Preparation process for improving mechanical properties of carbon fiber reinforced resin-based composite material

Abstract

According to the preparation process for the mechanical property of the carbon fiber reinforced resin-based composite material, the performance of the composite material is improved through molecular-level interface design and a multi-scale reinforced framework. Wherein the difunctional silane coupling agent integrates a DOPO phosphaphenanthrene flame-retardant group and a mercaptopropyl bonding unit into a whole, and the surface of the carbon nanofiber is etched under a plasma condition to form a Si-O-Ti hybrid network, so that the interfacial shear strength is improved, and meanwhile, the material is endowed with flame retardance. Various resin components in the resin matrix construct a three-dimensional toughening framework, and the chemically bonded composite carbon fibers are matched, so that the tensile strength, fracture toughness and the like of the resin matrix in various aspects are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and particularly relates to a preparation process of mechanical properties of carbon fiber reinforced resin matrix composite materials. BACKGROUND

[0002] The rapid development of new energy vehicles, 5G communication and artificial intelligence promotes the new generation of materials to not only have excellent mechanical properties, but also further lightweight and good electromagnetic shielding characteristics. Carbon fiber, as a kind of high-strength, high-toughness, high-shielding and new lightweight material, is highly valued. However, the surface of carbon fiber is smooth, the surface energy is low, the inertness is large, and there is a lack of chemically active functional groups, which makes it difficult to form effective interfacial bonding, limiting the further development and application of carbon fiber composite materials. Carbon fiber metallization is a very promising method. That is, different metals or alloys are plated on the surface of carbon fiber, so that the carbon fiber has excellent electromagnetic shielding performance on the basis of the original high performance, and the modification of coupling agent and compatibilizer can solve and improve the poor wetting between carbon fiber and resin and the problem of non-reaction interface.

[0003] Traditional carbon fiber reinforced composite materials have long been plagued by two major problems of weak interfacial bonding and manufacturing defects. In the field of interfacial engineering, although conventional plasma treatment can improve the surface roughness of the fiber, argon single element etching only increases mechanical embedding and cannot introduce sufficient chemical active sites, resulting in interfacial dependence on physical anchoring and unsatisfactory interlaminar shear strength. While silane coupling agent modification often uses single amino silane such as KH-550, which can bond with epoxy resin but lacks functional modification. In the face of stringent flame retardant requirements of aerospace, it is necessary to add bromine-based flame retardants, which causes the interfacial phase glass transition temperature to decrease and harmful gases to be released. Therefore, how to maximize the reinforcing effect of carbon fiber on the resin matrix is the research focus of the present application.

[0004] In terms of resin matrix reinforcement, directly mixing micron-sized toughening particles (such as CTBN rubber) can improve impact toughness, but it will cause the tensile modulus to decrease. Nano fillers (such as carbon tubes) form stress concentration points due to van der Waals forces, and the fatigue life is not durable enough. After obtaining the composite resin matrix material, it needs to be cured. The conventional and traditional hot pressing forming relies on heat conduction. If the thickness is thick, the temperature difference between the surface and the core of the thick plate will be large, the curing degree will be different, and the porosity will also increase. Although vacuum assisted forming can improve wettability, it is time-consuming and cannot eliminate sub-micron bubbles, and residual stress causes delamination failure during service. Therefore, how to perform corresponding efficient curing treatment on the composite resin matrix material is the research focus of the present application. SUMMARY

[0005] The application discloses a preparation process of carbon fiber reinforced resin matrix composite mechanical property, to solve the above and any potential problems in the prior art. In order to solve the above technical problems, the specific process of the application is:

[0006] Preparation of composite carbon nanofiber: carbon fiber is treated by low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, power 300W, 50Pa gas pressure, 25℃ for 5min, then 8-12 times mass of hybrid nanosol is added, 100-130℃, 3000rpm stirring for 10min;

[0007] Mixing of resin matrix: 82.5-85 parts of epoxy resin as matrix, preheated to 80℃, with the mass of epoxy resin as reference, 0.8-1.2% mass ratio of polyether ketone nanofiber and 0.2-0.5% mass ratio of aminated carbon nanotube are added, ultrasonic stirring at 60-80℃, frequency 25kHz, power 600W for 20min; 3-5% of composite carbon nanofiber is added, continue to stir for 15-20min, 7-10 parts of curing agent and 0.8-1.5 parts of accelerator are added, transfer into a vacuum planetary stirrer, revolution 30rpm and rotation 1200rpm, degassing at 60℃, -0.1MPa for 20min until no bubble overflow, to obtain the resin matrix composite material.

