalt acetylacetonate.

[0054] A method for preparing a fiber composite interlaminar toughening structure with self-healing function includes the following steps: A1: Preparation of the first thermally reversible cross-linked polymer microspheres and the second thermally reversible cross-linked polymer microspheres; A2: Preparation of interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry; A3: Preparation of fiber-reinforced layer, the steps include: impregnating reinforcing fibers in a resin matrix solution to obtain fiber prepreg; the reinforcing fibers are T700 carbon fibers (12K), and the resin matrix content is controlled at 35±2wt%; A4: Construction of a multi-layered interlayer toughening self-healing layer: The fiber prepreg obtained in A3 is cut into 300mm×300mm pieces and then laid layer by layer. An interface reinforcement layer slurry, an energy dissipation layer slurry, and a repair layer slurry are applied or sprayed between adjacent prepreg layers in sequence to form a three-layer structure interlayer toughening self-healing layer, thus obtaining a composite material layer. A5: Curing and molding: The composite material laminate structure after 16 layers is placed in an autoclave. During the curing process, each layer and the resin matrix undergo a co-curing reaction to form a stable multi-level interlayer toughened self-healing structure. A6: Post-treatment: After curing, allow to cool naturally to room temperature and demold to obtain the interlayer toughened structure of fiber composite material.

[0055] The preparation method of the first thermally reversible crosslinked polymer microspheres includes the following steps: B1: 0.1 mol of furanyl functionalized monomer and 0.1 mol of maleimide functionalized monomer were dissolved in 200 mL of dioxane at a molar ratio of 1:1. 0.5 g of initiator AIBN was added, and the mixture was subjected to free radical polymerization at 70 °C for 5 hours under nitrogen protection to obtain a first linear polymer containing furanyl and maleimide side groups. The furanyl functionalized monomer was furfuryl methacrylate, and the maleimide functionalized monomer was N-(4-hydroxyphenyl)maleimide methacrylate. B2: The first linear copolymer was dissolved in dichloromethane, and microspheres with a particle size of 50~200nm were prepared by a fine emulsion-solvent evaporation method; the microspheres were then heat-treated at 105℃ for 3 hours to induce a Diels-Alder cycloaddition reaction between the furan group and the maleimide group to form a cross-linked structure, thus obtaining the first thermally reversible cross-linked polymer microspheres with an equilibrium temperature of 110℃.

[0056] The steps for preparing polymer microspheres with a particle size of 50~200nm using a first linear polymer via a fine emulsion-solvent evaporation method are as follows: B3: Dissolve the first linear polymer mentioned above in dichloromethane to prepare a 7wt% polymer solution as the oil phase; add hexadecane as a co-stabilizer to the oil phase at an amount of 0.8% of the oil phase volume; B4: Dissolve polyvinyl alcohol (PVA, molecular weight 17000, degree of alcoholysis 88%) in deionized water to prepare a 1.9wt% aqueous solution as the aqueous phase; B5: Mix the oil phase and water phase at a volume ratio of 1:10, and emulsify them for 10 minutes at a speed of 10,000 rpm under ice-water bath conditions to form a stable oil-in-water (O / W) fine emulsion. B6: The resulting fine emulsion was stirred at 500 rpm for 17 hours at room temperature to allow the dichloromethane to slowly evaporate and the polymer microspheres to gradually solidify and precipitate. B7: The solidified microsphere suspension was centrifuged at 8000 rpm, the supernatant was discarded, and the microspheres were washed three times with deionized water and then twice with ethanol. The microspheres were then dried in a vacuum drying oven at 40℃ for 24 hours to obtain polymer microspheres with a particle size distribution between 50 and 200 nm.

[0057] The method for preparing the second thermally reversible crosslinked polymer microspheres includes the following steps: C1: 0.1 mol of a furanyl functionalized monomer containing electron-donating substituents and 0.1 mol of a maleimide functionalized monomer were dissolved in 200 mL of dioxane at a molar ratio of 1:1.1. 0.5 g of initiator AIBN was added, and the mixture was subjected to free radical polymerization at 70 °C for 6 hours under nitrogen protection to obtain a second linear polymer containing furanyl and maleimide side groups. The furanyl functionalized monomer containing electron-donating substituents was 5-methylfurfuryl methacrylate; the maleimide functionalized monomer was N-(4-hydroxyphenyl)maleimide methacrylate. C2: Microspheres with a particle size of 200~500nm were prepared using a second linear polymer via a fine emulsion-solvent evaporation method. After heat treatment at 136℃ for 3 hours, microspheres of the second thermally reversible crosslinked polymer with an equilibrium temperature of 140℃ were obtained.

