A method for repairing a scratch on a carbon fiber composite panel

Abstract

The application provides a carbon fiber composite plate scratch repairing method and belongs to the technical field of carbon fiber composite material repairing. The method comprises the following steps: identifying a part to be repaired, determining the damage condition of the part to be repaired; pretreating the part to be repaired; preparing a repairing material slurry, then spraying and curing to obtain a coating, and completing the repairing treatment; the repairing material slurry is mainly prepared from carbon fibers, epoxy resin and modified carbon nanotubes. The carbon fiber composite plate repaired by the method has a tensile strength recovery rate of 98%, the interface between the repairing area and the base material is firmly combined, and no falling phenomenon occurs after 500 cold and hot cycles.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite material repair technology, and in particular to a method for repairing scratches on carbon fiber composite plates. Background Technology

[0002] Carbon fiber composites, due to their superior properties such as high specific strength, high specific modulus, fatigue resistance, and corrosion resistance, have been widely used in aerospace, automotive manufacturing, and wind power generation. However, during manufacturing, assembly, and use, carbon fiber composite components inevitably suffer various types of damage, with surface scratches being the most common form. Although initially they may only affect appearance, if not repaired promptly, under continuous loads and environmental factors, scratches can expand into more serious structural damage, affecting the service life and safety of the components.

[0003] In existing technologies, the repair methods for carbon fiber composites mainly include two techniques: mechanical repair and adhesive repair. Mechanical repair treats surface defects through grinding and polishing, but the grinding depth must be controlled to avoid damaging the internal fiber structure. Adhesive repair, on the other hand, achieves damage repair by pasting patches or filling with repair materials, and is considered the repair technology with the best overall performance and the broadest application prospects. For example, patent application CN119239008A discloses a rapid repair method for aerospace carbon fiber composites, which involves cleaning, damage assessment, filling with repair materials, and autoclave curing. The repair materials include epoxy resin and chopped carbon fiber filaments. Patent application CN116749561A discloses a method for repairing carbon fiber composites under microwave plasma surface treatment, which improves surface activity through microwave plasma treatment, followed by pasting T800 prepreg for repair.

[0004] Carbon nanotubes (CNTs), as one-dimensional nanomaterials, possess extremely high mechanical properties and unique interfacial effects, making them considered ideal reinforcing phases for composite materials. One study used aminated carbon nanotube-reinforced resin pre-coating technology to repair carbon / glass laminates. The results showed that when the amount of aminated carbon nanotubes added increased to 3%, the compressive strength of the repaired laminate increased by 21% compared to the unreinforced group. Another study introduced multi-walled carbon nanotubes (MWCNTs) into UV-cured in-situ repair materials, finding that the flexural strength and modulus of the composite material increased by 14.01% and 45.2%, respectively, after the addition of MWCNTs.

[0005] However, the existing technology still has the following technical problems: (1) Carbon nanotubes are prone to agglomeration in the resin matrix and have poor dispersibility, resulting in microscopic defects inside the repair layer; (2) The interfacial bonding strength between the repair material and the matrix is ​​insufficient, and the performance recovery rate after repair needs to be improved.

[0006] Therefore, it is of great significance to develop a method for repairing scratches on carbon fiber composite boards that can effectively improve interfacial bonding and achieve rapid curing. Summary of the Invention

[0007] The purpose of this invention is to provide a method for repairing scratches on carbon fiber composite plates, so as to solve the problems of insufficient interfacial bonding strength between the repair material and the matrix and low performance recovery rate after repair in the prior art.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for repairing scratches on carbon fiber composite sheets, comprising the following steps: (1) Identify the part to be repaired and determine the extent of damage to the part to be repaired; (2) Pre-treat the area to be repaired; (3) Prepare the repair material slurry, then spray and cure it to obtain a coating and complete the repair treatment; The repair material slurry is mainly made of carbon fiber, epoxy resin and modified carbon nanotubes.

[0009] Preferably, in step (1), the specific process of the pretreatment is as follows: removing the surface oxide layer and stains, polishing, and finally wiping.

[0010] Preferably, the polishing area extends 2-3 mm beyond the edge of the scratch to form a gentle bevel.

[0011] Preferably, the mass ratio of the carbon fiber, epoxy resin, and modified carbon nanotubes is 20~40:100:5~10.

