Carbon fiber composite material and method for producing the same

Abstract

The application provides a carbon fiber composite material and a preparation method thereof, and belongs to the field of carbon fiber materials. The preparation method of the carbon fiber composite material comprises the following steps: providing a carbon fiber bundle; defining a first twisting zone, a transition zone and a second twisting zone along the length direction of the carbon fiber bundle, and arranging the transition zone between the first twisting zone and the second twisting zone; twisting the first twisting zone and the second twisting zone in opposite directions to obtain a precursor; immersing the precursor in a solidifiable resin system to obtain an intermediate; and performing a curing treatment on the intermediate to obtain a bidirectional-twisted node structure carbon fiber composite material. The preparation method of the carbon fiber composite material can effectively improve the internal stress distribution of the fiber bundle, improve the torsional resistance, and take into account the toughness and energy absorption capacity, so as to realize the coordinated optimization of the comprehensive performance of the carbon fiber composite material.

Description

Technical Field

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

[0002] Fiber-reinforced composite materials are widely used in aerospace, transportation and high-end equipment manufacturing fields due to their high specific strength, high specific stiffness and strong designability.

[0003] In related technologies, fiber composite materials use a single twisting method to improve torsional resistance. However, while improving torsional resistance, the single twisting process often leads to uneven stress distribution within the fiber bundle, which in turn weakens the material's toughness or energy absorption capacity, making it difficult to achieve a coordinated improvement in overall performance. Summary of the Invention

[0004] In view of the technical problems existing in the background art, the present application provides a carbon fiber composite material and a method for preparing the same. The method for preparing the carbon fiber composite material can effectively improve the stress distribution inside the fiber bundle, and improve the torsional performance while taking into account the toughness and energy absorption capacity, thereby achieving coordinated optimization of the comprehensive performance of the carbon fiber composite material.

[0005] To achieve the above objectives, in a first aspect, embodiments of this application provide a method for preparing carbon fiber composite materials, comprising: Provide carbon fiber bundles; A first twisting zone, a transition zone, and a second twisting zone are defined along the length of the carbon fiber bundle, with the transition zone located between the first twisting zone and the second twisting zone. The first twisting zone and the second twisting zone are twisted in opposite directions to obtain the precursor; The precursor is impregnated in a curable resin system to obtain an intermediate; The intermediate was cured to obtain a bidirectional twisted node structure carbon fiber composite material.

[0006] Furthermore, the twist level is the same in the first twist zone and the second twist zone; and / or, The twist in the first twisting zone is 50T / m-150T / m; and / or, The twist in the second twisting zone is 50T / m-150T / m; and / or, Along the length of the carbon fiber bundle, the first twisting zone and the second twisting zone have the same length; and / or, Along the length of the carbon fiber bundle, the length of the transition zone is less than or equal to the length of the first twisting zone and the second twisting zone.

[0007] Furthermore, the first twisting region and the second twisting region are twisted in opposite directions to obtain a precursor; the precursor is impregnated in a curable resin system to obtain an intermediate, comprising: A sizing agent is applied to the transition zone, and after the sizing agent solidifies, the first product is obtained. The first twisting region and the second twisting region in the first product are twisted in opposite directions to obtain the precursor; The first twisted region and the second twisted region of the precursor are impregnated separately in a curable resin system to obtain the second product; The qualizing agent coated in the transition region of the second product is removed to obtain the precursor; The precursor is impregnated entirely in a curable resin system to obtain an intermediate.

[0008] Furthermore, the qualitative agent includes a water-soluble polyvinyl alcohol solution, and the removal treatment includes steam thermal dissolution.

[0009] Furthermore, the water-soluble polyvinyl alcohol solution has a mass fraction of 5%-10%; and / or, The temperature for steam thermal melting is 50℃-75℃; and / or, Steam thermal dissolution is saturated steam thermal dissolution.

[0010] Furthermore, curable resin systems include epoxy resins, curing agents, and solvents.

[0011] Furthermore, the mass ratio of epoxy resin, curing agent, and solvent is (8–10):(1–3):(12–18); and / or, Epoxy resins include at least one of epoxy resin E44 and epoxy resin E51; and / or, The curing agent includes at least one of MeTHPA and BC-12; and / or, The solvent includes at least one of acetone and xylene.

[0012] Furthermore, the precursor is impregnated in a curable resin system to obtain an intermediate, comprising: The precursor is impregnated in a curable resin system and subjected to physical and / or chemical treatments to obtain an intermediate; wherein, Physical treatment includes at least one of vibration treatment, ultrasonic treatment, and heat treatment; Chemical treatments include polyPVA impregnation.

