High temperature resistant high toughness prepreg and method of making same

Abstract

The present application relates to a kind of high-temperature-resistant high-toughness prepreg and its preparation method, mainly solve the hot melt method prepreg with thermoplastic resin toughened epoxy resin matrix process operability is poor and the problem of poor carbon fiber impregnation effect, by using a kind of prepreg, with total mass is 100% by weight, including the following components: epoxy resin matrix: 22~35%;Reinforcing fiber: 50~70%;Toughening layer: 8~15%;Its characterized in that the toughening layer is at least one of the combination of containing epoxy resin and thermoplastic resin;The epoxy resin matrix is at least one of the combination of containing epoxy resin, thermoplastic resin and curing agent;The toughening layer is located in the side of the reinforcing fiber layer with the epoxy resin matrix technical scheme, preferably solve the problem, can be used for the preparation of various carbon fiber composite material main load-bearing structure.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and specifically relates to high-temperature resistant and high-toughness prepregs and their preparation methods. Background Technology

[0002] Advanced resin-based composite materials, reinforced with high-performance fibers such as carbon fiber and aramid fiber, are the preferred lightweight and high-strength structural materials for load-bearing structural components. They are widely used in aerospace, military, and automotive lightweighting, and their application is increasingly significant. One of the key performance indicators for advanced resin-based composite materials used in primary load-bearing structural components is the compressive strength after impact (CAI), which characterizes the composite material's resistance to low-velocity impact damage. Boeing's BMS8-276 standard requires that the CAI of composite materials used in the primary load-bearing structures of civil aircraft should reach 310 MPa. Therefore, improving the CAI of composite materials has always been a research hotspot in this field.

[0003] High carbon fiber toughness (CAI) requires composite materials to possess high toughness, and the main ways to improve toughness are through toughening of the matrix resin and interlaminar toughening. For matrix resin toughening, thermoplastic resins are preferred as toughening agents, ensuring that the heat resistance of the composite material is not reduced while improving toughness. Hexcel's patent EP2607411 uses polyethersulfone (PES) resin and polyamide (PA) particles to composite toughen and modify an epoxy resin matrix. PES exists in the epoxy resin in a completely dissolved state, while PA particles exist in a dispersed state. Carbon fiber prepregs prepared using this toughened resin matrix can achieve a CAI of 350 MPa. Because the thermoplastic resin content is close to 30 wt%, the viscosity of this toughened resin matrix is ​​very high, placing high demands on the mixing process of the resin matrix and subsequent coating and prepreg processes. Yi Xiaosu et al. proposed an "out-of-situ toughening" technology (CN1923506) to solve a series of process problems caused by the direct dissolution or dispersion of high-content thermoplastic resin in the resin matrix. "Off-site toughening" technology places thermoplastic resin, in the form of a film or powder, between two carbon fiber layers impregnated with a low-viscosity resin matrix, specifically improving the interlaminar toughness of the composite material, thereby significantly increasing the composite's CAI (co-adhesion integrity). Chinese patent CN104842619A provides a manufacturing process for a high-toughness multilayer prepreg, adding one or more toughening layers to a three-layer structure of resin layer-fiber layer-resin layer. These toughening layers exist in the form of films, powders, or fabrics, resulting in a toughened composite material with a CAI of 260 MPa. While the above toughening technologies achieve good toughening effects, they also bring other problems. For example, "off-site toughening" leads to a loss of interlaminar rigidity and prepreg viscosity, and the multilayer toughening structure reduces the volume content of reinforcing fibers, thus affecting the mechanical strength of the composite material. Summary of the Invention

[0004] One of the technical problems to be solved by this invention is that the existing thermoplastic resin toughening resin matrix has high viscosity, is difficult to prepare, has poor impregnation effect, and the prepreg laminate has low compressive strength after impact, making it difficult to meet the performance requirements of the main load-bearing structural components. This invention provides a high-temperature resistant and high-toughness prepreg, which obtains a low-viscosity and high-toughness resin matrix by reasonably distributing the amount of thermoplastic resin in the resin matrix and toughening layer, thus achieving good impregnation of the reinforcing fibers. By covering the surface of the reinforcing fibers with a toughening layer with a high thermoplastic resin content after impregnation, the compressive strength of the laminate after impact is significantly improved.

