A high shear resistance carbon fiber reinforced polyimide composite material and preparation method thereof

Abstract

The invention discloses a high-shear-resistant carbon fiber reinforced polyimide composite material and a preparation method thereof, which belongs to the technical field of carbon fiber composite materials and comprises the following steps: S1, slowly dripping a magnetic carbon nanotube dispersion into a polyimide solution and stirring and mixing to obtain a modified polyimide glue; S2, sequentially pulling a carbon fiber tow to a vibrator, an impregnation tank filled with the modified polyimide glue and an external magnetic field device, and finally fixing it on a roller arrangement machine, removing it after impregnation, magnetization, arrangement and curing, and removing excess organic solvent at high temperature to obtain a carbon fiber unidirectional prepreg; S3, stacking the carbon fiber unidirectional prepregs and hot-pressing them to obtain a carbon fiber reinforced polyimide composite material; the preparation method of the invention is simple, has low production cost, is easy to industrialize and mass-produce, and the obtained carbon fiber reinforced polyimide composite material has the advantages of high strength, high shear strength, good thermal stability and excellent processing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon fiber composite materials, and particularly relates to a high shear resistance carbon fiber reinforced polyimide composite material and a preparation method thereof. Background Art

[0002] Carbon fiber has the advantages of high temperature resistance, high strength, high modulus and light weight. It is widely used in aerospace, wind power, marine ships, automobiles, rail transportation and other fields. However, the technology of preparation, modification and material processing of carbon fiber composite materials is the main bottleneck for the development of carbon fiber composite materials for high-end applications. As the connecting "bond" between carbon fiber and resin matrix, the microstructure and bonding of the interface directly determine the ultimate performance and usability of carbon fiber composite materials, and it is also the weakest link in the overall performance of carbon fiber composite materials. Effective modification of the carbon fiber / matrix interface is an important way to improve the interface performance of fiber composite materials. At present, there are two main aspects of interface modification of carbon fiber composites: one is the surface modification of carbon fiber; the other is the modification of resin matrix.

[0003] Chinese patent application publication number CN117360009A discloses a polyimide composite material and a preparation method thereof. A polyimide composite material is prepared by designing and laying out carbon nanotube fiber cloth / polyimide prepreg as a skin layer, and then designing and laying out carbon fiber reinforced polyimide prepreg as a core layer. Although the electrical conductivity of the material is greatly improved, the interlaminar shear strength of the carbon fiber reinforced polyimide composite material is only slightly improved.

[0004] Chinese patent application publication number CN117802777A discloses a carbon fiber grafted with upright carbon nanotubes, a carbon fiber composite material, and a preparation method. Using a catalytic chemical deposition method, a bioactive glass coating is introduced onto the carbon fiber surface, rapidly growing upright carbon nanotubes on the surface. While this method significantly improves the mechanical properties of the material, it is not suitable for mass production due to the modification of the carbon fiber.

[0005] Chinese patent application publication number CN102181152A discloses a method for preparing a carbon nanotube-modified carbon fiber / polyimide resin multidimensional hybrid composite material. The method comprises the following steps: surface carboxylation and acylation of carbon nanotubes and carbon fibers, and then introduction of diamine or polyamine thereon. The amino-treated carbon nanotubes and polyimide resin are evenly mixed, and then the composite material is cured after vacuum debubbling with functionalized carbon fiber reinforcement to obtain a carbon nanotube-modified carbon fiber / polyimide resin multidimensional hybrid composite material. Although this method can improve the interlaminar shear strength by mixing carbon nanotubes, the disordered mixing state of carbon fibers and carbon nanotubes and the state in which most carbon nanotubes are grafted onto the surface of carbon fibers do not significantly improve the overall performance, and the complicated preparation process increases the cost.

[0006] Therefore, how to prepare carbon fiber reinforced polyimide composite materials with high shear strength in large quantities is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a high shear resistance carbon fiber reinforced polyimide composite material and a preparation method thereof, so that the prepared composite material has the advantages of high strength, high shear resistance, good thermal stability and excellent processing performance, and the preparation process is simple and easy to industrialize and mass produce.

