Aramid fiber / epoxy resin composite material and a method for preparing the same

Abstract

The application discloses an aramid fiber / epoxy resin composite material and a preparation method thereof, and belongs to the technical field of polymer compound compositions. The preparation method comprises the following steps: preparing modified aramid fibers and preparing an epoxy resin matrix; then, the epoxy resin matrix is coated on the modified aramid fibers to obtain pre-soaked materials, the pre-soaked materials are laminated, and the laminated pre-soaked materials are put into a mold for hot-pressing and curing to obtain the aramid fiber / epoxy resin composite material. The aramid fibers are subjected to surface modification treatment, the interface bonding performance of the aramid fibers and the resin matrix is enhanced, and the mechanical properties of the composite material are improved; meanwhile, carbon nanotubes are added into the epoxy resin matrix, the toughness and strength of the epoxy resin are improved, and thus the mechanical properties and structural stability of the composite material as a whole are improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer composition technology, specifically, this invention relates to an aramid fiber / epoxy resin composite material and its preparation method. Background Technology

[0002] Aramid fiber reinforced resin matrix composites possess lightweight, high strength, fatigue resistance, and impact resistance, demonstrating irreplaceable advantages in achieving lightweight, high-performance, and long-life applications in high-end equipment. They have become one of the preferred materials for the main structures of modern aircraft, aerospace equipment, and advanced defense machinery.

[0003] However, this material system faces two major challenges in its journey towards wider application: First, the smooth and inert surface characteristics of aramid fibers result in poor interfacial compatibility and weak bonding between them and the resin matrix, severely restricting the effective transfer of stress from the resin to the fiber. This makes it difficult to fully realize the theoretical reinforcement efficiency of the composite material and affects the stability of the overall mechanical properties. Second, in multi-layered composite structures, the reliance on thermosetting polymers such as epoxy resin as the interlayer matrix makes the intrinsic brittleness of these polymers prone to initiation and propagation of microcracks. This leads to insufficient anti-delamination ability and limited damage tolerance of the composite material under complex loads, posing a potential threat to the safety and reliability of the main load-bearing structure.

[0004] Therefore, innovative aramid fiber surface modification technology and resin matrix toughening technology are extremely important. By constructing a strong and tough synergistic interface and matrix microstructure, the strength, toughness and reliability of materials can be synergistically improved on a macroscopic scale. This is of great and far-reaching significance for supporting the increasingly demanding extreme environmental adaptability and long-term service safety of advanced composite materials for future high-end equipment. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these objectives and other advantages of the present invention, a method for preparing an aramid fiber / epoxy resin composite material is provided, comprising the following steps:

[0007] Step 1: Preparation of modified aramid fibers, including the following steps:

[0008] S11. Immerse the aramid fiber in a phosphate buffer solution, then place it in deionized water for ultrasonic treatment, and vacuum dry to obtain pretreated aramid fiber.

[0009] S12. Immerse the pretreated aramid fiber in an ethanol solution, then add bis(dioctylpyrophosphoryloxy)ethylene titanate, sonicate, then add nano titanium dioxide and polyethylene glycol 400, continue sonication, wash and vacuum dry to obtain modified aramid fiber.

[0010] Step 2: Prepare the epoxy resin matrix;

[0011] Step 3, Processing and Molding: The epoxy resin matrix is ​​coated onto the modified aramid fiber to obtain a pre-impregnated material. The pre-impregnated materials are stacked and placed in a mold for hot pressing and curing to obtain an aramid fiber / epoxy resin composite material.

[0012] Preferably, in S11, the aramid fiber is aramid fiber plain weave fabric or aramid fiber twill weave fabric with a thickness of 0.2~0.8mm; the pH of the phosphate buffer solution is 7.0~7.4; and the mass-volume ratio of aramid fiber, phosphate buffer solution and deionized water is 1g:15~30mL:15~30mL.