[0058] The steps for preparing microspheres with a particle size of 200~500 nm using a second linear polymer via a fine emulsion-solvent evaporation method are as follows: C3: Dissolve the above-mentioned second linear polymer in dichloromethane to prepare a 13wt% polymer solution as the oil phase; add no or only a very small amount (≤0.2%) of hexadecane as a stabilizer; C4: Polyvinyl alcohol (PVA, molecular weight 17000, degree of alcoholysis 88%) is dissolved in deionized water to prepare a 0.7wt% aqueous solution as the aqueous phase; C5: Mix the oil phase and water phase at a volume ratio of 1:7, and emulsify at 9000 rpm for 6 minutes at room temperature using a high-shear emulsifier to form an oil-in-water (O / W) fine emulsion. C6: The resulting fine emulsion was stirred at 400 rpm for 18 hours at room temperature to allow the dichloromethane to slowly evaporate and the polymer microspheres to gradually solidify and precipitate. C7: The solidified microsphere suspension was centrifuged at 7000 rpm, the supernatant was discarded, and the microspheres were washed three times with deionized water and then twice with ethanol. The microspheres were then dried in a vacuum drying oven at 40℃ for 24 hours to obtain polymer microspheres with a particle size distribution between 200 and 500 nm.

[0059] The preparation of the interface reinforcement layer slurry includes the following steps: adding nano-toughening filler, interface coupling agent, and thermosetting resin prepolymer to the organic solvent acetone, and dispersing them evenly at high speed of 8000 rpm for 30 minutes to obtain a bottom layer slurry with a solid content of 20 wt%. The preparation of the energy dissipation layer slurry includes the following steps: adding thermoplastic resin, thermosetting resin prepolymer, nano-conductive filler, and curing accelerator to an organic solvent, and dispersing them evenly at high speed of 8000 rpm for 30 minutes to obtain a middle layer slurry with a solid content of 25 wt%. The preparation of the repair layer slurry includes the following steps: adding the first thermally reversible cross-linked polymer microspheres, the second thermally reversible cross-linked polymer microspheres, the interfacial coupling agent, and the thermoplastic resin to the organic solvent acetone, and dispersing them evenly at high speed of 8000 rpm for 30 minutes to obtain an upper layer slurry with a solid content of 18 wt%; the interfacial coupling agent is coupling agent KH550.

[0060] In the process of sequentially applying interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry between adjacent prepreg layers, the dry film thickness of the interface reinforcement layer slurry is controlled to be 5~15μm, the dry film thickness of the energy dissipation layer is 10~25μm, the dry film thickness of the repair layer is 10~20μm, and the total dry film thickness of the three-layer interlayer toughening self-repairing layer is 25~60μm. The resin matrix is ​​a cyanate ester resin; The reinforcing fiber is T700-12K carbon fiber; The process parameters for curing in A5 include: heating rate of 2℃ / min, curing temperature of 160℃, curing pressure of 0.5MPa, and holding time of 4 hours.

[0061] In this invention, the thermoplastic resin in the energy dissipation layer does not participate in the crosslinking reaction. Its high content (25-45 parts) significantly dilutes the relative concentration of the thermosetting resin, reducing the curing rate. To achieve simultaneous co-curing of the three-layer structure, a curing accelerator, triphenylphosphine, must be added. This accelerator catalyzes the ring-opening crosslinking reaction of the thermosetting resin, compensating for the slowed curing caused by the dilution of the thermoplastic resin, and ensuring that the energy dissipation layer, the interface reinforcement layer, and the interlayer toughening self-healing layer complete curing within the same curing process window.

[0062] Comparative Example 1: A fiber composite material structure, based on Example 3, differs only in that a multi-level biomimetic interlayer toughening self-healing layer is not provided between adjacent fiber reinforcement layers.

[0063] Comparative Example 2: A fiber composite material structure, based on Example 3, except that no interface reinforcement layer is provided between adjacent fiber reinforcement layers.

[0064] Comparative Example 3: A fiber composite structure, based on Example 3, except that no energy dissipation layer is provided between adjacent fiber reinforcement layers.

[0065] Comparative Example 4: A fiber composite material structure, based on Example 3, except that no repair layer is provided between adjacent fiber reinforcement layers.