[0005] The second technical problem to be solved by the present invention is to provide a method for preparing a high-temperature resistant and high-toughness prepreg, which corresponds to the solution of the first technical problem.

[0006] The third technical problem to be solved by this invention is to provide an application method for a high-temperature resistant and high-toughness prepreg, which corresponds to the solution of the first technical problem.

[0007] To solve one of the above technical problems, the present invention adopts the following technical solution: a prepreg, comprising the following components by total mass of 100%:

[0008] Epoxy resin matrix: 22-35%;

[0009] Reinforcing fiber: 50-70%;

[0010] Toughening layer: 8-15%;

[0011] The toughening layer is composed of at least one of a combination containing epoxy resin and thermoplastic resin; the epoxy resin matrix is ​​composed of at least one of a combination containing epoxy resin, thermoplastic resin and curing agent; the toughening layer is located on the side of the reinforcing fiber layer with the epoxy resin matrix.

[0012] In the above technical solution, the toughening layer does not contain a curing agent.

[0013] In the above technical solution, the epoxy resin in the toughening layer and the epoxy resin in the epoxy resin matrix may be the same or different, and are independently selected from at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, and glycidylamine epoxy resin.

[0014] In the above technical solution, the curing agent is at least one of diaminodiphenyl sulfone or its derivatives, isomers such as those containing alkyl groups or halogen substituents on the benzene ring.

[0015] In the above technical solution, the epoxy resin matrix further includes a latent accelerator; the latent accelerator is preferably a boron-amine complex or a passivated imidazole.

[0016] In the above technical solution, the thermoplastic resin in the toughening layer and the thermoplastic resin in the epoxy resin matrix are the same or different; preferably, the thermoplastic resin is soluble in the epoxy resin; more preferably, at least one of polyethersulfone, polyetherimide, polyetheretherketone, and polysulfone.

[0017] In the above technical solution, by mass percentage, the epoxy resin matrix contains 100 parts epoxy resin, 0-20 parts thermoplastic resin, and 27-55 parts curing agent; the toughening layer contains 100 parts epoxy resin and 16-40 parts thermoplastic resin; more preferably, the content of thermoplastic resin in the toughening layer, as a percentage of the total mass of the toughening layer, is greater than the content of thermoplastic resin in the epoxy resin matrix, as a percentage of the total mass of the epoxy resin matrix.

[0018] In the above technical solution, the reinforcing fiber is at least one of carbon fiber, aramid fiber, glass fiber, and basalt fiber; the reinforcing fiber is in the form of continuous unidirectional fiber or fabric.

[0019] To solve the second technical problem mentioned above, the present invention adopts the following technical solution: a method for preparing a prepreg as described in any of the technical solutions for solving the first technical problem, comprising the following steps:

[0020] a) Preparation of epoxy resin matrix: Dissolve the required amount of thermoplastic resin in epoxy resin, cool down, add curing agent to obtain the epoxy resin matrix;

[0021] b) Resin film preparation: Thermoplastic resin toughened epoxy resin matrix is ​​uniformly coated on the surface of release paper on a hot melt coating machine to obtain the resin film;

[0022] c) Preparation of toughening layer: Dissolve the required amount of thermoplastic resin in epoxy resin to obtain a uniform and transparent melt. Apply the melt evenly to release paper on a hot melt coating machine to obtain the toughening layer.

[0023] d) Prepreg preparation: On a prepreg machine equipped with multiple winding and unwinding stations, the resin film is first impregnated onto the reinforcing fiber, and then the toughening layer is covered on the reinforcing fiber layer to obtain the prepreg.

[0024] In the above technical solution, after the toughening layer is covered on the reinforcing fiber layer in step d), it is preferable to cover it with a PE film and then roll it up to obtain the high-temperature resistant and high-toughness prepreg.

