In-situ repair method for damaged area of fiber reinforced resin matrix composite

Abstract

The invention discloses an in-situ repair method for a damaged area of a fiber reinforced resin matrix composite, which comprises the following steps of: forming a catalyst coating on the surface of the damaged area and applying infrared irradiation, so that directional ablation of resin is realized under a low-temperature condition, secondary damage of a matrix material is avoided, and the repairability of the composite is improved; carbon deposition is not generated on the surface of the carbon fiber, a certain oxygen-containing functional group is formed, meanwhile, in-situ arrangement and surface appearance of the fiber are kept, and an excellent interface condition is provided for subsequent resin re-impregnation or cementing repair; in the operation process, a composite material component or complex equipment does not need to be disassembled, local treatment can be directly carried out on site, the efficient, controllable and high-repeatability repairing process is achieved by adjusting infrared power, heating time and catalyst distribution, and the method is suitable for various types of fiber reinforced resin-based composite materials and has wide application prospects. The method can be popularized and applied to local repair of composite material structures such as aerospace, traffic transportation and wind power generation blades.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite material repair method, in particular to a method for in-situ repair of a damaged area of a fiber-reinforced resin-based composite material. BACKGROUND

[0002] Fiber resin-based composite materials are widely used in the fields of aerospace, automobiles, wind power generation and other high-performance material requirements due to their excellent specific strength, specific stiffness, corrosion resistance and other characteristics. However, during long-term service, fiber resin-based composite materials often suffer damages such as fiber breakage, resin cracking and interfacial debonding due to external impact, fatigue load or environmental factors. These damages may cause significant decrease in the mechanical properties of the material, and even in severe cases, endanger the safety of the structure. Therefore, timely repair of the damaged area to restore its mechanical properties is crucial to ensure the safe service of the composite material, prolong the service period and reduce the life cycle service cost. At present, the repair method for fiber resin-based composite materials mainly relies on excavation repair, which removes the resin and fiber in the damaged area and fills new materials to restore its performance. The quality of resin removal in the damaged area directly affects the bonding strength of the repair interface and the final repair effect. An ideal removal process should completely remove the damaged resin while avoiding secondary damage to the fibers in the matrix and ensuring good surface activity and wettability of the repair interface. Although the traditional mechanical polishing method is simple to operate, it is easy to cause scratches or fiber breakage in the matrix, and it is difficult to achieve selective and precise removal of the resin, resulting in reduced bonding performance of the repair interface. CN104384719A discloses a device and method for removing damaged areas of fiber-reinforced composite materials, which uses laser to remove the resin in the damaged area. However, the laser pulse energy is concentrated, which easily causes thermal damage or breakage of the fibers in the matrix; and carbon deposition layer is easily formed on the surface of the fibers after laser action, which affects the interfacial bonding strength between the subsequent patch resin and the fiber matrix. SUMMARY

[0003] The purpose of the present application is to conveniently repair the damaged area of the fiber-reinforced resin-based composite material in-situ and improve the bonding strength after repair, and a method for in-situ repair of the damaged area of the fiber-reinforced resin-based composite material is provided.

[0004] Technical solution: The in-situ repair method for the damaged area of the fiber-reinforced resin-based composite material according to the present application comprises the following steps:

[0005] Disperse the transition metal oxide in the solvent, stir and ultrasonically disperse to obtain a catalyst suspension;

[0006] Remove the debris, dust and oil stains on the surface of the damaged area of the composite material;

[0007] A catalyst coating is formed by uniformly depositing a catalyst suspension onto the surface of the damaged area.

[0008] Infrared heating is applied to the damaged area of ​​the deposited catalyst coating to promote the thermal decomposition and ablation of the resin in the damaged area, thereby completing the in-situ ablation of the resin in the damaged area.

[0009] Remove residual products from the damaged area;

[0010] The original matrix type of fiber and resin are selected and the damaged area is repaired in situ through vacuum flow process and heat curing.

