Method for single component thermoplastic resin multiscale toughened continuous fiber 3d printed thermoset composites

Abstract

A method for printing a single-component thermoplastic resin multi-scale toughening continuous fiber 3D printing thermosetting composite material, by regulating the dissolution degree of the thermoplastic resin in the thermosetting matrix, the thermoplastic resin in the dissolved state and the mixed state of the insoluble particles is used to modify the printing matrix, the dissolved resin undergoes phase separation to form a nanoscale thermoplastic phase, and the insoluble thermoplastic particles provide a particle toughening effect at the micron scale, realizing a multi-scale toughening system of a nanoscale thermoplastic phase composed of a single-component thermoplastic resin and micron-scale particles; the nanoscale thermoplastic phase is spontaneously formed by using the phase separation mechanism, the distribution is uniform, the multi-scale toughening phase is composed of a single component; and the composite material component is manufactured by combining the continuous fiber 3D printing process; the method has the advantages of simple process, high automation degree and suitability for the composite material 3D printing process, significantly improves the toughness of the 3D printing composite material component, and opens up the engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of 3D printing manufacturing of fiber-reinforced thermosetting composite materials and the field of composite material toughening technology, specifically to a method for 3D printing thermosetting composite materials with multi-scale toughening of continuous fibers using single-component thermoplastic resin. Background Technology

[0002] Fiber-reinforced thermosetting resin matrix composites possess excellent mechanical properties such as high specific strength, high specific modulus, and fatigue resistance, and are widely used in construction, automotive, military, and aerospace fields, making them outstanding engineering materials. Fiber-reinforced thermosetting resin matrix composites consist of fiber reinforcements and a thermosetting resin matrix. The reinforcing fibers, such as carbon fibers, have high strength along their fiber direction; the thermosetting resin, such as epoxy resin, forms a three-dimensional cross-linked network structure after curing, exhibiting high strength. However, due to the high degree of cross-linking after curing, the resin matrix is ​​brittle and has difficulty resisting impact loads. Fiber-reinforced composites bind the fibers together by impregnating and encapsulating them in the resin matrix, and the load is transferred through the resin matrix. Therefore, the resin matrix plays a decisive role in the performance of fiber-reinforced thermosetting resin matrix composites: high brittleness of the resin matrix results in composites that are not impact-resistant and difficult to apply in practical applications.

[0003] Traditional composite material manufacturing involves layer-by-layer fabrication using prepregs or prepreg tapes, laid out manually or robotically. After curing, the layers are bonded together with resin, resulting in weak interlayer properties. Furthermore, limitations in processing methods hinder the creation of complex and intricate structures, such as crystal lattices and lattice topologies. Continuous fiber 3D printing, a relatively new composite material manufacturing process, creates composite structures through the layer-by-layer deposition of single fiber bundles, significantly improving the flexibility and complexity of composite material manufacturing. However, composite materials manufactured using continuous fiber 3D printing are still additive manufacturing based on the principle of layer-by-layer accumulation. Therefore, interlayer bonding is poor, and interlayer properties are weak. Compared to the 80-100 MPa interlayer shear strength achieved by traditional manufacturing processes, the interlayer shear strength of printed thermosetting composites is only 50-65 MPa, while that of thermoplastic composites is even lower, reaching only 20-30 MPa. This often leads to interlayer shear failure, brittle fracture after impact, and delamination in the actual use of printed parts, significantly limiting the engineering application prospects of continuous fiber composite 3D printing.

[0004] Commonly used toughening methods for composite materials include interlaminar toughening and resin matrix toughening. Interlaminar toughening (Dong Huimin, Yi Xiaosu, An Xuefeng, et al. Research progress on interlaminar toughening of fiber-reinforced thermosetting polymer matrix composites [J]. Journal of Composite Materials, 2014, 31(2):13.) introduces a toughening layer, such as an electrospun fiber or nanomaterial layer, between the composite material layers. This layer hinders crack propagation and absorbs the energy of failure during interlaminar failure, thereby improving the interlaminar strength of the composite material. However, due to the poor compatibility between the toughening layer and the resin matrix, the addition of the toughening layer will introduce a toughening layer-resin matrix interface. This weak interfacial bonding will cause stress concentration, which will greatly reduce other properties of the composite material. In addition, interlaminar toughening has the problem of process applicability. Currently, the toughening layer is usually added between the layers by manual brushing or laying, which increases the complexity of the manufacturing process and is difficult to automate without manual intervention. This is contrary to the automation and flexibility of 3D printing process, so it is not suitable for toughening 3D printed composite materials. Resin matrix toughening (Ning N, Wang M, Zhou G, et al. Effect of polymer nanoparticle morphology on fracture toughness enhancement of carbon fiber reinforced epoxy composites[J]. Composites, Part B. Engineering, 2022(Apr.1):234.) involves modifying the resin matrix by adding toughening agents through chemical reactions or physical blending to improve the overall toughness of the resin matrix. However, this method usually alters the rheological and heat resistance properties of the resin, and excessively high matrix viscosity makes it difficult to meet the requirements of composite material manufacturing. Furthermore, the mixing of small-sized toughening agents (such as carbon nanotubes) presents dispersion problems, making them prone to agglomeration and impairing the performance of the composite material.