[0025] To solve the third technical problem mentioned above, the present invention adopts the following technical solution: the application of any of the prepreg materials described in the technical solutions for solving one of the technical problems.

[0026] The application of the above technical solution is not particularly limited. Those skilled in the art can apply the prepreg of the present invention according to existing process technology, for example, as a lightweight and high-strength structural material, which is widely used in many fields such as aerospace, military industry, and automotive lightweighting.

[0027] The advantages of using the high-temperature resistant and high-toughness prepreg and its preparation method provided by this invention are as follows:

[0028] 1) The resin matrix contains only a suitable amount or no thermoplastic resin toughening agent, while other toughening agents are covered on the surface of the prepreg in the form of a toughening layer, thereby ensuring that the resin matrix has a good impregnation effect on the reinforcing fibers.

[0029] 2) Except for the absence of curing agent, the toughening layer has the same composition as the resin matrix, but the content of thermoplastic resin is higher. Under the action of heating, pressurization and concentration difference, the components of the toughening layer and the resin matrix diffuse into each other, thereby ensuring a good interface between the toughening layer and the fiber layer impregnated with the resin matrix.

[0030] 3) Through the toughening layer, most of the thermoplastic resin is confined in the interlaminar region, thereby improving the interlaminar toughness and CAI of the composite material.

[0031] The high-temperature resistant and high-toughness prepreg prepared by adopting the technical solution of the present invention achieves good impregnation of reinforcing fibers, significantly improves the post-impact compressive strength of the laminate, and achieves good technical results.

[0032] The present invention will be further illustrated below through embodiments. Detailed Implementation

[0033] To further understand the present invention, preferred embodiments are described below with reference to examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims. [Example 1]

[0034] The fiber surface density was 125 g / m², prepared using Toray T700×12k carbon fiber. 2 The prepreg has the following composition:

[0035] Thermoplastic resin toughened epoxy resin matrix: 25wt%

[0036] T700×12k carbon fiber: 65wt%

[0037] Toughening layer: 10wt%

[0038] 1) Preparation of resin film

[0039] The resin matrix formulation consists of:

[0040] Tetrafunctional epoxy resin (XB 9721, Huntsman): 50 parts

[0041] Trifunctional epoxy resin (MY0510, Huntsman): 20 parts

[0042] Bisphenol A epoxy resin (CYD128, Baling Petrochemical): 30 parts

[0043] Polyethersulfone (5003P, Sumitomo, Japan): 16.5 parts

[0044] 4,4'-Diaminodiphenyl sulfone: 49 parts

[0045] Mixing process steps: Add polyethersulfone 5003P to the mixture of XB 9721, MY0510 and CYD128 epoxy resin, stir and heat to 150℃ under nitrogen protection, and after the PES is completely dissolved, cool down to 80℃, then add 4,4'-diaminodiphenylsulfone powder and mix evenly.

[0046] Resin film preparation: The above-mentioned resin matrix is ​​poured into the resin tank of a coating machine, and the resin matrix is ​​uniformly coated onto the release paper at a coating temperature of 90℃. The areal density of the resin film is 24 g / m³. 2 .

[0047] 2) Preparation of toughening layer

[0048] The toughening layer resin formulation consists of:

[0049] Tetrafunctional epoxy resin (XB 9721, Huntsman): 50 parts

[0050] Trifunctional epoxy resin (MY0510, Huntsman): 20 parts

[0051] Bisphenol A epoxy resin (CYD128, Baling Petrochemical): 30 parts

[0052] Polyethersulfone (5003P, Sumitomo, Japan): 38.9 parts

[0053] Mixing process steps: Add polyethersulfone 5003P to the mixture of XB 9721, MY0510 and CYD128 epoxy resin, stir and heat to 180°C under nitrogen protection, and after the PES is completely dissolved, cool to 120°C, discharge the material and cool to room temperature.