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] A method for preparing a high shear resistance carbon fiber reinforced polyimide composite material comprises the following steps:

[0010] S1. Preparation of modified polyimide glue

[0011] Adding polyimide powder to an organic solvent and stirring to dissolve to obtain a polyimide solution; adding magnetic carbon nanotubes to the organic solvent in multiple portions, stirring at alternating high and low speeds and dispersing with ultrasound to obtain a magnetic carbon nanotube dispersion; slowly adding the magnetic carbon nanotube dispersion dropwise to the polyimide solution and continuing stirring for 30-60 minutes to uniformly disperse the magnetic carbon nanotubes in the polyimide solution to obtain a modified polyimide glue;

[0012] S2. Preparation of carbon fiber unidirectional prepreg tape

[0013] The modified polyimide glue is poured into the impregnation tank, and the carbon fiber tow is then pulled to the vibrator, the impregnation tank and the external magnetic field device in sequence, and finally fixed on the roller arrangement machine. The two poles of the external magnetic field device are located on the left and right sides of the carbon fiber tow, and the magnetic field direction is perpendicular to the pulling direction of the carbon fiber tow. The magnetic field strength is 0.5-25T. After the carbon fiber tow is impregnated, magnetized, arranged and solidified, it is removed from the roller arrangement machine and further dried at high temperature to remove excess organic solvent to obtain a carbon fiber unidirectional prepreg. If the magnetic field strength is too small, it is not conducive to the orientation of magnetic carbon nanotubes. If the magnetic field strength is too large, it will consume too much electricity and increase production costs.

[0014] S3. Preparation of high shear resistance carbon fiber composite materials

[0015] The carbon fiber unidirectional prepreg tapes are stacked and hot-pressed at a temperature of 320-460°C and a pressure of 1-3 MPa to obtain a high shear resistance carbon fiber reinforced polyimide composite material; the number of stacked layers is 10-50, and the specific number of stacked layers is set according to the actual needs of the product to be molded.

[0016] The inventors found that the polyimide glue dissolved in an organic solvent can well infiltrate the carbon fiber tow after yarn unwinding. However, during curing on the subsequent roller arrangement machine, the polyimide resin will precipitate from between the carbon fiber filaments to the surface of the carbon fiber tow as the solvent evaporates. If the polyimide glue is not modified by adding magnetic carbon nanotubes, only a very small amount of polyimide resin will remain between the carbon fiber filaments, thereby affecting the mechanical properties of the carbon fiber reinforced polyimide composite material, especially the interlaminar shear strength.

[0017] Furthermore, the mass ratio of the polyimide powder to the organic solvent is 1:5; the polyimide powder is a soluble polyimide, and the molecular weight of the polyimide is 50,000-140,000. A polyimide with a molecular weight that is too low will result in insufficient mechanical properties of the composite material, while a polyimide with a molecular weight that is too high will prevent the polyimide powder from being completely dissolved in the organic solvent. The mass ratio of the magnetic carbon nanotubes to the organic solvent is 0.005-0.015:1; the organic solvent is any one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone. The amount of magnetic carbon nanotubes should not be excessive, as this will cause the magnetic carbon nanotubes to entangle and agglomerate with each other.

[0018] Furthermore, the magnetic carbon nanotubes are prepared by the following steps:

[0019] Step A1: After a metal nitrate and montmorillonite are subjected to cation exchange treatment, they are calcined and reduced under an inert gas protection to obtain a metal / montmorillonite catalyst. The metal / montmorillonite catalyst is then banbury mixed with waste polyolefin. The discharged material is cooled and crushed to obtain a waste polyolefin composite. The waste polyolefin composite is placed in a tubular furnace and heat-treated at 700-900° C. for 2-6 hours under an inert gas protection to obtain a carbon nanotube / montmorillonite hybrid material. The material is ultrasonically separated and then acidified to obtain modified carbon nanotubes.

