Self-repairing method of carbon fiber composite material in low-temperature environment

Abstract

The invention provides a self-repairing method of a carbon fiber composite material in a low-temperature environment, the carbon fiber composite material is easy to damage at a low temperature, and an existing self-repairing method has many problems such as complex preparation of a microcapsule technology, low repairing efficiency, non-uniform distribution of a hollow fiber technology, influence on mechanical properties, limited technical conditions of reversible covalent bonds, slow repairing and the like. The method comprises the steps of carbon fiber modification treatment, resin matrix optimization modification, intelligent microcapsule preparation, low-temperature initiator selection and addition, low-temperature mixing and vacuum treatment, low-temperature forming process optimization and the like. The principle is that the microcapsule releases the repairing agent during low-temperature damage, the initiator initiates cross-linking curing, and the flexible chain segment promotes repairing. According to the method, the material is high in self-repairing capacity at the low temperature, good performance is kept, reliable material technical support is provided for related equipment and structures in the low-temperature environment, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber composite materials, and particularly to a self-healing method for carbon fiber composite materials in a low-temperature environment. Background Art

[0002] Due to its excellent mechanical properties, high specific strength, high specific modulus, and good corrosion resistance, carbon fiber composite materials have been widely used in many high-end fields such as aerospace, automotive manufacturing, and energy. In the aerospace field, it is widely used in aircraft structural components such as wings and fuselages, which can effectively reduce the structural weight and improve the performance of the aircraft; in automotive manufacturing, it is used to manufacture body components and high-performance parts to improve the fuel efficiency and handling performance of the vehicle; in the energy field, components such as wind turbine blades made of carbon fiber composite materials can adapt to harsh working environments and improve energy conversion efficiency. However, when carbon fiber composite materials are used in a low-temperature environment, they face many severe challenges. Low temperature can increase the brittleness and reduce the toughness of the material, making it more prone to damage, such as matrix cracking, fiber fracture, and interlayer delamination. These damages not only reduce the mechanical properties of the material and affect the load-bearing capacity of the structure, but may also lead to catastrophic consequences, such as aircraft structural failure, automotive component damage, and wind turbine failure. Therefore, it is urgent to develop an effective self-healing method for carbon fiber composite materials in a low-temperature environment.

[0003] Currently, the self-healing methods for carbon fiber composite materials mainly include methods based on microcapsule technology, hollow fiber technology, and reversible covalent bonds. The self-healing method based on microcapsule technology encapsulates the healing agent in microcapsules. When the material is damaged, the microcapsules rupture and release the healing agent, thereby achieving the repair of the damage. For example, Patent CN118359895A discloses a carbon fiber composite material containing a microcapsule self-healing agent and its preparation method, which can achieve the self-healing of the composite material to a certain extent. However, the preparation process of microcapsules is complex, and parameters such as the thickness, strength of the capsule wall, and the encapsulation amount of the healing agent need to be precisely controlled. Otherwise, it is easy to cause the premature rupture of microcapsules during the material preparation process or the failure to rupture and release the healing agent effectively when damage occurs. In addition, the repair efficiency of this method is relatively low, and the repair effect for large-sized damages is not good. The hollow fiber technology fills the healing agent in hollow fibers. When the material is damaged, the hollow fibers rupture and the healing agent flows out for repair. However, it is difficult to ensure the uniform distribution of hollow fibers in the composite material, and local aggregation is likely to occur, affecting the uniformity of the repair effect. At the same time, the introduction of hollow fibers may change the mechanical properties of the composite material and reduce its strength and stiffness.

[0004] For example, the invention patent with application number CN202410059290.0 discloses an intelligent anti-corrosion coating material, its preparation method and application. The self-repair method of the anti-corrosion coating material adopts hollow fiber technology. In actual applications, it is found that although a certain degree of self-repair can be achieved, the mechanical properties of the material have decreased, and the repair ability for complex damage is limited. The self-repair method based on reversible covalent bonds uses reversible chemical reactions to achieve self-repair of materials, but this method usually requires specific reaction conditions, such as temperature, light, etc., and is greatly restricted in actual applications. Moreover, the formation and breaking process of reversible covalent bonds is relatively slow, which makes it difficult to meet the demand for rapid repair of damage.