[0054] Preparation of toughening layer: The toughening layer resin is placed in the resin tank of a coating machine, and the resin is uniformly coated onto the release paper at a coating temperature of 130℃, resulting in an areal density of 19.2 g / m². 2 The toughening layer.

[0055] 3) Prepreg preparation

[0056] Two rolls of resin film are placed on the upper and lower unwinding stations at the front of the prepreg machine, respectively, while the toughening layer is placed on the unwinding station in the middle of the prepreg machine. At the first and second heating rollers and heating plate, the upper and lower resin films impregnate the unidirectionally aligned carbon fibers. Then, the upper release paper is wound up, and the toughening layer is unwound from the middle unwinding station, covering the surface of the prepreg. At the third heating roller and heating plate, the toughening layer adheres to the surface of the prepreg. After cooling on the cooling plate, the upper release paper is wound up, covered with a PE film, and finally, the prepreg is wound up. The temperature of the first, second, and third heating rollers and heating plate of the prepreg machine is 110℃.

[0057] 4) Laminate preparation and performance evaluation:

[0058] Prepreg was cut to appropriate sizes according to GB / T 21239-2007 standard, and laid up in a [45 / 0 / -45 / 90]S sequence. It was then placed in an autoclave for curing at 120℃ / 1h + 180℃ / 2h at a heating rate of 2℃ / min. After curing, the laminate was cut to obtain test samples with dimensions of 150mm × 100mm × 5mm. The samples were then subjected to post-impact compressive strength testing according to the standard.

[0059]

Comparative Example 1

[0060] The fiber surface density was 125 g / m², prepared using Toray T700×12k carbon fiber. 2 The prepreg has the following composition:

[0061] Thermoplastic resin toughened epoxy resin matrix: 25wt%

[0062] T700×12k carbon fiber: 65wt%

[0063] Toughening layer: 10wt%

[0064] 1) Preparation of resin film

[0065] The resin matrix formulation consists of:

[0066] Tetrafunctional epoxy resin (XB 9721, Huntsman): 50 parts

[0067] Trifunctional epoxy resin (MY0510, Huntsman): 20 parts

[0068] Bisphenol A epoxy resin (CYD128, Baling Petrochemical): 30 parts

[0069] Polyethersulfone (5003P, Sumitomo, Japan): 16.5 parts

[0070] 4,4'-Diaminodiphenyl sulfone: 49 parts

[0071] Mixing process steps: Add polyethersulfone 5003P to the mixture of XB 9721, MY0510 and CYD128 epoxy resin, stir and heat to 150℃ under nitrogen protection, and after the PES is completely dissolved, cool down to 80℃, then add 4,4'-diaminodiphenylsulfone powder and mix evenly.

[0072] Resin film preparation: The above-mentioned resin matrix is ​​poured into the resin tank of a coating machine, and the resin matrix is ​​uniformly coated onto the release paper at a coating temperature of 90℃. The areal density of the resin film is 24 g / m³. 2 .

[0073] 2) Preparation of toughening layer

[0074] Polyethersulfone (5003P, Sumitomo, Japan) was dissolved in tetrahydrofuran to a concentration of 10%. The solution was coated onto a horizontally placed glass plate, and after the solvent evaporated, a surface density of 19.2 g / m² was obtained. 2 The toughening layer.

[0075] 3) Prepreg preparation

[0076] Two rolls of resin film are placed on the upper and lower unwinding stations at the front of the prepreg machine, respectively, while the toughening layer is placed on the unwinding station in the middle of the prepreg machine. At the first and second heating rollers and heating plate, the upper and lower resin films impregnate the unidirectionally aligned carbon fibers. After cooling on the cooling plate, the upper release paper is wound up, covered with a PE film, and finally the prepreg is wound up. The temperature of the first, second, and third heating rollers and heating plate of the prepreg machine is 110℃.

