Carbon fiber composite material honeycomb surface pinhole recess filling and verification method thereof

Abstract

The invention provides a carbon fiber composite material honeycomb surface pinhole recess filling method. The method comprises the following steps: preparing a composite material structure repairing adhesive; pouring an organic solvent into the sprinkling can, and spraying the organic solvent on the marked areas of the pinholes and the small recesses; the spraying time of the organic solvent does not exceed 10 seconds, and blade coating of the repairing adhesive is completed within 30 seconds after spraying; by means of the volatilization effect of volatile matter in the organic solvent, the glue solution is dripped into the pinholes and the small concave areas to be filled, and the smooth and continuous part surface is obtained; after the repairing glue is scraped, the composite material honeycomb part subjected to scrape coating is placed in a curing oven to be cured; after curing is completed, aluminum oxide waterproof abrasive paper is used for polishing the blade coating area so as to remove excessive glue liquid on the surface of the part; meanwhile, the invention further provides a verification method for the honeycomb surface of the carbon fiber composite material. Pinholes and small pits on the surface of the carbon fiber composite material honeycomb part can be filled, and the composite material honeycomb part meets the primer spraying requirement after a glue spraying mode is adopted.

Description

Technical Field

[0001] The present application belongs to the technical field of resin-based carbon fiber composite materials, and in particular, relates to a method for filling pinhole depressions on the surface of a carbon fiber composite honeycomb and verifying the method. Background Art

[0002] Carbon fiber composite materials have excellent properties such as high specific stiffness and high specific strength, and are widely used in aerospace equipment manufacturing. Honeycomb component manufacturing is an effective means to achieve lightweight high-performance composite materials. Resin-based carbon fiber composite honeycomb sandwich components are widely used in helicopter and fixed-wing aircraft fuselage structures. Safety is an important indicator of aviation equipment. Composite honeycomb sandwich components generally use glass fiber prepreg for different potential corrosion protection as the first layer on the outer surface of the part. It is a functional material and is mainly used for flame retardancy. At the same time, in order to meet the lightweight design requirements of the aircraft, the surface film is generally removed from the first layer at the honeycomb core position to meet the weight reduction requirements, as shown below Figure 1 shown.

[0003] At present, in the process of honeycomb structure parts forming, the honeycomb core of the wall panel mainly transmits pressure to the lower skin during the curing process. However, the honeycomb core is a weak rigidity material. When the external pressure is too large, it is easy to cause defects such as honeycomb core collapse, excessive shrinkage of honeycomb chamfers, and changes in honeycomb shape.

[0004] During the curing process, the upper and lower panels of the honeycomb core are bonded by adhesive film to form a closed inner cavity. Vacuuming can discharge the air trapped in the skin. Therefore, for air exhaust, the higher the pressure, the better. However, since the honeycomb core forms a closed inner cavity by bonding the upper and lower panels of the honeycomb core by adhesive film, after bagging, under the action of external pressure, negative pressure is easily formed in the inner cavity, causing the resin in the prepreg in the lower skin of the honeycomb to climb to the honeycomb core cell wall, such as Figure 2 As shown. The parts show vacuum on the film surface, characterized by a large porosity. Pinholes, small depressions, pits and other surface defects are formed on the composite parts. The presence of surface defects makes it difficult for composite honeycomb parts to obtain a smooth and uniform surface, making it difficult to meet the requirements of subsequent honeycomb parts painting.

[0005] Among them, pinholes refer to small holes or microporous surface defects that penetrate the surface of cured composite parts, generally with a diameter of 0.25mm (or less). Small pits are surface defects that can be filled with surface levelers or pit filling materials, and generally have a depth of no more than 0.05mm.