[0012] Preferably, the modified carbon nanotubes are prepared by: S1: Mix carbon nanotubes with hydrochloric acid solution and reflux at 60~80℃ for 6~8h to obtain carboxylated carbon nanotubes; S2: Carboxylated carbon nanotubes are dispersed in water, ammonia is added, and then tetraethyl silicate is added dropwise to react and obtain modified carbon nanotubes.

[0013] Preferably, the mass ratio of the carboxylated carbon nanotubes to tetraethyl silicate is 1:0.6~0.8.

[0014] Preferably, the repair material slurry also includes a photoinitiator.

[0015] Preferably, the repair material slurry is prepared by adding a photoinitiator to an epoxy resin, and then adding carbon fibers and modified carbon nanotubes to obtain the repair material slurry.

[0016] Preferably, the spraying pressure is 0.4~0.6 MPa, the spraying distance is 20~30 cm, and the coating thickness is controlled at 0.5~2 mm.

[0017] Preferably, the curing is performed using an ultraviolet-infrared composite light source with a wavelength of 365nm+ mid-wave infrared.

[0018] The beneficial effects of this invention are: (1) In this invention, carbon nanotubes are modified by hydrochloric acid carboxylation and silica grafting. The hydroxyl groups on the surface of silica can form hydrogen bonds with epoxy resin. At the same time, silica can fill the microscopic defects on the surface of carbon fibers to form a mechanical embedding effect. The introduction of silica has a bridging effect and significantly improves the interfacial properties between different reinforcing phases in the repair material.

[0019] (2) The carbon fiber composite plate repaired by the method of the present invention has a tensile strength recovery rate of up to 98%, the interface between the repaired area and the substrate is firmly bonded, and there is no detachment after 500 cycles of hot and cold.

[0020] (3) The repair method of the present invention is simple to operate. The scratches can be repaired in one spraying process, which not only meets the structural repair requirements, but also has good flatness and high appearance quality after repair. Detailed Implementation

[0021] This invention provides a method for repairing scratches on carbon fiber composite sheets, comprising the following steps: (1) Identify the part to be repaired and determine the extent of damage to the part to be repaired; (2) Pre-treat the area to be repaired; (3) Prepare the repair material slurry, then spray and cure it to obtain a coating and complete the repair treatment; The repair material slurry is mainly made of carbon fiber, epoxy resin and modified carbon nanotubes.

[0022] In this invention, the specific process of the pretreatment in step (1) is as follows: removing the surface oxide layer and stains, polishing, and finally wiping.

[0023] In this invention, the polishing range extends 2-3 mm beyond the edge of the scratch, preferably 3 mm, to form a gentle bevel.

[0024] In this invention, the mass ratio of carbon fiber, epoxy resin and modified carbon nanotubes is 20~40:100:5~10, preferably 25~35:100:6~9, and more preferably 30:100:7~8.

[0025] In this invention, the method for preparing the modified carbon nanotubes is as follows: S1: Mix carbon nanotubes with hydrochloric acid solution and reflux at 60~80℃ for 6~8h to obtain carboxylated carbon nanotubes; S2: Carboxylated carbon nanotubes are dispersed in water, ammonia is added, and then tetraethyl silicate is added dropwise to react and obtain modified carbon nanotubes.

[0026] In this invention, the mass ratio of carboxylated carbon nanotubes to tetraethyl silicate is 1:0.6~0.8, specifically 1:0.6, 1:0.7, or 1:0.8.

[0027] In this invention, the reaction time in step S2 is 2 to 4 hours, specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours.

[0028] In this invention, the repair material slurry also includes a photoinitiator.

[0029] In this invention, there are no special restrictions on the type of photoinitiator. In the examples and comparative examples, diaryliodonium salt is preferably used as the photoinitiator.

[0030] In this invention, the repair material slurry is prepared by adding a photoinitiator to an epoxy resin, and then adding carbon fibers and modified carbon nanotubes to obtain the repair material slurry.

[0031] In this invention, the spraying pressure is 0.4~0.6 MPa, preferably 0.5 MPa; the spraying distance is 20~30cm, preferably 22~28cm, and more preferably 25cm; the coating thickness is controlled at 0.5~2 mm, specifically 0.5mm, 1.0mm, 1.5mm, or 2.0mm.

[0032] In this invention, the curing is performed using an ultraviolet-infrared composite light source with a wavelength of 365nm+ mid-wave infrared.