[0011] Furthermore, by forming a catalyst coating on the damaged area and applying infrared irradiation, the resin can be directionally ablated at low temperatures, avoiding secondary damage to the matrix material. The infrared power, heating time, and catalyst distribution can be flexibly adjusted according to the size and shape of the damage, achieving efficient, controllable, and highly repeatable repair. This method can be widely applied in the local repair of composite material structures in aerospace, transportation, and wind turbine blades. During the resin ablation process, the composite catalyst not only lowers the thermal decomposition temperature of the resin but also effectively inhibits carbon deposition during the ablation process. In addition, the oxidation properties of the composite catalyst can also produce a mild oxidative modification effect on the fiber surface, introducing oxygen-containing functional groups into the matrix fiber surface, thereby increasing the polarity and chemical activity of the fiber surface, improving the wettability and interfacial adhesion between the fiber and the subsequent repair resin, promoting the re-establishment of interfacial chemical bonds, and achieving a more stable interfacial bond.

[0012] Furthermore, the transition metal oxide is Cr2O3, MnO2, or a combination of CuO and TiO2; the solvent is one of deionized water, ethanol, isopropanol, or ethylene glycol. The purity of the transition metal oxide is 99%, the particle size range is 50~500 nm, and the mass ratio of Cr2O3, MnO2, or CuO to TiO2 is 1:0.8~1:1.5. Carbon deposits can affect catalyst activity and resin dissolution. TiO2, under heating conditions, can promote resin dissolution and decomposition into smaller molecules. It also possesses a large specific surface area and adsorption capacity, high thermal conductivity, and surface oxygen migration ability. It adsorbs and further decomposes organic matter in the deposits, effectively eliminating surface carbon and improving catalytic reaction efficiency. Simultaneously, it avoids uneven heat conduction that could cause localized overheating and thermal damage to the device being repaired. Furthermore, TiO2's high thermal conductivity and adsorption properties allow it to easily combine with MnO2, CuO, and Cr2O3, thereby improving the overall thermal conductivity of the coating. Under infrared heating conditions, the composite catalytic system formed by MnO2, CuO, Cr2O3, and TiO2 achieves efficient resin dissolution through a multi-synergistic mechanism of heat conduction, electron transfer, and redox. MnO2, CuO, and Cr2O3, as variable-valence transition metal oxides, generate oxygen vacancies and active oxygen under thermal excitation, which then dissolve through MnO2… 4+ / Mn 3+ Cu 2+ / Cu + Cr 3+ / Cr 2+ The oxidation state cycle induces polarization and breakage of CO, C, and CN bonds in the resin molecules, significantly reducing the decomposition activation energy. Simultaneously, TiO2 possesses high thermal conductivity and surface oxygen migration capacity, enabling rapid and uniform heat transfer within the catalyst coating, avoiding localized overheating and thermal damage to the area to be repaired. Furthermore, its surface active oxygen oxidizes and removes carbon deposits formed on the fiber surface in the matrix; moreover, uniform heat conduction promotes Mn... 4+ / Mn 3+ Cu 2+ / Cu + Cr 3+ / Cr 2+ The improved valence state cycling efficiency further reduces the decomposition activation energy, significantly lowering the reaction temperature and time for resin ablation, thus enhancing the resin's catalytic ablation efficiency and preventing damage to undamaged areas during the repair process. Under the synergistic effect of these multiple components, the initial decomposition temperature of the resin in the damaged area decreases, the pyrolysis rate accelerates, and surface carbon residue is significantly reduced, ultimately achieving a precise, efficient, and stable infrared thermocatalytic ablation process in the damaged area.

[0013] Furthermore, the mass ratio of the transition metal oxide to the solvent is 1:8 to 1:15. The stirring speed for mixing the transition metal oxide and the solvent is 300 to 800 r / min, and the time is 10 to 15 min. The ultrasonic dispersion power is 100 to 200 W, and the time is 5 to 10 min. Stirring and ultrasonic dispersion improve the uniformity of mixing Cr2O3, MnO2 or CuO with TiO2, thus promoting the catalytic reaction.