[0008] The epoxy resin is a bisphenol type epoxy resin.

[0009] The preparation of the hybrid nanosol is as follows: 40 parts of tetraethyl orthosilicate and 40 parts of tetrabutyl titanate are mixed in 40 parts of 90% ethanol solution at a mass ratio of 3:1, and 5% mass of bifunctional silane coupling agent is added.

[0010] The preparation of the bifunctional silane coupling agent is as follows: 100 parts of DOPO is heated to 120℃ in molten state under nitrogen protection, 60 parts of 3-mercaptopropyl trimethoxysilane is added and continues to stir for 3h, then 50% mass fraction of 70% ethanol solution is supplemented, and 20 parts of tetraethoxysilane and 2 parts of tetrabutyl titanate are added, hydrolysis and condensation reaction is carried out at 80℃ for 4h, to obtain the bifunctional silane coupling agent.

[0011] The curing agent is methyl hexahydrophthalic anhydride.

[0012] The accelerator is 3-(3,4-dichlorophenyl)-1,1-dimethylurea.

[0013] The curing process of the resin matrix composite material prepared by the above preparation process is as follows:

[0014] Pre-compaction stage: After the resin-based composite material is loaded into the mold, it is heated to 80°C in a hot press at a heating rate of 5°C / min. Simultaneously, a vacuum is drawn to -0.095MPa and a pressure of 0.5MPa is applied. The pressure is maintained for 20 minutes to remove interlayer bubbles. During this period, the vacuum is briefly released to -0.08MPa every 5 minutes and then the vacuum is drawn again to enhance the degassing effect.

[0015] Infiltration stage: The temperature is programmed to rise from 80℃ to 100℃ at a rate of 1℃ / min, at which point the pressure rises to 0.5MPa. The temperature is then further increased to 130℃, and the pressure rises to 1.0MPa simultaneously. This 40-minute process is performed using intermittent microwave assistance at 1kW and 2.45GHz. Microwave irradiation is performed for 30 seconds every 90 seconds, followed by a 60-second pause. A total of 8 cycles are executed to promote resin penetration into the fiber bundle.

[0016] Main curing stage: The temperature rises to 150℃, the pressure increases to 2.0MPa, and continuous microwave irradiation of 3kW, 2.45GHz is started for 60min. The surface temperature fluctuation of the mold is monitored by an infrared thermal imager and is ≤±3℃. If the local temperature is >155℃, it will automatically switch to pulse mode, which is on for 10 seconds and off for 5 seconds.

[0017] Post-curing stage: Heat to 180℃, pressurize to 3.0MPa and hold for 120min, turn off the microwave and cool naturally at ≤2℃ / min. When the temperature drops to 120℃, reduce the pressure to 0.5MPa, and completely release the pressure and demold at 60℃. The mold pressure fluctuation is controlled within ±0.05MPa throughout the process.

[0018] The advantages and beneficial effects of this invention are as follows:

[0019] 1. This invention provides a preparation process for improving the mechanical properties of carbon fiber reinforced resin matrix composites. Nanoscale grooves and inorganic-organic hybrid structures are constructed on the carbon fiber surface through plasma etching and silicon-titanium hybrid sol spraying. The DOPO flame-retardant groups and mercapto click reaction characteristics of the bifunctional silane coupling agent enhance interfacial shear strength and impart good flame retardancy to the material. Multiple resin matrices combined with chemically bonded composite carbon fibers, along with suitable curing agents and accelerators, improve tensile strength and fracture toughness. The four-stage curing process not only significantly reduces porosity but also effectively penetrates the composite resin to eliminate residual stress and improve aging resistance.

[0020] 2. In the field of interface strengthening, this process improves the problem of weak interfacial bonding caused by the inertness of carbon fiber surfaces through the synergistic effect of low-temperature radio frequency plasma treatment and hybrid nanosol coating. A specific ratio of argon-oxygen mixed gas generates highly reactive oxygen free radicals under plasma excitation, which directionally etch the carbon fiber surface, increasing the specific surface area and introducing a large number of oxygen-containing polar functional groups such as carboxyl and hydroxyl groups onto the fiber surface. In the subsequently sprayed silicon-titanium hybrid sol, the silica network generated by the hydrolysis of tetraethyl orthosilicate provides rigid support, while the titanium dioxide crystals converted from tetrabutyl titanate impart ultraviolet shielding functionality. Together, they form a thick nano-inorganic-organic hybrid coating on the fiber surface. The DOPO phosphoranthroline is a bifunctional silane coupling agent whose PH bond in the DOPO phosphoranthroline ring can efficiently capture combustion free radicals, increasing the limiting oxygen index of the composite material. Meanwhile, the mercaptopropyl silane end undergoes a precise thiol-epoxy click reaction with the epoxy resin under heat treatment, forming a covalent bond interface with higher strength than traditional aminosilanes.

