Carbon fiber knitted fabric reinforced resin-based composite material and preparation method thereof

Abstract

The invention discloses a carbon fiber knitted fabric reinforced resin-based composite material and a preparation method thereof. The preparation method of the carbon fiber knitted fabric reinforced resin-based composite material comprises the following steps: (1) dipping carbon fibers serving as core yarns in a resin sizing agent and resin slurry, and carrying out pre-dipping treatment to obtain carbon fiber pre-dipped yarns; wherein the material of the resin slurry is selected from at least one of polyether-ether-ketone, nylon and polypropylene; (2) wrapping a plurality of resin yarns on the carbon fiber prepreg yarns in a Z-twist and S-twist bidirectional interweaving manner by using a wrapping machine to obtain resin core-spun yarns; and (3) by taking the resin yarns as weaving yarns and the resin covering yarns as weft insertion yarns, weaving by adopting a one-to-one variable plain stitch and needle-turning weft insertion knitting method to obtain the carbon fiber knitted fabric reinforced resin-based composite material. The resin infiltration effect and the fabric flexibility can be optimized, and the mechanical performance and the interlayer bonding strength of the composite material are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of textile technology and composite materials, and relates to a carbon fiber knitted cloth reinforced resin-based composite material and a preparation method thereof. Background Art

[0002] Carbon fiber reinforced resin-based composites, with their high strength-to-weight ratio, high damage tolerance, and designability, are in urgent demand for complex curved aerospace components (such as engine nacelles and wing-body fusions) and integrated battery pack housings for new energy vehicles. Initially, carbon fiber composites were mostly formed by directly mixing chopped fibers or randomly laid long fibers with resin. While this method achieved basic mechanical properties, it suffered from problems such as large performance dispersion due to random fiber orientation and high interface defect rates caused by complex resin infiltration paths.

[0003] To improve the directional arrangement of carbon fibers, carbon fiber weaving technology has emerged. Traditional two-dimensional plain / twill woven fabrics generally first weave radial carbon fibers and weft fibers into carbon fiber cloth, and then inject flowing resin into the carbon fiber cloth through resin transfer molding (RTM) technology. This carbon fiber cloth reinforced resin-based composite material can improve the interface defect rate and thus improve the mechanical properties of the composite material. However, the complex surface adaptability of this structure is poor, and the weak interface characteristics between its layers, which rely solely on resin bonding, lead to weak Z-direction performance and low interlaminar shear strength. The subsequent development of three-dimensional weaving technology has enhanced the adaptability of carbon fiber cloth to complex surfaces. However, because carbon fibers are easy to spread and damage, the weaving process will cause carbon fiber breakage problems, thereby affecting the overall performance. Even if a layer of setting agent is applied to the carbon fiber surface, the introduced solvent residue will increase the porosity of the composite material and reduce the mechanical properties. Furthermore, this carbon fiber fabric needs to be post-impregnated with resin, but it is easy to cause low resin content and uneven resin distribution within the carbon fiber bundles in the tightly interwoven areas. Although applying high pressure to force the resin to penetrate the fiber gaps can improve this situation, high pressure can easily cause fiber buckling, which will also affect the overall performance of the composite material. The difficulty lies in how to prepare carbon fiber cloth reinforced resin-based prepreg with uniform impregnation, excellent mechanical properties and adaptability to complex surfaces. Summary of the Invention

[0004] The purpose of the present invention is to provide a carbon fiber knitted cloth reinforced resin-based composite material and a preparation method thereof.

[0005] The technical problem to be solved by the present invention is to address the shortcomings of existing carbon fiber cloth-reinforced resin-based composite materials, particularly the problems of easy damage to carbon fibers during production, insufficient resin content within carbon fiber bundles, uneven resin distribution, and weak resin bonding between layers, which lead to reduced mechanical properties, poor impact resistance, and insufficient overall structural strength. The present invention uses carbon fiber prepreg / resin core-spun yarn to form a prepreg through a one-by-one plain stitch + turn-stitch weft inlay knitting process. The knitting process parameters are improved, the fabric structure and density are adjusted to adapt to irregular core molds, the resin impregnation effect and fabric flexibility are optimized, and the mechanical properties and interlayer bonding strength of the composite material are improved.