[0020] Step A2: ultrasonically dissolve the iron salt in deionized water, then add the modified carbon nanotubes and stir to disperse them. Heat to 70-90°C under nitrogen protection, slowly add 5wt% ammonia water dropwise to a pH of 8-10, stir and react for 0.5-2h, filter and wash the filter residue with deionized water until it is neutral to obtain magnetic carbon nanotubes.

[0021] Furthermore, the mass ratio of the montmorillonite to the metal nitrate is 1:0.1-0.3; the metal nitrate includes but is not limited to any one or more combinations of iron nitrate, nickel nitrate, cobalt nitrate, magnesium nitrate, aluminum nitrate, and manganese nitrate.

[0022] Furthermore, the mass ratio of the metal / montmorillonite catalyst to waste polyolefin is 1:80-100.

[0023] Furthermore, the usage ratio of the iron salt, deionized water and modified carbon nanotubes is 0.6-0.7 g:160-180 mL:0.4-0.45 g; the iron salt includes but is not limited to ferric chloride and ferrous chloride.

[0024] Furthermore, the alternating high-low speed stirring refers to stirring alternately between a low speed of 100-400 r / min and a high speed of 600-1000 r / min every 1 minute.

[0025] Furthermore, the up and down vibration frequency of the vibrator is 20-100 Hz and the amplitude is 1-5 mm; the roller temperature in the roller arrangement machine is 50-120° C., the arrangement tension is 4-15 N, and the arrangement speed is 10-25 m / min.

[0026] Furthermore, the thickness of the carbon fiber unidirectional prepreg tape is 0.01-0.5 mm; the ultra-thin carbon fiber unidirectional prepreg tape has good bendability and can be bent 0-180°, has simplified operation and excellent plasticity, and can be used to prepare various carbon fiber composite materials products with special structures.

[0027] A high shear resistance carbon fiber reinforced polyimide composite material is prepared by the above preparation method.

[0028] Beneficial effects:

[0029] 1. The present invention uses cheap waste polyolefin plastics as carbon source and prepares high value-added carbon nanotubes by catalytic cracking. The carbon nanotubes separated from montmorillonite are then acidified to obtain modified carbon nanotubes. Then, Fe 2+ and Fe 3+ The carbon nanotubes are co-precipitated and converted into magnetic nanoparticles, which are attached to the surface of the modified carbon nanotubes or embedded in their structure to obtain high-value magnetic carbon nanotubes. The carbon nanotubes of the present invention are derived from waste polyolefins, which helps reduce white pollution, realizes the concept of green environmental protection, and greatly reduces production costs.

[0030] 2. The present invention uses a vibrator to spread the carbon fiber tow, causing the carbon fiber tow to widen and thin, thereby ensuring that the carbon fiber tow is fully infiltrated with the modified polyimide adhesive. Due to the nano-size effect of the magnetic carbon nanotubes in the modified polyimide adhesive, the magnetic carbon nanotubes loaded on the carbon fiber monofilaments by electrostatic action bind the polyimide resin inside the carbon fiber tow through capillary action, thereby evenly distributing the polyimide resin in the carbon fiber tow, which is beneficial to improving the uniform stability of the carbon fiber reinforced polyimide composite material.

[0031] 3. The present invention applies an external magnetic field to make the magnetic carbon nanotubes oriented and arranged between the carbon fiber filaments. On the one hand, the dispersion of the magnetic carbon nanotubes is improved due to the repulsion of the magnetic carbon nanotubes in the magnetic field; on the other hand, under the action of the external magnetic field, the magnetic carbon nanotubes are oriented and arranged perpendicular to the carbon fiber bundles, so that the magnetic carbon nanotubes are overlapped between multiple carbon fiber filaments, forming a "network structure" with carbon fibers as warps and magnetic carbon nanotubes as wefts, so that the polyimide resin is better retained between the carbon fiber bundles, solving the problem of polyimide resin migrating to the surface of the carbon fiber bundles due to the volatilization of organic solvents in the composite material molding process, and providing a reliable solution for the preparation of high-performance carbon fiber reinforced composite materials; in addition, through the mechanical bite effect at the interface between the magnetic carbon nanotubes and the carbon fiber bundles, the interface performance of the carbon fiber reinforced polyimide composite material is significantly improved, especially the shear resistance is greatly improved.