[0013] Preferably, in step S11, the sample is soaked in a phosphate buffer solution for 30-90 minutes at a temperature of 25-35°C, and then subjected to ultrasonic treatment for 5-15 minutes.

[0014] Preferably, in step S12, the mass fraction of the ethanol solution is 50-90 wt%; the mass-to-volume ratio of the pretreated aramid fiber to the ethanol solution is 1 g: 20-40 mL; and the ultrasonic treatment temperature is 45-60 °C for 1-3 h.

[0015] Preferably, in S12, the mass ratio of pretreated aramid fiber, bis(dioctylpyrophosphoryloxy)ethylene titanate, nano titanium dioxide and polyethylene glycol 400 is 10:0.5~1.5:1~2:0.2~0.5.

[0016] Preferably, in step two, the specific method for preparing the epoxy resin matrix includes: mixing and stirring epoxy resin, curing agent, accelerator, coupling agent and carbon nanotubes evenly, and then degassing under vacuum to obtain the epoxy resin matrix.

[0017] Preferably, the epoxy resin is bisphenol A epoxy resin; the curing agent is methyltetrahydrophthalic anhydride; the accelerator is methyldiethanolamine; and the coupling agent is silane coupling agent KH550.

[0018] Preferably, the mass ratio of the epoxy resin, curing agent, accelerator, coupling agent and carbon nanotubes is 100:60~80:2~6:3~5:0.5~2.

[0019] Preferably, in step three, the mass ratio of epoxy resin matrix to modified aramid fiber in the preimpregnated material is 2~4:6~8; the preimpregnated material is stacked in 5~20 layers; the hot-press curing conditions are: maintaining a pressure of 5~12MPa, holding at 110~130℃ for 1~3h, raising the temperature to 140~165℃ and holding for 2~4h, and then raising the temperature to 170~190℃ and holding for 2~4h.

[0020] Preferably, when preparing the epoxy resin matrix, modified carbon nanotubes are used instead of traditional carbon nanotubes; the method for preparing the modified carbon nanotubes includes the following steps:

[0021] S21. Disperse carbon nanotubes in citric acid solution, sonicate at 70~90℃ for 1~3h, and wash with deionized water until neutral to obtain pretreated carbon nanotubes.

[0022] S22. Disperse the pretreated carbon nanotubes in an ethanol solution, add ethylenediamine and polyvinylpyrrolidone, stir at 80~100℃ for 3~5h, wash with deionized water, and vacuum dry to obtain functionalized carbon nanotubes.

[0023] S23. Add KH550 to an ethanol solution, add acetic acid to adjust the pH to 4-5, stir until homogeneous to obtain a silane solution; add nano-alumina to the silane solution, stir until homogeneous, heat to 60-80℃ and stir for 1-3 hours, wash with anhydrous ethanol, and vacuum dry to obtain silane-modified alumina.

[0024] S24. Functionalized carbon nanotubes, bis(dioctylpyrophosphonooxy)ethylene titanate and silane-modified alumina are added to an ethanol solution, stirred at 60-80℃ for 2-4 hours, allowed to stand at room temperature for 8-16 hours, washed with deionized water, and vacuum dried to obtain modified carbon nanotubes.

[0025] Preferably, in step S21, the concentration of the citric acid solution is 1~2 mol / L; and the mass-to-volume ratio of carbon nanotubes to citric acid solution is 1 g: 30~70 mL.

[0026] Preferably, in step S22, the mass-to-volume ratio of the pretreated carbon nanotubes to the ethanol solution is 1g:30~70mL; and the mass ratio of the pretreated carbon nanotubes, ethylenediamine, and polyvinylpyrrolidone is 10:5~20:0.5~2.

[0027] Preferably, in step S23, the mass-to-volume ratio of KH550 to ethanol solution is 1g:30~70mL; and the mass-to-volume ratio of nano-alumina to silane solution is 1g:10~30mL.