[0005] For example, the Chinese invention patent with application number CN202311586720.6 discloses a method for preparing a solvent-free dynamic epoxy resin and its composite materials. The self-healing carbon fiber composite material therein can only achieve self-healing function at an appropriate temperature based on the self-healing mechanism of reversible covalent bonds, resulting in unsatisfactory repair effect.

[0006] Therefore, the technical problem that needs to be solved urgently is: how to make carbon fiber composite materials better used in low-temperature environments, reduce the performance degradation of materials, and improve the wide range of applicability. Summary of the invention

[0007] The present invention is made to solve the above-mentioned problems, and its purpose is to provide a self-repair method for carbon fiber composite materials in a low-temperature environment, to ensure that the material can quickly and effectively start the self-repair mechanism after being damaged under low-temperature conditions, to achieve accurate repair of the damage, and to significantly improve the performance recovery of the material under low-temperature conditions, to effectively ensure its structural integrity and reliability, and thereby greatly extend the service life of the material in a low-temperature environment, providing solid and reliable material technology support for low-temperature engineering applications.

[0008] The present invention provides a self - repair method for carbon fiber composites in a low - temperature environment, which has the following characteristics: including: Step S1, carbon fiber modification treatment: Select carbon fibers and place them in a low - temperature plasma treatment device. Introduce a mixed gas of helium and oxygen, where the volume ratio of helium to oxygen is (3 - 5):1, and conduct treatment under low - temperature pressure to obtain modified carbon fibers; Step S2, optimization modification of the resin matrix: Select epoxy resin as the resin matrix, add a special modifier, and then add a chain extender and continue to react for a period of time to obtain modified epoxy resin; Step S3, preparation of intelligent microcapsules: Uniformly disperse bisphenol A epoxy resin and a high - efficiency emulsifier in deionized water, control the dosage of the emulsifier and the stirring speed to form a stable emulsion with a uniform particle size distribution. Then, slowly and steadily drip the melamine - formaldehyde resin prepolymer solution into the emulsion, and at the same time adjust the system pH, and react for a period of time at a certain temperature to promote the precise polymerization of melamine - formaldehyde resin on the surface of bisphenol A epoxy resin droplets to form microcapsules; Step S4, selection and addition of a low - temperature initiator: Select benzoyl peroxide as the low - temperature initiator, and mix it with the microcapsules in a mass ratio of 1:(8 - 12) to obtain microcapsules containing a low - temperature initiator; Step S5, low - temperature mixing and vacuum treatment: Mix the modified carbon fibers, modified epoxy resin, and microcapsules containing a low - temperature initiator in an accurate mass ratio of 6:3:1. First, use a high - speed stirrer to stir the mixture in a low - temperature environment to ensure that each component can be preliminarily and uniformly dispersed at low temperature, and at the same time avoid generating heat due to excessive stirring and affecting the low - temperature performance of the material. Subsequently, quickly transfer the mixed system to a vacuum environment for defoaming treatment to obtain carbon fiber composite raw materials; and Step S6, optimization of the low - temperature molding process: Impregnate the carbon fiber composite raw materials with resin and cure them to obtain carbon fiber composites.

[0009] In the self - repair method for carbon fiber composites in a low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the optimization of the low - temperature molding process includes a low - temperature molding process and a resin transfer molding process. When the carbon fiber composite is a component with a relatively simple shape, the low - temperature molding process is adopted, and it is maintained at a certain temperature and pressure for a period of time to ensure that the resin fully impregnates the carbon fiber and achieves precise curing and molding; when the carbon fiber composite is a component with a complex shape, a high - precision resin transfer molding process is selected, and it is maintained at a certain temperature and pressure for a period of time so that the resin can uniformly impregnate the carbon fiber in the complex mold cavity and perfectly cure, thereby obtaining a carbon fiber composite with excellent self - repair function.