[0014] Furthermore, the catalyst suspension is deposited on the surface of the damaged area by spraying or brushing, with a coating thickness of 50-200 μm after deposition. The thickness of the catalyst directly affects the contact efficiency between the resin and the active sites of the catalyst, as well as the efficiency of electron and ion transfer. A suitable thickness allows for sufficient energy absorption and the generation of active oxygen species under infrared irradiation, thereby achieving efficient and uniform dissolution of the resin. Simultaneously, it effectively inhibits carbon deposition and maintains high cleanliness of the fiber surface. Within this thickness range, the catalytic oxidation effect is moderate, introducing oxygen-containing functional groups such as hydroxyl, carboxyl, and carbonyl groups onto the fiber surface, enhancing surface polarity and chemical activity, and significantly strengthening the interfacial bonding strength between the repair resin and the matrix fiber. If the coating is too thin, the catalytic activity is insufficient, and the resin dissolution is incomplete; if it is too thick, thermal conductivity is limited, the reaction is uneven, and it may even lead to local overheating and fiber damage. Therefore, by rationally controlling the thickness of the catalyst coating, the synergistic optimization of precise resin removal, fiber surface cleaning, and interfacial activation can be achieved, thereby significantly improving the repair quality and mechanical property recovery effect of the composite material.

[0015] Furthermore, the infrared heating uses infrared radiation with a wavelength of 0.76~25μm, a heating power of 200~400W, and a heating time of 3~12 min.

[0016] Furthermore, the fibers in the fiber-reinforced resin matrix composite material are carbon fiber or glass fiber; the resin in the fiber-reinforced resin matrix composite material is epoxy resin, unsaturated polyester resin, vinyl ester resin, or phenolic resin; the in-situ repair method is applicable to resin cracking and fiber breakage damage. Fiber breakage damage repair also includes local trimming and removal of the broken fibers, followed by the laying of a new fiber layer consistent with the original structure to restore the continuity of the reinforcing phase. The newly laid fibers should maintain the same layup direction as the original fibers in the matrix to reduce fiber end peeling and stress concentration, and improve the structural integrity and load transfer efficiency of the repaired interface. Finally, using a vacuum infusion process, new resin of the same type is infused at a temperature of 30~45 ℃ and a vacuum degree controlled at -0.085~-0.1 MPa. Curing is then performed using a heat repair instrument at a temperature of 60~180℃ and a holding time of 0.5~2 hours to finally complete the repair.

[0017] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: 1. By forming a catalyst coating on the surface of the damaged area and applying infrared irradiation, the resin achieves directional ablation under low-temperature conditions, avoiding secondary damage to the matrix material and improving the repairability of the composite material; 2. During the in-situ removal process, carbon deposits are not generated on the carbon fiber surface, and certain oxygen-containing functional groups are formed, while maintaining the in-situ fiber arrangement and surface morphology, providing excellent interface conditions for subsequent resin re-impregnation or adhesive bonding repair; 3. The operation process does not require disassembling composite material components or complex equipment, and local treatment can be carried out directly on-site; 4. Infrared power, heating time, and catalyst distribution can be flexibly adjusted according to the size and shape of the damage, achieving a highly efficient, controllable, and repeatable repair process; 5. It is applicable to various types of fiber-reinforced resin-based composite materials, including carbon fiber, glass fiber, and their reinforced epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, etc., with a wide range of applications, and can be widely used in the local repair of composite material structures in aerospace, transportation, wind power blades, etc. Attached Figure Description

[0018] Figure 1 This is a macroscopic effect diagram of the resin after in-situ ablation according to the present invention;

[0019] Figure 2 These are microscopic images showing the effects of in-situ resin ablation in Examples 1-3 of the present invention.

[0020] Figure 3 These are microscopic images of the resin after in-situ ablation in Comparative Examples 1-2 of the present invention.