[0028] Preferably, in step S24, the mass ratio of functionalized carbon nanotubes, bis(dioctylpyrophosphoryloxy)ethylene titanate, and silane-modified alumina is 6~8:0.2~1:2~4; and the mass-volume ratio of functionalized carbon nanotubes to ethanol solution is 1g:10~30mL.

[0029] An aramid fiber / epoxy resin composite material is prepared by the preparation method described above.

[0030] The present invention includes at least the following beneficial effects: The present invention performs surface modification treatment on aramid fibers. First, the aramid fibers are immersed in a phosphate buffer solution (PBS buffer) for cleaning and activation, fully exposing the active groups such as amide groups on the surface of the aramid fibers, which is beneficial for subsequent reactions. Then, bis(dioctylpyrophosphonooxy)ethylene titanate is used to treat the aramid fibers, improving the surface reactivity and interfacial compatibility. On the one hand, it forms a stabilizing effect with the active groups on the surface of the aramid fibers; on the other hand, the long-chain alkyl groups in its molecule have good compatibility with the molecular chains of the resin matrix, which is beneficial for the stable bonding between the aramid fibers and the resin matrix. Next, nano-titanium dioxide is added. Under the action of bis(dioctylpyrophosphonooxy)ethylene titanate and polyethylene glycol, the nano-titanium dioxide is uniformly loaded on the surface of the aramid fibers, improving the surface roughness and surface activity of the aramid fibers. This, in turn, is beneficial for the mechanical interlocking and chemical bonding between the aramid fibers and the resin matrix, enhancing its interfacial bonding performance with the resin matrix and improving the mechanical properties of the composite material.

[0031] This invention incorporates carbon nanotubes into an epoxy resin matrix. The carbon nanotubes, acting as nanoparticle toughening materials, enhance the toughness and strength of the epoxy resin, thereby improving the overall mechanical properties and structural stability of the composite material. Furthermore, the invention modifies the carbon nanotubes to improve their dispersibility and interfacial compatibility, enabling them to disperse uniformly within the resin matrix, further enhancing the composite material's performance. First, citric acid is used to treat the carbon nanotubes, introducing active groups such as carboxyl groups. Then, they react with the amino groups in ethylenediamine to reduce interfacial energy and increase surface reactivity. Simultaneously, polyvinylpyrrolidone is added to improve dispersibility, ensuring sufficient contact between the reactants and promoting the reaction. Finally, the carbon nanotubes are blended with bis(dioctylpyrophosphate)ethylene titanate and silane-modified alumina to further improve their interfacial compatibility with the resin matrix and modified aramid fibers. The synergistic effect of the carbon nanotubes and alumina further enhances the toughness and strength of the epoxy resin.

[0032] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0033] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0034] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0035] Example 1

[0036] A method for preparing an aramid fiber / epoxy resin composite material includes the following steps:

[0037] Step 1: Preparation of modified aramid fibers:

[0038] S11. A aramid fiber plain weave fabric with a thickness of 0.4 mm and a size of 300 mm × 300 mm is immersed in PBS buffer (pH = 7.2) and soaked at 30 °C for 1 h. Then it is placed in deionized water and sonicated for 10 min. After vacuum drying, pretreated aramid fiber is obtained. The mass-volume ratio of aramid fiber plain weave fabric, PBS buffer and deionized water is 1 g: 20 mL: 20 mL.

[0039] S12. The pretreated aramid fiber was immersed in a 70wt% ethanol solution, and then bis(dioctylpyrophosphoryloxy)ethylene titanate was added. The mixture was ultrasonically treated at 55℃ for 2 hours. Then, nano-titanium dioxide and polyethylene glycol 400 were added, and the mixture was ultrasonically treated at 55℃ for 1 hour. The mixture was washed successively with anhydrous ethanol and deionized water, and then vacuum dried to obtain the modified aramid fiber. The mass-to-volume ratio of the pretreated aramid fiber to the 70wt% ethanol solution was 1g:30mL. The mass ratio of the pretreated aramid fiber, bis(dioctylpyrophosphoryloxy)ethylene titanate, nano-titanium dioxide, and polyethylene glycol 400 was 10:1:1.5:0.3.