[0066] In Examples 1-3, the carbon nanotubes used were surface-modified carbon nanotubes, in which at least one active functional group, including amino, carboxyl, or epoxy groups, was covalently grafted onto the surface of the carbon nanotubes using a chemical grafting method. Specifically, in Example 1, amino groups were covalently grafted onto the surface of the carbon nanotubes; in Example 2, carboxyl groups were covalently grafted onto the surface of the carbon nanotubes; and in Example 3, epoxy groups were covalently grafted onto the surface of the carbon nanotubes.

[0067] The surface modification method for the carbon nanotubes is as follows: Aminoation modification: 1 g of the above carboxylated carbon nanotubes were dispersed in 100 mL of dimethylformamide, 10 mL of ethylenediamine and 0.5 g of N,N'-dicyclohexylcarbodiimide were added, and the mixture was reacted at 60 °C for 24 hours. After filtration, washing and drying, amino-grafted carbon nanotubes with amino groups on the surface were obtained. The amount of amino grafting was about 2-5 wt%.

[0068] Carboxylation modification: Multi-walled carbon nanotubes (outer diameter 10~20nm, length 1~5μm) were added to a mixed acid of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), ultrasonically dispersed for 30 minutes, then refluxed and stirred at 70℃ for 4 hours. After cooling, they were diluted with deionized water, filtered, washed to pH=7, and vacuum dried at 80℃ for 12 hours to obtain carboxylated carbon nanotubes with carboxyl groups grafted on the surface. The amount of carboxyl groups grafted was about 3~8wt%.

[0069] Epoxy group modification: 1g of the above carboxylated carbon nanotubes were dispersed in toluene, 5mL of epichlorohydrin and 0.5mL of triethylamine were added, and the mixture was refluxed at 80℃ for 8 hours. After filtration, washing and drying, the modified carbon nanotubes with surface grafted epoxy groups were obtained.

[0070] To verify the ability of the interlayer toughening self-healing layer of the present invention to repair multiple cracks in the same crack region, DCB (double cantilever beam) specimens were prepared according to ASTM D5528 standard, and initial cracks were pre-induced using the DCB double cantilever beam method according to ASTM D5528 standard. Microcracks (initial crack length 5±0.5mm) were pre-induced between the layers in the structural specimens of Examples 1-3 and Comparative Examples 1-4.

[0071] Using the fiber composite interlaminar toughening structure prepared in Example 3, the damaged area was subjected to heat repair treatment: the first repair temperature was 110℃, the second repair temperature was 140℃, and each temperature was maintained for 30 minutes. After cooling to room temperature, the interlaminar fracture toughness (GIC) was retested, and the repair efficiency was calculated as: GIC after repair / initial GIC × 100%. The above cycle of "pre-crack → repair → test" was repeated 5 times, and the results are shown in Table 1.

[0072] Table 1. Changes in repair efficiency after multiple repair cycles.

[0073] As shown in Table 1, after five repair-destruction cycles, the repair efficiency of the composite material of the present invention remains above 89.0%, indicating that the self-healing mechanism based on the Diels-Alder reversible reaction has good reversibility and stability, and can achieve multiple repairs in the same crack area, significantly extending the service life of the composite material.

[0074] The type I interlaminar fracture toughness (GIC) of Example 3 and Comparative Examples 1-4 was tested respectively, and the results are shown in Table 2.

[0075] Table 2 Comparison of interlaminar fracture toughness of different samples

[0076] The results in Table 2 show that the GIC value of Example 3 of the present invention reaches 512 J / m. 2 Compared to Comparative Example 1, this represents a 99.2% improvement, exceeding the expected target of 50%. The GIC values ​​of Comparative Examples 2-4 ranged from 365 to 388 J / m³. 2 The results indicate that the absence of a single layer significantly affects the toughening effect, verifying the necessity of synergistic toughening of the three-layer structure.

[0077] Example 1 was compared with Comparative Example 4. The interlaminar fracture toughness (GIC), repair efficiency, and interfacial bonding strength of the two schemes were tested. The interface morphology was observed by SEM. The results are shown in Table 3.

[0078] Table 3 Performance comparison between Example 1 and Comparative Example 4

[0079] As shown in Table 3, in Comparative Example 4, the microcapsules and nanofillers have large size differences, making it difficult for them to be uniformly mixed in the resin matrix. This easily leads to their own agglomeration and interface defects, which become new stress concentration points, resulting in lower GIC and repair efficiency than in Example 1.