[0033] In this invention, after the coating has been cured, it still needs to undergo surface treatment and quality inspection.

[0034] In this invention, the surface treatment includes sequential grinding and polishing; the quality inspection is performed using X-ray non-destructive testing.

[0035] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1

[0037] 100 mL of 2 mol / L hydrochloric acid solution and 5 g of carbon nanotubes were mixed and refluxed at 70 °C for 7 h. After the reaction, the mixture was filtered, washed until neutral, and dried to obtain carboxylated carbon nanotubes. 100 mL of deionized water was added to 5 g of carboxylated carbon nanotubes, and the mixture was sonicated for 30 min. Then, 1.5 mL of 25% ammonia solution was added, followed by the slow addition of 3.5 g of tetraethyl silicate at a dropping rate of 3 mL / min. After the addition was complete, the mixture was reacted at room temperature for 3 h. The reaction product was filtered, washed repeatedly with ethanol and deionized water, and dried to obtain modified carbon nanotubes.

[0038] Preparation of repair material slurry: Weigh carbon fiber (T700 carbon fiber short filaments, 3 mm in length), alicyclic epoxy resin CY179 and modified carbon nanotubes according to a mass ratio of 30:100:8. First, add diaryliodonium salt photoinitiator (photoinitiator accounts for 0.5% of the mass of alicyclic epoxy resin CY179) to the alicyclic epoxy resin CY179, and then add modified carbon nanotubes and carbon fiber. Disperse ultrasonically for 30 min to obtain repair material slurry.

[0039] Select a carbon fiber composite board with scratches on the surface (size 200 mm × 200 mm × 3 mm, scratch depth 0.5 mm), wipe off the surface oil with acetone, and then use 400 grit sandpaper to sand the scratched area, extending the sanding range 2.5 mm beyond the edge of the scratch to form a gentle bevel. After sanding, wipe it clean with anhydrous ethanol and let it dry for later use.

[0040] The prepared carbon fiber composite sheets were loaded into the spraying equipment. The spraying pressure was set to 0.5 MPa and the spraying distance to 25 cm. The pre-treated scratched areas were sprayed, and the coating thickness was controlled to be 0.8 mm. Then, a 365 nm ultraviolet LED light source was used with an ultraviolet power density of 10 W / cm². 2 The infrared temperature is controlled at 80℃ for curing, and the curing time is 2 minutes. After curing, fine grinding and polishing are performed to make the surface flatness of the repaired carbon fiber composite board 0.05mm. X-ray non-destructive testing is then performed.

[0041] Example 2

[0042] The difference from Example 1 is that the amount of tetraethyl silicate added is 3g (the mass ratio of carboxylated carbon nanotubes to tetraethyl silicate is 1:0.6), while all other conditions are the same.

[0043] Example 3

[0044] The difference from Example 1 is that the amount of tetraethyl silicate added is 4g (the mass ratio of carboxylated carbon nanotubes to tetraethyl silicate is 1:0.8), while all other conditions are the same.

[0045] Example 4

[0046] The difference from Example 1 is that the mass ratio of carbon fiber, alicyclic epoxy resin CY179 and modified carbon nanotubes is 20:100:8, while all other conditions are the same.

[0047] Example 5

[0048] The difference from Example 1 is that the mass ratio of carbon fiber, alicyclic epoxy resin CY179 and modified carbon nanotubes is 40:100:8, while all other conditions are the same.

[0049] Example 6

[0050] The difference from Example 1 is that the mass ratio of carbon fiber, alicyclic epoxy resin CY179 and modified carbon nanotubes is 30:100:5, while all other conditions are the same.

[0051] Example 7

[0052] The difference from Example 1 is that the mass ratio of carbon fiber, alicyclic epoxy resin CY179 and modified carbon nanotubes is 30:100:10, while all other conditions are the same.

[0053] Comparative Example 1

[0054] The difference from Example 1 is that carbon nanotubes were added directly, while all other conditions were the same.

[0055] Comparative Example 2

[0056] The difference from Example 1 is that no modified carbon nanotubes are added. The preparation of the repair material slurry is as follows: carbon fiber (T700 carbon fiber short filaments, 3 mm in length) and alicyclic epoxy resin CY179 are weighed at a mass ratio of 30:100. First, a diaryliodonium salt photoinitiator (the photoinitiator accounts for 0.5% of the mass of alicyclic epoxy resin CY179) is added to the alicyclic epoxy resin CY179, and then the carbon fiber is added. The mixture is ultrasonically dispersed for 30 minutes to obtain the repair material slurry. All other conditions are the same.

