Anti-splitting carbon fiber rod body and preparation process thereof

Abstract

The invention discloses an anti-splitting carbon fiber rod body and a preparation process thereof, and belongs to the technical field of high-performance composite materials. The preparation method comprises the following steps: modifying chopped carbon fibers, dispersing in a dispersion suspension, mixing with PA66 fibers, preparing a carbon fiber felt, and carrying out mold pressing to obtain a carbon fiber rod body; placing continuous carbon fibers in an ethanol-acetone mixed solution, performing desizing and drying, adding the continuous carbon fibers and PA66 mixed fibers, and performing winding and fixing to obtain a carbon fiber rod body wound by the continuous carbon fibers; the carbon fiber and PA66 fiber mixed braided fabric is subjected to heating, winding, spiral coating and mold pressing, the carbon fiber rod body, the continuous fibers and the wound braided fabric are combined and solidified, cooling and demolding are conducted, and the anti-splitting carbon fiber rod body is obtained. Through the combination of a plurality of layers of structures, a composite protective layer which combines hardness and softness is formed, and the anti-splitting performance is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of high-performance composite materials technology, and in particular to a split-resistant carbon fiber rod and its preparation process. Background Technology

[0002] Carbon fiber rods are rod-shaped structural materials made of carbon fiber as reinforcement and composite with a matrix material. They have advantages such as lightweight, high strength, corrosion resistance, high temperature resistance, and low coefficient of expansion, and their cross-sectional shape and mechanical properties can be designed according to application requirements. They are mainly used in structural components in the aerospace field, wind turbine blade main beams and support rods in the energy and power field, support towers for high-voltage transmission lines, drive shafts in the rail transportation field, and lightweight components.

[0003] Existing carbon fiber rods mainly include resin-based, metal-based, and ceramic-based types. Resin-based carbon fiber rods include epoxy resin-based carbon fiber rods, unsaturated polyester resin-based carbon fiber rods, phenolic resin-based carbon fiber rods, and vinyl ester resin-based carbon fiber rods. Among these, epoxy resin-based carbon fiber rods suffer from limited temperature resistance, insufficient splitting resistance, complex processing, and poor environmental adaptability; unsaturated polyester resin-based carbon fiber rods suffer from poor temperature resistance, high brittleness, high curing shrinkage, and limited corrosion resistance; phenolic resin-based carbon fiber rods suffer from high brittleness, difficult processing, limited temperature resistance, and weak interfacial bonding; and vinyl ester resin-based carbon fiber rods suffer from high curing shrinkage, poor interfacial performance with carbon fibers, and high cost. Based on these technical problems, developing a carbon fiber rod with splitting resistance and strong interlayer bonding has become a pressing technical challenge in the current technology landscape. Summary of the Invention

[0004] Based on the technical problems to be solved by the present invention, the present invention adopts a structural design of "short fiber felt matrix + continuous fiber load-bearing layer + woven protective layer" and proposes a split-resistant carbon fiber rod and its preparation process.

[0005] One objective of this invention is to provide a method for preparing a split-resistant carbon fiber rod, comprising: S1. Short-cut carbon fibers are modified, dispersed in a dispersion suspension, mixed with PA66 fibers, carbon fiber felt is prepared, and molded to obtain carbon fiber rods; S2. Place the continuous carbon fiber in an ethanol-acetone mixed solution, remove the sizing, dry it, add the continuous carbon fiber and PA66 mixed fiber, wind and fix it to obtain a carbon fiber rod wound with continuous carbon fiber. S3. The carbon fiber and PA66 fiber mixed woven fabric is heated, wound, spirally wrapped, and molded to combine and solidify the carbon fiber rod, continuous fiber, and wound woven fabric. After cooling and demolding, the split-resistant carbon fiber rod is obtained.

[0006] Further, the process of modifying chopped carbon fibers, dispersing them in a dispersion suspension, mixing them with PA66 fibers to prepare carbon fiber felt, and molding them to obtain carbon fiber rods includes: S11. Place the short-cut carbon fibers in a KH550 modification solution. After modification, place the modified short-cut carbon fibers in a suspension containing polyethylene glycol and a dispersant and disperse them to obtain a modified short-cut carbon fiber dispersion suspension. S12. Pre-disperse PA66 fibers separately to obtain pre-dispersed PA66 fibers; S13. Add the pre-dispersed PA66 fibers to the modified short-cut carbon fiber dispersion suspension, disperse and mix to obtain the modified short-cut carbon fiber-PA66 fiber mixture. S14. Take out the modified short-cut carbon fiber-PA66 fiber mixture to obtain carbon fiber felt, and dry the carbon fiber felt to obtain carbon fiber / PA66 composite fiber felt. S15. The carbon fiber / PA66 composite fiber felt is molded to obtain a carbon fiber rod.