[0080] This invention pre-composite self-healing microspheres and nano-toughening fillers uniformly in a slurry to form a stable functional layer, avoiding the interface complexity and performance degradation problems caused by the lack of a repair layer in Comparative Example 4. After pre-inducing cracks in the interlaminar toughening structure of the fiber composite material in Example 3, repair treatments were performed at different temperatures to test the repair efficiency. Simultaneously, the thermal decomposition of the resin matrix was monitored. The results are shown in Table 4. The first thermally reversible crosslinked polymer microsphere is referred to as the first microsphere, and the second thermally reversible crosslinked polymer microsphere is referred to as the second microsphere.

[0081] Table 4. Repair efficiency and resin stability at different repair temperatures

[0082] As shown in Table 4, when the repair temperature is below 100℃, the Diels-Alder reverse reaction is not fully triggered, and the repair efficiency is below 70%. In the range of 100~120℃, the first microsphere is effectively triggered, and the repair efficiency can reach more than 85%. In the range of 130~150℃, the second microsphere is effectively triggered, and the repair efficiency can reach more than 90%.

[0083] When the repair temperature exceeds 150℃, the repair efficiency decreases for two reasons: first, the Diels-Alder crosslinking bonds in the microspheres undergo irreversible side reactions at excessively high temperatures; second, the resin matrix begins to thermally decompose, leading to a decline in matrix performance.

[0084] The repair temperature window (100~150℃) selected in this invention does not overlap with the conventional service temperature of the composite material (-50~80℃), thus avoiding accidental self-repair during service. Simultaneously, this temperature window is lower than the thermal decomposition temperature of the resin matrix (170℃), preventing damage to the matrix material. At the optimal repair temperature (110℃ for the first microsphere and 140℃ for the second microsphere), the repair efficiency can reach 85%~91%.

Claims

1. A fiber composite interlaminar toughening structure with self-healing function, characterized in that: It includes a fiber reinforcement layer and a resin matrix layer, and a multi-layered interlayer toughening self-healing layer is provided between adjacent fiber reinforcement layers. The interlayer toughening self-healing layer includes, from bottom to top, an interface reinforcement layer, an energy dissipation layer and a repair layer.

2. The fiber composite interlaminar toughening structure with self-healing function as described in claim 1, characterized in that: The interface reinforcement layer comprises the following components in parts by weight: 30-50 parts of nano-toughening filler, 5-15 parts of interface coupling agent, and 40-60 parts of thermosetting resin prepolymer. The energy dissipation layer comprises, by weight, the following components: 25-45 parts of thermoplastic resin, 30-50 parts of thermosetting resin prepolymer, 10-25 parts of nano-conductive filler, and 1-5 parts of curing accelerator.

3. The fiber composite interlaminar toughening structure with self-healing function as described in claim 1, characterized in that: The repair layer comprises the following components in parts by weight: 20-40 parts of first thermally reversible cross-linked polymer microspheres, 20-40 parts of second thermally reversible cross-linked polymer microspheres, 2-8 parts of interfacial coupling agent KH550, and 5-15 parts of thermoplastic resin; The first thermally reversible cross-linked polymer microspheres have a particle size distribution between 50 and 200 nm, and the Diels-Alder reversible reaction equilibrium temperature is 100 to 120 °C; the second thermally reversible cross-linked polymer microspheres have a particle size distribution between 200 and 500 nm, and the Diels-Alder reversible reaction equilibrium temperature is 130 to 150 °C.

4. The fiber composite interlaminar toughening structure with self-healing function as described in claim 2, characterized in that: The nano-toughening filler is selected from one or more of carbon nanotubes, graphene nanosheets, and nano-silica; and the surface of the nano-toughening filler is grafted with at least one functional group selected from amino, carboxyl, epoxy, or hydroxyl groups. The interface coupling agent is a silane coupling agent containing amino, epoxy, or vinyl functional groups.

5. The fiber composite interlaminar toughening structure with self-healing function as described in claim 2, characterized in that: The thermoplastic resin includes one or more of polyethersulfone, polyimide, and polyetherimide, and its glass transition temperature is higher than 150°C. The thermosetting resin prepolymer includes one or more of epoxy resin, bismaleimide resin, and cyanate ester resin; The nano-conductive filler is selected from one or more of carbon nanotubes, graphene nanosheets, and silver nanowires. The curing accelerator is one or more of triphenylphosphine, diisopropylbenzene peroxide, and cobalt acetylacetonate.