[0021] 3. The resin matrix uses epoxy resin as the continuous phase, and the polyetherketone (PEK-C) nanofibers, initially incorporated, form a three-dimensional through-network under high shear dispersion at 80℃. When the material is impacted, the crack pinning and fiber pull-out mechanisms improve impact toughness without sacrificing matrix stiffness. Aminated carbon nanotubes, with their high specific surface area, covalently bond between their surface amine and epoxy groups, constructing stress transfer bridges at the nanoscale, effectively delaying microcrack initiation and improving fatigue life. Surface-modified composite carbon fibers eliminate traditional interfacial weak zones through chemical bonding, improving tensile strength and fracture toughness. More significantly, the low viscosity of the methylhexahydrophthalic anhydride curing agent ensures uniform dispersion of the nanofillers, while the latent catalytic properties of the 3-(3,4-dichlorophenyl)-1,1-dimethylurea accelerator maintain the resin system's stability below 100℃, precisely triggering cross-linking upon heating to the penetration stage, ensuring the composite material maintains high strength even under harsh conditions such as high temperature and high humidity.

[0022] 4. In the four-stage curing process, the pre-compaction stage selects 80℃, the lowest resin viscosity point, and combines dynamic vacuum release with a pressure of 0.5 MPa. Vacuum is briefly released to -0.08 MPa every 5 minutes before re-vacuuming to thoroughly remove submicron-sized air bubbles trapped within the fiber bundles. The penetration stage uses a gradient temperature increase of 1℃ / min, allowing the resin viscosity to gradually decrease to the optimal flow point. Simultaneously applied pulsed microwaves induce directional vibration of resin molecules through dielectric polarization, reducing viscosity and promoting complete resin penetration into the fiber bundle gaps, resulting in a deeper penetration than conventional processes. The main curing stage generates heat through friction between epoxy polar molecules, achieving synchronous curing within the component. The post-curing stage allows the molecular chains to relax orderly along the fiber direction, reducing residual stress and ultimately controlling the component porosity and improving the uniformity of curing. Attached Figure Description

[0023] Figure 1 The image shown is a SEM image of the composite material corresponding to Example 1.

[0024] Figure 2 The image shows the SEM image of the composite material corresponding to Comparative Example 1.

[0025] Figure 3 This is a SEM image of the composite material corresponding to Comparative Example 5. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments. T800 grade carbon fiber (12K tow) was purchased from Toray New Materials (Guangdong) Co., Ltd. The carbon fiber (CF) filament was provided by Dalian Xingke Carbon Fiber Co., Ltd., model: T300-12K. Specific performance parameters are: bulk density 1.76 g / mm²; linear density 0.2 g / m²; fineness 7 μm; elongation 1.34-1.40%; tensile strength >3.3 GPa; elastic modulus approximately 230~260 GPa. The epoxy resin is bisphenol F type epoxy resin, purchased from Hubei Langbowan Biomedical Co., Ltd.

[0027] Example 1

[0028] Preparation of bifunctional silane coupling agent: Under nitrogen protection, 100 parts of DOPO were heated to a molten state at 120°C, 60 parts of 3-mercaptopropyltrimethoxysilane were added, and the reaction was stirred for 3 hours. Then, 50% of a 70% ethanol solution was added, followed by 20 parts of tetraethoxysilane and 2 parts of tetrabutyl titanate. The mixture was hydrolyzed and condensed at 80°C for 4 hours to obtain the bifunctional silane coupling agent.

[0029] Preparation of hybrid nanosol: 40 parts of total tetraethyl orthosilicate and tetrabutyl titanate were mixed in a 3:1 mass ratio in 40 parts of 90% ethanol solution, and 5% by mass of bifunctional silane coupling agent was added.

[0030] Preparation of composite carbon nanofibers: Carbon fibers were treated with low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, power 300W, gas pressure 50Pa, at 25℃ for 5min, and then 10 times the mass of hybrid nanosol was added, and stirred at 3000rpm for 10min at 120℃.