[0007] Further, the step of placing continuous carbon fibers in an ethanol-acetone mixed solution, removing the sizing agent, drying the fibers, adding the continuous carbon fibers and PA66 mixed fibers, winding and fixing them to obtain a carbon fiber rod wound with continuous fibers includes: S21. Place the continuous carbon fiber in an ethanol-acetone mixed solution, remove the sizing, take out the carbon fiber through a filter screen, and dry it to obtain dried continuous carbon fiber. S22. Fix the carbon fiber rod on the winding machine, and place the dried continuous carbon fiber and PA66 mixed fiber on the heating plate on the other side of the winding machine, heat it to the glass transition temperature, and wind and fix it on the carbon fiber rod to obtain a carbon fiber rod wound with continuous carbon fiber.

[0008] Further, the process of heating, winding, spirally wrapping, and molding the carbon fiber rod, continuous fibers, and wound fabric together to solidify the carbon fiber rod, continuous fibers, and wound fabric, followed by cooling and demolding, yields the split-resistant carbon fiber rod, comprising: S31. Replace the continuous carbon fiber with a mixed woven fabric of carbon fiber and PA66 fiber, place it on a heating plate, and heat it to the glass transition temperature to obtain a wound woven fabric. S32. The spiral-wrapped woven fabric is molded onto the carbon fiber rod that has been wound with continuous fibers; the carbon fiber rod, continuous fibers, and spiral-wrapped woven fabric are combined and cured, cooled and demolded to obtain the split-resistant carbon fiber rod.

[0009] Furthermore, in the ethanol-acetone mixed solution, the mass ratio of ethanol to acetone is (0.8~1.2):1.

[0010] Further, in S1 or S14, the drying temperature is 65℃~75℃; the molding temperature is 240℃~280℃, the molding pressure is 4.5~5.5MPa, and the molding time is 3~10min.

[0011] Furthermore, in S3 or S32, the molding temperature is 240℃~280℃, the molding pressure is 4.5~5.5MPa, and the molding time is 3~10min.

[0012] The second objective of this invention is to provide a split-resistant carbon fiber rod, which includes a split-resistant hollow carbon fiber rod or a split-resistant solid carbon fiber rod. The split-resistant hollow carbon fiber rod includes, from the outside to the inside, a woven carbon fiber covering layer (3), a discontinuous carbon fiber rod (2), and a continuous carbon fiber winding layer (1). The split-resistant solid carbon fiber rod includes, from the outside to the inside, a woven carbon fiber covering layer (3), a continuous carbon fiber winding layer (1), and a discontinuous carbon fiber rod (2).

[0013] Furthermore, the split-resistant carbon fiber rod includes the chopped carbon fiber and the continuous carbon fiber n-level reinforcement structure, where n is a natural number not less than 2; the split-resistant carbon fiber rod includes a thermoplastic resin matrix.

[0014] The third objective of this invention is to provide an application of split-resistant carbon fiber rods in the automotive, aerospace, and construction industries.

[0015] Compared with the prior art, the present invention proposes a split-resistant carbon fiber rod and its preparation process, which has the following beneficial effects: The anti-splitting carbon fiber rod proposed in this invention combines multiple layers. The porous plate structure formed by the inner layer of short-cut carbon fiber felt can disperse lateral stress and inhibit crack propagation, making the rod less prone to delamination or splitting under complex loads (such as bending and shearing). The continuous fibers in the middle layer can bear load in an directional manner to ensure axial strength. The woven fabric on the surface can be spirally wound to enhance circumferential strength and impact resistance, forming a composite protective layer that combines rigidity and flexibility, significantly improving the anti-splitting performance.

[0016] Furthermore, the split-resistant carbon fiber rod proposed in this invention provides high axial tensile strength through continuous carbon fiber in the middle layer, which can meet high load-bearing requirements; the spiral winding of the surface woven fabric gives the rod excellent torsional resistance and impact toughness; the staged two-stage molding process also reduces internal stress caused by resin shrinkage, improves interlayer bonding strength, makes the surface woven fabric more wear-resistant and resistant to environmental erosion, and extends its service life.