6. A method for preparing a fiber composite interlaminar toughening structure with self-healing function as described in any one of claims 1-5, characterized in that, Includes the following steps: A1: Preparation of the first thermally reversible cross-linked polymer microspheres and the second thermally reversible cross-linked polymer microspheres; A2: Preparation of interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry; A3: Preparation of fiber reinforcement layer, the steps include: impregnating the reinforcing fiber in a resin matrix to obtain fiber prepreg; A4: Construction of a multi-layered interlayer toughening self-healing layer: The fiber prepreg obtained in A3 is laid layer by layer, and the interface reinforcement layer slurry, energy dissipation layer slurry and repair layer slurry are sequentially coated or sprayed between adjacent prepreg layers to form a three-layer interlayer toughening self-healing layer, thus obtaining a composite material layer. A5: Curing and molding: The composite material laminate structure is heated and pressurized to form a stable multi-level interlayer toughened self-healing structure. A6: Post-treatment: After curing, allow to cool naturally to room temperature and demold to obtain the interlayer toughened structure of fiber composite material.

7. The method for preparing a fiber composite interlaminar toughening structure with self-healing function as described in claim 6, characterized in that: The preparation method of the first thermally reversible crosslinked polymer microspheres includes the following steps: B1: Furan-functionalized monomers and maleimide-functionalized monomers are dissolved in dioxane at a molar ratio of 1:0.8~1.2, and initiator AIBN is added. Free radical polymerization is carried out at 60~80℃ for 4~8 hours under nitrogen protection to obtain the first linear polymer containing furan and maleimide side groups. B2: Polymer microspheres with a particle size of 50~200nm were prepared using a first linear polymer via a fine emulsion-solvent evaporation method; the microspheres were then heat-treated at 100~110℃ for 2~4 hours to induce a Diels-Alder cycloaddition reaction between the furan groups and the maleimide groups, forming a cross-linked structure, thus obtaining the first thermally reversible cross-linked polymer microspheres with an equilibrium temperature of 100~120℃.

8. The method for preparing a self-healing fiber composite interlaminar toughening structure as described in claim 6, characterized in that: The method for preparing the second thermally reversible crosslinked polymer microspheres includes the following steps: C1: Furan-functionalized monomers containing electron-donating substituents and maleimide-functionalized monomers are dissolved in dioxane at a molar ratio of 1:0.8~1.2, and initiator AIBN is added. The free radical polymerization reaction is carried out at 60~80℃ for 4~8 hours under nitrogen protection to obtain a second linear polymer containing furan and maleimide side groups. C2: Microspheres with a particle size of 200~500nm were prepared using a second linear polymer via a fine emulsion-solvent evaporation method, and then heat-treated at 130~140℃ for 2~4 hours to obtain second thermally reversible crosslinked polymer microspheres with an equilibrium temperature of 130~150℃.

9. The method for preparing a fiber composite interlaminar toughening structure with self-healing function as described in claim 6, characterized in that: The preparation of the interface reinforcement layer slurry includes the following steps: adding nano-toughening filler, interface coupling agent, and thermosetting resin prepolymer to an organic solvent, and dispersing them evenly at a high speed of 7000~9000rpm for 20~40 minutes to obtain a bottom layer slurry with a solid content of 10~30wt%. The preparation of the energy dissipation layer slurry includes the following steps: adding thermoplastic resin, thermosetting resin prepolymer, nano-conductive filler, and curing accelerator to an organic solvent, and dispersing them evenly at a high speed of 7000~9000rpm for 20~40 minutes to obtain a middle layer slurry with a solid content of 15~35wt%. The preparation of the repair layer slurry includes the following steps: adding the first thermally reversible cross-linked polymer microspheres, the second thermally reversible cross-linked polymer microspheres, the interfacial coupling agent, and the thermoplastic resin to an organic solvent, and dispersing them evenly at a high speed of 7000~9000 rpm for 20~40 minutes to obtain an upper layer slurry with a solid content of 10~25wt%.

10. The method for preparing a fiber composite interlaminar toughening structure with self-healing function as described in claim 6, characterized in that: In the process of sequentially coating or spraying the interface reinforcement layer slurry, energy dissipation layer slurry, and repair layer slurry between adjacent prepreg layers, the dry film thickness of the interface reinforcement layer slurry is controlled to be 5~15μm, the dry film thickness of the energy dissipation layer is 10~25μm, the dry film thickness of the repair layer is 10~20μm, and the total dry film thickness of the three-layer interlayer toughening self-repairing layer is 25~60μm. The resin matrix is ​​one or more of epoxy resin, bismaleimide resin, or cyanate ester resin; The reinforcing fiber is carbon fiber; The coating or spraying method is one of spraying, scraping, or screen printing; The process parameters for curing in A5 include: heating rate of 1~3℃ / min, curing temperature of 120~200℃, curing pressure of 0.3~0.8MPa, and holding time of 2~6 hours.

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