Preparation method of presoaked stranded carbon fiber composite core

Abstract

The invention discloses a preparation method of a pre-impregnated stranded carbon fiber composite core, which comprises a core body formed by stranding and curing seven strands of impregnated carbon fiber yarn bundles, and the core body is prepared by the following process: step 1, carrying out resin impregnation treatment on carbon fiber yarns by adopting a pre-impregnation process to obtain impregnated carbon fiber yarns with controllable glue content; step 2, twisting seven strands of impregnated carbon fiber yarns into a strand of composite yarn bundle through bundle twisting equipment; and step 3, continuously feeding the composite yarn bundle into an extrusion die with segmented temperature control, and completing forming and thermocuring while applying pressure to obtain the pre-impregnated stranded carbon fiber composite core. According to the invention, the carbon fiber yarns are firstly subjected to impregnation treatment by adopting a pre-impregnation process, so that a glue solution can fully permeate into fiber gaps of the carbon fiber yarns, uniform combination of fibers and resin is ensured, and the problem of insufficient permeation of the glue solution in a traditional process of firstly twisting and then impregnating is effectively solved; and the interface bonding force and the mechanical property stability of the composite core are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon fiber composite materials, and more particularly to a preparation method of a pre-impregnated twisted carbon fiber composite core. BACKGROUND

[0002] Carbon fiber composite materials have been widely used in many high-end fields such as aerospace, rail transportation and power transmission due to their high strength, high modulus, lightweight and excellent corrosion resistance. As one of the key structural components, carbon fiber composite cores are often used in scenarios such as reinforced core bodies of high-voltage overhead conductors and lightweight structural support members, and their mechanical properties and structural stability directly determine the reliability, safety and service life of the end products.

[0003] Currently, the mainstream preparation processes of carbon fiber composite cores include pultrusion, winding and molding. Among them, although pultrusion has the advantages of continuous production and high efficiency, the core body prepared by pultrusion is usually a unidirectional parallel fiber structure, which leads to obvious deficiencies in transverse shear resistance, torsional performance and flexibility. Although winding can achieve precise control of fiber path and layer structure, thereby improving the overall mechanical properties, the process flow is complex, the equipment investment is large, the production cycle is long, and it is difficult to ensure sufficient resin impregnation of the fiber bundle during high-speed winding, which is prone to dry spots or rich glue areas, affecting product consistency. Molding is limited by mold size and demolding difficulty, and is difficult to apply to the manufacture of long-size continuous cores.

[0004] In addition, for twisted carbon fiber composite cores, the traditional process usually adopts the method of "dry twisting fibers first, then overall impregnation and curing". This method has the following significant defects: due to the small internal gap and dense structure of the fiber bundle after twisting, the subsequent glue solution is difficult to penetrate to the core, resulting in uneven impregnation of the inner and outer layers; at the same time, the interfacial bonding strength between the fiber and the resin is low, and early failure behaviors such as interfacial debonding, delamination and even fracture are prone to occur during service, which seriously affects the mechanical property stability and long-term use reliability of the product.

[0005] Therefore, it is urgent to break through the technical bottleneck and develop a preparation method of a pre-impregnated twisted carbon fiber composite core. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a pre-impregnated twisted carbon fiber composite core, which overcomes the above-mentioned defects in the prior art.

[0007] A preparation method of a pre-impregnated twisted carbon fiber composite core, comprising a core body formed by twisting and curing seven-gore impregnated carbon fiber yarns, wherein the core body is prepared by the following process: Step 1: resin impregnation treatment of carbon fiber yarns by pre-impregnation process to obtain impregnated carbon fiber yarns with controllable glue content; Step 2: Seven strands of the impregnated carbon fiber yarn are twisted into a strand of composite yarn by a bundle twisting device; Step 3: The composite yarn strand is continuously fed into a segmented temperature-controlled extrusion die, and the molding and thermal curing are completed at the same time under pressure to obtain the pre-impregnated twisted carbon fiber composite core.

[0008] Further, the pre-impregnation process in step 1 is carried out using a resin impregnation tank, the impregnation temperature is 40-60℃, and the impregnation time is 3-8min; the resin is at least one of epoxy resin, phenolic resin or vinyl ester resin.

[0009] The pre-impregnation process in step 1 is carried out using a resin impregnation tank, the impregnation temperature is 40-60℃, and the impregnation time is 3-8min; the resin is at least one of epoxy resin, phenolic resin or vinyl ester resin.