[0005] In summary, there is an urgent need for an easy-to-implement interlayer toughening method for thermosetting composite materials suitable for continuous fiber 3D printing, which does not introduce too many weak interfaces and has little impact on the overall performance of the composite material. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention aims to provide a method for 3D printing thermosetting composite materials using single-component thermoplastic resin multi-scale toughened continuous fibers. This method utilizes the different properties of the thermoplastic resin in its dissolved / undissolved states during curing to enhance the interlayer properties of the 3D printed composite material. By employing a phase separation mechanism, a uniformly distributed nanoscale thermoplastic phase is spontaneously formed, reducing interface introduction and preserving the overall performance of the 3D printed composite material. Furthermore, it has the potential to improve the composite material's heat resistance and other functional properties. The present invention has the advantages of simple process, high degree of automation, and suitability for composite material 3D printing processes, significantly improving the toughness of 3D printed composite material components and broadening its engineering application prospects.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for multi-scale toughening of thermoplastic resin continuous fiber 3D printing thermosetting composite materials using a single-component thermoplastic resin is disclosed. By controlling the solubility of thermoplastic resin in a thermosetting matrix, the printing matrix is ​​modified with a mixture of dissolved and insoluble particulate thermoplastic resin. The dissolved resin undergoes phase separation to form a nanoscale thermoplastic phase, while the insoluble thermoplastic particles provide a toughening effect at the micrometer scale. This achieves a multi-scale toughening system consisting of a nanoscale thermoplastic phase and micrometer-scale particles composed of a single-component thermoplastic resin. The nanoscale thermoplastic phase is spontaneously and uniformly distributed by utilizing the phase separation mechanism, and composite material components are manufactured using continuous fiber 3D printing technology.

[0009] A method for 3D printing thermosetting composite materials using multi-scale toughened continuous fibers from a single-component thermoplastic resin includes the following steps:

[0010] Step 1: Based on the thermodynamic properties of thermoplastic resin materials, such as polar force and dispersion force, analyze the thermodynamic compatibility between thermoplastic resin materials and thermosetting matrix materials using thermodynamic compatibility theory and solution space model, and calculate the relative energy difference between their molecules; the screening condition for thermoplastic resins is that the relative energy difference with the thermosetting matrix is ​​less than 1, and select compatible thermoplastic resins to prepare the printing matrix.

[0011] Step 2: Add a compatible thermoplastic resin to the thermosetting resin matrix, with the thermoplastic resin content being less than 15% by mass. Heat to the melting point and then raise the temperature to the solubility temperature of the thermoplastic resin. Maintain the temperature and continue stirring. Control the dissolution time according to the dissolution curve obtained from the experiment to dissolve less than 10 wt% of the thermoplastic resin. The content of dissolved thermoplastic resin is determined according to the phase separation gyroline theory. Control the amount of dissolved thermoplastic resin to form a discontinuous phase through phase separation, avoiding the aggregation and size increase of the thermoplastic phase. The remaining thermoplastic resin is uniformly mixed in the form of micron-sized particles, so that the thermoplastic resin forms a miscible dual-form in the resin matrix, with molecular dissolution and particle dispersion. Then, cool the resin matrix to below the dissolution temperature at a rate of greater than or equal to 30°C / min, add the curing agent, and stir to mix evenly to obtain a dual-form modified resin system.

[0012] Step 3: Based on the dual-morphology modified resin system, modified resin prepreg continuous fiber bundles are prepared for 3D printing through a prepreg mechanism. The prepared modified resin prepreg continuous fiber bundles are fed to the printing nozzle of the 3D printing equipment through a feeding roller. The printing nozzle heats and melts the modified resin prepreg continuous fiber bundles and extrudes them. The modified resin prepreg continuous fiber bundles are deposited layer by layer on the printing platform according to the printing trajectory, thus obtaining a continuous fiber composite preform.