[0017] Furthermore, the preparation process of the anti-splitting carbon fiber rod of the present invention uses short-cut carbon fiber felt, a low-cost material, to replace the continuous fibers in the traditional carbon fiber rod, which can significantly reduce the raw material cost; in addition, the staged molding process can also reduce the defect rate and improve the yield. Attached Figure Description

[0018] Figure 1 A schematic diagram of a split-resistant carbon fiber hollow rod structure according to an embodiment of the present invention is shown; Figure 2 A schematic diagram of a split-resistant solid carbon fiber rod structure according to an embodiment of the present invention is shown; Figure 3 A schematic diagram of the manufacturing process of a split-resistant carbon fiber rod according to an embodiment of the present invention is shown; Among them, 1. Continuous carbon fiber winding layer; 2. Non-continuous carbon fiber rod; 3. Braided carbon fiber covering layer. Detailed Implementation

[0019] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0020] Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art, and the reagents and materials in this invention are obtained from the market or other public channels.

[0021] The experimental materials and equipment involved in this invention mainly include, but are not limited to: Reagents: Carbon fiber, 25k, Jilin Chemical Fiber Group; PA66 fiber, Shenzhen Teli New Material Technology Co., Ltd.; PA6 fiber, Shenzhen Teli New Material Technology Co., Ltd.; KH550, analytical grade, Hong Kong Greenway New Material Technology Co., Ltd.; Polyethylene glycol, MV-70000, Shanghai Maclean Biochemical Technology Co., Ltd.; Polyacrylamide, analytical grade, Shanghai Maclean Biochemical Technology Co., Ltd.; Ethanol, analytical grade, Beijing Chemical Plant Co., Ltd.; Acetone, analytical grade, Beijing Chemical Plant Co., Ltd. instrument: High-temperature hot press, HBSCR-100T / 600AH, Qingdao Huabo Machinery Technology Co., Ltd.; Electric thermostatic drying oven, DHG-9000, Shanghai Jinghong Experimental Equipment Co., Ltd.; Ultrasonic cleaner, AK-100SD, Yujie Cleaning Equipment Co., Ltd.

[0022] The present invention discloses a split-resistant carbon fiber rod and its preparation process, the main technical principles of which include: By innovatively using PA66 (also known as Nylon 66 or Polyamide 66, a polymer material formed by the condensation polymerization of hexamethylenediamine and adipic acid) thermoplastic matrix to replace epoxy resin, and combining a composite structure of short fiber compression molding, continuous fiber spiral winding, and woven fabric covering, the melt permeability of PA66 is used to enhance the fiber-matrix interface bonding. At the same time, stress is dispersed through multi-level reinforcement design, ultimately achieving multi-dimensional optimization of splitting resistance, impact resistance, and process cost, meeting the stringent requirements of high-end application scenarios such as lightweight automotive components and aerospace structural parts.

[0023] Traditional carbon fiber rods often employ a composite structure of epoxy resin matrix and unidirectional continuous fibers. While possessing high axial strength, this structure suffers from drawbacks such as insufficient splitting resistance, complex manufacturing processes, and poor environmental adaptability. Firstly, epoxy resin is brittle and prone to interlaminar cracking under transverse stress, while the single continuous fiber arrangement leads to stress concentration, making it difficult to disperse shear force. Secondly, existing technologies typically require multiple layers of prepreg or metal reinforcement to improve splitting resistance, relying on autoclave curing processes, resulting in high costs and unreliable interfacial bonding. Furthermore, traditional rod surfaces are often protected with epoxy coatings or metal platings, which are prone to peeling and failure due to differences in thermal expansion coefficients. This invention addresses these issues by using a multi-level reinforcement structure of chopped and continuous fibers, combined with the melt-penetration characteristics of a thermoplastic resin matrix (such as PA66), to improve the composite material's transverse splitting resistance, interfacial bonding strength, and environmental durability. The chopped fiber molded matrix, the continuous fiber wound reinforcement layer, and the woven surface protective layer are integrated into a single composite, simplifying the manufacturing process while solving the technical problems of easy delamination and poor impact resistance in traditional carbon fiber rods.