[0032] 4. The preparation method of the present invention is simple, has low production cost, and is easy to industrialize and mass-produce. The obtained carbon fiber reinforced polyimide composite material has the advantages of high strength, high shear strength, good thermal stability and excellent processing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] Figure 1 is a scanning electron micrograph of a cross section of a carbon fiber unidirectional prepreg tape prepared in Example 6 of the present invention;

[0035] Figure 2 This is a scanning electron micrograph of the cross section of the carbon fiber unidirectional prepreg tape prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a magnetic carbon nanotube, which is prepared by the following steps:

[0039] Step A1, 1g of montmorillonite (Zhejiang Fenghong New Materials Co., Ltd.) was added to 200mL of deionized water and magnetically stirred for 1h, and then ultrasonicated for 4h to obtain a montmorillonite suspension; 0.3g of ferric nitrate hexahydrate was added to 10mL of deionized water and stirred to dissolve, and then poured into the montmorillonite suspension and stirred and immersed for 24h. After cation exchange treatment, the filter residue was filtered and dried at 100°C, ground and passed through a 200-mesh sieve, and then transferred to a quartz boat in a tube furnace. The tube furnace was first passed with argon for 30min, and then heated to 500°C at a heating rate of 5°C / min, calcined under argon protection for 3h, and cooled to room temperature to obtain an iron / montmorillonite catalyst; 0 1 g of iron / montmorillonite catalyst was uniformly mixed with 10 g of waste polyethylene, and then added to an internal mixer and internally mixed at a speed of 40 r / min and a temperature of 170°C. After the internal mixing torque curve was flat, the internal mixing was continued for 10 minutes. After the discharged material was cooled, it was crushed into powder using a multifunctional crusher to facilitate subsequent calcination to obtain a waste polyolefin composite. The waste polyolefin composite was placed in a tubular furnace and heat-treated at 900°C for 2 hours under argon protection. It was then cooled to room temperature to obtain a carbon nanotube / montmorillonite hybrid material. The carbon nanotubes were obtained by ultrasonic separation, and the carbon nanotubes were acidified with a mixed acid (volume ratio of concentrated sulfuric acid:concentrated nitric acid = 3:1) to obtain modified carbon nanotubes.

[0040] Step A2, ultrasonically dissolve 0.45g FeCl3·6H2O and 0.15g FeCl2·4H2O iron salts in 160mL deionized water, then add 0.4g modified carbon nanotubes and stir to disperse, heat to 80°C under nitrogen protection, slowly add 5wt% ammonia water at a rate of 1mL / min to a pH value of 9, stir and react for 1h, filter and wash the residue with deionized water until neutral, to obtain magnetic carbon nanotubes.

[0041] Example 2

[0042] This embodiment provides a magnetic carbon nanotube, which is prepared by the following steps:

[0043] Step A1, 1g of montmorillonite was added to 200mL of deionized water and magnetically stirred for 1h, and then ultrasonicated for 4h to obtain a montmorillonite suspension; 0.1g of nickel nitrate hexahydrate was added to 10mL of deionized water and stirred to dissolve, and then poured into the montmorillonite suspension and stirred and immersed for 24h. After cation exchange treatment, the filter residue was filtered and dried at 100°C, ground and passed through a 200-mesh sieve, and then transferred to a quartz boat in a tube furnace. The tube furnace was first passed with argon for 30min, then heated to 500°C at a heating rate of 5°C / min, calcined under argon protection for 3h, and cooled to room temperature to obtain a nickel / montmorillonite catalyst; 0.1 g of nickel / montmorillonite catalyst was uniformly mixed with 8 g of waste polypropylene, then added to an internal mixer and internally mixed at a speed of 40 r / min and a temperature of 170° C. After the internal mixing torque curve became flat, internal mixing was continued for 10 minutes. After the discharged material was cooled, it was crushed into powder using a multifunctional crusher for later calcination to obtain a waste polyolefin composite. The waste polyolefin composite was placed in a tubular furnace and heat-treated at 850° C. for 3 hours under argon protection, and then cooled to room temperature to obtain a carbon nanotube / montmorillonite hybrid material. The carbon nanotubes were obtained by ultrasonic separation, and the carbon nanotubes were acidified with concentrated hydrochloric acid to obtain modified carbon nanotubes.

