Repair methods for surface damage of metal materials used in aircraft

Abstract

This invention provides a method for repairing surface damage to aircraft metal materials, comprising the following steps: Step 1, damage removal: removing the damaged structure within the damaged area of ​​the metal, and grinding and cleaning the bonding surface; Step 2, patch processing; Step 3, preparing the adhesive solution, and applying the prepared adhesive to the bonding surface of the metal to be repaired before hardening; Step 4, applying the adhesive solution to the surface of the patch prepared in Step 2, and pasting the patch onto the bonding surface of the metal to be repaired; Step 5, sealing: vacuum sealing the pasted patch; Step 6, curing at 21℃~25℃, removing the sealing material after curing, and trimming and grinding the patch boundaries to complete the repair. This repair method uses fiber composite materials to quickly repair surface damage to aircraft metal materials, thereby restoring the structural functionality.

Description

Technical Field

[0001] This invention relates to the field of metal material repair, and in particular to a method for repairing surface damage of metal materials used in aircraft. Background Technology

[0002] Aluminum alloy structural components of a certain type of aircraft, such as fuselage panels, wing panels, wing spars, cargo hold floors, and fuel tanks, are mostly made of 2XXX and 7XXX series aluminum alloys, which have poor weldability. During scheduled maintenance, structural damage mainly manifests as corrosion, cracks, fractures, notches, and holes. During service, these structural damages, under external impacts and alternating loads, will cause stress concentration, leading to continuous damage expansion and a decline in the mechanical properties of the structural components. To restore structural integrity and extend service life, timely and appropriate repair of damaged areas is necessary. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for repairing surface damage of metal materials for aircraft, which uses fiber composite materials to quickly repair the surface damage of metal materials for aircraft, so as to restore the structural function.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for repairing surface damage of metal materials for aircraft, comprising the following steps:

[0005] Step 1: Damage removal. Remove the damaged structure in the metal damage area and grind and clean the adhesive surface.

[0006] Step 2: Patch processing;

[0007] Step 3: Prepare the adhesive solution and apply it to the bonding surface of the metal to be repaired before it hardens.

[0008] Step 4: Apply adhesive to the surface of the patch prepared in Step 2, and then attach the patch to the adhesive surface of the metal to be repaired.

[0009] Step 5: Sealing. Vacuum seal the pasted patch.

[0010] Step 6: Curing at 21℃~25℃. After curing, remove the encapsulation material, trim and polish the patch edges to complete the repair.

[0011] In the preferred embodiment, in step one, before cleaning the metal damage area, the surface paint layer near the metal damage area is first polished and the dirt near the damage area is cleaned. Then, damage detection and evaluation are performed, and the damage boundary and repair boundary are drawn. The outline of the repair boundary is drawn by extending 20mm to 30mm outward from the cutting outline of the damage area as a reference.

[0012] In the preferred embodiment, in step one, after grinding and cleaning the adhesive surface, a release cloth with adhesive is laid on the non-repair area.

[0013] In the preferred embodiment, in step two, the patch includes glass cloth and carbon cloth. The glass cloth and carbon cloth are cut to a length of 5mm to 10mm beyond the repair boundary, and the 0° fiber direction is required to be consistent with the flight direction.

[0014] In a preferred embodiment, in step three, the adhesive is either SY-49 adhesive or SY-37 adhesive. Components A and B of SY-49 adhesive are prepared at a mass ratio of 5:2, and components A and B of SY-37 adhesive are prepared at a mass ratio of 10:9.

[0015] In the preferred embodiment, in step four, adhesive is first evenly applied to the surface of the glass cloth, and the glass cloth is laid as the first layer in the area to be bonded. After laying, the glass cloth is pressed with a roller to remove air bubbles and make it completely adhere to the repair surface. Then, carbon cloth is laid, adhesive is evenly applied to the surface of the carbon cloth, and the cut carbon cloth is laid on the upper layer of the glass cloth in sequence. Each layer must be laid and checked.

[0016] In a preferred embodiment, the amount of adhesive applied to the glass cloth and carbon cloth is 280 g / m². 2 ~340g / m 2 .