[0024] Based on the above principles, this invention proposes a method for preparing a split-resistant carbon fiber rod. The main raw materials used are carbon fiber and thermoplastic resin fiber PA66. The main preparation process consists of three parts: first, short-cut carbon fibers and resin fibers are formed into a thermoplastic composite rod; then, continuous fibers and fiber braids are wound around the rod to form a reinforcing layer, thereby forming a split-resistant carbon fiber composite rod. Specifically, the method includes: The first step involves placing chopped carbon fibers in a KH550 modification solution. After modification, the modified chopped carbon fibers are dispersed in a suspension containing polyethylene glycol and a dispersant to obtain a modified chopped carbon fiber dispersion suspension. PA66 fibers are pre-dispersed separately to obtain pre-dispersed PA66 fibers. The pre-dispersed PA66 fibers are added to the modified chopped carbon fiber dispersion suspension, dispersed, and mixed to obtain a modified chopped carbon fiber-PA66 fiber mixture. The modified chopped carbon fiber-PA66 fiber mixture is then removed to obtain a carbon fiber felt. The carbon fiber felt is dried to obtain a carbon fiber / PA66 composite fiber felt. The carbon fiber / PA66 composite fiber felt is then molded to obtain a carbon fiber rod. The second step involves placing the continuous carbon fiber in an ethanol-acetone mixed solution to remove the slurry, then removing the carbon fiber through a filter screen and drying it to obtain dried continuous carbon fiber. The carbon fiber rod is then fixed on a winding machine, and on the other side of the winding machine, the continuous carbon fiber and PA66 mixed fiber are placed on a heating plate and heated to the glass transition temperature. The mixture is then wound and fixed onto the carbon fiber rod to obtain a carbon fiber rod wound with continuous fiber. The third step involves replacing the continuous fibers with a mixed woven fabric of carbon fiber and PA66 fiber, placing it on a heating plate, heating it to the glass transition temperature to obtain a wound woven fabric, spirally wrapping the wound woven fabric around the carbon fiber rod wound with continuous fibers, molding it, combining and curing the carbon fiber rod, continuous fibers, and wound woven fabric, cooling and demolding to obtain the split-resistant carbon fiber rod.

[0025] Specifically, see Figure 3 The preparation of the split-resistant carbon fiber rod includes: (1) Preparation of discontinuous carbon fiber rods Short carbon fibers (40-80 mm) were placed in a 3%-10% KH550 modification solution. After modification, the carbon fibers were placed in a suspension containing polyethylene glycol and Triton X-100 dispersant and dispersed at room temperature with ultrasonic assistance. Simultaneously, PA66 fibers were pre-dispersed separately in deionized water. Thermoplastic resin fibers such as PA6, PEEK, PEKK, and PPS can also be selected.

[0026] Pre-dispersed PA66 fibers are added to a carbon fiber dispersion suspension. The mass ratio of carbon fiber to PA66 can be 1:9, 2:8, 3:7, 4:6, 5:5, or other ratios that meet the objectives of this invention. The mixture is then ultrasonically mixed and dispersed. During ultrasonic dispersion, a stirring rod can be used to continuously agitate the fibers, accelerating the dispersion until the mixture is homogeneous. After mixing, the carbon fiber and PA66 fiber mixture is removed, and the resulting carbon fiber felt is placed in a drying oven and dried at 70°C for one day to obtain a carbon fiber / PA66 composite fiber felt. The completely dried carbon fiber felt is placed in a molding press and molds (rod-shaped, strip-shaped, or block-shaped) that meet the preparation requirements of this invention. It is then hot-pressed at 260°C and 5MPa for 5 minutes to obtain carbon fiber rods. The molding time, temperature, and pressure are adjusted appropriately according to the fiber type and the resin's melting temperature.

[0027] (2) Continuous fiber winding Continuous carbon fibers, such as carbon fiber, glass fiber, and basalt fiber, are placed in a mixed solution of ethanol and acetone in a 1:1 mass ratio for desizing. After desizing, the carbon fibers are removed through a filter and then dried. The carbon fiber rod is fixed on a winding machine, and on the other side, continuous carbon fibers and PA66 mixed fibers are placed on a heating plate and wound and fixed onto the carbon fiber rod.

[0028] The rod is fixed in the winding device so that the heated continuous fiber can be heated in time. The temperature of the heating plate is controlled near the glass transition temperature of the resin fiber. At this time, the slight viscosity of the resin can be used to tightly wind and combine the continuous fiber and the carbon fiber rod.

[0029] (3) Covering of fiber woven fabrics After tightly winding a layer of continuous fiber, the continuous fiber is removed and replaced with a mixed woven fabric of carbon fiber and PA66. The fiber woven fabric can be a plain weave, twill weave, or satin weave fabric made of a mixture of fiber and resin. The winding process is repeated to spirally wrap the woven fabric around the continuous fiber layer. After winding, the rod is placed in a molding press and its mold and hot-pressed again at 260℃ and 5MPa for 5 minutes to combine and cure the carbon fiber rod, continuous fiber, and wound woven fabric. After cooling and demolding, a split-resistant carbon fiber composite rod is obtained.

[0030] In step (3), the winding device used in step (2) is selected, and the continuous fiber side is promptly replaced with a fiber braided fabric after step (2). The fiber braided fabric is made of the same material as the matrix used in step (1).