[0044] Step A2, ultrasonically dissolve 0.48g FeCl3·6H2O and 0.18g FeCl2·4H2O iron salts in 170mL deionized water, then add 0.43g modified carbon nanotubes and stir to disperse, heat to 90°C under nitrogen protection, slowly add 5wt% ammonia water at a rate of 1mL / min to a pH value of 10, stir and react for 0.5h, filter and wash the residue with deionized water until neutral, to obtain magnetic carbon nanotubes.

[0045] Example 3

[0046] This embodiment provides a magnetic carbon nanotube, which is prepared by the following steps:

[0047] Step A1, 1g of montmorillonite was added to 200mL of deionized water and magnetically stirred for 1h, and then ultrasonicated for 4h to obtain a montmorillonite suspension; 0.2g of cobalt nitrate hexahydrate was added to 10mL of deionized water and stirred to dissolve, and then poured into the montmorillonite suspension and stirred and immersed for 24h. After cation exchange treatment, the filter residue was filtered and dried at 100°C, ground and passed through a 200-mesh sieve, and then transferred to a quartz boat in a tube furnace. The tube furnace was first passed with argon for 30min, then heated to 500°C at a heating rate of 5°C / min, calcined under argon protection for 3h, and cooled to room temperature to obtain a cobalt / montmorillonite catalyst; 0 1 g of cobalt / montmorillonite catalyst was uniformly mixed with 9 g of waste polyethylene, and then added to an internal mixer and internally mixed at a speed of 40 r / min and a temperature of 170° C. After the internal mixing torque curve was flat, the internal mixing was continued for 10 minutes. After the discharged material was cooled, it was crushed into powder using a multifunctional crusher to facilitate subsequent calcination to obtain a waste polyolefin composite; the waste polyolefin composite was placed in a tubular furnace and heat-treated at 700° C. for 6 hours under inert gas protection, and then cooled to room temperature to obtain a carbon nanotube / montmorillonite hybrid material, and the carbon nanotubes were obtained by ultrasonic separation, and the carbon nanotubes were acidified with concentrated hydrochloric acid to obtain modified carbon nanotubes;

[0048] Step A2, ultrasonically dissolve 0.5g FeCl3·6H2O and 0.2g FeCl2·4H2O iron salts in 180mL deionized water, then add 0.45g modified carbon nanotubes and stir to disperse, heat to 70°C under nitrogen protection, slowly add 5wt% ammonia water at a rate of 1mL / min to a pH value of 8, stir and react for 2h, filter and wash the residue with deionized water until neutral, to obtain magnetic carbon nanotubes.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 3 is that the operation of step A2 is not performed, and the modified carbon nanotubes are directly used in the subsequent comparative examples.

[0051] Example 4

[0052] This embodiment provides a high shear resistance carbon fiber reinforced polyimide composite material, which is prepared by the following preparation method:

[0053] S1. Add 10 g of polyimide powder to 50 g of N,N-dimethylacetamide and stir and dissolve at a speed of 300 r / min to obtain a polyimide solution; add 0.05 g of the magnetic carbon nanotubes obtained in Example 1 to 10 g of N,N-dimethylacetamide in 4 portions, stir alternately at high and low speeds of 400 r / min and 1000 r / min every 1 min for 2 h, and then ultrasonicate for 30 min to obtain a magnetic carbon nanotube dispersion; slowly add the above magnetic carbon nanotube dispersion dropwise to the polyimide solution and stir and mix for 30 min to uniformly disperse the magnetic carbon nanotubes in the polyimide solution to obtain a modified polyimide glue;