[0013] Furthermore, the curing process includes thermosetting; and / or, The diameter of the single filaments in the carbon fiber bundle is 5μm–7μm; and / or, The carbon fiber bundles are 3K–12K in size; and / or, The thickness of the resin coating layer in carbon fiber composites is 20μm–50μm.

[0014] Secondly, this application also proposes a carbon fiber composite material, which is prepared by the above-described method for preparing carbon fiber composite materials.

[0015] The beneficial effects of this application are as follows: In the technical solution of this application, by setting a transition zone and a first twisting zone and a second twisting zone with opposite twisting directions along the length direction of the carbon fiber bundle, the carbon fiber composite material has the specific characteristics of bidirectional twisting, which enables it to form a zoned stress and graded response mechanism when subjected to torsional loads. Different structural sections undertake the functions of load transfer, deformation coordination, and energy dissipation under torsional loads, thereby changing the stress mode of traditional single twist or untwisted structures where the load is concentrated in a local area. This is conducive to achieving a reasonable distribution of torsional loads within the material and improving the stress uniformity of the overall structure. Since the transition zone is not twisted and is located between the first twisting zone and the second twisting zone, forming a buffer area in the continuous structure along the length direction, when the composite material is subjected to torsional loads, the transition zone can effectively weaken the stress abrupt change at the junction of the twisted structure, reduce the degree of stress concentration, and inhibit the initiation and propagation of cracks in the axial direction. From the structural design level, this improves the problem of interface cracking or sudden failure of composite materials under torsional loads, which is conducive to improving the structural stability and safety of the material during service.

[0016] In summary, by introducing sections with different twist directions and structural functions into the same carbon fiber bundle, the material can maintain a certain load-bearing capacity while also having corresponding deformation adjustment and energy dissipation capabilities when subjected to torsional loads. This alleviates the design limitations of existing technologies that make it difficult to balance torsional strength and deformation capacity, and broadens the application range of carbon fiber composite materials under complex torsional load conditions.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0019] Figure 1Image of the carbon fiber composite material of Example 1 Figure 2 Image of the carbon fiber composite material of Example 2 Figure 3 Image of the carbon fiber composite material of Example 3 Figure 4 Image of carbon fiber composite material for Comparative Example 1 Figure 5 The diagrams show the torsion angle-torque of Examples 1-3 and Comparative Example 1. Figure 6 The reverse twist torsion angle-torque diagrams are for Examples 1-3 and Comparative Example 1; Figure 7 Image of a bidirectional torsion meter. Detailed Implementation

[0020] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0022] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0025] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0026] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0027] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0028] Fiber-reinforced composite materials are widely used in aerospace, transportation and high-end equipment manufacturing fields due to their high specific strength, high specific stiffness and strong designability.

[0029] In related technologies, fiber composite materials use a single twisting method to improve torsional resistance. However, while improving torsional resistance, the single twisting process often leads to uneven stress distribution within the fiber bundle, which in turn weakens the material's toughness or energy absorption capacity, making it difficult to achieve a coordinated improvement in overall performance.

[0030] To address the aforementioned technical problems, in a first aspect, embodiments of this application provide a method for preparing carbon fiber composite materials, comprising: Provide carbon fiber bundles; A first twisting zone, a transition zone, and a second twisting zone are defined along the length of the carbon fiber bundle, with the transition zone located between the first twisting zone and the second twisting zone. The first twisting zone and the second twisting zone are twisted in opposite directions to obtain the precursor; The precursor is impregnated in a curable resin system to obtain an intermediate; The intermediate was cured to obtain a bidirectional twisted node structure carbon fiber composite material.

[0031] In the technical solution of this application, by setting a transition zone and a first twisting zone and a second twisting zone with opposite twisting directions along the length direction of the carbon fiber bundle, the carbon fiber composite material has the specific characteristics of bidirectional twisting, which enables it to form a zoned stress and graded response mechanism when subjected to torsional loads. Different structural sections undertake the functions of load transfer, deformation coordination, and energy dissipation under torsional loads, thereby changing the stress mode of traditional single twist or untwisted structures where the load is concentrated in a local area. This is conducive to achieving a reasonable distribution of torsional loads within the material and improving the stress uniformity of the overall structure. Since the transition zone is not twisted and is located between the first twisting zone and the second twisting zone, forming a buffer area in the continuous structure along the length direction, when the composite material is subjected to torsional loads, the transition zone can effectively weaken the stress abrupt change at the junction of the twisted structure, reduce the degree of stress concentration, and inhibit the initiation and propagation of cracks in the axial direction. From the structural design level, this improves the problem of interface cracking or sudden failure of composite materials under torsional loads, which is conducive to improving the structural stability and safety of the material during service.