[0031] The split-resistant carbon fiber rod can be used in the automotive, aerospace, and construction industries. The method is simple and the resulting composite material has good split-resistant properties.

[0032] Example 1 This invention proposes a method for preparing split-resistant carbon fiber rods.

[0033] Mainly includes: (1) Preparation of discontinuous carbon fiber rods Continuous carbon fibers (T700 grade, 12K) were placed in a mixed solution of ethanol and acetone at a mass ratio of 1:1 and desized at room temperature for 2 hours. After desizing, the carbon fibers were removed through a filter and then dried at 40°C. After drying, the continuous fibers were cut into 50mm short carbon fibers and placed in a 5% KH550 modification solution. After modification, the carbon fibers were dispersed in a suspension containing 0.025 wt% polyethylene glycol and 0.1 wt% Triton X-100 for 30 minutes. At the same time, PA66 fibers were pre-dispersed separately in deionized water for 1 hour.

[0034] Pre-dispersed PA66 fibers were added to a carbon fiber dispersion suspension at a mass ratio of 3:7. The mixture was then ultrasonically mixed and dispersed, with stirring using a stirring rod to accelerate fiber dispersion until homogeneous. After mixing, the carbon fiber and PA66 fiber mixture was extracted using a papermaking method. The resulting carbon fiber felt was then placed in a drying oven and dried at 70°C for one day to obtain a carbon fiber / PA66 composite fiber felt. The completely dried carbon fiber felt was then placed in a molding press and its rod-shaped mold and hot-pressed at 260°C and 5MPa for 5 minutes to obtain a discontinuous carbon fiber rod.

[0035] (2) Continuous fiber winding The discontinuous carbon fiber rod is fixed on a winding machine. On the other side, a mixture of continuous carbon fiber and PA66 (mass ratio 3:7) is placed on a heating plate. After the heating plate is heated to 150°C, the winding machine is started, and the continuous fiber is wound at a 45° angle after passing through the heating plate. Taking advantage of the slightly sticky properties of PA66 at this time, it is tightly wound and fixed to the carbon fiber rod.

[0036] (3) Covering of woven fabrics After tightly winding a layer of continuous fiber, the continuous fiber is removed and replaced with carbon fiber / PA66 plain weave fabric. The winding process is repeated, with the fabric spirally wrapped around the continuous fiber layer. After winding, the rod is placed in the mold cavity of a molding machine and hot-pressed again at 260℃ and 5MPa for 5 minutes to allow PA66 to melt and penetrate the interlayer interface, thereby achieving the bonding and solidification of the carbon fiber rod, continuous fiber, and wound fabric. Subsequently, the cooling program in the equipment is started, and the material is cooled to room temperature at a cooling rate of 10℃ / min. After the workpiece cools to room temperature, it is demolded to obtain a splitting-resistant carbon fiber composite rod.

[0037] result: Please see Figure 1 The prepared split-resistant carbon fiber composite rod exhibits a multi-layered structure. The outer layer is a carbon fiber braid completely impregnated with PA66 resin; the middle layer is a continuous, wound fiber layer to enhance the load-bearing capacity of the carbon fiber rod along the vertical axis; and the inner layer is a discontinuous carbon fiber rod prepared by mixing short-cut carbon fibers with PA66 fibers, providing the basic load-bearing capacity for the entire structure. Three-point bending and tensile tests showed a bending strength of 570.1 MPa and a tensile strength of 326.9 MPa. The failure mode of all samples was brittle fracture, with no obvious delamination and no axial splitting failure during the tests.

[0038] Example 2 This invention proposes another method for preparing split-resistant carbon fiber rods.

[0039] Mainly includes: (1) Preparation of discontinuous carbon fiber rods Continuous carbon fibers (T700 grade, 12K) were placed in a mixed solution of ethanol and acetone at a mass ratio of 1:1 and desized at room temperature for 4 hours. After desizing, the carbon fibers were removed through a filter and then dried at 70°C. After drying, the continuous fibers were cut into 80mm short carbon fibers and placed in a 7% KH550 modification solution. After modification, the carbon fibers were dispersed in a suspension containing 0.025 wt% polyethylene glycol and 0.1 wt% Triton X-100 for 30 minutes. At the same time, PA66 fibers were pre-dispersed separately in deionized water for 2 hours.