[0017] In the preferred embodiment, step five involves vacuum sealing the pasted patch as follows: a porous isolation film is laid on top of the patch, ensuring that the porous isolation film extends beyond the repair area; then, a breathable felt and a vacuum bag film are laid in sequence; sealing putty is applied around the vacuum bag film; and finally, the vacuum bag film is vacuum-sealed and compacted.

[0018] This invention provides a method for repairing surface damage to aircraft metal materials. By utilizing the adhesive properties of an adhesive, a high-strength fiber-reinforced composite material patch is bonded to the surface of a defective or damaged metal structure. This strengthens the damaged component, maximizing the restoration of load-bearing characteristics, thereby restoring the structure's functionality and extending its service life. Composite material repair primarily relies on adhesive bonding, thus it is not limited by structural type or geometry. Regardless of the thickness or size of the damaged area, composite material adhesive bonding repair can be performed, making it particularly suitable for repairing structural damage where accessibility is poor or disassembly is inconvenient. When the damaged structure is subjected to external loads, the load is transferred through the adhesive layer to the composite material patch area, sharing part of the load and thus restoring the load-bearing capacity of the damaged structure, achieving the repair effect. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0020] Figure 1 This is a process flow diagram of the present invention;

[0021] Figure 2 Draw a schematic diagram of the damage boundary and the repair boundary; Detailed Implementation

[0022] like Figure 1 As shown, a method for repairing surface damage of aircraft metal materials includes the following steps:

[0023] Step 1: Clean the damaged area. Sand the paint layer near the damaged metal area and clean away any dirt or grime. Specifically, sand the paint layer near the damaged metal area clean. Use a vacuum cleaner to remove all dust, dirt, or other contaminants from the damaged area and its surroundings. Use a cotton swab or cloth dampened with acetone or ethyl acetate to clean the dirt near the damaged metal area.

[0024] Damage detection and assessment involves detecting and assessing damage in the affected area, and drawing damage and repair boundaries, such as... Figure 2 As shown, the outline of the repair boundary is drawn by extending the cut contour line of the damaged area outward by 20mm to 30mm at equal intervals.

[0025] Damage removal: Cut along the drawn repair boundary to remove damaged structures within the metal damage area, including corrosion, chips, etc. Inspect the cut area to ensure all damage to be removed is completely removed. Smooth the edges of the cut using 150# and 240# dry sandpaper in sequence. Sand and clean the bonding surface: Sand the bonding surface with 150# to 240# dry sandpaper, and use a vacuum cleaner to remove all dust, dirt, or other contaminants from the bonding area and surrounding area. Wipe the bonding area and surrounding area clean with degreased gauze or cotton cloth soaked in acetone or ethyl acetate until clean. Lay adhesive release cloth A005 on non-repair areas to facilitate subsequent adhesive application and prevent adhesive from being applied to non-repair areas.

[0026] Step 2: Patch processing. The patch includes glass cloth and carbon cloth. SW280 glass cloth and T300 carbon cloth are selected. The glass cloth and carbon cloth are cut 5mm to 10mm beyond the repair boundary contour. The 0° fiber direction must be consistent with the flight direction. The patch can be circular, elliptical, or rectangular. See [link to relevant documentation]. Figure 2 .

[0027] The patch thickness is designed based on a repair stiffness ratio s of 1 to 1.2.

[0028] s = E patch T patch / Eplate T plate ;

[0029] In the formula: E is the elastic modulus of the material, T is the material thickness, patch represents a patch, and plate represents the aluminum alloy plate being repaired.

[0030] Step 3: Prepare the adhesive solution. Apply the prepared adhesive to the bonding surface of the metal material to be repaired before it hardens. The adhesive solution is SY-49 or SY-37 adhesive, which has high shear strength and peel strength. It cures at a temperature of 21℃~25℃ and a pressure of 0.05MPa~0.3MPa, belonging to a room temperature curing system.

[0031] The components A and B of SY-49 adhesive are prepared at a mass ratio of 5:2, and the components A and B of SY-37 adhesive are prepared at a mass ratio of 10:9. After weighing according to the ratio, mix thoroughly and stir until the color is uniform, and ensure that the pressure is applied during the working period (before hardening).