[0006] During the molding process of composite honeycomb parts, pinholes and small depressions on the surface of the parts are unavoidable. However, the surface quality requirements of composite materials are extremely high. The surface with pinholes and small depressions needs to be repaired to meet the subsequent spraying of primer (paint) and topcoat. The method for repairing surface pinholes and small depressions is to scrape the hole-filling putty on the surface of the part. The function is a colored paste, which is used to fill the pinholes before painting to obtain a smooth and uniform surface. Because the filling putty is granular and not easy to fill into the pinholes, the effect of this method is not ideal, it is difficult to meet the surface quality requirements of composite parts, and it affects the subsequent primer spraying. The cycle is long, and it often requires 2-3 times of repeated scraping and drying to meet the surface quality requirements of the parts. At the same time, the primer (paint) spraying can meet the requirements of the adhesion of the paint layer of the parts. Summary of the invention

[0007] Purpose of the invention: This application aims to solve the surface defects (pores, pits, small depressions and glue-poor areas) such as pinholes and small depressions on the surface of composite parts, and fill the pinholes before painting to obtain a smooth and uniform surface.

[0008] In a first aspect, the present application provides a method for filling pinhole depressions on a carbon fiber composite honeycomb surface, the method comprising:

[0009] Prepare adhesive for repairing composite materials;

[0010] Pour the organic solvent into a spray bottle and use it to spray on the marked areas of pinholes and small depressions;

[0011] The organic solvent spraying time should not exceed 10 seconds, and the repair glue should be scraped within 30 seconds after spraying. By utilizing the volatilization effect of the volatile components in the organic solvent, the glue is dripped into the pinholes and small concave areas to fill them up to obtain a smooth and continuous part surface.

[0012] After the repair glue is applied, the composite honeycomb component is placed in a curing furnace for curing;

[0013] After curing, sand the scraped area with aluminum oxide waterproof sandpaper to remove excess glue on the surface of the part.

[0014] Preferably, before configuring the adhesive for repairing the composite material structure, the method further comprises:

[0015] The wiping cloth is soaked in water, and after being twisted until no water drops, it is used to wipe the polished composite parts, wherein the wiping method is horizontal and vertical cross wiping.

[0016] Preferably, the wiping cloth is soaked in water, twisted until no water drops, and then used to wipe the polished composite parts, wherein the wiping method is horizontally and vertically cross wiping before, and further includes:

[0017] Sand with water sandpaper until the surface is smooth.

[0018] Preferably, before sanding with water sandpaper until the surface is smooth, the method further comprises:

[0019] Mark pinholes and small depressions on the surface of composite honeycomb parts.

[0020] Preferably, after the curing is completed, the scraping area is polished with aluminum oxide waterproof sandpaper to remove excess glue on the surface of the part, and the method further comprises:

[0021] Water film inspection is performed after water polishing the surface of composite parts.

[0022] Preferably, after water polishing the surface of the composite material part and performing water film inspection, the method further comprises:

[0023] After drying, spray the primer.

[0024] Preferably, the scraping method is vertical and horizontal cross-scraping, and the scraping is performed sequentially according to the marked areas.

[0025] In a second aspect, the present application also provides a carbon fiber composite honeycomb surface verification method, the method comprising:

[0026] Use pressure-sensitive protective tape to completely secure the wet liner package. The liner must remain soaked with water throughout the 20-24 hour period.

[0027] After 24 hours, remove the water-soaked pad and absorb the water on the surface. After absorbing the water, immediately test the bonding strength as follows:

[0028] Allow the tape to remain on the surface for at least 30 seconds, lift one end of the flat substrate protective tape, about 45° to 90° to the test surface, and pinch this end of the flat substrate protective tape with your fingers, and tear off the rest of the flat substrate protective tape on the surface of the specimen in a quick and sudden motion;

[0029] If there is no primer film falling off, it is qualified.

[0030] Preferably, before completely fixing the wet liner package with the pressure-sensitive protective tape, the method further comprises:

[0031] Wipe the test area with a clean wipe dampened with acetone, do not allow the solvent to dry naturally on the surface, and wipe it dry with a clean wipe;

[0032] Use cotton material to make a pad, 5mm square or with a minimum diameter of 5mm and a thickness greater than 3mm; soak the pad completely with deionized water and place it on the test surface;

[0033] Cover the wet pad with a piece of transparent polyethylene film, with the polyethylene-coated side facing the wet pad.