[0054] S2. Pour the modified polyimide glue into the impregnation tank, and then pull the carbon fiber tow to the vibrator, the impregnation tank and the external magnetic field equipment in sequence, and finally fix it on the roller arrangement machine. The two poles of the external magnetic field equipment are located on the left and right sides of the carbon fiber tow, and the magnetic field direction is perpendicular to the pulling direction of the carbon fiber tow. The magnetic field intensity is 0.5T. Turn on the vibrator and the roller arrangement machine, and keep the up and down vibration frequency of the vibrator at 100Hz and the amplitude at 1mm; the roller temperature in the roller arrangement machine is 500℃, the arrangement tension is 8N, and the arrangement speed is 25m / min. After the carbon fiber tow is impregnated, magnetized, arranged and cured, it is removed from the roller arrangement machine, and after high-temperature drying to further remove excess organic solvent, a carbon fiber unidirectional prepreg with a thickness of 0.05mm is obtained;

[0055] S3. Ten layers of carbon fiber unidirectional prepreg tapes are stacked, hot-pressed at a temperature of 320°C and a pressure of 1 MPa for 2 h, and then the pressure is released after the temperature is lowered to 200°C to obtain a high shear resistance carbon fiber reinforced polyimide composite material.

[0056] Example 5

[0057] This embodiment provides a high shear resistance carbon fiber reinforced polyimide composite material, which is prepared by the following preparation method:

[0058] S1. Add 10 g of polyimide powder to 50 g of N,N-dimethylformamide and stir and dissolve at a speed of 600 r / min to obtain a polyimide solution; add 0.1 g of the magnetic carbon nanotubes obtained in Example 2 to 10 g of N,N-dimethylformamide in 5 times, stir alternately at high and low speeds of 100 r / min and 600 r / min every 1 min for 3 h, and then ultrasonicate for 20 min to obtain a magnetic carbon nanotube dispersion; slowly add the above magnetic carbon nanotube dispersion dropwise to the polyimide solution and stir and mix for 40 min to uniformly disperse the magnetic carbon nanotubes in the polyimide solution to obtain a modified polyimide glue;

[0059] S2. Pour the modified polyimide glue into the impregnation tank, and then pull the carbon fiber tow to the vibrator, impregnation tank and external magnetic field equipment in sequence, and finally fix it on the roller arrangement machine. The two poles of the external magnetic field equipment are located on the left and right sides of the carbon fiber tow, and the magnetic field direction is perpendicular to the pulling direction of the carbon fiber tow. The magnetic field strength is 15T. Turn on the vibrator and the roller arrangement machine, and keep the vibrator's up and down vibration frequency at 50Hz and the amplitude at 3mm; the roller temperature in the roller arrangement machine is 80°C, the arrangement tension is 4N, and the arrangement speed is 10m / min. After impregnation, magnetization, arrangement and curing, the carbon fiber tow is removed from the roller arrangement machine, and after high-temperature drying to further remove excess organic solvent, a carbon fiber unidirectional prepreg with a thickness of 0.01mm is obtained;

[0060] S3. Ten layers of carbon fiber unidirectional prepreg tapes are stacked, hot-pressed at a temperature of 400°C and a pressure of 2 MPa for 1.5 h, and then the pressure is released after the temperature is lowered to 200°C to obtain a high shear resistance carbon fiber reinforced polyimide composite material.

[0061] Example 6

[0062] This embodiment provides a high shear resistance carbon fiber reinforced polyimide composite material, which is prepared by the following preparation method:

[0063] S1. Add 10 g of polyimide powder to 50 g of N-methylpyrrolidone and stir and dissolve at a speed of 900 r / min to obtain a polyimide solution; add 0.15 g of the magnetic carbon nanotubes obtained in Example 3 to 10 g of N-methylpyrrolidone in 5 portions, stir alternately at high and low speeds of 300 r / min and 800 r / min every 1 min for 3 h, and then ultrasonicate for 10 min to obtain a magnetic carbon nanotube dispersion; slowly add the above magnetic carbon nanotube dispersion dropwise to the polyimide solution and stir and mix for 60 min to uniformly disperse the magnetic carbon nanotubes in the polyimide solution to obtain a modified polyimide glue;