[0010] In the self - repair method for carbon fiber composites in a low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, in Step S1, the treatment temperature is - 30°C to - 20°C, the treatment pressure is 0.08 - 1 MPa, and the treatment time is 20 - 30 min.

[0011] In the self - healing method of carbon fiber composite materials under low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the special modifier is a polyurethane prepolymer containing flexible chain segments, and the synthesis conditions of the special modifier are: reacting diisocyanate and polyether diol in a molar ratio of (1 - 2):1 at 40 - 60 °C for 1 - 3 h.

[0012] In the self - healing method of carbon fiber composite materials under low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the chain extender is 1,4 - butanediol, and the chain - extending reaction time after adding the chain extender in step S2 is 1 - 2 h.

[0013] In the self - healing method of carbon fiber composite materials under low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the pH of the system in step S3 is adjusted to 4 - 5.

[0014] In the self - healing method of carbon fiber composite materials under low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the reaction temperature after adjusting the pH of the system in step S3 is 30 - 50 °C, and the reaction time is 2 - 3 h.

[0015] In the self - healing method of carbon fiber composite materials under low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the low - temperature environment in step S5 is - 10 °C to - 20 °C.

[0016] In the self - healing method of carbon fiber composite materials under low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the rotation speed of the high - speed stirrer in step S5 is 500 - 800 r / min, the stirring time is 30 - 50 min, and the defoaming treatment time in a vacuum environment is 20 - 40 min.

[0017] In the self - healing method of carbon fiber composite materials under low - temperature environment provided by the present invention, it may also have the following characteristics: Among them, the forming temperature of the low - temperature forming process is - 10 °C to - 20 °C, the forming pressure is 8 - 10 MPa, and the forming time is 4 - 6 h; the temperature of the resin transfer molding process is - 10 °C to - 20 °C, the pressure is 5 - 7 MPa, and the time is 5 - 7 h.

[0018] Functions and effects of the invention

[0019] The self - healing method of carbon fiber composite materials under low - temperature environment involved in the present invention has the following beneficial effects:

[0020] 1. The method of the present invention enables carbon fiber composite materials to exhibit efficient self - healing ability under low - temperature environment, effectively extends the service life of materials under low - temperature working conditions, and greatly improves the reliability and safety of low - temperature equipment and structures.

[0021] 2. Through innovative low-temperature plasma treatment of carbon fiber, meticulous modification of the resin matrix, and reasonably optimized preparation processes, it is ensured that the material still has extremely high strength, modulus, and good toughness in a low-temperature environment.

[0022] 3. An innovative combination of specific carbon fiber, resin matrix, intelligent microcapsule repair agent, and low-temperature initiator is adopted, and combined with unique low-temperature treatment and forming processes to prepare a self-healing carbon fiber composite material. This material system and process design provide a brand-new solution for the self-healing of carbon fiber composite materials in a low-temperature environment, breaking through the limitations of traditional technologies in low-temperature self-healing.

[0023] 4. This composite material can be widely applied to multiple fields such as polar scientific research equipment, low-temperature liquid storage containers, aerospace low-temperature components, deep-sea submarine hulls, etc. It is of great significance for improving the reliability, safety, and service life of equipment and structures in a low-temperature environment, and will provide strong material technology support for the development of these fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a microscopic schematic diagram of the microcapsule distribution in the flat self-healing carbon fiber composite material in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to make the technical means, creative features, achieved purposes, and effects of the present invention easy to understand, the following embodiments in conjunction with the drawings specifically elaborate on the self-healing method of the carbon fiber composite material in a low-temperature environment of the present invention.

[0026] Embodiment

[0027] The self-healing method of the carbon fiber composite material in a low-temperature environment in this embodiment specifically includes the following steps:

[0028] Step S1, carbon fiber modification treatment.

[0029] Select T700 12k carbon fiber, carefully place it into an advanced low-temperature plasma treatment device, strictly introduce a mixed gas of helium and oxygen with a volume ratio of 4:1 according to the set process parameters, and treat it at -30°C and 0.08 MPa for 25 min to obtain modified carbon fiber.

[0030] Step S2, optimized modification of the resin matrix.

