A method for preparing a biomimetic multilayer gradient interlocking structure to optimize continuous fiber prepreg yarn

Abstract

The application discloses a preparation method of a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg yarn and belongs to the technical field of continuous fiber reinforced composite materials. The idea of a biomimetic bamboo structure design is introduced, a fine combination of simple composition, complex structure and gradient combination is achieved, and the structure and mechanical properties of the prepreg yarn are improved in toughness and strength through the design of the gradient structure. The gradient structure-function characteristics of natural bamboo materials are simulated to manufacture a biomimetic structure-function integrated material. The material is designed according to the relationship between the gradient structure, the interface bonding mode and the mechanical properties, and the key problem of improving the toughness and strength of the continuous fiber prepreg yarn is solved.

Description

Technical Field

[0001] This invention belongs to the field of continuous fiber reinforced composite materials technology, specifically relating to a method for preparing continuous fiber prepreg with a biomimetic multilayer gradient interlocking structure. Background Technology

[0002] Continuous fiber reinforced composites have long been widely used in various industries such as aerospace, automotive, energy, and sporting goods due to their high specific strength and specific stiffness. Traditional manufacturing methods such as compression molding, pultrusion, and winding are effective, but they are often accompanied by material waste and cost issues.

[0003] Additive manufacturing, also known as 3D printing, has gained widespread attention in recent years for its ability to create complex parts directly from digital models. This technology reduces material waste, provides design freedom, and shortens the cycle time from design to prototyping to production.

[0004] An integrated approach that combines continuous fiber prepreg with additive manufacturing overcomes the limitations of traditional composite material manufacturing while leveraging the flexibility of additive manufacturing. This approach is often referred to as "continuous fiber 3D printing" or "continuous fiber additive manufacturing".

[0005] Currently, ensuring the uniform impregnation of thermoplastic resin within the continuous fibers during the preparation of continuous fiber prepregs is a challenge. Uneven impregnation can lead to voids in the prepregs, affecting the mechanical properties of the final product. Furthermore, not all thermoplastic resins are suitable for continuous fiber prepreg preparation; resin selection must consider its melt temperature, flowability, and fiber compatibility, limiting the range of materials available. Additionally, the dispersion of the continuous fiber bundles during impregnation is also an issue. Poor dispersion can result in localized fiber accumulation or entanglement, impacting the final product's performance. Simultaneously, the fibers may suffer mechanical damage during processing, reducing their strength.

[0006] Currently, researchers and industry are employing various strategies to optimize preparation methods to address the above issues. These strategies primarily involve improving impregnation processes, fiber protection and dispersion, equipment innovation, developing new resins, and enhancing their compatibility with fibers. Patent CN112622094A discloses a method and apparatus for forming high-quality thermoplastic resin-based continuous fiber prepreg tow, which improves the volume fraction and performance of the prepreg by optimizing the continuous fiber spreading process. Patent CN114179251B discloses a system and method for preparing continuous fiber-reinforced thermoplastic composite prepreg, which mainly improves the forming performance of the continuous fiber prepreg through the coordination between device components.

[0007] However, in the additive manufacturing process of continuous fiber prepreg, the brittleness and low strength of continuous fiber prepreg generally result in poor printing processability, and the performance of continuous fiber components cannot be further improved. There are currently no reports on solutions to this problem.

[0008] Many natural bio-based fiber composite materials possess multi-scale, multi-level composite structures, which play a crucial role in the macroscopic properties and functions of the materials. Natural biomaterials such as shells, trees, and bamboo, despite their simple composition, possess excellent comprehensive mechanical properties through intricate structural combinations. For example, multi-layered composite materials, represented by shells, and fiber composite materials, represented by trees and bamboo, exhibit high strength, high toughness, and impact resistance. From a biological perspective, this is a result of organisms adapting to their environment during long-term natural evolution, embodying profound principles of materials design and mechanics.