[0040] Step 2: Preparation of epoxy resin matrix: Bisphenol A epoxy resin E-51, curing agent methyltetrahydrophthalic anhydride, accelerator methyldiethanolamine, silane coupling agent KH550 and carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm are mixed and stirred evenly in a mass ratio of 100:70:5:4:1, and then degassed under vacuum to obtain epoxy resin matrix;

[0041] Step 3, Processing and Molding: The epoxy resin matrix is ​​uniformly coated onto the modified aramid fiber to obtain a pre-impregnated material. The mass ratio of epoxy resin matrix to modified aramid fiber in the pre-impregnated material is 3:7. Ten layers of pre-impregnated material are stacked. The stacked pre-impregnated material is placed in a mold and hot-pressed in a hot press, maintaining a pressure of 8 MPa. The temperature is maintained at 120℃ for 2 hours, then raised to 155℃ for 3 hours, and then raised to 180℃ for 3 hours. After cooling, it is taken out to obtain the aramid fiber / epoxy resin composite material.

[0042] Example 2

[0043] A method for preparing an aramid fiber / epoxy resin composite material includes the following steps:

[0044] Step 1: Preparation of modified aramid fibers:

[0045] S11. A aramid fiber plain weave fabric with a thickness of 0.4 mm and a size of 300 mm × 300 mm is immersed in PBS buffer (pH = 7.2) and soaked at 30 °C for 1 h. Then it is placed in deionized water and sonicated for 10 min. After vacuum drying, pretreated aramid fiber is obtained. The mass-volume ratio of aramid fiber plain weave fabric, PBS buffer and deionized water is 1 g: 20 mL: 20 mL.

[0046] S12. The pretreated aramid fiber was immersed in a 70wt% ethanol solution, and then bis(dioctylpyrophosphoryloxy)ethylene titanate was added. The mixture was ultrasonically treated at 55℃ for 2 hours. Then, nano-titanium dioxide and polyethylene glycol 400 were added, and the mixture was ultrasonically treated at 55℃ for 1 hour. The fiber was washed successively with anhydrous ethanol and deionized water, and then vacuum dried to obtain the modified aramid fiber. The mass-to-volume ratio of the pretreated aramid fiber to the 70wt% ethanol solution was 1g:30mL. The mass ratio of the pretreated aramid fiber, bis(dioctylpyrophosphoryloxy)ethylene titanate, nano-titanium dioxide, and polyethylene glycol 400 was 10:0.5:1:0.2.

[0047] Step 2: Preparation of epoxy resin matrix: Bisphenol A epoxy resin E-51, curing agent methyltetrahydrophthalic anhydride, accelerator methyldiethanolamine, silane coupling agent KH550 and carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm are mixed and stirred evenly in a mass ratio of 100:70:5:4:1, and then degassed under vacuum to obtain epoxy resin matrix;

[0048] Step 3, Processing and Molding: The epoxy resin matrix is ​​uniformly coated onto the modified aramid fiber to obtain a pre-impregnated material. The mass ratio of epoxy resin matrix to modified aramid fiber in the pre-impregnated material is 3:7. Ten layers of pre-impregnated material are stacked. The stacked pre-impregnated material is placed in a mold and hot-pressed in a hot press, maintaining a pressure of 8 MPa. The temperature is maintained at 120℃ for 2 hours, then raised to 155℃ for 3 hours, and then raised to 180℃ for 3 hours. After cooling, it is taken out to obtain the aramid fiber / epoxy resin composite material.