[0021] Figure 4 These are microscopic images of the resin after in-situ ablation in Comparative Examples 3-5 of the present invention.

[0022] Figure 5 This is the Raman spectrum of carbon fibers after in-situ resin ablation according to the present invention;

[0023] Figure 6 This is a diagram showing the tensile strength of a single filament of carbon fiber after in-situ resin ablation according to the present invention.

[0024] Figure 7 This is a comparison diagram of the interfacial shear strength of carbon fibers after in-situ resin ablation according to the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings. All reagents used are commercially available.

[0026] Example 1

[0027] To address the cracking damage of the epoxy resin matrix in carbon fiber reinforced epoxy resin matrix composites during service, a method for in-situ repair of damage in these composites is provided, with the following process steps:

[0028] Step 1: Weigh 10 g of chromium oxide (Cr2O3) powder with a purity of 99% and a particle size of approximately 80 nm and 8 g of titanium dioxide (TiO2) powder with a purity of 99% and a particle size of approximately 50 nm, and add them to 144 g of anhydrous ethanol; premix using mechanical stirring (300 r / min for 15 min), and then disperse using ultrasonication (100 W for 10 min) to break up agglomerated particles and improve uniformity. The resulting Cr2O3 / TiO2 catalyst suspension is light green, uniformly dispersed, and has good stability. No obvious sedimentation was observed after standing for 1 h.

[0029] Step 2: Wipe the damaged area with acetone solution to remove oil, dust and loose debris, then blow it dry with compressed air to ensure the damaged area is clean and dry, providing a sufficient contact interface for the subsequent catalytic degradation reaction;

[0030] Step 3: The prepared Cr2O3 / TiO2 catalyst suspension is uniformly sprayed onto the surface of the damaged area using a pneumatic spraying method, with the spraying thickness controlled to be about 50 μm; after spraying, it is left to stand at room temperature for 10 min to allow the ethanol solvent to evaporate naturally, forming a thin layer of composite catalyst with firm adhesion and uniform surface.

[0031] Step 4: Place the area sprayed with composite catalyst under an infrared heating device and heat it with a mid-wave infrared radiation source with a wavelength of 0.76μm. Set the irradiation power to 380 W and the heating time to 5 min. After infrared treatment, the resin matrix in the damaged area is selectively removed, and the fiber structure remains intact without secondary damage.

[0032] Step 5: After infrared heating is completed, the volatile products and catalyst particles generated by the reaction are removed by a vacuum pumping system; then, the surface of the treated area is rinsed with a low-pressure dry air stream to remove residual particles; finally, a lint-free wiping cloth with a small amount of ethanol is used to clean the surface to ensure that the area is clean and the fibers are well exposed.

[0033] Step Six: Place the cleaned damaged area of ​​the sample in a vacuum flow system and use the vacuum flow method for resin repair. Select the same type of epoxy resin and curing agent system as the original substrate (mass ratio 100:35). Control the vacuum degree at -0.085 MPa and maintain it for 10 min to remove pores and adsorbed gases. Set the flow temperature to 45 ℃ to reduce resin viscosity and enhance wettability. Flow time is 5 min until the damaged area is completely filled. After completion, cure at 120 ℃ for 2 h using a heat repair instrument to ensure sufficient resin crosslinking.

[0034] During this process, the Cr2O3 / TiO2 composite catalyst layer rapidly heats up after absorbing infrared energy. TiO2, acting as a high thermal conductivity carrier, ensures uniform heat transfer and prevents localized overheating. Simultaneously, Cr2O3 undergoes a valence state transition under thermal excitation (Cr2O3 / TiO2 / TiO2 / TiO2 / TiO2). 3+ / Cr 2+ (Cyclic), under the synergistic effect of TiO2, surface active oxygen and oxygen vacancies are generated; these active species can induce the polarization of covalent bonds such as CO, CC, CN in epoxy resin molecules and reduce their fracture energy, thereby realizing the local catalytic cracking of the resin matrix; the cracking products are mainly CO, CO2 and low molecular weight hydrocarbon gases, which volatilize and escape under the action of heat flow, and the redox properties of TiO2 further promote the surface carbon oxidation reaction.