[0006] The present invention provides a method for preparing a carbon fiber knitted fabric reinforced resin-based composite material, comprising the following steps: 1) impregnating carbon fiber as a core yarn in a resin sizing agent and a resin slurry for prepreg treatment to obtain carbon fiber prepreg yarn;

[0007] Wherein, the material of the resin slurry is selected from at least one of polyetheretherketone, nylon and polypropylene;

[0008] 2) using a wrapping machine, wrapping a plurality of resin yarns on the carbon fiber prepreg in a bidirectional manner of Z twist and S twist to obtain a resin core-covered yarn;

[0009] 3) The resin yarn is used as the braiding yarn and the resin core-spun yarn is used as the weft yarn, and a one-time-one-change plain needle and transfer needle weft inlay knitting method is adopted to weave to obtain a carbon fiber knitted cloth reinforced resin-based composite material.

[0010] In the above preparation method, the material of the resin yarn is selected from at least one of polyetheretherketone, nylon and polypropylene;

[0011] The resin sizing agent includes at least one of ethylene-methyl acrylate-glycidyl methacrylate, cyclohexanone, and polyetheretherketone solution with carboxyl group (also known as Peek solution with carboxyl group).

[0012] In the above preparation method, the carboxyl-containing polyetheretherketone solution is prepared according to the following steps: 4,4'-difluorobenzophenone, phenolphthalein (abbreviated as PPL), phenolphthalein, potassium carbonate, dimethyl sulfoxide and toluene are mixed, and when the temperature is raised to 120-140°C, the entire system begins to be water-containing, and water vapor is obviously present in the water separator. The reflux reaction is continued at 120-140°C for 2-4 hours, and then heated to 160-180°C for 4-6 hours to obtain the carboxyl-containing polyetheretherketone.

[0013] In the above-mentioned preparation method, the post-reaction system for preparing the carboxyl-containing polyetheretherketone solution is treated as follows: After the reaction is completed, dilute hydrochloric acid is added to dilute the solution, filter the solution to obtain a polymer, grind the polymer, wash it with water, and dry it in a vacuum drying oven at 120°C for 6 hours. The reaction is carried out in a three-necked flask equipped with a mechanical stirrer, a condenser reflux device, and a water separator. The mixture is heated to 160-180°C for 4-6 hours, during which toluene is recycled.

[0014] In the above preparation method, in step 2), the wrapping parameters of the wrapping machine are as follows: the wrapping speed can be 1200-1400 m / h (specifically 1200 m / h), and the twist can be 1800-2400 twists / m (specifically 2400 twists / m).

[0015] In the above preparation method, in step 2), the number of the resin yarns may be 2 to 16.

[0016] In the above preparation method, in step 3), the alternate plain stitch and transfer stitch knitting method is as follows: the plain stitch and transfer stitch adopt an alternate regular change, that is, in the knitting needle arrangement, every other needle performs one action, and the adjacent needle performs another action, the action being plain stitch or transfer stitch, specifically, every other needle performs plain stitch and the adjacent needle performs transfer stitch;

[0017] A knitting machine is used, and the parameters of the knitting machine are as follows: the number of needles can be 200 to 300 needles, the number of revolutions can be 100 to 200 revolutions, the front bed weaving density can be 10 to 15, the rear bed weaving density can be 6 to 12, the pulling WB can be 1.0 to 1.5, and the machine speed can be 0.2 to 0.4 m / s; specifically, the number of needles can be 222 needles, the number of revolutions can be 114 revolutions, the front bed weaving density can be 11, the rear bed weaving density can be 9.5, the pulling WB can be 1.0, and the machine speed can be 0.3 m / s.

[0018] In the above preparation method, in step 3), the carbon fiber knitted fabric reinforced resin-based composite material obtained by weaving is a single-layer, multi-layer or irregularly shaped integrated fabric structure.

[0019] In the present invention, based on the mass of the core-spun yarn, the amount of the resin sizing agent can be 1-2 wt%, and the amount of the resin slurry can be generally 10-25 wt% according to the required resin content ratio of the product;

[0020] The devices used for the prepreg treatment are fixed in the order of an unwinder, a tension controller, a drying drum, a sizing tank, an impregnation tank, a winder and a plurality of yarn guide rollers;

[0021] The sizing agent is added to the sizing tank, the resin slurry is added to the impregnation tank, the temperature of the drying cylinder can be set to 150-400°C, the output tension of the tension controller can be 1.5-3N, and the speed of the winder can be set to 0.2-0.4m / s.