[0032] In summary, by introducing sections with different twist directions and structural functions into the same carbon fiber bundle, the material can maintain a certain load-bearing capacity while also having corresponding deformation adjustment and energy dissipation capabilities when subjected to torsional loads. This alleviates the design limitations of existing technologies that make it difficult to balance torsional strength and deformation capacity, and broadens the application range of carbon fiber composite materials under complex torsional load conditions.

[0033] Furthermore, it is worth mentioning that the carbon fiber composite material prepared by this technical solution can achieve parametric design of the torsional response characteristics of the composite material by adjusting the twist direction, twist degree and length of each section, and has good structural adaptability and design flexibility.

[0034] It can be explained that the carbon fiber bundle is kept twisted after twisting and subsequent steps are carried out to avoid untwisting, thereby ensuring the stability of the helical structure and ensuring the consistency and reliability of the torsional resistance of the final composite material.

[0035] Specifically, the two ends of the carbon fiber bundle can be fixed and a certain tension can be applied to maintain the tension of the fiber bundle during the twisting process.

[0036] Understandably, by precisely adjusting the twist, the torsional strength and torsional stiffness of the final carbon fiber composite material can be designed in a directional manner to meet the specific needs of different application scenarios, thus realizing the "programmability" of material properties.

[0037] In some embodiments, the twisting degree of the first twisting zone and the second twisting zone is the same.

[0038] In this embodiment, by symmetrically setting the twist degree of the first twisting zone and the second twisting zone, the carbon fiber composite material has excellent mechanical symmetry when subjected to bidirectional torsional load, which simplifies the structural and performance design and is beneficial to actual production and manufacturing.

[0039] In some embodiments, the twist of the first twisting zone is 50T / m-150T / m.

[0040] In this embodiment, by controlling the twist within the range of 50T / m–150T / m, the overall continuity and stability of the carbon fiber bundle can be ensured while forming a moderate geometric constraint relationship between the carbon fibers. This is beneficial for achieving coordinated force and load transfer between fibers under torsional loads. When the twist is within this range, it can avoid the problems of loose fiber bundle structure and insufficient interfacial interaction caused by excessively low twist, and also prevent the adverse effects of excessively high twist causing excessive fiber bending and internal stress concentration. This helps to balance structural stability and deformation coordination, and improve the comprehensive mechanical adaptability of the composite material under torsional loads.

[0041] In some embodiments, the twist of the second twisting zone is 50T / m-150T / m.

[0042] In this embodiment, by controlling the twist within the range of 50T / m–150T / m, the overall continuity and stability of the carbon fiber bundle can be ensured while forming a moderate geometric constraint relationship between the carbon fibers. This is beneficial for achieving coordinated force and load transfer between fibers under torsional loads. When the twist is within this range, it can avoid the problems of loose fiber bundle structure and insufficient interfacial interaction caused by excessively low twist, and also prevent the adverse effects of excessively high twist causing excessive fiber bending and internal stress concentration. This helps to balance structural stability and deformation coordination, and improve the comprehensive mechanical adaptability of the composite material under torsional loads.

[0043] In some embodiments, the first twisting region and the second twisting region have the same length along the length direction of the carbon fiber bundle.

[0044] In this embodiment, by symmetrically setting the lengths of the first and second twisting zones, the carbon fiber composite material exhibits a symmetrical mechanical response. Specifically, when a torsional load is applied from either direction, the symmetrical segment length setting allows the twisting zones on both sides to produce coordinated deformation behavior, avoiding uneven load distribution or premature local failure caused by length differences, thereby improving the overall structural reliability and service life of the material. Furthermore, this symmetry also simplifies parameter control in the manufacturing process.

[0045] Along the length of the carbon fiber bundle, the length of the transition zone is less than or equal to the length of the first twisting zone and the second twisting zone.

[0046] In this embodiment, by limiting the length of the transition zone to no more than the length of the twisting zone, the transition zone can play a role in stress buffering and crack suppression without excessively weakening the overall load-bearing capacity of the carbon fiber composite material under torsional load.