[0035] Example 2

[0036] To address fiber fracture damage in carbon fiber reinforced epoxy resin composites during service, an in-situ repair method based on a MnO2 / TiO2 composite catalytic system is provided. The specific steps are as follows:

[0037] Step 1: Weigh 10 g of 99% pure manganese dioxide (MnO2) powder with an average particle size of approximately 500 nm and 15 g of 99% pure titanium dioxide (TiO2) powder with a particle size of approximately 70 nm, and add them to 250 g of ethylene glycol as a dispersion medium. Premix using mechanical stirring (800 r / min, 10 min), then ultrasonically disperse (100 W, 10 min) to break up agglomerated particles and improve mixing uniformity. The resulting MnO2 / TiO2 catalyst suspension is black, uniformly dispersed, and has good stability. No significant sedimentation was observed after standing for 1 h, meeting the requirements of the spraying process.

[0038] Step 2: Wipe the surface of the damaged area with acetone solution to remove oil, dust and loose debris; then blow it dry with compressed air to ensure that the surface of the damaged area is clean and dry, so as to provide a sufficient contact interface for the subsequent catalytic degradation reaction.

[0039] Step 3: The prepared MnO2 / TiO2 catalyst suspension was uniformly sprayed onto the surface of the damaged area using an atomization spraying method, with the deposition thickness controlled to be approximately 200 μm. After spraying, the mixture was allowed to stand at room temperature for 10 min to allow the ethylene glycol solvent to evaporate naturally, and the catalyst was uniformly adhered to the surface to form a dense and continuous composite catalyst layer.

[0040] Step 4: Place the area where the composite catalyst is sprayed under the infrared heating device and heat it with a mid-wave infrared radiation source with a wavelength of 10μm. Set the irradiation power to 250 W and the heating time to 12 min. The resin matrix in the damaged area is selectively ablated, exposing the complete carbon fiber structure.

[0041] Step 5: After infrared heating is completed, start the vacuum pumping system (vacuum degree -0.08 MPa) to remove the gaseous products and residual catalyst particles generated by pyrolysis. Then, use a low-pressure dry air stream to rinse the surface of the treated area to remove surface particles, and then use a lint-free cloth soaked in ethanol to clean the surface to ensure that the fiber interface is clean and free of residual impurities.

[0042] Step Six: Cutting and Removing Broken Fibers: Based on the layup angle and number of layers of the original composite material, cut carbon fiber prepreg of the same specifications and lay it in layers within the repair area, ensuring it aligns with the original layer structure to reduce fiber end peeling and stress concentration. Then, use a vacuum infusion method for resin infusion repair. Specific process parameters are as follows: use epoxy resin and curing agent of the same type as the raw materials (mass ratio 100:35); set the infusion temperature to 45℃ to reduce resin viscosity and improve fiber wettability; control the vacuum degree at -0.085 MPa and hold the pressure for 10 minutes to ensure sufficient air bubble removal; infusion time is approximately 12 minutes until the repair area is completely filled; cure at 120℃ for 2 hours using a heat repair machine to complete the repair.

[0043] In this process, TiO2 absorbs infrared energy and rapidly heats up, forming a uniform thermal field. This promotes the valence state transformation of MnO2 and the generation of oxygen vacancies. Under thermal excitation, MnO2 undergoes Mn oxidation. 4+ / Mn 3+ The redox cycle releases surface active oxygen and oxygen vacancies. These active species can induce the polarization of C–O, C–C and C–N bonds in epoxy resin molecules and reduce their breaking energy, thereby achieving directional catalytic cracking of the resin matrix. At the same time, TiO2 has good thermal conductivity and surface oxidation ability at high temperature, which can further oxidize and remove carbon deposits.