[0064] S2. Pour the modified polyimide glue into the impregnation tank, and then pull the carbon fiber tow to the vibrator, the impregnation tank and the external magnetic field equipment in sequence, and finally fix it on the roller arrangement machine. The two poles of the external magnetic field equipment are located on the left and right sides of the carbon fiber tow, and the direction of the magnetic field is perpendicular to the pulling direction of the carbon fiber tow. The magnetic field strength is 25T. Turn on the vibrator and the roller arrangement machine, and keep the up and down vibration frequency of the vibrator at 20Hz and the amplitude at 5mm; the roller temperature in the roller arrangement machine is 120℃, the arrangement tension is 15N, and the arrangement speed is 15m / min. After the carbon fiber tow is impregnated, magnetized, and arranged and solidified, it is removed from the roller arrangement machine, and after high-temperature drying to further remove excess organic solvent, a carbon fiber unidirectional prepreg with a thickness of 0.1mm is obtained; Figure 1 As shown in the figure, the polyimide resin is evenly distributed inside the carbon fiber unidirectional prepreg tape without obvious precipitation.

[0065] S3. Ten layers of carbon fiber unidirectional prepreg tapes are stacked, hot-pressed at a temperature of 460°C and a pressure of 3 MPa for 1 hour, and then the pressure is released after the temperature is lowered to 200°C to obtain a high shear resistance carbon fiber reinforced polyimide composite material.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 6 is that the magnetic carbon nanotubes prepared in Example 3 are not added in step S1, and the other raw materials and steps are the same. Figure 2 As shown in FIG. 2 , the polyimide resin is accumulated on the surface of the carbon fiber unidirectional prepreg tape, and only a small amount of polyimide resin remains between the carbon fiber monofilaments.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 6 is that the modified carbon nanotubes prepared in Comparative Example 1 are used to replace the magnetic carbon nanotubes prepared in Example 3 in equal amounts, and the remaining steps and raw materials are the same.

[0070] Comparative Example 4

[0071] The difference between this comparative example and Example 6 is that the magnetic field intensity in step S2 is 0, that is, the carbon fiber tow is not magnetized, and the remaining steps are the same.

[0072] Performance tests were performed on Examples 4 to 6 and Comparative Examples 2 to 4. According to the GB / T 1449-2005 standard, the flexural properties of the carbon fiber reinforced polyimide composite materials were tested using a CMT 6104 electronic universal testing machine from Shenzhen Xinsansi Company. According to the GB / T 1450.1-2005 standard, the interlaminar shear properties of the carbon fiber reinforced polyimide composite materials were tested using a CMT 6104 electronic universal testing machine from Shenzhen Xinsansi Company. A thermogravimetric analyzer (model TG2) from Mettler Toledo, Switzerland, was used to test the thermal stability of the carbon fiber reinforced polyimide composite materials by thermogravimetric analysis by heating the temperature from room temperature to 800° C. in an air atmosphere, and the temperature T at which the composite material lost 5% of its weight during thermal decomposition was recorded. d5% , Temperature T when thermal decomposition weight loss is 10% d10% and the temperature T when the thermal decomposition weight loss is 30% d30% The results are shown in Table 1:

[0073] Table 1

[0074]

[0075] It can be seen from the data in Table 1 that the mechanical properties and thermal stability of the carbon fiber reinforced polyimide composite materials prepared in Examples 4 to 6 are significantly better than those of the carbon fiber reinforced polyimide composite materials prepared in Comparative Examples 2 to 4. This is because the directionally arranged magnetic carbon nanotubes and the carbon fiber tows form a "network structure", which can better retain the polyimide resin between the carbon fiber tows. The magnetic carbon nanotubes can also act as a link between the carbon fiber tows and the polyimide resin, forming a mechanical meshing effect between the carbon fiber tows and the polyimide resin, thereby improving the interfacial bonding strength and thus improving the mechanical properties and thermal stability of the composite material.