[0049] Example 3

[0050] A method for preparing an aramid fiber / epoxy resin composite material includes the following steps:

[0051] Step 1: Preparation of modified aramid fibers:

[0052] S11. A aramid fiber plain weave fabric with a thickness of 0.4 mm and a size of 300 mm × 300 mm is immersed in PBS buffer (pH = 7.2) and soaked at 30 °C for 1 h. Then it is placed in deionized water and sonicated for 10 min. After vacuum drying, pretreated aramid fiber is obtained. The mass-volume ratio of aramid fiber plain weave fabric, PBS buffer and deionized water is 1 g: 20 mL: 20 mL.

[0053] S12. The pretreated aramid fiber was immersed in a 70wt% ethanol solution, and then bis(dioctylpyrophosphoryloxy)ethylene titanate was added. The mixture was ultrasonically treated at 55℃ for 2 hours. Then, nano-titanium dioxide and polyethylene glycol 400 were added, and the mixture was ultrasonically treated at 55℃ for 1 hour. The fiber was washed successively with anhydrous ethanol and deionized water, and then vacuum dried to obtain the modified aramid fiber. The mass-to-volume ratio of the pretreated aramid fiber to the 70wt% ethanol solution was 1g:30mL. The mass ratio of the pretreated aramid fiber, bis(dioctylpyrophosphoryloxy)ethylene titanate, nano-titanium dioxide, and polyethylene glycol 400 was 10:1.5:2:0.5.

[0054] Step 2: Preparation of epoxy resin matrix: Bisphenol A epoxy resin E-51, curing agent methyltetrahydrophthalic anhydride, accelerator methyldiethanolamine, silane coupling agent KH550 and carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm are mixed and stirred evenly in a mass ratio of 100:70:5:4:1, and then degassed under vacuum to obtain epoxy resin matrix;

[0055] Step 3, Processing and Molding: The epoxy resin matrix is ​​uniformly coated onto the modified aramid fiber to obtain a pre-impregnated material. The mass ratio of epoxy resin matrix to modified aramid fiber in the pre-impregnated material is 3:7. Ten layers of pre-impregnated material are stacked. The stacked pre-impregnated material is placed in a mold and hot-pressed in a hot press, maintaining a pressure of 8 MPa. The temperature is maintained at 120℃ for 2 hours, then raised to 155℃ for 3 hours, and then raised to 180℃ for 3 hours. After cooling, it is taken out to obtain the aramid fiber / epoxy resin composite material.

[0056] Example 4

[0057] The preparation method in this embodiment is basically the same as that in Example 1, except that in Example 4, modified carbon nanotubes are used instead of carbon nanotubes when preparing the epoxy resin matrix; the preparation method of the modified carbon nanotubes includes the following steps:

[0058] S21. Disperse 10g of carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm in 500mL of 1mol / L citric acid solution, sonicate at 80℃ for 2h, and wash with deionized water until neutral to obtain pretreated carbon nanotubes.

[0059] S22. Disperse 10g of pretreated carbon nanotubes in 500mL of 50wt% ethanol solution, add 10g of ethylenediamine and 1g of polyvinylpyrrolidone, stir at 90℃ for 4h, wash with deionized water, and vacuum dry to obtain functionalized carbon nanotubes.

[0060] S23. Add 2g KH550 to 100mL of 90wt% ethanol solution, add acetic acid to adjust pH=5, stir evenly to obtain silane solution; add 5g nano alumina to 100mL silane solution, stir evenly, heat to 70℃ and stir for 2h, wash with anhydrous ethanol, and vacuum dry to obtain silane modified alumina.