[0047] In some embodiments, the first twisting region and the second twisting region are twisted in opposite directions to obtain a precursor; the precursor is impregnated in a curable resin system to obtain an intermediate, comprising: A sizing agent is applied to the transition zone, and after the sizing agent solidifies, the first product is obtained. The first twisting region and the second twisting region in the first product are twisted in opposite directions to obtain the precursor; The first twisted region and the second twisted region of the precursor are impregnated separately in a curable resin system to obtain the second product; The qualizing agent coated in the transition region of the second product is removed to obtain the precursor; The precursor is impregnated entirely in a curable resin system to obtain an intermediate.

[0048] In this embodiment, by coating the transition zone with a stabilizing agent, the fiber arrangement in the transition zone can be fixed during twisting, preventing unexpected twisting deformation or fiber misalignment during the twisting operation and ensuring that the transition zone remains untwisted. After the stabilizing agent solidifies to form a temporary support, the first and second twisting zones are twisted in reverse. At this time, the transition zone remains stable due to the constraint of the stabilizing agent, thereby ensuring the precise forming of the bidirectional twisted structure. By sequentially impregnating and initially curing the first and second twisting zones with resin, each twisting segment is gradually fixed and formed while obtaining a uniform resin distribution, thereby avoiding untwisting caused by fiber relaxation or flow disturbance during the overall impregnation process, which is beneficial to maintaining the stability and forming consistency of the bidirectional twisted structure. Specifically, in one embodiment, segmented impregnation can be vertical impregnation. In addition, the stabilizing agent can form a protective layer after solidification, preventing contamination of the transition zone during segmented impregnation. The removal of the sizing agent in the subsequent process can restore the original untwisted fiber arrangement in the transition zone, making it easier to perform overall impregnation. This ensures that a continuous and uniform resin matrix is ​​formed between the transition zone and the twisted zones on both sides, thereby obtaining a carbon fiber composite material with good interfacial bonding and a complete structure.

[0049] In some embodiments, the qualitative agent comprises a water-soluble polyvinyl alcohol solution, and the removal treatment comprises steam thermal dissolution.

[0050] In this embodiment, by using a water-soluble polyvinyl alcohol solution as a sizing agent, its good film-forming and water-soluble properties can be utilized to form a stable temporary protective layer after solidification, effectively fixing the fiber arrangement in the transition zone. In subsequent processing, the sizing agent can be efficiently and thoroughly removed by steam thermal dissolution, avoiding adverse effects of residues on the interface properties of the composite material. At the same time, the steam treatment process is mild and controllable, and will not damage the structural integrity of the carbon fiber bundles.

[0051] In some embodiments, the water-soluble polyvinyl alcohol solution has a mass fraction of 5%-10%.

[0052] In this embodiment, by controlling the mass fraction of the water-soluble polyvinyl alcohol solution within the range of 5%-10%, the qualifier can have sufficient viscosity and film-forming strength.

[0053] In some embodiments, the temperature for steam thermal dissolution is 50°C-75°C.

[0054] In this embodiment, by controlling the temperature of steam thermal dissolution within the range of 50°C to 75°C, the water-soluble polyvinyl alcohol precipitant can be fully dissolved and removed.

[0055] In some embodiments, vapor thermal dissolution is saturated vapor thermal dissolution.

[0056] In this embodiment, the water-soluble polyvinyl alcohol sizing agent can be fully dissolved and removed by saturated steam thermal dissolution.

[0057] In some embodiments, the curable resin system includes an epoxy resin, a curing agent, and a solvent.

[0058] In this embodiment, epoxy resin is used as a continuous phase matrix to coat and connect carbon fibers and form a load-bearing skeleton after curing. The curing agent and epoxy resin undergo a cross-linking reaction to build a stable three-dimensional network structure, thereby endowing the composite material with the required mechanical properties. The solvent is used to regulate the viscosity and flowability of the resin system during the impregnation stage, promote the full penetration of the resin into the fiber bundle and twisted structure, and create conditions for the uniform distribution and stable curing of the resin during the subsequent volatilization process. The synergistic effect of the above three factors achieves effective impregnation and reliable curing of the resin.

[0059] In some embodiments, the mass ratio of epoxy resin, curing agent and solvent is (8–10):(1–3):(12–18).

[0060] In this embodiment, by limiting the mass ratio of epoxy resin, curing agent and solvent to (8-10): (1-3): (12-18), the viscosity of the system can be adjusted by the solvent, so that the resin can uniformly impregnate the fiber or fill the mold, thereby improving the processing performance; at the same time, by controlling the amount of curing agent, the appropriate curing rate and crosslinking density of the resin can be achieved, ensuring the mechanical properties and structural integrity of the composite material after curing.

[0061] In some embodiments, the epoxy resin includes at least one of epoxy resin E44 and epoxy resin E51.