[0009] Bamboo, native to China, boasts numerous types, strong adaptability, and a wide distribution. Like other woods, bamboo is a natural long-fiber reinforced composite material composed of cellulose, hemicellulose, and lignin, widely used in construction, handicrafts, and papermaking. However, bamboo differs in that it possesses an intricate structure and superior performance; its modulus of elasticity and strength are twice that of ordinary wood. Among tens of thousands of plants, bamboo can be considered a typical lightweight and efficient biological structure with excellent mechanical properties, exhibiting high stiffness, high strength, and stable performance. Previous research on bamboo has focused on its biological anatomy, chemical composition, and mechanical properties, but research on its biomimetic structural design is scarce.

[0010] Bamboo has a specific stiffness 2 to 5 times higher than steel, but a density 10 times lower, only 0.55 to 1.15 g / cm³. Furthermore, bamboo's slenderness ratio can reach 1 / 160 to 1 / 260, a feat difficult to achieve with conventional biological or mechanical structures. The superior mechanical properties of bamboo are inseparable from its meticulous and regular macro- and micro-structural forms. Related literature reports that the cross-sectional distribution of bamboo exhibits a gradient pattern, which disperses stress, thus contributing to its excellent mechanical properties. Summary of the Invention

[0011] To address the aforementioned technical problems, this invention provides a method for preparing continuous fiber prepreg with a biomimetic multilayer gradient interlocking structure. It introduces the concept of biomimetic bamboo structure design, achieving enhanced toughness and mechanical properties of the prepreg through a refined combination of "simple composition, complex structure, and gradient composite," using gradient structure design. It simulates the gradient structure and functional characteristics of natural bamboo to create a biomimetic integrated structure-function material. By mimicking the relationship between its gradient structure, interface bonding, and mechanical properties, the material design solves the key problem of simultaneously improving the toughness and strength of continuous fiber prepreg.

[0012] The objective of this invention is achieved through the following technical solution: A method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg includes the following steps: Step 1: Selection of continuous fibers; Step 2: Desizing of continuous fiber filaments; Step 3: Surface treatment of continuous fiber filaments; Step 4: Grafting of continuous fiber surfaces; Step 5: Resin impregnation; Step 6: Multi-layer gradient prepreg forming.

[0013] Preferably, in step one, the continuous fiber is carbon fiber or Kevlar fiber.

[0014] Preferably, in step two, the continuous fiber filaments pass through a high-temperature roller device at a temperature of 220~320℃ and a speed of 2~15r / min to remove the sizing agent from the surface.

[0015] Preferably, in step three, the degummed and dried fibers are surface-treated in a solvent bath, and then washed and dried in a deionized water bath.

[0016] Preferably, the solvent bath is concentrated nitric acid, concentrated hydrochloric acid, or concentrated sulfuric acid.

[0017] Preferably, in step four, the continuous fibers are subjected to surface grafting of the activator in a dendritic macromolecular mixed solution under the following conditions: the pH of the macromolecular mixed solution is controlled at 4.5~7.5, the solution temperature is controlled at 4~25℃, and the reaction time is 30~240 min.

[0018] Preferably, the dendritic macromolecular mixed solution is a solution of dendritic macromolecules with amino and hydroxyl groups, and the mass fraction of the macromolecular solution is 10~40 wt%.

[0019] Preferably, in step five, a suitable thermoplastic resin is selected as the matrix material, and the continuous fiber is uniformly impregnated in the resin melt pool at an impregnation temperature of 200~500℃, a speed of 2~20 r / min, and an impregnation melt pressure of 0.01MPa~0.1MPa.

[0020] Preferably, the resin is nylon resin, polycarbonate, polylactic acid, polyetherimide, or polyetheretherketone.