[0031] Toluene diisocyanate and polyether diol were reacted at a molar ratio of 3:2 at 50 °C for 2 h to synthesize a self-made polyurethane prepolymer modifier. Epoxy resin was accurately weighed, and 15% by mass of the self-made polyurethane prepolymer modifier was added. Under the condition of constant-temperature stirring, they were fully mixed evenly to ensure that the modifier was uniformly dispersed in the resin matrix. Subsequently, 1,4-butanediol was added and reacted for 1.5 h to obtain modified epoxy resin.

[0032] Step S3, preparation of intelligent microcapsules.

[0033] 100 g of E-51 epoxy resin and 3 g of sodium dodecyl sulfate emulsifier were dispersed in 500 ml of deionized water at a stirring speed of 600 r / min and a temperature of 50 °C to form a stable emulsion system. Then, the melamine-formaldehyde resin prepolymer solution was slowly dropped into the emulsion at a precisely controlled dropping speed of 2 ml / min. In the melamine-formaldehyde resin prepolymer solution, the mass of melamine-formaldehyde resin was 50 g. At the same time, the pH value of the system was adjusted to be stably maintained at 4, and the reaction was continued for 3 hours in a constant-temperature environment of 40 °C to form microcapsules.

[0034] Step S4, selection and addition of low-temperature initiator.

[0035] Benzoyl peroxide and microcapsules were mixed at a mass ratio of 1:10 under low temperature and light-shielded conditions to ensure that the benzoyl peroxide initiator was evenly distributed on the surface of the microcapsules, obtaining microcapsules containing a low-temperature initiator, which prepared for the subsequent low-temperature-initiated self-healing reaction.

[0036] Step S5, low-temperature mixing and vacuum treatment.

[0037] Figure 1 It is a microscopic schematic diagram of the microcapsule distribution in the flat self-healing carbon fiber composite material in the embodiment of the present invention.

[0038] The treated carbon fiber 10, modified resin 30 and microcapsules containing initiator 20 were mixed in a low-temperature mixing device according to an accurate ratio of 6:3:1 by mass. First, in a low-temperature environment of -10 °C, a high-speed stirrer was used to stir at an accurate speed of 600 r / min for 40 min. By real-time monitoring of the temperature and torque changes, the mixing uniformity was ensured. Then, the mixed system was quickly transferred to a vacuum degassing device, and degassing was carried out at a vacuum degree of -0.09 MPa for 30 min. By observing the bubble discharge situation and density change, it was ensured that the degassing was complete, obtaining the carbon fiber composite raw material as shown in Figure 1 Figure.

[0039] Step S6, optimization of low-temperature molding process.

[0040] The degassed mixed system is carefully injected into a mold that is pre-designed and precisely machined. Using a low-temperature forming process, it is maintained for 5 hours under a low-temperature environment of -20°C and a pressure condition of 8 MPa, and finally 100 carbon fiber composite materials with self-healing function are obtained.

[0041] The working principle of the embodiment of the present invention is as follows:

[0042] In a low-temperature environment, when the carbon fiber composite material is damaged, the microcapsules rupture and precisely release the bisphenol A epoxy resin repair agent. At the same time, the benzoyl peroxide low-temperature initiator stably decomposes to generate free radicals according to the predetermined decomposition kinetic law under low-temperature conditions, and efficiently initiates the rapid and effective cross-linking and curing reaction between the epoxy resin and the unreacted functional groups in the resin matrix. During this process, the flexible chain segments in the modified resin matrix, relying on their unique molecular structure and flexibility at low temperatures, can still maintain a certain molecular motion ability in the low-temperature environment, actively promoting the rapid diffusion of the repair agent and its full integration with the matrix, thereby effectively filling and repairing the damaged part and restoring the structural integrity and mechanical properties of the material. The entire self-healing process is a complex process of multi-factor synergistic action, and each component closely cooperates under a low-temperature environment to jointly achieve efficient self-healing.