[0062] In this embodiment, epoxy resin E44, a commonly used bisphenol A type epoxy resin, has a suitable molecular weight and epoxy value. The benzene rings in its molecular structure endow the resin system with good rigidity and heat resistance, while the number of epoxy groups ensures sufficient crosslinking reaction with the curing agent, providing good matrix support and interfacial bonding strength for carbon fiber composites. Epoxy resin E51 has a relatively low viscosity and a high epoxy value. When used in combination with E44, it not only further optimizes the flowability of the resin system, facilitating penetration into the helical gaps of twisted carbon fiber bundles, but also improves the mechanical properties and chemical stability of the cured resin matrix by increasing the crosslinking density. The combination of the two allows for flexible adjustment of the ratio according to specific performance requirements, achieving precise control of the composite matrix properties.

[0063] In some embodiments, the curing agent includes at least one of MeTHPA and BC-12.

[0064] In this embodiment, MeTHPA is used as an anhydride curing agent to achieve cross-linking and curing through a ring-opening reaction with epoxy resin. The reaction process is relatively mild and the system has a long pot life, which is beneficial for maintaining low viscosity during the impregnation stage, thereby promoting the full penetration of resin into the carbon fiber bundles and twisted structures. BC-12, as a promoting or latent curing system, can effectively initiate or accelerate the cross-linking reaction of epoxy resin under heating conditions, which helps to form a dense and stable cross-linked network structure while ensuring molding efficiency, and improves the bonding stability of the resin matrix and fiber interface. By selecting MeTHPA and BC-12, a coordinated balance can be achieved between resin impregnation fluidity, curing process controllability and post-curing structural stability, thereby meeting the molding and performance requirements of the composite material of this invention.

[0065] In some embodiments, the solvent includes at least one of acetone and xylene.

[0066] In this embodiment, acetone, with its low viscosity and strong dissolving power, effectively reduces the overall viscosity of the epoxy resin system during the impregnation stage. This facilitates the rapid penetration of the resin into the carbon fiber bundles and twisted structures, and allows for faster evaporation in subsequent processes, creating conditions for uniform resin distribution. Xylene, with its moderate evaporation rate and good swelling effect, maintains the fluidity of the resin system during the impregnation and initial curing stages, preventing uneven resin distribution or premature surface curing caused by excessively rapid solvent evaporation. By selecting acetone and xylene, a balance can be achieved between resin system viscosity control, penetration efficiency, and evaporation process stability, thereby improving the consistency and reliability of composite material molding.

[0067] In some embodiments, the precursor is impregnated into a curable resin system to obtain an intermediate, comprising: The precursor is impregnated in a curable resin system and subjected to physical and / or chemical treatments to obtain an intermediate; wherein, Physical treatment includes at least one of vibration treatment, ultrasonic treatment, and heat treatment; Chemical treatments include polyPVA impregnation.

[0068] In this embodiment, vibration treatment promotes resin flow and penetration within the carbon fiber bundle and twisted structure, effectively eliminating air bubbles in the fiber gaps and improving the uniformity and density of resin impregnation. Ultrasonic treatment utilizes the microjets generated by cavitation effect and the local high-temperature and high-pressure environment to further enhance resin wetting and penetration onto the fiber surface, improving the interfacial bonding quality between the fiber and resin. Heat treatment reduces the viscosity of the resin system, accelerates molecular motion, promotes full diffusion of resin within the fiber bundle, and provides suitable temperature conditions for subsequent curing reactions. PolyPVA impregnation treatment forms a transition layer on the carbon fiber surface, improving the compatibility and interfacial bonding strength between the fiber and the epoxy resin matrix, and reducing the risk of interfacial failure during stress transfer. The above physical and chemical treatments can be implemented individually or in combination, and the process parameters can be adjusted according to actual needs.

[0069] In some embodiments, the curing process includes a thermosetting process.

[0070] In this embodiment, thermosetting effectively improves the mechanical strength and wear resistance of the material by enhancing the internal forces through covalent bonds between molecular chains. Compared to room temperature curing, thermosetting shortens the molding cycle and improves production efficiency, while ensuring stable performance of the material in subsequent use environments.

[0071] In some embodiments, the temperature for thermosetting is (80°C-180°C).

[0072] In this embodiment, the thermosetting temperature is precisely controlled within an optimized range of 120℃-150℃. This temperature range allows the epoxy resin and curing agent to undergo sufficient and uniform cross-linking at a relatively fast reaction rate, promoting the formation of a complete and stable three-dimensional network structure in the resin matrix.