[0031] Mixing of the resin matrix: Using 83.8 parts of epoxy resin as the matrix, preheat to 80℃, add 1% by mass of polyetherketone nanofibers and 0.3% by mass of aminated carbon nanotubes, and ultrasonically stir for 20 min at 70℃, frequency 25kHz, power 600W; then add 4% of composite carbon nanofibers, continue stirring for 18 min, add 9 parts of methylhexahydrophthalic anhydride and 1.1 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, transfer to a vacuum planetary mixer, revolve at 30 rpm and rotate at 1200 rpm, and degas at 60℃ and -0.1MPa for 20 min until no bubbles overflow, to obtain the resin-based composite material.

[0032] Pre-compaction: After the resin-based composite material is loaded into the mold, it is heated to 80°C in a hot press at a heating rate of 5°C / min. Simultaneously, a vacuum is drawn to -0.095MPa and a pressure of 0.5MPa is applied. The pressure is maintained for 20 minutes to remove interlayer bubbles. During this period, the vacuum is briefly released to -0.08MPa every 5 minutes and then the vacuum is drawn again to enhance the degassing effect.

[0033] Infiltration stage: The temperature is programmed to rise from 80℃ to 100℃ at a rate of 1℃ / min, at which point the pressure rises to 0.5MPa. The temperature is then further increased to 130℃, and the pressure rises to 1.0MPa simultaneously. This 40-minute process is performed using intermittent microwave assistance at 1kW and 2.45GHz. Microwave irradiation is performed for 30 seconds every 90 seconds, followed by a 60-second pause. A total of 8 cycles are executed to promote resin penetration into the fiber bundle.

[0034] Main curing stage: The temperature is raised to 150℃, the pressure is increased to 2.0MPa, and continuous microwave irradiation of 3kW, 2.45GHz is started for 60min. The surface temperature fluctuation of the mold is monitored by infrared thermal imager and is ≤±3℃.

[0035] Post-curing stage: Heat to 180℃, pressure to 3.0MPa and maintain for 120min, turn off microwave and cool naturally at 2℃ / min, when the temperature drops to 120℃, reduce pressure to 0.5MPa, and completely depressurize and demold at 60℃. The mold pressure fluctuation is controlled within ±0.05MPa throughout the process.

[0036] Example 2

[0037] Preparation of bifunctional silane coupling agent: Under nitrogen protection, 100 parts of DOPO were heated to a molten state at 120°C, 60 parts of 3-mercaptopropyltrimethoxysilane were added, and the reaction was stirred for 3 hours. Then, 50% of a 70% ethanol solution was added, followed by 20 parts of tetraethoxysilane and 2 parts of tetrabutyl titanate. The mixture was hydrolyzed and condensed at 80°C for 4 hours to obtain the bifunctional silane coupling agent.

[0038] Preparation of hybrid nanosol: 40 parts of total tetraethyl orthosilicate and tetrabutyl titanate were mixed in a 3:1 mass ratio in 40 parts of 90% ethanol solution, and 5% by mass of bifunctional silane coupling agent was added.

[0039] Preparation of composite carbon nanofibers: Carbon fibers were treated with low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, 300W power, 50Pa pressure, 25℃ for 5 min, and then 8 times the mass of hybrid nanosol was added, and stirred at 3000rpm for 10 min at 130℃.

[0040] Mixing of the resin matrix: Using 82.5 parts of epoxy resin as the matrix, preheat to 80℃, add 0.8% by mass of polyetherketone nanofibers and 0.5% by mass of aminated carbon nanotubes, and ultrasonically stir for 20 min at 60℃, frequency 25kHz, power 600W; then add 3% of composite carbon nanofibers, continue stirring for 20 min, add 10 parts of methylhexahydrophthalic anhydride and 1.5 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, transfer to a vacuum planetary mixer, revolve at 30 rpm and rotate at 1200 rpm, and degas at 60℃ and -0.1MPa for 20 min until no bubbles overflow, to obtain the resin-based composite material.

[0041] Pre-compaction: After the resin-based composite material is loaded into the mold, it is heated to 80°C in a hot press at a heating rate of 5°C / min. Simultaneously, a vacuum is drawn to -0.095MPa and a pressure of 0.5MPa is applied. The pressure is maintained for 20 minutes to remove interlayer bubbles. During this period, the vacuum is briefly released to -0.08MPa every 5 minutes and then the vacuum is drawn again to enhance the degassing effect.

[0042] Infiltration stage: The temperature is programmed to rise from 80℃ to 100℃ at a rate of 1℃ / min, at which point the pressure rises to 0.5MPa. The temperature is then further increased to 130℃, and the pressure rises to 1.0MPa simultaneously. This 40-minute process is performed using intermittent microwave assistance at 1kW and 2.45GHz. Microwave irradiation is performed for 30 seconds every 90 seconds, followed by a 60-second pause. A total of 8 cycles are executed to promote resin penetration into the fiber bundle.