[0061] S24. Add 7g of functionalized carbon nanotubes, 0.5g of bis(dioctylpyrophosphoryloxy)ethylene titanate and 3g of silane-modified alumina to 150mL of 50wt% ethanol solution, stir at 70℃ for 3h, let stand at room temperature for 12h, wash with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0062] Example 5

[0063] The preparation method in this embodiment is basically the same as that in Example 1, except that in Example 5, modified carbon nanotubes are used instead of carbon nanotubes when preparing the epoxy resin matrix; the preparation method of the modified carbon nanotubes includes the following steps:

[0064] S21. Disperse 10g of carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm in 500mL of 1mol / L citric acid solution, sonicate at 80℃ for 2h, and wash with deionized water until neutral to obtain pretreated carbon nanotubes.

[0065] S22. Disperse 10g of pretreated carbon nanotubes in 500mL of 50wt% ethanol solution, add 10g of ethylenediamine and 1g of polyvinylpyrrolidone, stir at 90℃ for 4h, wash with deionized water, and vacuum dry to obtain functionalized carbon nanotubes.

[0066] S23. Add 7g of functionalized carbon nanotubes and 0.5g of bis(dioctylpyrophosphoryloxy)ethylene titanate to 150mL of 50wt% ethanol solution, stir at 70℃ for 3h, let stand at room temperature for 12h, wash with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0067] Compared to Example 4, this example does not add silane-modified alumina when preparing modified carbon nanotubes.

[0068] Example 6

[0069] The preparation method in this embodiment is basically the same as that in Example 1, except that in Example 6, modified carbon nanotubes are used instead of carbon nanotubes when preparing the epoxy resin matrix; the preparation method of the modified carbon nanotubes includes the following steps:

[0070] S21. Disperse 10g of carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm in 500mL of 1mol / L citric acid solution, sonicate at 80℃ for 2h, and wash with deionized water until neutral to obtain pretreated carbon nanotubes.

[0071] S22. Disperse 10g of pretreated carbon nanotubes in 500mL of 50wt% ethanol solution, add 10g of ethylenediamine and 1g of polyvinylpyrrolidone, stir at 90℃ for 4h, wash with deionized water, and vacuum dry to obtain functionalized carbon nanotubes.

[0072] S23. Add 2g KH550 to 100mL of 90wt% ethanol solution, add acetic acid to adjust pH=5, stir evenly to obtain silane solution; add 5g nano alumina to 100mL silane solution, stir evenly, heat to 70℃ and stir for 2h, wash with anhydrous ethanol, and vacuum dry to obtain silane modified alumina.

[0073] S24. Add 7g of functionalized carbon nanotubes and 3g of silane-modified alumina to 150mL of 50wt% ethanol solution, stir at 70℃ for 3h, let stand at room temperature for 12h, wash with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0074] Compared to Example 4, this example does not add bis(dioctylpyrophosphate) ethylene titanate when preparing modified carbon nanotubes.

[0075] Example 7

[0076] The preparation method in this embodiment is basically the same as that in Example 1, except that in Example 7, functionalized carbon nanotubes are used instead of carbon nanotubes when preparing the epoxy resin matrix; the preparation method of the functionalized carbon nanotubes includes the following steps:

[0077] S21. Disperse 10g of carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm in 500mL of 1mol / L citric acid solution, sonicate at 80℃ for 2h, and wash with deionized water until neutral to obtain pretreated carbon nanotubes.

[0078] S22. Disperse 10g of pretreated carbon nanotubes in 500mL of 50wt% ethanol solution, add 10g of ethylenediamine and 1g of polyvinylpyrrolidone, stir at 90℃ for 4h, wash with deionized water, and vacuum dry to obtain functionalized carbon nanotubes.

[0079] Compared to Example 4, this example adds functionalized carbon nanotubes to the epoxy resin matrix.

[0080] Example 8

[0081] The preparation method of this embodiment is basically the same as that of Embodiment 1, except that in Embodiment 8, modified carbon nanotubes are used instead of carbon nanotubes when preparing the epoxy resin matrix; the preparation method of the modified carbon nanotubes includes the following steps:

[0082] S21. Disperse 10g of carbon nanotubes with a diameter of 10~20nm and a length of 20~40μm in 500mL of 1mol / L citric acid solution, sonicate at 80℃ for 2h, and wash with deionized water until neutral to obtain pretreated carbon nanotubes.