[0073] In some implementations, the thermosetting time is (2h-4h).

[0074] In this embodiment, the thermosetting time is set within the range of 2h-4h. Within this time period, the crosslinking reaction between the epoxy resin and the curing agent can proceed more thoroughly, while also helping to control production energy consumption and costs.

[0075] In some embodiments, the diameter of the single filament in the carbon fiber bundle is 5 μm–7 μm.

[0076] In this embodiment, by controlling the diameter of the monofilaments in the carbon fiber bundle within the range of 5μm-7μm, the arrangement density and contact state between fibers during twisting can be optimized while ensuring that the monofilaments themselves have high tensile strength and modulus. The finer monofilament diameter makes it easier for the fiber bundle to form a tight and regular helical structure during twisting, and the gap distribution between adjacent monofilaments is more uniform, providing a good microscopic channel for the subsequent full impregnation of the resin system. At the same time, monofilaments within this diameter range have moderate rigidity and flexibility, making them less prone to brittle fracture or excessive bending damage during twisting, and better maintaining the integrity of the helical structure, thereby ensuring the stability of the load-bearing capacity and torsional resistance of the carbon fiber skeleton in the final composite material.

[0077] In some embodiments, the carbon fiber bundles are 3K–12K in size.

[0078] In this embodiment, 3K-12K carbon fiber bundles exhibit good operability and structural adaptability in the twisting process of this invention. 3K carbon fiber bundles (composed of approximately 3000 monofilaments) are relatively thin, making it easier to control the uniformity of the helical structure during twisting, and are suitable for preparing precision components with high requirements for dimensional accuracy and torsional uniformity. 12K carbon fiber bundles (composed of approximately 12000 monofilaments), on the other hand, have a higher fiber volume content, and after twisting and curing, they can form a more robust load-bearing skeleton, suitable for large structural components requiring higher overall strength and stiffness. Thus, while ensuring process feasibility, flexible matching of the mechanical properties and structural dimensions of composite materials is achieved for different application scenarios.

[0079] In some embodiments, the thickness of the resin coating layer in the carbon fiber composite material is 20 μm–50 μm.

[0080] In this embodiment, by controlling the thickness of the resin coating layer within the range of 20μm-50μm, a continuous and uniform resin matrix protective layer can be formed on the surface of the carbon fiber bundle. This ensures that the resin fully impregnates and effectively bonds the fiber bundle, while avoiding material weight gain and rigidity reduction due to excessive resin layer thickness.

[0081] Secondly, this application also proposes a carbon fiber composite material, which is prepared by the above-described method for preparing carbon fiber composite materials.

[0082] It is worth mentioning that the carbon fiber composite material obtained by this invention is applicable to fields such as aerospace, high-end equipment manufacturing, and smart textiles.

[0083] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0084] I. Preparation Method Example 1 Carbon fiber bundles are provided, with a single filament diameter of 5μm; the specification of the carbon fiber bundles is 3K.

[0085] A first twisting zone, a transition zone, and a second twisting zone are defined along the length of the carbon fiber bundle, with the transition zone located between the first twisting zone and the second twisting zone. A sizing agent is applied to the transition zone and immediately dried with hot air at 60°C for 1 minute to form a temporary protective layer, while maintaining a constant tension of 0.5 cN / dtex. After the sizing agent solidifies, the first product is obtained; wherein the sizing agent is a 10 wt% water-soluble polyvinyl alcohol (PVA) solution.

[0086] The first twisting zone and the second twisting zone in the first product are twisted in opposite directions (i.e., one clockwise and the other counterclockwise) to obtain the precursor; wherein the twist is 50T / m.

[0087] After dissolving epoxy resin E44 in acetone, the curing agent MeTHPA was added and stirred until dissolved, resulting in a curable resin system. The mass ratio of epoxy resin, curing agent, and solvent was 9:2:15.

[0088] The first twisted region of the precursor is vertically immersed in a curable resin system for 15 minutes, rotated 180°, and the second twisted region of the precursor is vertically immersed in the curable resin system for 15 minutes to obtain the second product. The qualitative agent coated in the transition region of the second product is passed through saturated hot steam at 60°C for 5 minutes to obtain the precursor; The precursor was impregnated in a curable resin system and subjected to mechanical vibration at an amplitude of 5 mm and a frequency of 2 Hz for 20 minutes to obtain an intermediate. The intermediate is mounted on a special fixture and left at room temperature for 3 hours to evaporate the solvent, and then heat-cured at 120°C for 3 hours.