[0043] Main curing stage: The temperature is raised to 150℃, the pressure is increased to 2.0MPa, and continuous microwave irradiation of 3kW, 2.45GHz is started for 60min. The surface temperature fluctuation of the mold is monitored by infrared thermal imager and is ≤±3℃.

[0044] Post-curing stage: Heat to 180℃, pressurize to 3.0MPa and maintain for 120min, turn off the microwave and cool naturally at 1℃ / min. When the temperature drops to 120℃, reduce the pressure to 0.5MPa, and completely depressurize and demold at 60℃. The mold pressure fluctuation is controlled within ±0.05MPa throughout the process.

[0045] Example 3

[0046] Preparation of bifunctional silane coupling agent: Under nitrogen protection, 100 parts of DOPO were heated to a molten state at 120°C, 60 parts of 3-mercaptopropyltrimethoxysilane were added, and the reaction was stirred for 3 hours. Then, 50% of a 70% ethanol solution was added, followed by 20 parts of tetraethoxysilane and 2 parts of tetrabutyl titanate. The mixture was hydrolyzed and condensed at 80°C for 4 hours to obtain the bifunctional silane coupling agent.

[0047] Preparation of hybrid nanosol: 40 parts of total tetraethyl orthosilicate and tetrabutyl titanate were mixed in a 3:1 mass ratio in 40 parts of 90% ethanol solution, and 5% by mass of bifunctional silane coupling agent was added.

[0048] Preparation of composite carbon nanofibers: Carbon fibers were treated with low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, power 300W, gas pressure 50Pa, at 25℃ for 5min, and then 12 times the mass of hybrid nanosol was added, and stirred at 3000rpm for 10min at 100℃.

[0049] Mixing of the resin matrix: Using 82.5 parts of epoxy resin EPON 828 as the matrix, preheat to 80℃, add 1.2% by mass of polyetherketone nanofibers and 0.2% by mass of aminated carbon nanotubes, and ultrasonically stir for 20 min at 80℃, frequency 25kHz, power 600W; then add 5% of composite carbon nanofibers, continue stirring for 15 min, add 7 parts of methylhexahydrophthalic anhydride and 0.8 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, transfer to a vacuum planetary mixer, revolve at 30 rpm and rotate at 1200 rpm, and degas at 60℃ and -0.1MPa for 20 min until no bubbles overflow, to obtain the resin-based composite material.

[0050] Pre-compaction: After the resin-based composite material is loaded into the mold, it is heated to 80°C in a hot press at a heating rate of 5°C / min. Simultaneously, a vacuum is drawn to -0.095MPa and a pressure of 0.5MPa is applied. The pressure is maintained for 20 minutes to remove interlayer bubbles. During this period, the vacuum is briefly released to -0.08MPa every 5 minutes and then the vacuum is drawn again to enhance the degassing effect.

[0051] Infiltration stage: The temperature is programmed to rise from 80℃ to 100℃ at a rate of 1℃ / min, at which point the pressure rises to 0.5MPa. The temperature is then further increased to 130℃, and the pressure rises to 1.0MPa simultaneously. This 40-minute process is performed using intermittent microwave assistance at 1kW and 2.45GHz. Microwave irradiation is performed for 30 seconds every 90 seconds, followed by a 60-second pause. A total of 8 cycles are executed to promote resin penetration into the fiber bundle.

[0052] Main curing stage: The temperature rises to 150℃, the pressure increases to 2.0MPa, and continuous microwave irradiation of 3kW, 2.45GHz is started for 60min. If the local temperature is >155℃, it will automatically switch to pulse mode, which is on for 10 seconds and off for 5 seconds.

[0053] Post-curing stage: Heat to 180℃, pressure to 3.0MPa and maintain for 120min, turn off microwave and cool naturally at 2℃ / min, when the temperature drops to 120℃, reduce pressure to 0.5MPa, and completely depressurize and demold at 60℃. The mold pressure fluctuation is controlled within ±0.05MPa throughout the process.

[0054] Comparative Example 1

[0055] Carbon nanofiber preparation: Carbon fibers were treated with low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, power 300W, gas pressure 50Pa, 25℃ for 5min.