[0013] Step four involves placing the printed continuous fiber composite preform into a heating device, where high temperature triggers a curing reaction in the curing agent. As the curing reaction proceeds, the dissolved thermoplastic molecules undergo "reaction-induced phase separation," forming nanoscale thermoplastic spherulites that are uniformly dispersed in the resin phase, creating an "island structure." By controlling the curing temperature and time, the rate and duration of phase separation are managed, thereby regulating the size and morphology of the thermoplastic phase. The nanoscale thermoplastic phase formed by the single-component thermoplastic resin and the micron-scale particles form a multi-scale toughening system. This system enhances the interlaminar strength of the composite material through both improved resin matrix toughness and particle toughening mechanisms. Furthermore, the compatibility of the single-component materials creates an interaction that provides a synergistic toughening effect. After curing, a 3D-printed composite component with good toughness and interlaminar strength is obtained.

[0014] The thermoplastic resin in step one is selected by thermodynamic analysis. Currently known thermoplastic resins that meet this condition are one of phenolphthalein polyaryletherketone (PEK-C), polyetherimide (PEI), polyethersulfone (PES), polyetherketone (PEK), polyetheretherketone (PEEK), and polysulfone (PSF).

[0015] The thermosetting resin matrix in step one is one of epoxy resin, cyanate ester resin, phenolic resin, and bismaleimide resin.

[0016] The curing agent in step two is one or a mixture of imidazole curing agents, dicyandiamide curing agents, aromatic diamine curing agents, and acid anhydride curing agents.

[0017] In step two, a dual-morphology modified resin system was prepared using a solubility control method, comprising a micron-level thermoplastic particle dispersion phase, a molecular-level thermoplastic molecular dissolved homogeneous phase, and a uniformly dispersed curing agent; to ensure good printability of the matrix, its matrix viscosity at 120°C does not exceed 100 Pa·s.

[0018] The continuous fiber in step three is one or more of the following polymer fibers: carbon fiber, glass fiber, aramid fiber, basalt fiber, polyimide fiber, etc.

[0019] The heating equipment in step four is one of the following: high-temperature oven, heating furnace, heating plate, and heating blanket.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention adopts the method of calculating whether thermoplastic resin materials can be dissolved in thermosetting matrix by thermodynamic parameters, rather than frequent experimental attempts, which reduces the workload, material and energy consumption, and lowers the cost.

[0022] (2) The present invention uses a thermoplastic resin with good thermodynamic compatibility with thermosetting resin matrix. By utilizing its unique properties, it can be made compatible with thermosetting resin matrix to form a homogeneous system. Then, the thermodynamic compatibility state of the system is changed by the curing reaction induction method, so that thermoplastic molecules spontaneously separate to form a uniformly distributed nanoscale thermoplastic phase. This solves the problem of dispersion of nano-toughening phase and achieves nanoscale toughening effect on resin matrix.

[0023] (3) The present invention uses a solubility control method to modify a single-component thermoplastic resin into a thermosetting resin through molecular dissolution and particle dispersion in a miscible dual-form. Compared with the traditional method, only one interface is introduced to protect the overall performance of the composite material. Furthermore, the solubility control method is used to control the morphology of the thermoplastic resin, which is simple and does not require frequent addition of materials.

[0024] (4) The present invention significantly improves the flexibility of the resin matrix by dissolving and modifying the resin matrix with thermoplastic resin, and has little impact on the viscosity of the resin matrix, thus meeting the needs of various composite material preparation processes, including 3D printing.

[0025] (5) This invention uses a continuous fiber reinforced composite material 3D printing process to manufacture composite material structures. The process is flexible and can realize the 3D printing manufacturing of various complex structures, such as lattice structures, variable stiffness structures, and honeycomb structures. This invention significantly improves the designability and manufacturability of high-toughness composite materials, providing new methods and ideas for engineering fields such as aerospace, and opening up the application prospects of 3D printed composite materials.

[0026] (6) This invention introduces a single-component thermoplastic resin into the resin matrix in a dual form of molecular dissolution and particle mixing during the resin preparation stage through "solubility regulation" and "reaction induction". During the curing stage, "reaction-induced phase separation" is initiated to precipitate dissolved thermoplastic molecules to form a nanoscale thermoplastic phase, which, together with uniformly dispersed micron-scale thermoplastic particles, toughens the composite material at multiple scales, significantly improving the interlaminar strength of the composite material.