[0021] Preferably, in step six, the interlocking filler is uniformly dispersed in the solvent, and the continuous fiber prepreg from step five is passed through the interlocking filler coagulation bath. The interlocking filler is dispersed on the surface of the continuous fiber and in the pores where the resin is not fully impregnated, forming a chemically interlocked structure. The outer layer of resin of the continuous fiber fully crystallizes to form a reinforcing layer, and the inner layer of resin does not complete the crystallization process after cooling and coagulation bath, forming a toughening layer.

[0022] Preferably, the interlocking filler is made of carbon nanotubes, graphene, or halloysite.

[0023] Preferably, the solvent is DMF or methanol.

[0024] The beneficial effects of this technical solution are as follows: I. The present invention provides a method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg, which introduces the idea of ​​biomimetic structural design. Through the precise combination of "simple composition, complex structure, gradient composite, and mechanical interlocking", the prepreg achieves toughened and enhanced structural and mechanical properties through the dual design of structure and materials.

[0025] II. The present invention provides a method for preparing a continuous fiber prepreg with a biomimetic multilayer gradient interlocking structure. Through reasonable structural and process design, it solves the problems of low strength and high brittleness of continuous fiber prepreg prepared by existing technologies.

[0026] Third, the present invention provides a method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg, which adopts the concept of structure-function integration, integrates material design and process design, and simplifies the preparation process of continuous fiber filament while obtaining a prepreg with a complex hierarchical structure.

[0027] IV. The present invention provides a method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg. The material design and process design methods adopted can not only improve the toughness and strength of the continuous fiber prepreg, but also improve the compatibilizer between the fiber and the resin, and solve the problem of pore defects in the prepreg. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the bamboo structure from macroscopic to microscopic levels. Figure 2 This is a schematic diagram of the multi-layer gradient interlocking structure of the continuous fiber prepreg of the present invention; Figure 3 This is a schematic diagram of the dendritic macromolecular encapsulation structure of an embodiment of the present invention; Figure 4 This is a schematic diagram of the interlocking structure according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a multi-layer gradient interlocking structure according to an embodiment of the present invention; Detailed Implementation The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0029] like Figures 1-2 As shown, the preparation method of biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg includes the following steps: (1) Fiber selection: Select a suitable continuous fiber filament. Generally, the continuous fiber filament can be any type or model of polymer sold on the market, or a matrix raw material prepared according to existing technology. For better illustration and to provide a preferred technical solution, it includes, but is not limited to, carbon fiber, Kevlar fiber, depending on the performance requirements of the desired final product.

[0030] (2) Desizing of continuous fiber filaments: The continuous fiber filaments pass through a high-temperature roller device at a temperature of 220~320℃ and a speed of 2~15 r / min to remove the sizing agent on the surface.

[0031] (3) Surface treatment of continuous fiber filament: The degummed and dried fiber is surface treated in a solvent bath, then washed and dried in a deionized water bath. The solvent bath includes, but is not limited to, concentrated nitric acid, concentrated hydrochloric acid, concentrated sulfuric acid, etc.

[0032] (4) Continuous fiber surface grafting: Continuous fibers are surface grafted through a dendritic macromolecule mixed solution. The activator is used under the following conditions: the pH of the macromolecule mixed solution is controlled at 4.5~7.5, the solution temperature is controlled at 4~25℃, the reaction time is 30~240 min, and the mass fraction of the macromolecule solution is 10~40 wt%. Generally, the macromolecule can be any type or model of dendritic macromolecules sold on the market, or a matrix raw material prepared according to existing technology. For better illustration and to provide a preferred technical solution, it includes, but is not limited to, dendritic macromolecules with amino and hydroxyl groups.

[0033] (5) Resin Impregnation: Select a suitable thermoplastic resin as the matrix material. Generally, the matrix can be any type or model of polymer sold on the market, or a matrix raw material prepared according to existing technology. The impregnation temperature is 200~500℃, the speed is 2~20 r / min, and the impregnation melt pressure is 0.01MPa~0.1MPa. For better illustration and to provide a preferred technical solution, it includes, but is not limited to, nylon resin (PA), polycarbonate (PC), polylactic acid (PLA), polyetherimide (PEI), polyetheretherketone (PEEK), etc. The continuous fiber is uniformly impregnated in the resin melt pool.