[0056] Mixing of the resin matrix: Using 83.8 parts of epoxy resin as the matrix, preheat to 80℃, add 1% by mass of polyetherketone nanofibers and 0.3% by mass of aminated carbon nanotubes, and ultrasonically stir for 20 min at 70℃, frequency 25kHz, power 600W; then add 11% of the above-treated carbon nanofibers, continue stirring for 18 min, add 9 parts of methylhexahydrophthalic anhydride and 1.1 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, transfer to a vacuum planetary mixer, revolve at 30 rpm and rotate at 1200 rpm, and degas at 60℃ and -0.1MPa for 20 min until no bubbles overflow, to obtain the resin-based composite material.

[0057] Pre-compaction: After the resin-based composite material is loaded into the mold, it is heated to 80°C in a hot press at a heating rate of 5°C / min. Simultaneously, a vacuum is drawn to -0.095MPa and a pressure of 0.5MPa is applied. The pressure is maintained for 20 minutes to remove interlayer bubbles. During this period, the vacuum is briefly released to -0.08MPa every 5 minutes and then the vacuum is drawn again to enhance the degassing effect.

[0058] Infiltration stage: The temperature is programmed to rise from 80℃ to 100℃ at a rate of 1℃ / min, at which point the pressure rises to 0.5MPa. The temperature is then further increased to 130℃, and the pressure rises to 1.0MPa simultaneously. This 40-minute process is performed using intermittent microwave assistance at 1kW and 2.45GHz. Microwave irradiation is performed for 30 seconds every 90 seconds, followed by a 60-second pause. A total of 8 cycles are executed to promote resin penetration into the fiber bundle.

[0059] Main curing stage: The temperature is raised to 150℃, the pressure is increased to 2.0MPa, and continuous microwave irradiation of 3kW, 2.45GHz is started for 60min. The surface temperature fluctuation of the mold is monitored by infrared thermal imager and is ≤±3℃.

[0060] Post-curing stage: Heat to 180℃, pressure to 3.0MPa and maintain for 120min, turn off microwave and cool naturally at 2℃ / min, when the temperature drops to 120℃, reduce pressure to 0.5MPa, and completely depressurize and demold at 60℃. The mold pressure fluctuation is controlled within ±0.05MPa throughout the process.

[0061] Comparative Example 2

[0062] Preparation of hybrid nanosol: 40 parts of total tetraethyl orthosilicate and tetrabutyl titanate were mixed in a 3:1 mass ratio in 40 parts of 90% ethanol solution, and 5% by mass of γ-aminopropyltriethoxysilane was added.

[0063] Preparation of composite carbon nanofibers: Carbon fibers were treated with low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, power 300W, gas pressure 50Pa, at 25℃ for 5min, and then 10 times the mass of hybrid nanosol was added, and stirred at 3000rpm for 10min at 120℃.

[0064] Mixing of the resin matrix: Using 83.8 parts of epoxy resin as the matrix, preheat to 80℃, add 1% by mass of polyetherketone nanofibers and 0.3% by mass of aminated carbon nanotubes, and ultrasonically stir for 20 min at 70℃, frequency 25kHz, power 600W; then add 4% of composite carbon nanofibers, continue stirring for 18 min, add 9 parts of methylhexahydrophthalic anhydride and 1.1 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, transfer to a vacuum planetary mixer, revolve at 30 rpm and rotate at 1200 rpm, and degas at 60℃ and -0.1MPa for 20 min until no bubbles overflow, to obtain the resin-based composite material.

[0065] Pre-compaction: After the resin-based composite material is loaded into the mold, it is heated to 80°C in a hot press at a heating rate of 5°C / min. Simultaneously, a vacuum is drawn to -0.095MPa and a pressure of 0.5MPa is applied. The pressure is maintained for 20 minutes to remove interlayer bubbles. During this period, the vacuum is briefly released to -0.08MPa every 5 minutes and then the vacuum is drawn again to enhance the degassing effect.

[0066] Infiltration stage: The temperature is programmed to rise from 80℃ to 100℃ at a rate of 1℃ / min, at which point the pressure rises to 0.5MPa. The temperature is then further increased to 130℃, and the pressure rises to 1.0MPa simultaneously. This 40-minute process is performed using intermittent microwave assistance at 1kW and 2.45GHz. Microwave irradiation is performed for 30 seconds every 90 seconds, followed by a 60-second pause. A total of 8 cycles are executed to promote resin penetration into the fiber bundle.

[0067] Main curing stage: The temperature is raised to 150℃, the pressure is increased to 2.0MPa, and continuous microwave irradiation of 3kW, 2.45GHz is started for 60min. The surface temperature fluctuation of the mold is monitored by infrared thermal imager and is ≤±3℃.