[0027] (7) The present invention uses the principle of phase separation to separate and precipitate the thermoplastic phase. Based on the principle of interface crystallization, the precipitated thermoplastic phase tends to precipitate on and near the surface of thermoplastic microparticles of the same composition, which can increase the surface roughness of thermoplastic microparticles. Compared with existing methods, it can significantly improve the interface between thermoplastic particles and resin matrix, reduce stress concentration, and improve the interface bonding between thermoplastic particles and thermosetting matrix. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for 3D printing thermosetting composite materials using multi-scale toughened continuous fibers with a single-component thermoplastic resin, as described in Example 1.

[0029] Figure 2 This is an SEM image of the multi-scale toughening system of nanoscale thermoplastic phase and micron-scale particles composed of a single-component thermoplastic resin as described in Example 1.

[0030] Figure 3 The results show the interlaminar shear strength of the composite material before and after toughening in Example 1. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1, referring to Figure 1 A method for 3D printing thermosetting composite materials using multi-scale toughened continuous fibers from a single-component thermoplastic resin, comprising the following steps, by weight:

[0033] Step 1: Select thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin and thermosetting bisphenol A epoxy resin as raw materials. Substitute the thermodynamic parameters of thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin into the Hansen solubility model and calculate that its relative energy difference with bisphenol A epoxy resin is 0.77 < 1. Therefore, it has good compatibility with bisphenol A epoxy resin and can be used to prepare printing substrate.

[0034] Step 2: Add 10 parts of thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin 1 to 100 parts of thermosetting bisphenol A epoxy resin matrix 2, heat to melt and raise the temperature to the solubility temperature of thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin 1 of 200℃, keep warm and stir continuously. Control the dissolution time to 45 minutes according to the PEK-C dissolution curve obtained in the experiment, so that 7 parts of thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin 1 dissolves and 3 parts of thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin 1 are uniformly mixed in the form of particles, so that thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin 1 forms a miscible dual form of molecular dissolution 3 and particle dispersion 4 in bisphenol A epoxy resin matrix 2; then cool the resin matrix to below the dissolution temperature at a rate of 30℃ / min, at which point add 20 parts of DDS curing agent 5 and stir to mix evenly to obtain a dual-form modified resin system 6.

[0035] In this embodiment, the particle size distribution of the thermoplastic phenolphthalein-based polyaryletherketone (PEK-C) resin 1 is 10-60 μm; the DDS curing agent 5 is a thermally initiated curing agent, diaminodiphenyl sulfone (DDS); the matrix viscosity of the dual-morphology modified resin system 6 is 42.2 Pa·s at 120°C.

[0036] Step 3: After preparing the dual-morphology modified resin system 6, add it to the prepreg tank 7 and pass the continuous fiber bundle 8 into the prepreg tank. The prepreg tank contains a V-shaped set of extrusion rollers 9. The continuous fiber bundle 8 passes through the extrusion rollers 9 in sequence. The pressure makes the resin matrix uniformly impregnate the continuous fiber bundle 8, thus obtaining the modified resin prepreg continuous fiber bundle 10 for 3D printing. The modified resin prepreg continuous fiber bundle 10 is conveyed to the printing nozzle 12 of the 3D printing equipment through the feeding roller 11. The printing nozzle 12 heats and melts the modified resin prepreg continuous fiber bundle 10 and extrudes it. The modified resin prepreg continuous fiber bundle 10 is deposited layer by layer on the printing platform according to the printing trajectory, thus printing the continuous fiber composite material structure preform 13.

[0037] In this embodiment, the continuous fiber bundle 8 is T300-3K continuous carbon fiber;

[0038] Step four: The printed continuous fiber composite material preform 13 is placed in the heating device 14, where the high temperature initiates a curing reaction in the curing agent. As the curing reaction proceeds, the 7 parts of thermoplastic phenolphthalein polyaryletherketone (PEK-C) resin 1 undergo phase separation to form a thermoplastic spherulite phase with a size of 100-200 nm, forming an "island structure," through the control of curing temperature and time. The nanoscale thermoplastic phase formed by the single-component thermoplastic resin and the micron-scale particles form a multi-scale toughening system, which improves the interlaminar strength of the composite material through the improvement of the resin matrix toughness and the particle toughening mechanism, respectively. Furthermore, the good compatibility of the single-component materials leads to interaction, providing a synergistic toughening effect. After curing, a composite material component 15 with good toughness and interlaminar strength is obtained.