[0040] Pre-dispersed PA66 fibers were added to a carbon fiber dispersion suspension at a mass ratio of 5:5. The mixture was ultrasonically mixed and dispersed, with stirring using a stirring rod to accelerate fiber dispersion until homogeneous. After mixing, the carbon fiber and PA66 fiber mixture was extracted using a papermaking method. The resulting carbon fiber felt was then placed in a drying oven and dried at 70°C for one day to obtain a carbon fiber / PA66 composite fiber felt. The completely dried carbon fiber felt was then placed in a molding press and its rod-shaped mold and hot-pressed at 260°C and 8MPa for 8 minutes to obtain a discontinuous carbon fiber rod.

[0041] (2) Continuous fiber winding The discontinuous carbon fiber rod is fixed on a winding machine, and on the other side, a continuous fiber mixture of carbon fiber (T800 grade, 24K) and PA66 in a 7:3 mass ratio is placed on a heating plate. After the heating plate is heated to 180°, the winding machine is started, and the continuous fiber is wound twice at 30° after passing through the heating plate. Taking advantage of the slightly adhesive properties of PA66 at this time, it is tightly wound and fixed to the carbon fiber rod.

[0042] (3) Covering of woven fabrics After tightly winding a layer of continuous fiber, the continuous fiber is removed and replaced with carbon fiber / PA66 twill weave fabric. The winding process is repeated, with the weave fabric spirally wrapped around the continuous fiber layer. After winding, the rod is placed in the mold cavity of a molding machine and hot-pressed again at 260℃ and 10MPa for 10 minutes to allow PA66 to melt and penetrate the interlayer interface, bonding and solidifying the carbon fiber rod, continuous fiber, and wound weave fabric. Subsequently, the cooling program in the equipment is started, and the rod is cooled to room temperature at a cooling rate of 10℃ / min. After the workpiece cools to room temperature, it is demolded to obtain a splitting-resistant carbon fiber composite rod.

[0043] result: Please see Figure 1 The prepared split-resistant carbon fiber composite rod exhibits a multi-layered distribution. The outer layer is a carbon fiber braid completely impregnated with PA66 resin; the middle layer is a continuous fiber layer wound to improve the load-bearing capacity of the carbon fiber rod in the vertical axis; and the inner layer is a discontinuous carbon fiber rod prepared by mixing short-cut carbon fibers and PA66 fibers, providing the basic load-bearing capacity of the whole. Three-point bending and tensile tests showed a bending strength of 594.4 MPa and a tensile strength of 361.7 MPa. The failure mode of all samples was brittle fracture, with no obvious delamination and no axial splitting failure during the tests. Compared with the test results in Example 1, the difference in mechanical properties stems from the different central carbon fiber rod. Adjusting the ratio of CF to PA66 to 5:5 improved the material's mechanical properties without splitting, demonstrating that the split-resistant carbon fiber composite rod of this invention can be designed and produced to best meet the needs of different application scenarios, avoiding performance waste or insufficient performance of a single product.

[0044] Example 3 This invention proposes another method for preparing split-resistant carbon fiber rods.

[0045] Mainly includes: (1) Preparation of carbon fiber rod Continuous carbon fibers (T700 grade, 12K) were placed in a mixed solution of ethanol and acetone at a mass ratio of 1:1 and desized at room temperature for 2 hours. After desizing, the carbon fibers were removed through a filter and then dried at 40°C. After drying, the continuous fibers were cut into 30mm short carbon fibers and placed in a 5% KH550 modification solution. After modification, the carbon fibers were dispersed in a suspension containing 0.025 wt% polyethylene glycol and 0.1 wt% Triton X-100 for 30 minutes. At the same time, PA66 fibers were pre-dispersed separately in deionized water for 1 hour.

[0046] Pre-dispersed PA66 fibers were added to a carbon fiber dispersion suspension at a mass ratio of 8:2. The mixture was then ultrasonically mixed and dispersed, with stirring using a stirring rod to accelerate fiber dispersion until homogeneous. After mixing, the carbon fiber and PA66 fiber mixture was extracted using a papermaking method. The resulting carbon fiber felt was then placed in a drying oven and dried at 70°C for one day to obtain a carbon fiber / PA66 composite fiber felt.

[0047] (2) Continuous fiber winding A stainless steel rod is fixed on a winding machine to serve as the mandrel for producing the rod body. On the other side, a continuous carbon fiber and PA66 (mass ratio 5:5) mixture is placed on a heating plate. After the heating plate is heated to 200°C, the winding machine is started, and the continuous fiber is wound at a 60° angle after passing through the heating plate. Taking advantage of the slightly sticky properties of PA66 at this time, it is tightly wound and fixed to the stainless steel rod. Subsequently, the stainless steel mandrel with the continuous carbon fiber is held at 200°C.