[0034] (6) Multi-layer gradient prepreg forming: The interlocking filler is uniformly dispersed in the solution. The filler includes, but is not limited to, carbon nanotubes, graphene, halloysite, etc., and the solvent includes, but is not limited to, DMF, methanol, etc. The continuous fiber prepreg from step (5) is passed through the interlocking filler coagulation bath. The interlocking filler is dispersed on the surface of the continuous fiber and in the pores where the resin is not fully impregnated, forming a chemically interlocked structure. In addition, the outer resin of the continuous fiber is fully crystallized to form a reinforcing layer, and the inner resin is not fully crystallized after cooling and coagulation bath to form a toughening layer.

[0035] The beneficial effects of this technical solution are as follows: I. The present invention provides a method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg, which introduces the idea of ​​biomimetic structural design. Through the precise combination of "simple composition, complex structure, gradient composite, and mechanical interlocking", the prepreg achieves toughened and enhanced structural and mechanical properties through the dual design of structure and materials.

[0036] II. The present invention provides a method for preparing a continuous fiber prepreg with a biomimetic multilayer gradient interlocking structure. Through reasonable structural and process design, it solves the problems of low strength and high brittleness of continuous fiber prepreg prepared by existing technologies.

[0037] Third, the present invention provides a method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg, which adopts the concept of structure-function integration, integrates material design and process design, and simplifies the preparation process of continuous fiber filament while obtaining a prepreg with a complex hierarchical structure.

[0038] IV. The present invention provides a method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg. The material design and process design methods adopted can not only improve the toughness and strength of the continuous fiber prepreg, but also improve the compatibilizer between the fiber and the resin, and solve the problem of pore defects in the prepreg.

[0039] Example In this embodiment, continuous carbon fiber is used as the continuous fiber material to prepare gradient interlocking structure continuous fiber prepreg.

[0040] The fibers and resins used to prepare continuous fiber prepregs mainly include the following components: 50 parts of continuous fiber 50 parts resin; A total of 100 copies.

[0041] The continuous fiber is selected as 1K continuous carbon fiber, and the resin is selected as nylon resin.

[0042] The raw materials for the surface treatment solution of continuous fibers mainly include the following components: 100 parts solvent A total of 100 copies.

[0043] The solvent bath is selected as concentrated nitric acid.

[0044] The dendritic macromolecular solution used for grafting continuous fibers mainly comprises the following components: 50 parts of dendritic macromolecules 100 parts of dispersant 50 parts activator; A total of 200 copies.

[0045] Among them, the dendritic macromolecule is selected as polyamide-amine dendritic macromolecule (PAMAM), the dispersant is selected as dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc), and the activator is selected as 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) or N-hydroxysuccinimide (NHS).

[0046] The raw materials for the interlocking packing solution used to form chemical-mechanical interlocking mainly include the following components: 50 parts of interlocking packing 100 parts solvent 50 parts activator; A total of 200 copies.

[0047] The interlocking filler is selected as carboxylated carbon nanotubes (CNTs-COOH), the solvent is selected as dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc), and the activator is selected as 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HCl) and N-hydroxysuccinimide (NHS).

[0048] like Figures 3-5 As shown, the above-mentioned method for preparing a multilayer gradient interlocking structure for continuous fiber prepreg includes the following steps: (1) Continuous carbon fibers pass through a high-temperature roller device at a temperature of 220~320℃ and a speed of 2~15 r / min to remove the sizing agent on the surface.

[0049] (2) The degummed and dried fibers (1) above are surface treated in a concentrated nitric acid bath, and then washed and dried in a deionized water bath.