[0010] Further, the impregnated carbon fiber yarn obtained in step 1 has a resin content of 30%-50%; after impregnation, excess resin is removed by a guide roller, and the pressure applied by the guide roller is 0.2-0.5MPa.

[0011] The impregnated carbon fiber yarn in step 1 has a resin content of 30%-50%, and a too high resin content will increase the weight of the composite core and reduce the mechanical properties, while a too low resin content cannot guarantee effective bonding between the fibers. After impregnation, excess resin is removed by a guide roller, and the pressure of the guide roller is 0.2-0.5MPa, which can precisely control the stability of the resin content.

[0012] Further, after impregnation, the resin is removed by a guide roller, and the impregnated carbon fiber yarn is dried at 60-80℃ for 2-5min to remove volatile components and bubbles.

[0013] Further, the twisting speed of the bundle twisting device in step 2 is 100-300r / min, and the twisting pitch is 50-200mm, which can be adjusted according to the diameter of the composite core and the use requirements. A reasonable twisting pitch can ensure that the seven strands of impregnated carbon fiber yarn are tightly combined, and improve the torsional resistance and structural stability of the composite core. During the twisting process, the tension of the seven strands of impregnated carbon fiber yarn is kept uniform, and the tension range is 5-15N, which can avoid problems such as uneven tension, eccentricity, etc. after twisting the composite yarn strand.

[0014] Furthermore, the extrusion die described in step 3 includes, in sequence along the material travel direction, a feeding section, a forming section, and a curing section; The temperature of the feeding section is 60-80℃, the temperature of the molding section is 100-120℃, and the temperature of the curing section is 140-160℃. The composite yarn bundle is held in the mold for 5-15 minutes, and the extrusion pressure is 5-15 MPa. The cross-section forming and resin curing are completed simultaneously under the pressure of 5-15 MPa. After curing, the core is cooled, drawn and cut to a fixed length to obtain the finished pre-impregnated stranded carbon fiber composite core.

[0015] The extrusion die described in step 3 includes a feeding section, a forming section, and a curing section, employing segmented temperature control. The temperature of the feeding section is 60-80℃, used to preheat the composite yarn bundle and soften the resin for subsequent extrusion molding. The temperature of the forming section is 100-120℃, allowing the resin to initially cure and form a stable core structure. The temperature of the curing section is 140-160℃, ensuring complete resin curing and improving the mechanical properties of the composite core. The residence time of the composite yarn bundle in the die is 5-15 minutes to ensure full resin curing. The extrusion pressure is 5-15 MPa, which can be adjusted according to the diameter and density requirements of the composite core to ensure a dense composite core structure and reduce internal porosity.

[0016] Furthermore, the diameter of the single filament of the carbon fiber yarn is 5-10μm, and the number of filaments in each carbon fiber yarn bundle is 1000-6000. Selecting carbon fiber yarn with these parameters can ensure the mechanical properties of the composite core while facilitating impregnation and stranding processes.

[0017] Furthermore, the diameter of the core after curing is 5-20mm, which can be adjusted according to actual usage requirements. The tensile strength of the core is ≥1800MPa, and the elastic modulus is ≥150GPa. It has excellent mechanical properties and can meet the usage requirements of different scenarios.

[0018] By adopting the above technical solution, the present invention has the following beneficial effects: (1) The present invention adopts the process route of "pre-impregnation followed by stranding" to achieve full and uniform impregnation of resin at the fiber monofilament scale. This effectively overcomes the defects of insufficient resin penetration and weak interfacial bonding caused by the dense structure in the traditional "dry stranding followed by overall impregnation" process. It significantly enhances the interfacial bonding strength between the fiber and the resin, and improves the consistency of the mechanical properties of the composite core and its long-term service stability.

[0019] (2) This invention forms a composite yarn bundle with a spiral interlocking structure by twisting seven pre-impregnated carbon fiber yarn bundles together with precisely controlled twist pitch and tension. This not only ensures uniform internal stress distribution, but also significantly improves the shear resistance, torsional stiffness and bending flexibility of the composite core. It effectively makes up for the shortcomings of traditional unidirectional pultruded cores, which are brittle and prone to delamination, and expands its application potential under dynamic loads or complex working conditions.