[0022] The present invention also provides the carbon fiber knitted cloth reinforced resin-based composite material prepared by the above preparation method.

[0023] The present invention has the following beneficial effects:

[0024] 1. Solve the problem of uneven impregnation of prepreg materials

[0025] The present invention utilizes resin core-spun yarn to weave carbon fiber into a single-layer, multi-layer or irregular-shaped integrated fabric structure through a one-time-changing plain needle + transfer needle weft insertion knitting process. Overall, the resin is evenly distributed in the fabric, solving the problem of uneven impregnation of carbon fiber prepreg materials; improving the manufacturing quality and production efficiency of composite materials, reducing defects generated during the production process, and enhancing the overall performance of the final product.

[0026] 2. Improved the adaptability of woven prepreg to complex surfaces, facilitating the molding of irregular preforms

[0027] Carbon fiber knitted fabric reinforced resin-based composite materials are prepared through a one-time change plain needle + transfer needle weft knitting process; the resin core-spun yarn uses a yarn spool to form a yarn mesh, which is formed by coils strung together. There is a large expansion space around the coils, and the angle of the carbon fiber core-spun yarn can be adjusted at will to adapt to complex surfaces; the overall fabric has excellent stretchability and elasticity, can adapt to deformations of various sizes, and fit tightly to irregular-shaped core molds, which is conducive to the molding of irregular preforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the knitted structure of the carbon fiber prepreg / resin core-spun yarn according to the present invention.

[0029] Figure 2 Actual photo of the carbon fiber / polyetheretherketone knitted fabric described in this Example 1. DETAILED DESCRIPTION

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0031] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0032] The present invention combines prepreg wrapping technology with knitting technology, utilizes a carbon fiber prepreg / resin core-spun yarn with high resin content, high structural stability and highly uniform woven structure, the prepreg resin type is consistent with the yarn resin type, and is prepared into a carbon fiber knitted cloth reinforced resin-based prepreg through a one-by-one change plain needle + needle transfer weft knitting process, aiming to overcome the problems of insufficient resin content, uneven distribution, weak interlayer bonding and lack of adaptability to complex surfaces in the prior art.

[0033] The present invention provides a method for preparing a carbon fiber knitted fabric reinforced resin-based composite material, comprising the following steps: 1) impregnating carbon fiber as a core yarn in a resin sizing agent and a resin slurry, performing a prepreg treatment, and obtaining a carbon fiber prepreg;

[0034] Wherein, the material of the resin slurry is selected from at least one of polyetheretherketone, nylon and polypropylene;

[0035] 2) using a wrapping machine, wrapping a plurality of resin yarns on the carbon fiber prepreg in a bidirectional manner of Z twist and S twist to obtain a resin core-covered yarn;

[0036] 3) The resin yarn is used as the braiding yarn and the resin core-spun yarn is used as the weft yarn, and a one-time-one-change plain needle and transfer needle weft inlay knitting method is adopted to weave to obtain a carbon fiber knitted cloth reinforced resin-based composite material.

[0037] Example 1: Preparation method of carbon fiber / polyetheretherketone core-spun yarn woven fabric

[0038] The carbon fiber / polyetheretherketone core-spun yarn woven fabric of this embodiment includes a 3k / T700 continuous carbon fiber core yarn located in the center of the yarn and two 238D / 30F polyetheretherketone filaments (such as Figure 2 The coverage of the core-spun yarn is as high as 99% and the tensile strength is as high as 200 MPa.