[0043] Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A self-healing method for carbon fiber composites under low-temperature environments, characterized in that Specifically, it includes the following steps: Step S1, carbon fiber modification treatment: Select carbon fibers and place them in a low-temperature plasma treatment device. Introduce a mixed gas of helium and oxygen, where the volume ratio of helium to oxygen is (3 - 5):1, and conduct the treatment under low-temperature pressure to obtain modified carbon fibers; Step S2, optimization modification of the resin matrix: Select epoxy resin as the resin matrix, add a special modifier, and then add a chain extender and continue to react for a period of time to obtain modified epoxy resin; Step S3, preparation of intelligent microcapsules: Uniformly disperse bisphenol A epoxy resin and a high-efficiency emulsifier in deionized water, control the dosage of the emulsifier and the stirring speed to form a stable emulsion with a uniform particle size distribution. Then, slowly and steadily drip the melamine-formaldehyde resin prepolymer solution into the emulsion, while adjusting the pH of the system, and react at a certain temperature for a period of time to promote the precise polymerization of the melamine-formaldehyde resin on the surface of the bisphenol A epoxy resin droplets to form microcapsules; Step S4, selection and addition of a low-temperature initiator: Select benzoyl peroxide as the low-temperature initiator and mix it with the microcapsules in a mass ratio of 1:(8 - 12) to obtain microcapsules containing the low-temperature initiator; Step S5, low-temperature mixing and vacuum treatment: Mix the modified carbon fibers, the modified epoxy resin, and the microcapsules containing the low-temperature initiator in an exact mass ratio of 6:3:

1. First, use a high-speed stirrer to stir the mixture in a low-temperature environment to ensure that each component can be preliminarily and uniformly dispersed at low temperature, while avoiding heat generation due to excessive stirring that affects the low-temperature performance of the material. Subsequently, quickly transfer the mixed system to a vacuum environment for degassing treatment to obtain a carbon fiber composite raw material; And Step S6, optimization of the low-temperature forming process: Fully impregnate the carbon fiber composite raw material with resin and cure it to obtain a carbon fiber composite material.

2. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, characterized in that: Among them, The optimization of the low-temperature forming process includes a low-temperature forming process and a resin transfer molding process. When the carbon fiber composite material is a component with a relatively simple shape, the low-temperature forming process is adopted and maintained at a certain temperature and pressure for a period of time to ensure that the resin fully impregnates the carbon fiber and achieves precise curing and forming; when the carbon fiber composite material is a component with a complex shape, the high-precision resin transfer molding process is selected and maintained at a certain temperature and pressure for a period of time, so that the resin can uniformly impregnate the carbon fiber in the complex mold cavity and be perfectly cured, thereby obtaining a carbon fiber composite material with excellent self-healing function.

3. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, characterized in that: Among them, In step S1, the treatment temperature is -30°C to -20°C, the treatment pressure is 0.08 to 1 MPa, and the treatment time is 20 to 30 min.

4. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, characterized in that: Among them, The special modifier is a polyurethane prepolymer containing a flexible chain segment. The synthesis conditions of the special modifier are as follows: The diisocyanate and the polyether diol are reacted at a molar ratio of (1-2):1 at 40-60°C for 1-3 h.

5. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, wherein: Among them, The chain extender is 1,4-butanediol, and the chain extension reaction time after adding the chain extender in step S2 is 1-2 h.

6. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, wherein: Among them, The pH of the system in step S3 is adjusted to 4-5.

7. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, wherein: Among them, The reaction temperature after adjusting the pH of the system in step S3 is 30-50°C, and the reaction time is 2-3 h.

8. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, wherein: Among them, The low-temperature environment in step S5 is -10°C to -20°C.

9. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 1, wherein: Among them, The rotation speed of the high-speed stirrer in step S5 is 500-800 r / min, the stirring time is 30-50 min, and the defoaming treatment time in a vacuum environment is 20-40 min.

10. The self-healing method of the carbon fiber composite material under a low-temperature environment according to claim 2, wherein: Among them, The forming temperature of the low-temperature forming process is -10°C to -20°C, the forming pressure is 8-10 MPa, and the forming time is 4-6 h; the temperature of the resin transfer molding process is -10°C to -20°C, the pressure is 5-7 MPa, and the time is 5-7 h.

Images