[0020] (3) The present invention adopts a segmented temperature-controlled extrusion die, which completes the cross-section forming and resin curing simultaneously while applying pressure. Through the gradient temperature control strategy of preheating and softening in the feeding section, preliminary shaping in the forming section, and full cross-linking in the curing section, combined with precise pressure control of 5-15MPa, the process is simplified, production efficiency is improved, internal pores are effectively eliminated, and a high-density, high-performance composite core is obtained, which significantly extends the service life of the product.

[0021] (4) The entire preparation process of this invention has clear and continuously controllable parameters. Key indicators such as core diameter (5-20mm) and mechanical properties (tensile strength ≥1800MPa, elastic modulus ≥150GPa) can be flexibly adjusted according to the actual application scenario. It has strong process compatibility, reasonable equipment investment, and high yield. It has good repeatability and large-scale production capability, and has significant economic value and broad market application prospects. Detailed Implementation

[0022] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0023] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0024] Example 1: A pre-impregnated stranded carbon fiber composite core, comprising the following steps: Step 1: Select carbon fiber yarn with a single filament diameter of 7μm and a bundle of 3000 filaments, and put it into the epoxy resin impregnation tank of the prepreg equipment for impregnation treatment. Control the impregnation temperature at 50℃ and the impregnation time at 5min. After impregnation, remove excess resin by a guide roller with a pressure of 0.3MPa to obtain impregnated carbon fiber yarn with a resin content of 40%. Then dry it at 70℃ for 3min to remove moisture and air bubbles from the resin. Step 2: Introduce the seven strands of resin-impregnated carbon fiber yarn treated in Step 1 into the bundling equipment, adjust the bundling speed to 200 r / min, the bundling pitch to 120 mm, and the tension to 10 N, and bund the seven strands of yarn into a composite yarn bundle. Step 3: The stranded composite yarn bundle is continuously fed into the extrusion mold through a traction device. The temperature of the mold feeding section is adjusted to 70℃, the forming section temperature to 110℃, and the curing section temperature to 150℃. The extrusion pressure is 10MPa, and the residence time of the composite yarn bundle in the mold is controlled to be 10min, so that the composite yarn bundle can be cured at the same time as extrusion molding. After curing, it is cooled to room temperature by a cooling device, and then drawn and cut to obtain a pre-impregnated stranded carbon fiber composite core with a diameter of 10mm.

[0025] The composite core product prepared in this embodiment was subjected to performance testing. The results showed that the tensile strength was 1950 MPa, the elastic modulus was 162 GPa, the structure was dense with no obvious pores, and the torsional resistance was excellent.

[0026] Example 2: A method for preparing a pre-impregnated stranded carbon fiber composite core, comprising the following steps: Step 1: Select carbon fiber yarn with a single filament diameter of 5μm and a bundle of 1000 filaments, and put it into the phenolic resin impregnation tank of the prepreg equipment for impregnation treatment. Control the impregnation temperature at 40℃ and the impregnation time at 3min. After impregnation, remove excess resin by a guide roller with a pressure of 0.2MPa to obtain impregnated carbon fiber yarn with a resin content of 30%. Then dry it at 60℃ for 2min to remove moisture and air bubbles from the resin. Step 2: Introduce the seven strands of resin-impregnated carbon fiber yarn treated in Step 1 into the bundling equipment, adjust the bundling speed to 100 r / min, the bundling pitch to 50 mm, and the tension to 5 N, and bund the seven strands of yarn into a composite yarn bundle. Step 3: The stranded composite yarn bundle is continuously fed into the extrusion mold through a traction device. The temperature of the mold feeding section is adjusted to 60℃, the forming section temperature to 100℃, and the curing section temperature to 140℃. The extrusion pressure is 5MPa, and the residence time of the composite yarn bundle in the mold is controlled to be 5min, so that the composite yarn bundle can be cured at the same time as extrusion molding. After curing, it is cooled to room temperature by a cooling device, and then drawn and cut to obtain a pre-impregnated stranded carbon fiber composite core with a diameter of 5mm.

[0027] The performance of the composite core product prepared in this embodiment was tested, and the results showed that the tensile strength was 1820 MPa, the elastic modulus was 153 GPa, the structure was dense with no obvious pores, and the torsional resistance was good.