[0089] Example 2 Compared with Example 1, the difference is that the twist of Example 2 is 100T / m. The other steps are roughly the same and will not be described in detail here. The carbon fiber composite material of Example 2 is obtained.

[0090] Example 3 Compared with Example 1, the difference is that the twist of Example 3 is 150T / m. The other steps are roughly the same and will not be described in detail here. The carbon fiber composite material of Example 3 is obtained.

[0091] Example 4 Compared with Example 1, the difference is that the curable resin system of Example 4 is different, and the epoxy resin ratio is increased. Specifically, the mass ratio of epoxy resin, curing agent and solvent is 12:5:15. The remaining steps are roughly the same and will not be described in detail here. The carbon fiber composite material of Example 4 is obtained.

[0092] Comparative Example 1 Compared with Example 1, the difference is that the preset twist of Comparative Example 1 is 0T / m (i.e. no twisting). The other steps are roughly the same and will not be described in detail here. The carbon fiber composite material of Comparative Example 1 is obtained.

[0093] Comparative Example 2 Compared with Example 1, the difference is that no transition zone is set (that is, the length of the transition zone is 0). The rest of the steps are roughly the same and will not be described in detail here, thus obtaining the carbon fiber composite material of Comparative Example 2.

[0094] Comparative Example 3 Compared with Example 1, the difference is that the twisting direction of the first twisting zone and the second twisting zone is the same, and the other steps are roughly the same, which will not be described in detail here, thus obtaining the carbon fiber composite material of Comparative Example 3.

[0095] II. Testing Methods The three-dimensional surface morphology of the composite material was characterized using a three-dimensional optical microscope. The testing equipment was a HIROX RH-2000 three-dimensional digital microscope equipped with a high-resolution imaging module. During the test, an appropriate magnification was selected based on the sample size, ranging from 50× to 500×. The test was conducted at room temperature, without requiring any conductive or surface treatment of the samples.

[0096] To evaluate the torsional resistance of the prepared carbon fiber composite material, this invention uses a self-developed vertical torsion tester to test the mechanical properties of the samples. The vertical torsion tester includes a base, a servo drive system, upper and lower clamping devices, and a torque sensor. The torque sensor is used to collect the torque changes of the sample in real time during the torsion process, and the control system is used to record the torque-torsion angle curve.

[0097] Before testing, the prepared carbon fiber composite material was cut into 100mm long samples and fixed in the upper and lower clamps of a vertical torsion tester, ensuring that the sample axis was coaxial with the rotation axis of the tester to avoid the influence of off-center loading. During the test, the upper clamp remained fixed, while the lower clamp was torsionally or bidirectionally at a constant torsional speed under the control of the servo drive system.

[0098] The test conditions were set as follows: the effective length of the sample was 100 mm; the torsion speed was 1 r / min; the test was conducted at normal temperature and humidity, and the sample was not isolated from air during the test.

[0099] During the test, the torque change and corresponding torsional angle of the specimen were continuously recorded until the specimen failed or reached the set maximum torsional angle. Based on the measured maximum torque and the specimen geometry, the torsional strength and torsional modulus of the carbon fiber composite material were calculated to characterize its torsional resistance.

[0100] III. Analysis of Test Results for Each Embodiment and Comparative Example Table 1 shows the torsional properties of Examples 1-3 and Comparative Example 1. Table 2 shows the reverse twist performance of Examples 1-3 and Comparative Example 1. from Figures 1 to 4 From this, we can obtain: Figure 1 (50T / m) is Example 1. Figure 2 (100T / m) is Example 2. Figure 3 (150T / m) is Example 3. Figure 4 (0T / m) is Comparative Example 1. The twisted carbon fiber composite material has a distinct helical structure.

[0101] from Figure 5 From the diagram, we can see that: the top left (0T / m) is Comparative Example 1, the top right (50T / m) is Example 1, the top right (100T / m) is Example 2, and the bottom left (150T / m) is Example 3. When twisted in the direction of twist, the torsional strength of the twisted carbon fiber composite material is higher than that of the untwisted one. This indicates that the twisted carbon fiber composite material has a reinforcing and toughening effect.

[0102] from Figure 6 From the diagram, we can see that: the top left (0T / m) is Comparative Example 1, the top right (50T / m) is Example 1, the top right (100T / m) is Example 2, and the bottom left (150T / m) is Example 3. When twisted against the twist direction, the toughness of the twisted carbon fiber composite material is higher than that of the untwisted carbon fiber composite material. This indicates that the twisted carbon fiber composite material has a reinforcing and toughening effect.