[0048] (3) Coating of carbon fiber composite felt First, the composite felt prepared in step 1 is cut to dimensions equal to the circumference and length of the stainless steel rod, allowing the carbon fiber felt to be wound around the rod once. Then, the cut carbon fiber composite felt is wound around the stainless steel mandrel, which is under heat treatment. Next, a molding machine is started to pre-compress the material at 2 MPa and 200°C, ensuring the felt adheres tightly to the stainless steel mandrel wound with continuous carbon fibers.

[0049] (4) Covering of woven fabrics After tightly winding a layer of carbon fiber felt, the continuous fibers on the winding machine are removed and replaced with a plain weave fabric of carbon fiber / basalt fiber / PA66. The winding process is repeated, spirally wrapping the fabric around the carbon fiber felt layer. After winding, the rod is placed in the mold cavity of a molding machine and hot-pressed again at 240℃ and 6MPa for 5 minutes to allow PA66 to melt and penetrate the interlayer interface, bonding and solidifying the carbon fiber rod, continuous fibers, and wound fabric. Subsequently, the cooling program in the equipment is started, and the rod is cooled to room temperature at a cooling rate of 10℃ / min. After the workpiece cools to room temperature, it is demolded to obtain a splitting-resistant carbon fiber composite rod.

[0050] result: Please see Figure 2The prepared split-resistant carbon fiber composite rod exhibits a multi-layered distribution. The outer layer is a carbon fiber / basalt braid completely impregnated with PA66 resin. The middle layer is a discontinuous carbon fiber rod prepared by mixing short-cut carbon fibers with PA66 fibers, providing the basic load-bearing capacity. The inner layer is a continuous fiber layer used to improve the load-bearing capacity of the carbon fiber rod along the vertical axis. Three-point bending and tensile tests showed a bending strength of 603.2 MPa and a tensile strength of 367.5 MPa. The failure mode of all samples was brittle fracture, with no obvious delamination and no axial splitting failure during the tests. Compared with the test results in Example 2, the difference in mechanical properties stems from the different outer fiber braids. By replacing the pure carbon fiber braid with a carbon fiber / basalt fiber hybrid braid, the bending strength of the material was effectively improved. This demonstrates that the split-resistant carbon fiber composite rod of this invention can be designed and produced to best meet the needs of different application scenarios, avoiding performance waste or insufficient performance of a single product.

[0051] Comparative Example A performance comparison experiment was conducted between the split-resistant carbon fiber rod prepared by this invention and the carbon fiber rod of the prior art.

[0052] Mainly includes: By winding continuous fiber bundles onto a stainless steel mandrel and impregnating it with the same PA66 resin, the rod matrix was made consistent with that of Examples 1, 2, and 3. The stainless steel rod wound with continuous carbon fibers was then placed in a rod-shaped mold and hot-pressed again at 260°C and 5 MPa for 5 minutes to allow the PA66 to melt and permeate the continuous fibers. Subsequently, the cooling program in the equipment was initiated, and the rod was cooled to room temperature at a cooling rate of 10°C / min under pressure. After the workpiece cooled to room temperature, it was demolded to obtain a splitting-resistant carbon fiber composite rod.

[0053] result: The results of three-point bending and tensile tests showed that the bending strength and tensile strength of the carbon fiber rod prepared in the comparative example were only 313.6 MPa and 230.4 MPa, respectively, and significant splitting occurred in the three-point bending test. This phenomenon is due to the lack of carbon fiber support between the continuous fiber bundles, causing the load to be transmitted to only the PA66 resin matrix, which has a weak load-bearing capacity. Therefore, stress concentration fracture occurs, and after the initial fracture, the crack propagates rapidly due to the lack of carbon fiber restraint, thus forming a splitting fracture.

[0054] It should be noted that the term "comprising," or any other variation thereof, is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0055] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for preparing a split-resistant carbon fiber rod, characterized in that, include: S1. Short-cut carbon fibers are modified, dispersed in a dispersion suspension, mixed with PA66 fibers, carbon fiber felt is prepared, and molded to obtain carbon fiber rods; S2. Place the continuous carbon fiber in an ethanol-acetone mixed solution, remove the sizing, dry it, add the continuous carbon fiber and PA66 mixed fiber, wind and fix it to obtain a carbon fiber rod wound with continuous carbon fiber. S3. The carbon fiber and PA66 fiber mixed woven fabric is heated, wound, spirally wrapped, and molded to combine and solidify the carbon fiber rod, continuous fiber, and wound woven fabric. After cooling and demolding, the split-resistant carbon fiber rod is obtained.