[0076] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0077] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high shear resistance carbon fiber reinforced polyimide composite material, characterized in that: The steps include: S1, adding polyimide powder to an organic solvent and stirring to dissolve to obtain a polyimide solution; adding magnetic carbon nanotubes to the organic solvent in multiple portions, stirring at alternating high and low speeds and dispersing by ultrasound to obtain a magnetic carbon nanotube dispersion; slowly adding the magnetic carbon nanotube dispersion dropwise to the polyimide solution and continuing to stir to obtain a modified polyimide glue; S2. The carbon fiber tow is sequentially drawn to a vibrator, an impregnation tank filled with modified polyimide glue, and an external magnetic field device, and finally fixed on a roller arrangement machine. The two poles of the external magnetic field device are located on the left and right sides of the carbon fiber tow. The magnetic carbon nanotubes are arranged perpendicular to the carbon fiber tow so that the magnetic carbon nanotubes are overlapped between multiple carbon fiber filaments, forming a "network structure" with carbon fibers as warp and magnetic carbon nanotubes as weft. After impregnation, magnetization, arrangement and curing, the carbon fiber tow is removed from the roller arrangement machine and dried to obtain a carbon fiber unidirectional prepreg tape; S3. The carbon fiber unidirectional prepreg tapes are stacked and hot-pressed at a temperature of 320-460° C. and a pressure of 1-3 MPa to obtain a high shear resistance carbon fiber reinforced polyimide composite material.

2. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 1, characterized in that: The mass ratio of the polyimide powder to the organic solvent is 1:5; the polyimide powder is a soluble polyimide, and the molecular weight of the polyimide is 50,000-140,000; the mass ratio of the magnetic carbon nanotubes to the organic solvent is 0.005-0.015:1; the organic solvent is any one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

3. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 1, characterized in that: The magnetic carbon nanotubes are prepared by the following steps: Step A1: After subjecting a metal nitrate and montmorillonite to cation exchange treatment, the metal / montmorillonite catalyst is calcined and reduced under an inert gas atmosphere to obtain a metal / montmorillonite catalyst. The metal / montmorillonite catalyst is then banbury mixed with waste polyolefins. The discharged material is cooled and crushed to obtain a waste polyolefin composite. The waste polyolefin composite is heat treated under an inert gas atmosphere at 700-900° C. for 2-6 hours to obtain a carbon nanotube / montmorillonite hybrid material. The material is ultrasonically separated and then acidified to obtain modified carbon nanotubes. Step A2: ultrasonically dissolve the iron salt in deionized water, then add the modified carbon nanotubes and stir to disperse them. Heat to 70-90°C under nitrogen protection, slowly add 5wt% ammonia water dropwise to a pH of 8-10, stir and react for 0.5-2h, filter and wash the filter residue with deionized water until it is neutral to obtain magnetic carbon nanotubes.

4. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 3, characterized in that: The mass ratio of the montmorillonite to the metal nitrate is 1:0.1-0.3; the metal nitrate includes but is not limited to any one or more combinations of ferric nitrate, nickel nitrate, cobalt nitrate, magnesium nitrate, aluminum nitrate, and manganese nitrate.

5. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 3, characterized in that: The mass ratio of the metal / montmorillonite catalyst to waste polyolefin is 1:80-100.

6. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 3, characterized in that: The usage ratio of the iron salt, deionized water and modified carbon nanotubes is 0.6-0.7 g:160-180 mL:0.4-0.45 g; the iron salt is ferric chloride and ferrous chloride.

7. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 1, characterized in that: The alternating high and low speed stirring refers to stirring alternately between a low speed of 100-400 r / min and a high speed of 600-1000 r / min every 1 minute.

8. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 1, characterized in that: The up and down vibration frequency of the vibrator is 20-100 Hz, and the amplitude is 1-5 mm; the roller temperature in the roller arrangement machine is 50-120° C., the arrangement tension is 4-15 N, and the arrangement speed is 10-25 m / min.

9. The method for preparing a high shear resistance carbon fiber reinforced polyimide composite material according to claim 1, characterized in that: The thickness of the carbon fiber unidirectional prepreg tape is 0.01-0.5 mm.

10. A high shear resistance carbon fiber reinforced polyimide composite material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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