[0034] Beneficial technical effects of this application:

[0035] The method described in the present invention can fill the pinholes (generally with a diameter of 0.25 mm or less) and small depressions (generally with a depth of no more than 0.05 mm) on the surface of carbon fiber composite honeycomb parts. After spraying, the composite honeycomb parts meet the primer spraying requirements (the paint layer bonding strength meets the requirements: when the wet cloth is kept on the coated surface for 20h-24h for testing, there should be no primer film falling off). BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a typical honeycomb sandwich component layup provided in the embodiment of the present application;

[0037] Figure 2 It is a schematic diagram of the theoretical model of negative pressure in the honeycomb cavity provided in the embodiment of the present application;

[0038] Figure 3 It is a schematic diagram of the water drop effect provided in an embodiment of the present application;

[0039] Figure 4 It is a process flow chart provided in the embodiment of the present application;

[0040] Figure 5 is a schematic diagram of placing a wet pad provided in an embodiment of the present application;

[0041] Figure 6 It is a schematic diagram of a typical flat substrate protection tape test provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] The present invention mainly describes a method for filling pinholes and small depressions on the surface of carbon fiber composite honeycomb parts. The technical solution is as follows: using the "water drop" principle, spray an organic solvent (optionally ethanol or acetone) on the pinholes and small depressions on the surface of the polished composite honeycomb sandwich parts, quickly scrape the glue, and use the volatilization effect of the volatile components in the organic solvent to drip the glue into the pinholes and small depressions to fill them up to obtain a smooth and continuous part surface. The water drop effect is as follows Figure 3 shown.

[0043] See also Figure 4 , the specific implementation steps provided by this application are as follows:

[0044] 1. Mark the pinholes and small depressions on the surface of the composite honeycomb. To ensure the integrity of the filling of the pinholes and small depressions on the surface, the size of the marked area shall not exceed 300mmx300mm, and the scraping treatment of one area shall be completed within 1 minute.

[0045] 2. Use 180 grit sandpaper or above to polish until the surface is smooth.

[0046] 3. Soak a clean rag in water, twist it until no water drops, and then use it to wipe the polished composite parts in a cross-wiping manner: horizontal wiping-vertical wiping-horizontal wiping.

[0047] 4. Prepare adhesive for repairing composite materials structures.

[0048] 5. Pour the acetone into a clean spray pot and spray it on the pinholes and small concave areas. The present invention requires a high-pressure spray pot with fine atomization to spray the atomized acetone from the high-pressure spray pot on the surface pinholes and small concave areas.

[0049] 6. Spraying of acetone should not exceed 10 seconds each time, and the scraping of the repair glue should be completed within 30 seconds after spraying. The scraping method is: vertical scraping-horizontal scraping-vertical scraping cross scraping, scraping in sequence according to the marked area.

[0050] 7. After the repair glue is applied, the composite honeycomb component is placed in a curing furnace for curing.

[0051] 8. After curing, use No. 180 aluminum oxide water-resistant sandpaper to polish the scraped area to remove excess glue on the surface of the part, and inspect the water film after water polishing the surface of the composite part.

[0052] 9. After drying, spray the primer to check the filling effect of pinholes and small pits (choose a brightly colored primer to facilitate the filling inspection of pinholes and small pits).

[0053] 10. Primer spraying and curing.

[0054] 11. The test method for paint adhesion is as follows: Wipe the test area with a clean wiper dampened with acetone. Do not allow the solvent to dry naturally on the surface, wipe it dry with a clean wiper; Use cotton material to make a pad, 5mm square or minimum diameter 5mm, and thicker than 3mm; Saturate the pad completely with deionized water and place it on the test surface; Cover the wet pad with a piece of polyethylene transparent film, with the polyethylene side facing the wet pad. Use pressure-sensitive protective tape to completely secure the wet pad package. During the entire 20h-24h period, the pad must remain soaked with water as follows Figure 5 shown.