[0039] The curing process conditions used in this embodiment are 120℃-2h + 170℃-1h.

[0040] Step four employs a "reaction-induced phase separation" method to alter the thermodynamic compatibility between the thermoplastic resin and the thermosetting matrix, causing phase separation of the thermoplastic resin. The size and morphology of the phases are controlled through the curing process. When the heating rate is below 5°C / min, the thermoplastic resin grows uniformly to form a regular spherical thermoplastic phase, with most particles separating and uniformly dispersed in the matrix. When the heating rate is equal to or higher than 5°C / min, the thermoplastic resin aggregates faster, forming a thermoplastic phase with a certain aspect ratio, and they come into contact with each other. The faster the rate, the greater the deformation tendency of the thermoplastic phase, the larger its size, the more contact it has with each other, and the lower its distribution uniformity. The size and distribution of the thermoplastic phase are controlled through the curing process according to requirements to achieve different degrees of improvement in the toughness of the resin matrix.

[0041] In step four, a multi-scale toughening system consisting of a nanoscale thermoplastic phase and micron-scale particles composed of a single-component thermoplastic resin was formed through a method of dissolution regulation and curing reaction induction. The micron-scale thermoplastic microparticles absorb interlaminar fracture energy, prevent crack propagation, and improve interlaminar strength by generating particle plastic deformation, particle pull-out, and shielding crack tips at the micron scale. Meanwhile, the nanoscale thermoplastic phase improves the toughness of the resin matrix. The resin matrix undergoes toughness failure, which consumes energy. The good compatibility and interfacial attraction provided by the single-component material cause the thermoplastic phase to be distributed on the surface of the thermoplastic particles and interact with each other, improving the interfacial bonding of the composite material and further synergistically improving the interlaminar strength of the composite material.

[0042] Reference Figure 2 , Figure 2 SEM images of the multi-scale toughening system consisting of a nanoscale thermoplastic phase and micron-scale particles composed of a single-component thermoplastic resin, as presented in this embodiment, are given, demonstrating the feasibility of the method proposed in this invention. Furthermore, the multi-scale toughening effect of the single-component thermoplastic resin is experimentally verified. Figure 3 As shown, the interlaminar shear strength of the untoughened composite material (Control), the composite material toughened by thermoplastic particles alone (Particle), the composite material toughened by thermoplastic solution alone (Dissolved), and the multi-scale toughened composite material of the single-component thermoplastic resin proposed by this method were compared. The interlaminar shear strength of the untoughened composite material was 72.10167 MPa. After reaction-induced multi-scale toughening with thermoplastic PEK-C resin in this embodiment, the interlaminar shear strength of the composite material reached 85.2834 MPa, which is an increase of 18%.

Claims

1. A method for 3D printing thermosetting composite materials using multi-scale toughened continuous fibers from a single-component thermoplastic resin, characterized in that: By controlling the solubility of thermoplastic resin in a thermosetting matrix, the printing matrix is ​​modified with a mixture of dissolved and insoluble particulate thermoplastic resin. The dissolved resin undergoes phase separation to form a nanoscale thermoplastic phase, while the insoluble thermoplastic particles provide a toughening effect at the micrometer scale. This achieves a multi-scale toughening system consisting of a nanoscale thermoplastic phase and micrometer-scale particles composed of a single-component thermoplastic resin. The nanoscale thermoplastic phase is spontaneously formed and uniformly distributed by the phase separation mechanism, and composite material components are manufactured using continuous fiber 3D printing technology. The thermoplastic resin is one of phenolphthalein polyaryletherketone (PEK-C), polyetherimide (PEI), polyethersulfone (PES), polyetherketone (PEK), polyetheretherketone (PEEK), and polysulfone (PSF); the thermosetting resin matrix is ​​one of epoxy resin, cyanate ester resin, phenolic resin, and bismaleimide resin.