[0039] 1. Preparation of modified Peek sizing agent with carboxyl group: Step 1: Under nitrogen atmosphere, add 4,4'-difluorobenzophenone, PPL (phenolphthalein), phenolphthalein, potassium carbonate, dimethyl sulfoxide and toluene to a 100mL three-necked flask equipped with a mechanical stirrer, a condensing reflux device and a water separator. Heat up and start mechanical stirring. When the temperature reaches 130°C, the whole system begins to be water-containing, and water vapor is obviously present in the water separator. At this time, the temperature is maintained at 130°C and the reflux reaction is continued for 3 hours to remove the by-product water molecules. The mixture in the three-necked flask is heated to 170°C and reacted for 5 hours. In this process, toluene is recycled. Step 2: After the above reaction is completed, the viscous polymer solution in the three-necked flask is slowly poured into a diluted hydrochloric acid solution for discharge, and the polymer is filtered to obtain the polymer. The polymer is ground and washed with deionized water. Finally, the mixture was dried in a vacuum oven at 120°C for 6 hours to obtain PEKC-COOH polymer (i.e., Peek solution with carboxyl groups, used as a sizing agent). PEKC-COOH polymers with different carboxyl group contents were prepared using the same method. For example, PEKC-COOH-0, PEKC-COOH-3, PEKC-COOH-5, and PEKC-COOH-7 represent polymers with four different PPL mole fractions (0%, 3%, 5%, and 7%) in phenolphthalein / phenolphthalein.

[0040] 2. According to the carbon fiber prepreg technical requirements, a 3k / T700 carbon fiber (CF) yarn is fixed in a high-strength fiber prepreg system in the order of an unwinder, a drying drum, a sizing tank, an impregnation tank, and multiple yarn guide rollers. 500 mL of a carboxyl-modified Peek sizing agent is added to the sizing tank, and 500 mL of a uniformly dispersed carboxyl-modified Peek turbid solution (the solvent can be dichloromethane) is added to the impregnation tank. The Peek powder content is 25 wt%, and the drying drum temperature is set to 300 ° C. Carbon fiber prepreg processing is performed to obtain polyetheretherketone (Peek) yarn (i.e., resin core-spun yarn, referred to as Peek yarn).

[0041] 3. Use a wire splitter to wind 238D / 30F polyetheretherketone yarn onto the resin bobbin of the wrapping machine at a constant tension. The winding parameters are: winding speed 2000 rpm, line speed 100 rpm, and yarn length 1500 m.

[0042] 4. Using the prepreg-treated carbon fiber (CF) as the core yarn and Peek yarn as the covering yarn, place two resin bobbins wrapped with Peek yarn on the bobbins of a wrapping machine to prepare CF / Peek core-spun yarn. The wrapping machine parameters are set as follows: wrapping speed: 1200 m / h, twist: 2400 twists / m.

[0043] 5. Design a single-sided weft insertion structure using PEEK resin yarn as the braiding yarn and CF / PEEK resin core-spun yarn as the weft insertion yarn. A STOLL E7.2 computerized flat knitting machine was used with 222 needles, 114 rpm, a front bed weaving density of 11, a rear bed weaving density of 9.5, a draw ratio of 1.0, and a machine speed of 0.3 m / s to prepare a carbon fiber knitted fabric reinforced with a resin-based prepreg, referred to as a carbon fiber-polyetheretherketone composite material.

[0044] Example 2

[0045] The preparation method is the same as that in Example 1, except that the polyetheretherketone in step 3 is replaced by polypropylene, and the prepared carbon fiber knitted cloth reinforced resin-based prepreg is referred to as carbon fiber-polypropylene composite material.

[0046] Example 3

[0047] The preparation method is the same as that in Example 1, except that the polyetheretherketone in step 3 is replaced by nylon 66, and the prepared carbon fiber knitted cloth reinforced resin-based prepreg is referred to as carbon fiber-nylon 66 composite material.

[0048] The mechanical properties of the thermoplastic resin-based carbon fiber knitted prefabricated fabrics developed in Examples 1-3 above are shown in Table 1:

[0049] As can be seen from Table 1, the thermoplastic resin matrix (nylon 66, polypropylene, polyetheretherketone) significantly reduces the density (lightweight) and greatly improves the toughness (not easy to brittle fracture) of the composite materials (carbon fiber knitted cloth reinforced resin-based prepreg) prepared in Examples 1-3 of the present invention, but sacrifices some strength and drape. For example, the carbon fiber-polyetheretherketone composite material in Example 1 of the present invention has the highest tensile strength and the lowest density. For example, the carbon fiber-nylon 66 composite material in Example 3 of the present invention has the highest elongation at break, high strength, and strong toughness.