[0044] Example 3

[0045] To address fiber fracture damage in carbon fiber reinforced unsaturated polyester resin matrix composites during service, an in-situ repair method based on a CuO / TiO2 composite catalytic system is provided for fiber reinforced resin matrix composites.

[0046] Step 1: Weigh 10 g of copper oxide (CuO) powder with a purity of 99% and an average particle size of approximately 500 nm, and 15 g of titanium dioxide (TiO2) powder with a purity of 99% and a particle size of approximately 100 nm, and add them to 375 g of deionized water; premix by mechanical stirring (800 r / min, 10 min), and then ultrasonically disperse (200 W, 5 min) to break up agglomerated particles and improve mixing uniformity; the resulting CuO / TiO2 catalyst suspension is black, uniformly dispersed, and has good stability. After standing for 1 h, there is no obvious sedimentation, which meets the requirements of the spraying process.

[0047] Step 2: Wipe the surface of the damaged area with acetone solution to remove oil, dust and loose debris; then blow it dry with compressed air to ensure that the surface of the damaged area is clean and dry, so as to provide a sufficient contact interface for the subsequent catalytic degradation reaction.

[0048] Step 3: The prepared CuO / TiO2 catalyst suspension is uniformly sprayed onto the surface of the damaged area using a pneumatic spraying method, and the deposition thickness is controlled to be about 200 μm. After spraying, the mixture is left to stand at room temperature for 30 min to allow the deionized water solvent to evaporate naturally, and the catalyst is uniformly attached to the surface to form a dense and continuous composite catalyst layer.

[0049] Step 4: Place the damaged area of ​​the sprayed composite catalyst under the infrared heating device and heat it with a mid-wave infrared radiation source with a wavelength of 25 μm. The irradiation power is set to 300 W and the heating time is 8 min. The resin matrix of the damaged area is selectively ablated, exposing the complete carbon fiber structure.

[0050] Step 5: After infrared heating is completed, start the vacuum pumping system (vacuum degree -0.08 MPa) to remove the gaseous products and residual catalyst particles generated by pyrolysis; then rinse the surface of the treated area with a low-pressure dry air stream to remove surface particles; then use a lint-free wiping cloth soaked in ethanol to clean the surface to ensure that the fiber interface is clean and free of residual impurities.

[0051] Step Six: Cutting and Removing Broken Fibers: Based on the layup angle and number of layers of the original composite material, cut carbon fiber prepreg of the same specifications and lay it in layers within the repair area, ensuring it aligns with the original layer structure to reduce fiber end peeling and stress concentration. Then, use a vacuum infusion method for resin infusion repair. Specific process parameters are as follows: Use the same type of unsaturated polyester resin and accelerator as the raw material (mass ratio 100:30); set the infusion temperature to 40 ℃ to reduce resin viscosity and improve fiber wettability; control the vacuum degree at -0.09 MPa and hold for 5 minutes to ensure sufficient air bubble removal; infusion time is approximately 12 minutes until the repair area is completely filled; then, use a heat repair machine to cure at 80 ℃ for 2 hours to complete the repair.

[0052] After absorbing infrared energy, TiO2 rapidly heats up and forms a uniform thermal field, promoting the valence state transformation of CuO and the generation of oxygen vacancies. Under thermal excitation, CuO undergoes Cu oxidation. 2+ / Cu + The redox cycle releases surface active oxygen and oxygen vacancies, which can induce oxidative cracking of polyester segments; at the same time, TiO2 has good thermal conductivity and surface oxidation ability at high temperature, which can further oxidize and remove carbon deposits.

[0053] Comparative Example 1

[0054] To illustrate the effects of infrared heating time and power on resin ablation efficiency, comparative examples 1-2 were designed.

[0055] Unlike Example 1, step four uses a mid-wave infrared radiation source with a wavelength of 0.76 μm for heating, with an irradiation power set to 150 W and a heating time of 2 min. Steps five and six are omitted, and the removal of the resin matrix in the damaged area is compared.