2. The method for preparing the split-resistant carbon fiber rod according to claim 1, characterized in that, The process of modifying short-cut carbon fibers, dispersing them in a dispersion suspension, mixing them with PA66 fibers, preparing carbon fiber felt, and molding them to obtain carbon fiber rods includes: S11. Place the short-cut carbon fibers in a KH550 modification solution. After modification, place the modified short-cut carbon fibers in a suspension containing polyethylene glycol and a dispersant and disperse them to obtain a modified short-cut carbon fiber dispersion suspension. S12. Pre-disperse PA66 fibers separately to obtain pre-dispersed PA66 fibers; S13. Add the pre-dispersed PA66 fibers to the modified short-cut carbon fiber dispersion suspension, disperse and mix to obtain the modified short-cut carbon fiber-PA66 fiber mixture. S14. Take out the modified short-cut carbon fiber-PA66 fiber mixture to obtain carbon fiber felt, and dry the carbon fiber felt to obtain carbon fiber / PA66 composite fiber felt. S15. The carbon fiber / PA66 composite fiber felt is molded to obtain a carbon fiber rod.

3. The method for preparing the split-resistant carbon fiber rod according to claim 1, characterized in that, The process involves placing continuous carbon fibers in an ethanol-acetone mixture, removing the sizing agent, drying the fibers, adding the continuous carbon fibers and PA66 mixed fibers, winding and fixing the mixture to obtain a carbon fiber rod wound with continuous fibers, comprising: S21. Place the continuous carbon fiber in an ethanol-acetone mixed solution, remove the sizing, take out the carbon fiber through a filter screen, and dry it to obtain dried continuous carbon fiber. S22. Fix the carbon fiber rod on the winding machine, and place the dried continuous carbon fiber and PA66 mixed fiber on the heating plate on the other side of the winding machine, heat it to the glass transition temperature, and wind and fix it on the carbon fiber rod to obtain a carbon fiber rod wound with continuous carbon fiber.

4. The method for preparing the split-resistant carbon fiber rod according to claim 1, characterized in that, The process involves heating, winding, spiral-wrapping, and molding a mixed woven fabric of carbon fiber and PA66 fiber to combine and solidify the carbon fiber rod, continuous fibers, and woven fabric. Cooling and demolding then yields the split-resistant carbon fiber rod. S31. Replace the continuous carbon fiber with a mixed woven fabric of carbon fiber and PA66 fiber, place it on a heating plate, and heat it to the glass transition temperature to obtain a wound woven fabric. S32. The spiral-wrapped woven fabric is molded onto the carbon fiber rod that has been wound with continuous fibers; the carbon fiber rod, continuous fibers, and spiral-wrapped woven fabric are combined and cured, cooled and demolded to obtain the split-resistant carbon fiber rod.

5. The method for preparing the split-resistant carbon fiber rod according to claim 1, characterized in that, In the ethanol-acetone mixed solution, the mass ratio of ethanol to acetone is (0.8~1.2):

1.

6. The method for preparing the split-resistant carbon fiber rod according to claim 2, characterized in that, The drying temperature is 65℃~75℃; the molding temperature is 240℃~280℃, the molding pressure is 4.5~5.5MPa, and the molding time is 3~10min.

7. The method for preparing the split-resistant carbon fiber rod according to claim 4, characterized in that, The molding temperature is 240℃~280℃, the molding pressure is 4.5~5.5MPa, and the molding time is 3~10min.

8. A split-resistant carbon fiber rod, characterized in that, The splitting-resistant carbon fiber rod was prepared according to any one of claims 1 to 7. The split-resistant carbon fiber rod includes a split-resistant hollow carbon fiber rod or a split-resistant solid carbon fiber rod; The split-resistant carbon fiber hollow rod body includes, from the outside to the inside, a woven carbon fiber covering layer (3), a discontinuous carbon fiber rod body (2), and a continuous carbon fiber winding layer (1). The split-resistant carbon fiber solid rod includes, from the outside to the inside, a woven carbon fiber covering layer (3), a continuous carbon fiber winding layer (1), and a non-continuous carbon fiber rod (2).

9. The split-resistant carbon fiber rod according to claim 8, characterized in that, The split-resistant carbon fiber rod includes the chopped carbon fiber and the continuous carbon fiber n-level reinforcement structure, where n is a natural number not less than 2; The split-resistant carbon fiber rod comprises a thermoplastic resin matrix.

10. The application of the split-resistant carbon fiber rod prepared by the method of any one of claims 1 to 7 or the split-resistant carbon fiber rod of any one of claims 8 to 9 in the fields of automobiles, aerospace, and construction.

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