[0050] Table 1

[0051]

[0052] Example 4

[0053] The thermoplastic resin-based carbon fiber knitted prefabricated fabric developed in Examples 1-3 was cured by high-temperature hot pressing. The curing process was as follows: five layers of thermoplastic resin-based carbon fiber knitted prefabricated fabric were laid orthogonally at 0 / 90 degrees on the male mold of a molding press; the prefabricated fabric was molded at 85°C and 10 MPa for 10 minutes to complete the preforming process and trim the edges; the prefabricated fabric was then molded at 130°C and 20 MPa for 40 minutes to complete the curing process; the pressure was then maintained at 20 MPa and the temperature was lowered to 85°C. For irregular products, an autoclave molding method is required.

[0054] After curing, the thermoplastic resin-based carbon fiber knitted prefabricated fabric transitioned from flexibility to rigidity, with mechanical properties shown in Table 2. As shown in Table 2, after curing, the carbon fiber-polyetheretherketone composite material in Example 1 exhibited the strongest overall mechanical properties (especially strength and rigidity) and was the lightest. The carbon fiber-polypropylene composite material in Example 1 exhibited the best toughness, with acceptable strength and lightness. The carbon fiber-nylon 66 composite material in Example 3 exhibited relatively balanced but somewhat mediocre properties among the three. In practical applications, the choice of material depends on the final application's priority for strength, rigidity, toughness, and weight.

[0055] Table 2

[0056]

[0057] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a carbon fiber knitted fabric reinforced resin-based composite material, comprising the following steps: 1) impregnating a carbon fiber core yarn into a resin sizing agent and a resin slurry for prepreg treatment to obtain a carbon fiber prepreg; in, The material of the resin slurry is selected from at least one of polyetheretherketone, nylon and polypropylene; 2) using a wrapping machine, wrapping a plurality of resin yarns on the carbon fiber prepreg in a bidirectional manner of Z twist and S twist to obtain a resin core-covered yarn; 3) The resin yarn is used as the braiding yarn and the resin core-spun yarn is used as the weft yarn, and a one-time-one-change plain needle and transfer needle weft inlay knitting method is adopted to weave to obtain a carbon fiber knitted cloth reinforced resin-based composite material.

2. The preparation method according to claim 1, characterized in that The material of the resin yarn is selected from at least one of polyetheretherketone, nylon and polypropylene; The resin sizing agent includes at least one of ethylene-methyl acrylate-glycidyl methacrylate, cyclohexanone, and polyetheretherketone solution with carboxyl group.

3. The preparation method according to claim 1 or 2, characterized in that The polyetheretherketone solution with a carboxyl group is prepared according to the following steps: 4,4'-difluorobenzophenone, phenolphthalein, phenolphthalein, potassium carbonate, dimethyl sulfoxide and toluene are mixed, and when the temperature is raised to 120-140°C, the entire system begins to be water-containing, and water vapor is obviously generated in the water separator, and the reflux reaction is continued at 120-140°C for 2-4 hours, and then the temperature is raised to 160-180°C for reaction for 4-6 hours to obtain the polyetheretherketone with a carboxyl group.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step 2), the wrapping parameters of the wrapping machine are as follows: the wrapping speed is 1200-1400 m / h, and the twist is 1800-2400 twists / m.

5. The preparation method according to any one of claims 1 to 4, characterized in that In step 2), the number of the resin yarns is 2 to 16.

6. The preparation method according to any one of claims 1 to 5, characterized in that In step 3), the one-by-one change of plain needle and transfer needle inlaid weft knitting method is as follows: the plain needle and transfer needle adopt a regular change of one by one, that is, in the knitting needle arrangement, every other needle performs one action, and the adjacent needle performs another action, and the action is plain needle or transfer needle; a knitting machine is used, and the parameters of the knitting machine are as follows: the number of needles is 200-300 needles, the number of revolutions is 100-200 revolutions, the front bed weaving density is 10-15, the rear bed weaving density is 6-12, the pulling WB is 1.0-1.5, and the machine speed is 0.2-0.4 m / s.

7. The preparation method according to any one of claims 1 to 6, characterized in that In step 3), the carbon fiber knitted fabric reinforced resin-based composite material obtained by weaving is a single-layer, multi-layer or irregularly shaped integrated fabric structure.

8. The carbon fiber knitted fabric reinforced resin-based composite material prepared by the preparation method according to any one of claims 1 to 7.

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