[0083] S22. Disperse 10g of pretreated carbon nanotubes in 500mL of 50wt% ethanol solution, add 10g of ethylenediamine and 1g of polyvinylpyrrolidone, stir at 90℃ for 4h, wash with deionized water, and vacuum dry to obtain functionalized carbon nanotubes.

[0084] S23. Add 7g of functionalized carbon nanotubes, 0.5g of bis(dioctylpyrophosphoryloxy)ethylene titanate and 3g of nano-alumina to 150mL of 50wt% ethanol solution, stir at 70℃ for 3h, let stand at room temperature for 12h, wash with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0085] Compared to Example 4, in this example, unmodified nano-alumina was directly added when preparing modified carbon nanotubes.

[0086] Comparative Example 1

[0087] The preparation method of this comparative example is basically the same as that of Example 1, except that: in Comparative Example 1, no modification treatment is performed on the aramid fiber plain weave fabric.

[0088] Comparative Example 2

[0089] The preparation method of this comparative example is basically the same as that of Example 1, except that carbon nanotubes are not added when preparing the epoxy resin matrix in Comparative Example 2.

[0090] Comparative Example 3

[0091] The preparation method of this comparative example is basically the same as that of Example 1, except that in Comparative Example 3, bis(dioctylpyrophosphate) ethylene titanate is not used when preparing modified aramid fibers.

[0092] Comparative Example 4

[0093] The preparation method of this comparative example is basically the same as that of Example 1, except that in Comparative Example 4, deionized water was used instead of PBS buffer when preparing modified aramid fibers.

[0094] The flexural strength and interlaminar shear strength of the aramid fiber / epoxy resin composites prepared in the examples and comparative examples were tested. The flexural strength of the composite samples was obtained using a universal testing machine according to ASTM D7264. The interlaminar shear strength of the composite samples was obtained using a universal testing machine according to ASTM D2344. The test results are shown in Table 1. It can be seen that the interlaminar shear strength and flexural strength of the aramid fiber / epoxy resin composites prepared in Examples 1-3 of this invention are higher than those in Comparative Examples 1-4. In Examples 4-8, after modification with carbon nanotubes, the interlaminar shear strength and flexural strength of the composites were further improved.

[0095] Table 1

[0096]

[0097] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for producing an aramid fiber / epoxy resin composite material, characterized by, The method comprises the following steps: Step one, preparation of modified aramid fiber, comprising the following steps: S11, aramid fiber is immersed in phosphate buffer solution for soaking, and then is placed in deionized water for ultrasonic treatment, and is vacuum dried to obtain pretreated aramid fiber; wherein, the pH of the phosphate buffer solution is 7.0-7.4; S12, the pretreated aramid fiber is immersed in an ethanol solution, then bis (dioctyl pyrophosphoric acyloxy) ethylene titanate is added, ultrasonic treatment is performed, then nano titanium dioxide and polyethylene glycol 400 are added, ultrasonic treatment is continued, and washing, vacuum drying are performed to obtain modified aramid fiber; Step two, preparation of an epoxy resin matrix: the epoxy resin, curing agent, accelerator, coupling agent and modified carbon nanotube are uniformly mixed and stirred, and vacuum degassing is performed to obtain the epoxy resin matrix; Step three, processing and molding: the epoxy resin matrix is coated on the modified aramid fiber to obtain a pre-impregnated material, the pre-impregnated material is stacked, and is placed in a mold for hot pressing and curing to obtain an aramid fiber / epoxy resin composite material; In the step two, the preparation method of the modified carbon nanotube comprises the following steps: S21, the carbon nanotube is dispersed in a citric acid solution, ultrasonic treatment is performed at 70-90 DEG C for 1-3 h, and washing is performed with deionized water until neutral to obtain pretreated carbon nanotube; S22, the pretreated carbon nanotube is dispersed in an ethanol solution, ethylenediamine and polyvinylpyrrolidone are added, stirring is performed at 80-100 DEG C for 3-5 h, washing is performed with deionized water, and vacuum drying is performed to obtain functionalized carbon nanotube; S23, KH550 is added to an ethanol solution, acetic acid is added to adjust the pH to 4-5, and uniform stirring is performed to obtain a silane solution; nano alumina is added to the silane solution, uniform stirring is performed, and then the temperature is raised to 60-80 DEG C for stirring for 1-3 h, anhydrous ethanol is used for washing, and vacuum drying is performed to obtain silane modified alumina; S24, the functionalized carbon nanotube, bis (dioctyl pyrophosphoric acyloxy) ethylene titanate and silane modified alumina are added to an ethanol solution, stirring is performed at 60-80 DEG C for 2-4 h, standing is performed at room temperature for 8-16 h, washing is performed with deionized water, and vacuum drying is performed to obtain modified carbon nanotube.