[0103] Table 1 shows that the torsional strength of Examples 1-4 is higher than that of Comparative Examples 1-3, indicating that twisting carbon fibers and then combining them with resin can effectively improve the torsional properties of carbon fiber composites.

[0104] Table 2 shows that the torsional strength of Examples 1-4 is higher than that of Comparative Examples 1-3, indicating that twisting the carbon fiber and then combining it with resin can improve the torsional strength by twisting the material in any direction.

[0105] Here, it is worth mentioning that, as Figure 7 As shown, the torsional load in the test method of this application is applied from one end, and the torque needs to be gradually transmitted along the length through resin shear and interfacial action. Therefore, the deformation and damage of the material exhibit significant spatial non-uniformity. Untwisting or twisting behavior first occurs near the loaded end and gradually extends to the other end, rather than being a synchronous response along the entire length. Therefore, even if the structure is geometrically symmetrical, its mechanical response does not possess strict symmetry.

[0106] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing carbon fiber composite material, characterized in that, include: Provide carbon fiber bundles; A first twisting region, a transition region, and a second twisting region are defined along the length of the carbon fiber bundle, with the transition region located between the first twisting region and the second twisting region. The first twisting zone and the second twisting zone are twisted in opposite directions to obtain a precursor. The precursor is impregnated in a curable resin system to obtain an intermediate; The intermediate is cured to obtain a bidirectional twisted node structure carbon fiber composite material.

2. The method for preparing carbon fiber composite material according to claim 1, characterized in that, The first twisting zone and the second twisting zone have the same degree of twist; and / or, The twist of the first twisting zone is 50T / m-150T / m; and / or, The twist in the second twisting zone is 50T / m-150T / m; and / or, Along the length of the carbon fiber bundle, the first twisted region and the second twisted region have the same length; and / or, Along the length of the carbon fiber bundle, the length of the transition zone is less than or equal to the lengths of the first twisted zone and the second twisted zone.

3. The method for preparing carbon fiber composite material according to claim 1, characterized in that, The first twisting region and the second twisting region are twisted in opposite directions to obtain a precursor. The precursor is impregnated in a curable resin system to obtain an intermediate, comprising: A sizing agent is applied to the transition region, and after the sizing agent solidifies, a first product is obtained. The first twisted region and the second twisted region in the first product are twisted in opposite directions to obtain a precursor. The first twisted region and the second twisted region of the precursor are impregnated separately in a curable resin system to obtain a second product; The qualitative agent coated on the transition region of the second product is removed to obtain the precursor; The precursor is impregnated entirely in a curable resin system to obtain an intermediate.

4. The method for preparing carbon fiber composite material according to claim 3, characterized in that, The qualitative agent comprises a water-soluble polyvinyl alcohol solution, and the removal treatment comprises steam thermal dissolution.

5. The method for preparing carbon fiber composite material according to claim 4, characterized in that, The water-soluble polyvinyl alcohol solution has a mass fraction of 5%-10%; and / or, The temperature for the steam thermal dissolution is 50℃-75℃; and / or, The steam thermal dissolution is saturated steam thermal dissolution.

6. The method for preparing carbon fiber composite material according to claim 1, characterized in that, The curable resin system includes epoxy resin, curing agent, and solvent.

7. The method for preparing carbon fiber composite material according to claim 6, characterized in that, The mass ratio of the epoxy resin, the curing agent, and the solvent is (8–10):(1–3):(12–18); and / or, The epoxy resin includes at least one of epoxy resin E44 and epoxy resin E51; and / or, The curing agent includes at least one of MeTHPA and BC-12; and / or, The solvent includes at least one of acetone and xylene.

8. The method for preparing carbon fiber composite material according to claim 1, characterized in that, The process of impregnating the precursor in a curable resin system to obtain an intermediate includes: The precursor is impregnated in a curable resin system and subjected to physical and / or chemical treatments to obtain an intermediate; wherein, The physical treatment includes at least one of vibration treatment, ultrasonic treatment and heat treatment; The chemical treatment includes polyPVA impregnation.

9. The method for preparing carbon fiber composite material according to claim 1, characterized in that, The curing process includes thermosetting; and / or, The diameter of the single filament in the carbon fiber bundle is 5μm–7μm; and / or, The carbon fiber bundles are of specification T3003K–12K; and / or, The thickness of the resin coating layer in the carbon fiber composite material is 20μm–50μm.

10. A carbon fiber composite material, characterized in that, It is prepared by the method for preparing carbon fiber composite material according to any one of claims 1-9.

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