[0055] After 24 hours, remove the water-soaked pad and absorb the water on the surface. Immediately after absorbing the water (within 2 minutes), test the bonding strength as follows:

[0056] Allow the tape to remain on the surface for at least 30 seconds, lift one end of the flat substrate protective tape, about 45° to 90° to the test surface, and pinch this end of the flat substrate protective tape with your fingers. With a quick and sudden movement, tear off the rest of the flat substrate protective tape attached to the surface of the specimen, as follows Figure 6 shown.

[0057] 12. Carry out paint layer adhesion test. Test standard: there should be no primer film falling off.

Claims

1. A method for filling pinhole depressions on the surface of a carbon fiber composite honeycomb, characterized in that: The method comprises: Prepare adhesive for repairing composite materials; Pour the organic solvent into a spray bottle and use it to spray on the marked areas of pinholes and small depressions; The organic solvent spraying time should not exceed 10 seconds, and the repair glue should be scraped within 30 seconds after spraying. By utilizing the volatilization effect of the volatile components in the organic solvent, the glue is dripped into the pinholes and small concave areas to fill them up to obtain a smooth and continuous part surface. After the repair glue is applied, the composite honeycomb component is placed in a curing furnace for curing; After curing, sand the scraped area with aluminum oxide waterproof sandpaper to remove excess glue on the surface of the part.

2. The method according to claim 1, characterized in that Before configuring the adhesive for repairing composite material structure, the method further includes: Soak the wiping cloth in water, twist the wiping cloth until no water drops, and then use it to wipe the polished composite parts, wherein the wiping method is horizontal and vertical cross wiping.

3. The method according to claim 2, characterized in that The method of soaking the wiping cloth in water, twisting the wiping cloth until no water drops, and then using the wiping cloth to wipe the polished composite parts, wherein the wiping method is horizontally and vertically cross wiping, further comprises: Sand with water sandpaper until the surface is smooth.

4. The method according to claim 3, characterized in that Before the surface is polished with water sandpaper until it is smooth, the method further comprises: Mark pinholes and small depressions on the surface of composite honeycomb parts.

5. The method according to claim 1, characterized in that After the curing is completed, the scraping area is polished with aluminum oxide water-resistant sandpaper to remove excess glue on the surface of the part, and the method further includes: Water film inspection is performed after water polishing the surface of composite parts.

6. The method according to claim 5, characterized in that After the water film inspection is performed after the surface of the composite material part is polished with water, the method further includes: After drying, spray the primer.

7. The method according to claim 1, characterized in that The scraping method is vertical and horizontal cross scraping, scraping in sequence according to the marked areas.

8. A carbon fiber composite honeycomb surface verification method, characterized in that: The method comprises: Use pressure-sensitive protective tape to completely secure the wet liner package. The liner must remain soaked with water throughout the 20-24 hour period. After 24 hours, remove the water-soaked pad and absorb the water on the surface. After absorbing the water, immediately test the bonding strength as follows: Allow the tape to remain on the surface for at least 30 seconds, lift one end of the flat substrate protective tape, about 45° to 90° to the test surface, and pinch this end of the flat substrate protective tape with your fingers, and tear off the rest of the flat substrate protective tape on the surface of the specimen in a quick and sudden motion; If there is no primer film falling off, it is qualified.

9. The method according to claim 8, characterized in that Before completely fixing the wet liner package with the pressure-sensitive protective tape, the method further comprises: Wipe the test area with a clean wipe dampened with acetone, do not allow the solvent to dry naturally on the surface, and wipe it dry with a clean wipe; Use cotton material to make a pad, 5mm square or with a minimum diameter of 5mm and a thickness greater than 3mm; soak the pad completely with deionized water and place it on the test surface; Cover the wet pad with a piece of transparent polyethylene film, with the polyethylene-coated side facing the wet pad.

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