2. The method for preparing an aramid fiber / epoxy resin composite material as described in claim 1, characterized in that, In the S11, the aramid fiber is aramid fiber plain cloth or aramid fiber twill cloth, and the thickness is 0.2-0.8 mm; the mass / volume ratio of the aramid fiber, the phosphate buffer solution and the deionized water is 1 g: 15-30 mL: 15-30 mL.

3. The method for preparing an aramid fiber / epoxy resin composite material as described in claim 1, characterized in that, In the S11, the soaking in the phosphate buffer solution is performed for 30-90 min, and the temperature is 25-35 DEG C; the ultrasonic treatment is performed for 5-15 min.

4. The method for preparing an aramid fiber / epoxy resin composite material as described in claim 1, characterized in that, In the S12, the mass fraction of the ethanol solution is 50-90 wt%; the mass / volume ratio of the pretreated aramid fiber and the ethanol solution is 1 g: 20-40 mL; the ultrasonic treatment temperature is 45-60 DEG C, and the time is 1-3 h.

5. The method of claim 2, wherein the aramid fiber / epoxy resin composite is prepared by the steps of: a) mixing the aramid fiber and the epoxy resin; b) heating the mixture to a temperature of about 100°C to about 150°C; c) applying pressure to the mixture; and d) cooling the mixture to room temperature. In the S12, the mass ratio of the pretreated aramid fiber, bis (dioctyl pyrophosphoric acyloxy) ethylene titanate, nano titanium dioxide and polyethylene glycol 400 is 10: 0.5-1.5: 1-2: 0.2-0.

5.

6. The method for preparing an aramid fiber / epoxy resin composite material as described in claim 1, characterized in that, The epoxy resin is bisphenol A epoxy resin; the curing agent is methyl tetrahydrophthalic anhydride; the accelerator is methyldiethanolamine; and the coupling agent is silane coupling agent KH550.

7. The method for preparing an aramid fiber / epoxy resin composite material as described in claim 1, characterized in that, The mass ratio of the epoxy resin, the curing agent, the accelerator, the coupling agent and the modified carbon nanotube is 100:60-80:2-6:3-5:0.5-2.

8. The method for preparing an aramid fiber / epoxy resin composite material as described in claim 1, characterized in that, In the third step, the mass ratio of the epoxy resin matrix and the modified aramid fiber in the pre-impregnated material is 2-4:6-8; the pre-impregnated material is stacked in 5-20 layers; and the heat pressing and curing conditions are as follows: keeping a pressure of 5-12 MPa, heat preservation at 110-130 DEG C for 1-3 h, heat preservation at 140-165 DEG C for 2-4 h, and heat preservation at 170-190 DEG C for 2-4 h.

9. An aramid fiber / epoxy resin composite material, characterized by, Prepared by the preparation method of any one of claims 1-8.

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