[0077] 4) Laminate preparation and performance evaluation:

[0078] Cut the prepreg to appropriate dimensions according to the requirements of GB / T 21239-2007, lay them up, and insert a toughening layer between two layers of prepreg. The prepreg layup sequence is [45 / 0 / -45 / 90]. S The laminate was placed in an autoclave for curing. The curing process was 120℃ / 1h + 180℃ / 2h, with a heating rate of 2℃ / min. After curing, the laminate was cut to obtain test samples with dimensions of 150mm×100mm×5mm. The samples were then subjected to impact compressive strength testing according to standards.

[0079]

Examples 2-3

[0080] The difference from Example 1 is that in Examples 2 and 3, the thermoplastic resin was replaced with polyetherimide (Ultem 1010, Sabic) and polyetheretherketone (VICTREX 90P), respectively.

[0081]

Examples 4-6

[0082] The difference from Example 1 is that in Examples 4 to 6, the carbon fiber was replaced with Shanghai Petrochemical SCF 35S-12k, Toray T800S-24k and Toray T800H-12k, respectively.

[0083]

Example 7

[0084] The fiber surface density was 150 g / m² prepared using Toray T800s×24k carbon fiber. 2 The prepreg has the following composition:

[0085] Thermoplastic resin toughened epoxy resin matrix: 25wt%

[0086] T700×12k carbon fiber: 65wt%

[0087] Toughening layer: 10wt%

[0088] 1) Preparation of resin film

[0089] The resin matrix formulation consists of:

[0090] Tetrafunctional epoxy resin (XB 9721, Huntsman): 40 parts

[0091] 5,5-Dimethylhydantoin epoxy resin (MHR-070, Hubei Xitai Company): 30 parts

[0092] Bisphenol A epoxy resin (CYD128, Baling Petrochemical): 30 parts

[0093] Polyethersulfone (5003P, Sumitomo, Japan): 19.8 parts

[0094] 3,3'-Diaminodiphenyl sulfone: 45.6 parts

[0095] Mixing process steps: Add polyethersulfone 5003P to the mixture of XB 9721, MHR-070 and CYD128 epoxy resin, stir and heat to 150°C under nitrogen protection, and after the PES is completely dissolved, cool down to 80°C, then add 4,4'-diaminodiphenylsulfone powder and mix evenly.

[0096] Resin film preparation: The above-mentioned resin matrix is ​​poured into the resin tank of a coating machine, and the resin matrix is ​​uniformly coated onto the release paper at a coating temperature of 90℃. The areal density of the resin film is 28.5 g / m³. 2 .

[0097] 2) Preparation of toughening layer

[0098] The toughening layer resin formulation consists of:

[0099] Tetrafunctional epoxy resin (XB 9721, Huntsman): 40 parts

[0100] 5,5-Dimethylhydantoin epoxy resin (MHR-070, Hubei Xitai Company): 30 parts

[0101] Bisphenol A epoxy resin (CYD128, Baling Petrochemical): 30 parts

[0102] Polyethersulfone (5003P, Sumitomo, Japan): 37 parts

[0103] Mixing process steps: Add polyethersulfone 5003P to the mixture of XB 9721, MHR-070 and CYD128 epoxy resin, stir and heat to 180°C under nitrogen protection, and after the PES is completely dissolved, cool to 120°C, discharge the material and cool to room temperature.

[0104] Preparation of toughening layer: The toughening layer resin is placed in the resin tank of a coating machine, and the resin is uniformly coated onto the release paper at a coating temperature of 130℃, resulting in an areal density of 23.8 g / m². 2 The toughening layer.

[0105] The prepreg and laminate preparation process is the same as in Example 1.