[0056] Comparative Example 2

[0057] Unlike Example 1, step four uses a mid-wave infrared radiation source with a wavelength of 0.76 μm for heating, with an irradiation power set to 450 W and a heating time of 15 min. Steps five and six are omitted, and the removal of resin matrix in the damaged area is compared.

[0058] pass Figure 2 , 3 Table 1 shows the microscopic effects of in-situ resin ablation in Comparative Example 1 and Comparative Examples 1-2. It can be seen from the figure that the infrared heating ablation of resin in Comparative Example 1 has lower energy and shorter time, resulting in incomplete resin decomposition and more residue. In contrast, the infrared heating ablation of resin in Comparative Example 2 has higher energy and longer time, resulting in greater heat impact on the carbon fiber surface and excessive oxidation of the surface.

[0059] Comparative Example 3

[0060] To illustrate the advantages of composite catalysts, comparative examples 3-6 were designed.

[0061] Unlike Example 1, in step one, only 10 g of chromium oxide (Cr2O3) powder with a purity of 99% and a particle size of about 80 nm was weighed and added to 80 g of anhydrous ethanol. After being mixed evenly, it was used as a catalyst coating material. Steps five and six were omitted to compare the removal of the resin matrix in the damaged area.

[0062] Comparative Example 4

[0063] Unlike Example 1, in step one, only 12 g of titanium dioxide (TiO2) powder with a purity of 99% and a particle size of about 50 nm was weighed and added to 120 g of anhydrous ethanol. After being mixed evenly, it was used as a catalyst coating material. Steps five and six were omitted to compare the removal of the resin matrix in the damaged area.

[0064] Comparative Example 5

[0065] Unlike Example 1, in step one, only 10 g of manganese dioxide (MnO2) powder with a purity of 99% and an average particle size of about 150 nm was weighed and added to 100 g of ethylene glycol. After being mixed evenly, it was used as a catalyst coating material. Steps five and six were omitted to compare the removal of the resin matrix in the damaged area.

[0066] Comparative Example 6

[0067] Unlike Example 1, in step one, only 10 g of copper oxide (CuO) powder with a purity of 99% and an average particle size of about 500 nm was weighed and added to 150 g of deionized water. After mixing evenly, it was used as a catalyst coating material. Steps five and six were omitted to compare the removal of the resin matrix in the damaged area.

[0068] The surface properties of the carbon fibers after in-situ resin ablation in the above examples and Comparative Examples 1-2 were tested, as detailed in Table 1. The tensile properties of the repaired damaged areas in Examples 1-3 were tested, as detailed in Table 2.

[0069] Table 1. Surface element and functional group distribution of carbon fibers after resin ablation.

[0070]

[0071] pass Figure 1 , Figure 2 Macro / micro morphology analysis shows that the in-situ repair method of the fiber-reinforced resin matrix composite material of the present invention can realize in-situ and directional ablation of resin on the fiber surface. The carbon fiber surface after resin ablation is smooth and free of residual resin or carbon deposits, providing a good interface for subsequent repair.

[0072] Analysis of Table 1 shows that, compared with the original carbon fiber, the oxygen element and oxygen-containing functional groups on the surface of the carbon fiber after resin ablation in Examples 1-3 increased slightly, indicating that the carbon fiber was slightly oxidized during the resin ablation process. However, the increase in oxygen-containing functional groups helps to improve the surface activity of the carbon fiber, which is beneficial to improving the bonding strength of the repair interface.

[0073] Further analysis Figure 5 It can be seen that the I of the carbon fiber after the resin dissolves G / I D The results are very close to those of the original carbon fiber, which indicates that the resin melting process did not affect the graphitization structure of the carbon fiber, thus helping to maintain its mechanical properties.