[0057] Performance tests were conducted on the carbon fiber composite panels after the above-mentioned repair treatment: (1) Tensile properties were tested according to ASTM D3039 standard. The strength recovery rate after repair (%) = strength after repair / strength of the original undamaged plate × 100%. The tensile strength of the original undamaged carbon fiber composite plate was 850 MPa. The test results are shown in Table 1.

[0058] (2) Cold and hot cycle test conditions: -55℃~150℃, each temperature is maintained for 30 min, the number of cycles is 500, observe whether the repair area has defects such as debonding and blistering, and the surface flatness is measured by laser confocal microscope. The test results are shown in Table 1.

[0059] Table 1 Test results of the repaired carbon fiber composite panels

[0060] Comparing the test results of Examples 1, 2 and 3, it can be seen that the tensile strength recovery rate increases with the increase of TEOS dosage, reaching a maximum of 99.8%, which proves that the addition of modified carbon nanotubes can improve the effect of repair treatment.

[0061] Comparing the test results of Examples 1, 4, and 5, it can be seen that the repair effect is best when the amount of carbon fiber added accounts for 30% of the epoxy resin mass. Comparing the test results of Examples 1, 6, and 7, it can be seen that the higher the amount of modified carbon nanotubes added, the better the repair effect. However, considering the economy and slurry viscosity, adding according to Example 1 can already achieve excellent repair effects.

[0062] Comparing the test results of Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that adding modified carbon nanotubes increased the tensile strength recovery rate by 5.8 percentage points compared to unmodified carbon nanotubes, and by 18 percentage points compared to when no carbon nanotubes were added.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for repairing scratches on carbon fiber composite panels, characterized in that, Includes the following steps: (1) Identify the part to be repaired and determine the extent of damage to the part to be repaired; (2) Pre-treat the area to be repaired; (3) Prepare the repair material slurry, then spray and cure it to obtain a coating and complete the repair treatment; The repair material slurry is mainly made of carbon fiber, epoxy resin and modified carbon nanotubes.

2. The method for repairing scratches on carbon fiber composite plates according to claim 1, characterized in that, In step (1), the specific process of the pretreatment is as follows: removing the surface oxide layer and stains, polishing, and finally wiping.

3. The method for repairing scratches on carbon fiber composite plates according to claim 2, characterized in that, The polishing area extends 2-3mm beyond the edge of the scratch, forming a gentle bevel.

4. The method for repairing scratches on carbon fiber composite sheets according to any one of claims 1 to 3, characterized in that, The mass ratio of the carbon fiber, epoxy resin, and modified carbon nanotubes is 20~40:100:5~10.

5. The method for repairing scratches on carbon fiber composite plates according to claim 4, characterized in that, The method for preparing the modified carbon nanotubes is as follows: S1: Mix carbon nanotubes with hydrochloric acid solution and reflux at 60~80℃ for 6~8h to obtain carboxylated carbon nanotubes; S2: Carboxylated carbon nanotubes are dispersed in water, ammonia is added, and then tetraethyl silicate is added dropwise to react and obtain modified carbon nanotubes.

6. The method for repairing scratches on carbon fiber composite plates according to claim 5, characterized in that, The mass ratio of the carboxylated carbon nanotubes to tetraethyl silicate is 1:0.6~0.

8.

7. The method for repairing scratches on carbon fiber composite plates according to claim 5 or 6, characterized in that, The repair material slurry also includes a photoinitiator.

8. The method for repairing scratches on carbon fiber composite plates according to claim 7, characterized in that, The repair material slurry is prepared by adding a photoinitiator to epoxy resin, followed by adding carbon fiber and modified carbon nanotubes to obtain the repair material slurry.

9. The method for repairing scratches on carbon fiber composite sheets according to claim 2, 3, 6, or 8, characterized in that, The spraying pressure is 0.4~0.6 MPa, the spraying distance is 20~30 cm, and the coating thickness is controlled at 0.5~2 mm.

10. The method for repairing scratches on carbon fiber composite plates according to claim 1, characterized in that, The curing process uses an ultraviolet-infrared composite light source with a wavelength of 365nm+ mid-wave infrared.

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