[0106]

Example 8

[0107] The fiber surface density was 150 g / m², prepared using Toray T800S×24k carbon fiber. 2 The prepreg has the following composition:

[0108] Thermoplastic resin toughened epoxy resin matrix: 25wt%

[0109] T700×12k carbon fiber: 65wt%

[0110] Toughening layer: 10wt%

[0111] 1) Preparation of resin film

[0112] The resin matrix formulation consists of:

[0113] Trifunctional epoxy resin (MY0510, Huntsman): 30 parts

[0114] 5,5-Dimethylhydantoin epoxy resin (MHR-070, Hubei Xitai Company): 30 parts

[0115] Bisphenol F epoxy resin (DER 354, DOW): 40 parts

[0116] Polyethersulfone (5003P, Sumitomo, Japan): 25.7 parts

[0117] 4,4'-Diaminodiphenyl sulfone: 45.8 parts

[0118] Mixing process steps: Add polyethersulfone 5003P to the mixture of MY0510, MHR-070 and DER 354 epoxy resins, stir and heat to 150°C under nitrogen protection, and after the PES is completely dissolved, cool down to 80°C, then add 4,4'-diaminodiphenylsulfone powder and mix evenly.

[0119] Resin film preparation: The above-mentioned resin matrix is ​​poured into the resin tank of a coating machine, and the resin matrix is ​​uniformly coated onto the release paper at a coating temperature of 90℃. The areal density of the resin film is 28.5 g / m³. 2 .

[0120] 2) Preparation of toughening layer

[0121] The toughening layer resin formulation consists of:

[0122] Trifunctional epoxy resin (MY0510, Huntsman): 30 parts

[0123] 5,5-Dimethylhydantoin epoxy resin (MHR-070, Hubei Xitai Company): 30 parts

[0124] Bisphenol F epoxy resin (DER 354, DOW): 40 parts

[0125] Polyethersulfone (5003P, Sumitomo, Japan): 42.8 parts

[0126] Mixing process steps: Add polyethersulfone 5003P to the mixture of MY0510, MHR-070 and DER 354 epoxy resin, stir and heat to 180°C under nitrogen protection, and after the PES is completely dissolved, cool to 120°C, discharge the material, and cool to room temperature.

[0127] Preparation of toughening layer: The toughening layer resin is placed in the resin tank of a coating machine, and the resin is uniformly coated onto the release paper at a coating temperature of 130℃, resulting in an areal density of 23.8 g / m². 2 The toughening layer.

[0128] The prepreg and laminate preparation process is the same as in Example 1.

[0129]

Comparative Example 1

[0130] The fiber surface density was 125 g / m², prepared using Toray T700×12k carbon fiber. 2 The prepreg has the following composition:

[0131] Thermoplastic resin toughened epoxy resin matrix: 25wt%

[0132] T700×12k carbon fiber: 65wt%

[0133] Toughening layer: 10wt%

[0134] 1) Preparation of resin film

[0135] The resin matrix formulation consists of:

[0136] Tetrafunctional epoxy resin (XB 9721, Huntsman): 50 parts

[0137] Trifunctional epoxy resin (MY0510, Huntsman): 20 parts

[0138] Bisphenol A epoxy resin (CYD128, Baling Petrochemical): 30 parts

[0139] Polyethersulfone (5003P, Sumitomo, Japan): 16.5 parts

[0140] 4,4'-Diaminodiphenyl sulfone: 49 parts

[0141] Mixing process steps: Add polyethersulfone 5003P to the mixture of XB 9721, MY0510 and CYD128 epoxy resin, stir and heat to 150℃ under nitrogen protection, and after the PES is completely dissolved, cool down to 80℃, then add 4,4'-diaminodiphenylsulfone powder and mix evenly.

[0142] Resin film preparation: The above-mentioned resin matrix is ​​poured into the resin tank of a coating machine, and the resin matrix is ​​uniformly coated onto the release paper at a coating temperature of 90℃. The areal density of the resin film is 24 g / m³. 2 .

[0143] 2) Preparation of toughening layer

[0144] Polyethersulfone (5003P, Sumitomo, Japan) was dissolved in tetrahydrofuran to a concentration of 10%. The solution was coated onto a horizontally placed glass plate, and after the solvent evaporated, a surface density of 19.2 g / m² was obtained. 2 The toughening layer.