[0068] Post-curing stage: Heat to 180℃, pressure to 3.0MPa and maintain for 120min, turn off microwave and cool naturally at 2℃ / min, when the temperature drops to 120℃, reduce pressure to 0.5MPa, and completely depressurize and demold at 60℃. The mold pressure fluctuation is controlled within ±0.05MPa throughout the process.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 1 is that 3-mercaptopropyltrimethoxysilane is replaced with γ-aminopropyltriethoxysilane in this comparative example; otherwise, it is the same as in Example 1.

[0071] Comparative Example 4

[0072] The difference between this comparative example and Example 1 is that methylhexahydrophthalic anhydride is replaced with diethylenetriamine in this comparative example; otherwise, it is the same as in Example 1.

[0073] Comparative Example 5

[0074] The difference between this comparative example and Example 1 is that 3-(3,4-dichlorophenyl)-1,1-dimethylurea is replaced with benzyldimethylamine in this comparative example; the rest is the same as in Example 1.

[0075] Comparative Example 6

[0076] The difference between this comparative example and Example 1 is that methylhexahydrophthalic anhydride is replaced with diethylenetriamine and 3-(3,4-dichlorophenyl)-1,1-dimethylurea is replaced with benzyldimethylamine; the rest is the same as in Example 1.

[0077] Comparative Example 7

[0078] Preparation of bifunctional silane coupling agent: Under nitrogen protection, 100 parts of DOPO were heated to a molten state at 120°C, 60 parts of 3-mercaptopropyltrimethoxysilane were added, and the reaction was stirred for 3 hours. Then, 50% of a 70% ethanol solution was added, followed by 20 parts of tetraethoxysilane and 2 parts of tetrabutyl titanate. The mixture was hydrolyzed and condensed at 80°C for 4 hours to obtain the bifunctional silane coupling agent.

[0079] Preparation of hybrid nanosol: 40 parts of total tetraethyl orthosilicate and tetrabutyl titanate were mixed in a 3:1 mass ratio in 40 parts of 90% ethanol solution, and 5% by mass of bifunctional silane coupling agent was added.

[0080] Preparation of composite carbon nanofibers: Carbon fibers were treated with low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, power 300W, gas pressure 50Pa, at 25℃ for 5min, and then 10 times the mass of hybrid nanosol was added, and stirred at 3000rpm for 10min at 120℃.

[0081] Mixing of the resin matrix: Using 83.8 parts of epoxy resin as the matrix, preheat to 80℃, add 1% by mass of polyetherketone nanofibers and 0.3% by mass of aminated carbon nanotubes, and ultrasonically stir for 20 min at 70℃, frequency 25kHz, power 600W; then add 4% of composite carbon nanofibers, continue stirring for 18 min, add 9 parts of methylhexahydrophthalic anhydride and 1.1 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, transfer to a vacuum planetary mixer, revolve at 30 rpm and rotate at 1200 rpm, and degas at 60℃ and -0.1MPa for 20 min until no bubbles overflow, to obtain the resin-based composite material.

[0082] After the resin-based composite material was loaded into the mold, it was first pre-cured at 90°C for 45 minutes in a hot press to remove volatiles and initiate gelation. Then, the temperature was increased to 130°C at a rate of 2°C / min for primary curing, and held at this temperature for 90 minutes to allow the resin to fully cross-link. Finally, it was cured at 170°C for 150 minutes. The entire curing process was carried out under a pressure of 0.6 MPa.

[0083] Experiment 1: Performance Testing

[0084] According to GB / T 3362-2017, the tensile properties of carbon fiber multifilament were tested using a universal testing machine with a fiber bundle length of 150 mm and a tensile rate of 20 mm / min. Each sample was tested 6 times and the average value was taken. Then the tensile strength and elastic modulus of the sample were calculated.

[0085] The elongation at break was determined in accordance with GB / T 1040.3-2006. A universal testing machine equipped with an extensometer was used to perform tensile tests on the specimens. Each specimen was tested 6 times and the average value was taken.

[0086] Porosity: GB / T 3365-2008 specifies the porosity determination method, which uses the density method. The mass of the sample is measured by an analytical balance after drying, impregnation and saturation, and the porosity is calculated by formula in combination with the theoretical density of the composite material.