[0050] (3) The above (2) continuous fibers are surface grafted through a polyamide-amine dendritic macromolecule (PAMAM) mixed solution.

[0051] (4) The above (3) continuous fibers are uniformly impregnated in a nylon resin melting pool.

[0052] (5) The continuous fiber prepreg from step (4) is passed through a carboxylated carbon nanotube solution. The carboxylated carbon nanotubes are uniformly dispersed on the surface of the continuous fiber and in the pores where the resin is not fully impregnated, forming a chemically interlocked structure. In addition, the outer resin of the continuous fiber is fully crystallized to form a reinforcing layer, and the inner resin is not fully crystallized after cooling and solidification bath to form a toughening layer.

[0053] Test methods: The tensile properties of continuous fiber prepreg were tested using a universal testing machine according to the method specified in GB / T 3362-2017, the tensile properties of continuous fiber additive manufacturing parts were tested using the method specified in ASTM D 3039, and the bending properties of continuous fiber additive manufacturing parts were tested using the method specified in ASTM D 790.

[0054] The test results are shown in Table 1:

[0055] It can be seen that the continuous fiber prepreg filaments prepared by the above method provided in this application have significantly improved mechanical properties and better bonding performance compared with traditional melt-impregnated continuous fiber prepreg filaments. Therefore, the additively manufactured parts have significantly improved mechanical properties compared with the parts made of traditional melt-impregnated continuous fiber prepreg filaments, and have great application potential.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a continuous fiber prepreg with a biomimetic multilayer gradient interlocking structure, characterized in that, Includes the following steps: Step 1, Selection of Continuous Fiber: The continuous fiber is made of carbon fiber or Kevlar fiber; Step 2: Desizing of continuous fiber filaments; Step 3: Surface treatment of continuous fiber filaments: The degummed and dried fibers are surface treated in a solvent bath, then washed and dried in a deionized water bath; The solvent bath uses concentrated nitric acid or concentrated sulfuric acid; Step 4: Continuous fiber surface grafting: The continuous fibers are surface grafted through a dendritic macromolecule mixed solution, wherein the dendritic macromolecule mixed solution is a solution of dendritic macromolecules with amino and hydroxyl groups; Step 5: Resin impregnation; Step Six: Multi-layer gradient prepreg forming: The interlocking filler is uniformly dispersed in a solvent. The continuous fiber prepreg from Step Five is passed through an interlocking filler coagulation bath. The interlocking filler is dispersed on the surface of the continuous fiber and in the pores where the resin is not fully impregnated, forming a chemically interlocked structure. The outer layer of the continuous fiber forms a reinforcing layer, and the inner resin forms a toughening layer. The interlocking filler is made of carbon nanotubes, graphene, or halloysite.

2. The method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg according to claim 1, characterized in that: In step two, the continuous fiber filaments pass through a high-temperature roller device at a temperature of 220~320℃ and a speed of 2~15 r / min to remove the sizing agent from the surface.

3. The method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg according to claim 2, characterized in that: In step four, the activator is used under the following conditions: the pH of the macromolecular mixed solution is controlled at 4.5-7.5, the solution temperature is controlled at 4-25℃, and the reaction time is 30-240 min.

4. The method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg according to claim 3, characterized in that: The mass fraction of the dendritic macromolecular mixed solution is 10~40 wt%.

5. The method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg according to claim 4, characterized in that: In step five, a suitable thermoplastic resin is selected as the matrix material, and the continuous fiber is uniformly impregnated in the resin molten pool at a temperature of 200~500℃, a speed of 2~20 r / min, and a molten impregnation pressure of 0.01MPa~0.1MPa.

6. The method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg according to claim 5, characterized in that: The resin used is nylon resin, polycarbonate, polylactic acid, polyetherimide, or polyetheretherketone.

7. The method for preparing a biomimetic multilayer gradient interlocking structure optimized continuous fiber prepreg according to claim 6, characterized in that: The solvent used is DMF or methanol.

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