[0074] Further analysis Figure 6 It can be seen that after the resin is dissolved, the tensile strength of the carbon fiber monofilament can be maintained at more than 90% of the original carbon fiber, and the Young's modulus can be maintained at about 95% of the original carbon fiber. This indicates that the resin dissolution process has little effect on the tensile strength of the carbon fiber monofilament and greatly preserves the tensile strength of the carbon fiber monofilament.

[0075] Further analysis Figure 7 It can be seen that the interfacial shear strength of the carbon fiber after resin melting can maintain more than 85% of that of the original carbon fiber, indicating that the repaired interface can achieve good load transfer.

[0076] Table 2 Performance test results of the repaired device

[0077]

[0078] Analysis of Table 2 shows that, for resin cracking damage, the in-situ repair method for the damaged area of ​​fiber-reinforced resin matrix composites can restore the tensile properties to more than 95% of the undamaged area; for fiber breakage damage, the in-situ repair method for the damaged area of ​​fiber-reinforced resin matrix composites can restore the tensile properties to more than 85% of the undamaged area.

[0079] pass Figure 2 and 4 Comparing the microscopic images of the in-situ resin ablation in Examples 1 and 3-6, it can be seen from the figures that the ablation effect of Comparative Examples 3-6 was poor when only one of Cr2O3, MnO2, CuO, or TiO2 was used. Specifically, Comparative Examples 3, 5, and 6 used Cr2O3, MnO2, or CuO alone, without the addition of TiO2, resulting in varying degrees of carbon deposition on the fiber surface; while Comparative Example 4, using TiO2 alone, resulted in incomplete resin decomposition, all of which would affect the bonding performance between the fiber and the newly added resin.

Claims

1. A method for in-situ repair of damaged areas in fiber-reinforced resin-based composite materials, characterized in that, Includes the following steps: A catalyst suspension was obtained by dispersing transition metal oxides in a solvent, stirring, and ultrasonically dispersing them. Remove debris, dust, and oil from the damaged area of ​​the composite material. A catalyst coating is formed by uniformly depositing a catalyst suspension onto the surface of the damaged area. Infrared heating is applied to the damaged area of ​​the deposited catalyst coating to promote the thermal decomposition and ablation of the resin in the damaged area, thereby completing the in-situ ablation of the resin in the damaged area. Remove residual products from the damaged area; The original matrix type of fiber and resin are selected and the damaged area is repaired in situ through vacuum flow process and heat curing.

2. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 1, characterized in that, The transition metal oxide is a composition of Cr2O3, MnO2, or CuO and TiO2 in a mass ratio of 1:0.8 to 1:1.5; the solvent is one of deionized water, ethanol, isopropanol, or ethylene glycol.

3. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 2, characterized in that, The purity of the transition metal oxide is 99%, and the particle size range is 50~500 nm.

4. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 2, characterized in that, The mass ratio of the transition metal oxide to the solvent is 1:8 to 1:

15.

5. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 4, characterized in that, When the transition metal oxide is mixed with the solvent, the stirring speed is 300-800 r / min and the time is 10-15 min, and the power of the ultrasonic disperser is 100-200W and the time is 5-10 min.

6. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 1, characterized in that, The catalyst suspension is deposited on the surface of the damaged area by spraying or brushing.

7. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 6, characterized in that, The thickness of the coating after the catalyst suspension is deposited is 50~200 μm.

8. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 1, characterized in that, The infrared heating uses infrared radiation with a wavelength of 0.76~25 μm, a heating power of 200~400 W, and a heating time of 3~12 min.

9. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 1, characterized in that, The vacuum degree of the vacuum flow is controlled at -0.085 to -0.1 MPa, and the flow temperature is 30 to 45°C.

10. The in-situ repair method for damaged areas of fiber-reinforced resin-based composite materials according to claim 1, characterized in that, The fibers in the fiber-reinforced resin matrix composite material are carbon fiber or glass fiber; the resin in the fiber-reinforced resin matrix composite material is epoxy resin, unsaturated polyester resin, vinyl ester resin or phenolic resin; the in-situ repair method is applicable to resin cracking and fiber breakage damage.

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