2. A method for 3D printing thermosetting composite materials using multi-scale toughened continuous fibers from a single-component thermoplastic resin, characterized in that... Includes the following steps: Step 1: Based on the thermodynamic performance parameters of the thermoplastic resin material, analyze the thermodynamic compatibility between the thermoplastic resin material and the thermosetting matrix material using thermodynamic compatibility theory and dissolution space model, and calculate the relative energy difference of their molecules. The selection criteria for thermoplastic resins are that the relative energy difference with the thermosetting matrix is ​​less than 1, and thermoplastic resins with compatibility are selected to prepare the printing matrix. Step 2: Add a compatible thermoplastic resin to the thermosetting resin matrix, with the thermoplastic resin content being less than 15% by mass. Heat to the melting point and then raise the temperature to the thermoplastic resin's dissolution temperature. Maintain the temperature and continue stirring, controlling the dissolution time according to the experimentally obtained dissolution curve, so that less than 10 wt% of the thermoplastic resin dissolves. The dissolved thermoplastic resin content is determined based on the phase separation gyroline theory. Control the amount of dissolved thermoplastic resin to form a discontinuous phase through phase separation. The remaining thermoplastic resin is uniformly mixed in the form of micron-sized particles, so that the thermoplastic resin forms a miscible dual-form in the resin matrix, with both molecular dissolution and particle dispersion. Then, cool the resin matrix to below the dissolution temperature at a rate of ≥30℃ / min, add the curing agent, and stir to mix evenly to obtain a dual-form modified resin system. Step 3: Based on the dual-morphology modified resin system, modified resin prepreg continuous fiber bundles are prepared by a prepreg mechanism for 3D printing to obtain continuous fiber composite preforms. Step four involves placing the continuous fiber composite preform into a heating device. The high temperature triggers a curing reaction in the curing agent, causing the dissolved thermoplastic molecules to undergo "reaction-induced phase separation," forming a nanoscale thermoplastic spherulitic phase that is uniformly dispersed in the resin phase, creating an "island structure." By controlling the curing temperature and time, the rate and duration of phase separation are controlled, thereby regulating the size and morphology of the thermoplastic phase. The nanoscale thermoplastic phase formed by the single-component thermoplastic resin and the micron-scale particles form a multi-scale toughening system. This system enhances the interlaminar strength of the composite material through both the improved toughness of the resin matrix and the toughening mechanism of the particles. Furthermore, the compatibility of the single-component materials creates an interaction that provides a synergistic toughening effect. After curing, a 3D-printed composite component with good toughness and interlaminar strength is obtained.

3. The method according to claim 2, characterized in that: The curing agent in step two is one or a mixture of imidazole curing agents, dicyandiamide curing agents, aromatic diamine curing agents, and acid anhydride curing agents.

4. The method according to claim 2, characterized in that: In step two, a dual-morphology modified resin system was prepared using a solubility control method, comprising a micron-level thermoplastic particle dispersion phase, a molecular-level thermoplastic molecular dissolved homogeneous phase, and a uniformly dispersed curing agent; its matrix viscosity at 120°C does not exceed 100 Pa·s.

5. The method according to claim 2, characterized in that: The continuous fiber in step three is one or a mixture of polymer continuous fibers such as carbon fiber, glass fiber, aramid fiber, basalt fiber, and polyimide fiber.

6. The method according to claim 2, characterized in that: The heating equipment in step four is one of the following: high-temperature oven, heating furnace, heating plate, and heating blanket.

7. The method according to claim 2, characterized in that: In step four, the "reaction-induced phase separation" method is used to change the thermodynamic compatibility between the thermoplastic resin and the thermosetting matrix, causing the thermoplastic resin to undergo phase separation. The size and morphology of the phase are controlled by the curing process. When the heating rate is lower than 5℃ / min, the thermoplastic resin grows uniformly to form a regular spherical thermoplastic phase, which is uniformly dispersed in the matrix. When the heating rate is equal to or higher than 5℃ / min, the thermoplastic resin aggregates faster, forming a thermoplastic phase and coming into contact with each other; The faster the heating rate, the greater the tendency of the thermoplastic phase to deform, the larger its size, the more contact it has with each other, and the lower its distribution uniformity.

8. The method according to claim 2, characterized in that: In step four, a multi-scale toughening system consisting of a nanoscale thermoplastic phase and micron-scale particles composed of a single-component thermoplastic resin was formed by dissolution regulation and curing reaction induction. Micron-scale thermoplastic microparticles absorb interlaminar fracture energy, prevent crack propagation, and improve interlaminar strength by inducing particle plastic deformation, particle pull-out, and shielding crack tips at the micron scale. Meanwhile, nanoscale thermoplastic phases improve the toughness of the resin matrix, and the resin matrix undergoes ductile failure, which consumes energy. Single-component materials distribute the thermoplastic phase on the surface of thermoplastic particles and generate interactions, improving the interfacial bonding of the composite material and synergistically improving the interlaminar strength of the composite material.

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