[0087] The results are shown in Table 1 below:

[0088] Table 1

[0089] Group Tensile strength / MPa Elastic modulus / GPa Elongation at break / % Porosity / % Example 1 167 8.7 1.64 0.37 Example 2 165 8.5 1.63 0.41 Example 3 158 8.3 1.68 0.45 Comparative Example 1 98 5.8 1.42 1.85 Comparative Example 2 132 7.7 1.51 1.04 Comparative Example 3 123 7.0 1.46 1.14 Comparative Example 4 118 6.8 1.37 1.08 Comparative Example 5 115 6.7 1.36 1.07 Comparative Example 6 116 6.5 1.32 1.01 Comparative Example 7 120 6.9 1.35 1.09

Claims

1. A preparation process for the mechanical properties of carbon fiber reinforced resin matrix composites, characterized in that, The process is as follows: Preparation of composite carbon nanofibers: Carbon fibers were treated with low-temperature radio frequency plasma, Ar:O2=4:1 mixed gas, 300W power, 50Pa pressure, 25℃ for 5min, and then 8-12 times the mass of hybrid nanosol was added, and stirred at 3000rpm for 10min at 100-130℃. Mixing of the resin matrix: Using 82.5-85 parts of epoxy resin as the matrix, preheat to 80℃, add 0.8-1.2% by mass of polyetherketone nanofibers and 0.2-0.5% by mass of aminated carbon nanotubes, and ultrasonically stir for 20 min at 60-80℃, frequency 25kHz, power 600W; then add 3-5% of composite carbon nanofibers, continue stirring for 15-20 min, add 7-10 parts of curing agent and 0.8-1.5 parts of accelerator, transfer to a vacuum planetary mixer, revolve at 30 rpm and rotate at 1200 rpm, and degas at 60℃ and -0.1MPa for 20 min until no bubbles overflow, to obtain the resin-based composite material; The epoxy resin is a bisphenol type epoxy resin.

2. The preparation process according to claim 1, characterized in that, The hybrid nanosol was prepared by mixing 40 parts of tetraethyl orthosilicate and tetrabutyl titanate in a 3:1 mass ratio in 40 parts of 90% ethanol solution, and adding 5% by mass of bifunctional silane coupling agent.

3. The preparation process according to claim 2, characterized in that, The bifunctional silane coupling agent was prepared as follows: Under nitrogen protection, 100 parts of DOPO were heated to a molten state at 120°C, 60 parts of 3-mercaptopropyltrimethoxysilane were added, and the reaction was stirred for 3 hours. Then, 50% of a 70% ethanol solution was added, followed by 20 parts of tetraethoxysilane and 2 parts of tetrabutyl titanate. The mixture was then subjected to a hydrolysis-condensation reaction at 80°C for 4 hours to obtain the bifunctional silane coupling agent.

4. The preparation process according to claim 1, characterized in that, The curing agent is methylhexahydrophthalic anhydride.

5. The preparation process according to claim 1, characterized in that, The accelerator is 3-(3,4-dichlorophenyl)-1,1-dimethylurea.

6. A curing process for a resin-based composite material obtained according to the preparation process described in claim 1, characterized in that, The specific curing process is as follows: Pre-compaction stage: After the resin-based composite material is loaded into the mold, it is heated to 80°C in a hot press at a heating rate of 5°C / min. Simultaneously, a vacuum is drawn to -0.095MPa and a pressure of 0.5MPa is applied. The pressure is maintained for 20 minutes to remove interlayer bubbles. During this period, the vacuum is briefly released to -0.08MPa every 5 minutes and then the vacuum is drawn again to enhance the degassing effect. Infiltration stage: The temperature is programmed to rise from 80℃ to 100℃ at a rate of 1℃ / min, at which point the pressure rises to 0.5MPa. The temperature is then further increased to 130℃, and the pressure rises to 1.0MPa simultaneously. This 40-minute process is performed using intermittent microwave assistance at 1kW and 2.45GHz. Microwave irradiation is performed for 30 seconds every 90 seconds, followed by a 60-second pause. A total of 8 cycles are executed to promote resin penetration into the fiber bundle. Main curing stage: The temperature rises to 150℃, the pressure increases to 2.0MPa, and continuous microwave irradiation of 3kW, 2.45GHz is started for 60min. The surface temperature fluctuation of the mold is monitored by an infrared thermal imager and is ≤±3℃. If the local temperature is >155℃, it will automatically switch to pulse mode, which is on for 10 seconds and off for 5 seconds. Post-curing stage: Heat to 180℃, pressurize to 3.0MPa and hold for 120min, turn off the microwave and cool naturally at ≤2℃ / min. When the temperature drops to 120℃, reduce the pressure to 0.5MPa, and completely release the pressure and demold at 60℃. The mold pressure fluctuation is controlled within ±0.05MPa throughout the process.

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