[0028] Example 3: A method for preparing a pre-impregnated stranded carbon fiber composite core, comprising the following steps: Step 1: Select carbon fiber yarn with a single filament diameter of 10μm and a bundle of 6000 filaments, and put it into the vinyl resin impregnation tank of the prepreg equipment for impregnation treatment. Control the impregnation temperature at 60℃ and the impregnation time at 8min. After impregnation, remove excess resin by a guide roller with a pressure of 0.5MPa to obtain impregnated carbon fiber yarn with a resin content of 50%. Then dry it at 80℃ for 5min to remove moisture and air bubbles from the resin. Step 2: Introduce the seven strands of resin-impregnated carbon fiber yarn treated in Step 1 into the bundling equipment, adjust the bundling speed to 300 r / min, the bundling pitch to 200 mm, and the tension to 15 N, and bund the seven strands of yarn into a composite yarn bundle. Step 3: The stranded composite yarn bundle is continuously fed into the extrusion mold through a traction device. The temperature of the mold feeding section is adjusted to 80℃, the forming section temperature to 120℃, and the curing section temperature to 160℃. The extrusion pressure is 15MPa, and the residence time of the composite yarn bundle in the mold is controlled to be 15min, so that the composite yarn bundle can be cured at the same time as extrusion molding. After curing, it is cooled to room temperature by a cooling device, and then drawn and cut to obtain a pre-impregnated stranded carbon fiber composite core with a diameter of 20mm.

[0029] The composite core product prepared in this embodiment was subjected to performance testing. The results showed that the tensile strength was 2010 MPa, the elastic modulus was 168 GPa, the structure was dense with no obvious pores, and the torsional resistance was excellent.

[0030] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a pre-impregnated stranded carbon fiber composite core, characterized in that: The composite core comprises a core body formed by twisting and curing seven strands of impregnated carbon fiber yarn; The core is obtained through the following preparation process: Step 1: The carbon fiber yarn is impregnated with resin using a pre-impregnation process to obtain resin-impregnated carbon fiber yarn with controllable resin content. Step 2: The seven strands of the impregnated carbon fiber yarn are twisted together into a composite yarn bundle using a twisting device; Step 3: The composite yarn bundle is continuously fed into a segmented temperature-controlled extrusion mold, and molding and thermosetting are completed while pressure is applied to obtain the pre-impregnated stranded carbon fiber composite core.

2. The method for preparing a pre-impregnated stranded carbon fiber composite core according to claim 1, characterized in that: The pre-impregnation process described in step 1 is carried out in a resin impregnation tank, with an impregnation temperature of 40-60℃ and an impregnation time of 3-8 minutes; the resin is at least one of epoxy resin, phenolic resin or vinyl ester resin.

3. The method for preparing a pre-impregnated stranded carbon fiber composite core according to claim 1, characterized in that: The resin content of the impregnated carbon fiber yarn obtained in step 1 is 30%-50%; after impregnation, excess resin is removed by a guide roller, and the pressure applied by the guide roller is 0.2-0.5 MPa.

4. The method for preparing a pre-impregnated stranded carbon fiber composite core according to claim 1, characterized in that: After impregnation, the adhesive is removed by guide rollers and dried at 60-80℃ for 2-5 minutes to remove volatiles and air bubbles.

5. The method for preparing a pre-impregnated stranded carbon fiber composite core according to claim 1, characterized in that: The stranding speed of the stranding equipment in step 2 is 100-300 r / min, and the twist pitch is 50-200 mm. During the stranding process, the tension of each strand of impregnated carbon fiber yarn is kept uniform, and the tension of a single strand is controlled within the range of 5-15 N.

6. The method for preparing a pre-impregnated stranded carbon fiber composite core according to claim 1, characterized in that: The extrusion die described in step 3 includes, in sequence, a feeding section, a forming section, and a curing section along the material travel direction; The temperature of the feeding section is 60-80℃, the temperature of the molding section is 100-120℃, and the temperature of the curing section is 140-160℃. The residence time of the composite yarn bundle in the mold is 5-15 min, and the extrusion pressure is 5-15 MPa; The cross-section forming and resin curing are completed simultaneously under a pressure of 5-15MPa; after curing, the core is cooled, pulled and cut to a fixed length to obtain the finished pre-impregnated stranded carbon fiber composite core.

7. The method for preparing a pre-impregnated stranded carbon fiber composite core according to claim 1, characterized in that: The carbon fiber yarn is composed of carbon fibers with a single filament diameter of 5-10μm, and each carbon fiber yarn contains 1000-6000 single filaments.

8. The method for preparing a pre-impregnated stranded carbon fiber composite core according to claim 1, characterized in that: The outer diameter of the core is 5-20mm, the tensile strength is not less than 1800MPa, and the elastic modulus is not less than 150GPa.