[0145] 3) Prepreg preparation

[0146] Two rolls of resin film are placed on the upper and lower unwinding stations at the front of the prepreg machine, respectively, while the toughening layer is placed on the unwinding station in the middle of the prepreg machine. At the first and second heating rollers and heating plate, the upper and lower resin films impregnate the unidirectionally aligned carbon fibers. After cooling on the cooling plate, the upper release paper is wound up, covered with a PE film, and finally the prepreg is wound up. The temperature of the first, second, and third heating rollers and heating plate of the prepreg machine is 110℃.

[0147] 4) Laminate preparation and performance evaluation:

[0148] Cut the prepreg to appropriate dimensions according to the requirements of GB / T 21239-2007, lay them up, and insert a toughening layer between two layers of prepreg. The prepreg layup sequence is [45 / 0 / -45 / 90]. S The laminate was placed in an autoclave for curing. The curing process was 120℃ / 1h + 180℃ / 2h, with a heating rate of 2℃ / min. After curing, the laminate was cut to obtain test samples with dimensions of 150mm×100mm×5mm. The samples were then subjected to impact compressive strength testing according to standards.

[0149] [Comparative Examples 2-3]

[0150] The prepreg and laminate were prepared in the same manner as in Comparative Example 1, using SCF 35S×12k and Toray T800S×24k carbon fibers, respectively.

[0151] Appendix 1

[0152]

Claims

1. A prepreg, comprising, by weight 100%, the following components: Epoxy resin matrix: 22~35%; Reinforcing fiber: 50~70%; Toughening layer: 8~15%; The toughening layer is located on the side of the reinforcing fiber layer with the epoxy resin matrix; By weight, the epoxy resin matrix contains 100 parts epoxy resin, more than 0 parts and less than or equal to 20 parts thermoplastic resin, and 27-55 parts curing agent; the toughening layer contains 100 parts epoxy resin, 16-40 parts thermoplastic resin, and no curing agent; the content of thermoplastic resin in the toughening layer, as a percentage of the total mass of the toughening layer, is greater than the content of thermoplastic resin in the epoxy resin matrix, as a percentage of the total mass of the epoxy resin matrix. The epoxy resin in the toughening layer may be the same as or different from the epoxy resin in the epoxy resin matrix, and is independently selected from at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, and glycidyl amine epoxy resin. The curing agent is diaminodiphenyl sulfone or its derivatives or isomers, wherein the derivatives or isomers of diaminodiphenyl sulfone contain at least one of alkyl or halogen substituents on the benzene ring; The thermoplastic resin in the toughening layer may be the same as or different from the thermoplastic resin in the epoxy resin matrix, wherein the thermoplastic resin is at least one of polyethersulfone, polyetherimide, polyetheretherketone, and polysulfone. The reinforcing fiber is at least one of carbon fiber, aramid fiber, glass fiber, and basalt fiber.

2. The prepreg according to claim 1, characterized in that The epoxy resin matrix also contains a latent accelerator.

3. The prepreg according to claim 2, characterized in that The latent promoter is a boron-amine complex or a passivated imidazole.

4. The prepreg according to claim 1, wherein The reinforcing fiber is in the form of a continuous unidirectional fiber or fabric.

5. A method for preparing a prepreg as described in any one of claims 1 to 4, comprising the following steps: a) Preparation of epoxy resin matrix: Dissolve the required amount of thermoplastic resin in epoxy resin, cool down, add curing agent to obtain the epoxy resin matrix; b) Resin film preparation: Thermoplastic resin toughened epoxy resin matrix is ​​uniformly coated on the surface of release paper on a hot melt coating machine to obtain the resin film. c) Preparation of toughening layer: Dissolve the required amount of thermoplastic resin in epoxy resin to obtain a uniform and transparent melt. Apply the melt evenly to release paper on a hot melt coating machine to obtain the toughening layer. d) Prepreg preparation: On a prepreg machine equipped with multiple winding and unwinding stations, the resin film is first impregnated onto the reinforcing fiber, and then the toughening layer is covered on the reinforcing fiber layer to obtain the prepreg.

6. The application of a prepreg as described in any one of claims 1 to 4 in lightweight, high-strength structural materials.

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