[0032] Step 4: Apply adhesive to the surface of the patch prepared in Step 2. Use a scraper or brush to apply the adhesive evenly, ensuring that the adhesive completely covers the bonding surface.

[0033] The patch is then adhered to the bonding surface of the metal to be repaired. First, adhesive is evenly applied to the surface of the fiberglass cloth, with an application rate of 280g / m². 2 ~340g / m 2 Then, lay the cut glass cloth as the first layer on the area to be bonded. After laying it, use a roller to remove air bubbles and compact the glass cloth to ensure it adheres completely to the surface to be repaired. Next, lay carbon cloth and evenly apply adhesive to its surface at a rate of 280g / m². 2 ~340g / m 2 Then, lay the cut carbon cloth on top of the glass cloth in sequence. The number of carbon cloth layers is determined according to the thickness and material of the metal material to be repaired. Each layer must be laid and checked one by one. Each layer should be laid accurately and kept flat. Use a pressure roller to make it completely adhere to the previous layer. There should be no "bridging", "wrinkling" or "bringing in foreign objects". There should be no missing glue or insufficient glue.

[0034] Step 5: Sealing. Vacuum seal the pasted patch. Place a perforated release liner on top of the patch, ensuring it extends a certain distance beyond the repair area. Then, layer a breathable felt and a vacuum bag film. Apply sealant around the perimeter of the vacuum bag film, and then vacuum-tighten it to a vacuum level of at least -0.090 MPa. Make holes in the vacuum bag film and connect a vacuum nozzle to an air compressor to create a vacuum. This vacuuming process compacts the patch and removes air from between layers. During the vacuuming process, check for leaks. If any leaks are found, reseal the vacuum seal to ensure it is leak-free.

[0035] Step Six: Curing at 21℃~25℃. If the temperature is insufficient, use an electric blanket or heat repair device. After curing, remove the encapsulation material and adhesive release cloth. Trim and sand the patch edges, using 180# and 360# sandpaper to sand the outer edge of the patch skin to the repair boundary, sanding the outer surface until smooth and flat. Use a vacuum cleaner to clean all dust and dirt from the repair area and surrounding area. Use degreased cotton gauze or a cotton cloth soaked in acetone or ethyl acetate to clean the dirt near the repair area.

[0036] Quality inspection: Visual inspection, tapping test and ultrasonic testing are used to check whether there is delamination after repair. The outer surface of the repaired area is smooth and flat, and the repaired area and the unrepaired area are smoothly transitioned. The repaired area is free of impurities, the fibers are not obviously broken, and there is no obvious phenomenon of insufficient glue or excessive glue. The repair is completed.

[0037] Metal structure damage is repaired using fiber composite materials. High-strength fiber-reinforced composite material patches are bonded to the surface of the defective or damaged metal structure with the help of adhesives to strengthen the damaged components, restore load transfer characteristics to the greatest extent, and achieve the purpose of restoring the functionality of the structure and extending its service life.

[0038] Composite material bonding repair of metal structures has advantages such as minimal structural weight increase, high design flexibility, good fatigue resistance, good seismic performance, good corrosion resistance, and wide applicability. Composite material repair mainly relies on bonding, so it is not limited by the type and geometry of the structure. Regardless of the thickness or size of the damaged area, composite material bonding repair can be performed. It is particularly suitable for repairing structural damage that is difficult to access or disassemble.

[0039] Damaged metal structures are repaired using composite material bonding. When the damaged structure is subjected to external loads, the load is transferred to the composite material patch area through the adhesive layer, sharing part of the load and thus restoring the load-bearing capacity of the damaged structure, achieving a repair effect. After repairing a certain type of aircraft's damaged metal structure using the repair method of this invention, in-situ repair or rapid off-site repair of aircraft metal structural damage is achieved, reducing repair costs by 30% and shortening the repair cycle.

Claims

1. A method for repairing surface damage of metal materials used in aircraft, characterized in that, Includes the following steps: Step 1: Damage removal. Remove the damaged structure in the metal damage area and grind and clean the adhesive surface. Step 2: Patch processing; The patch includes glass cloth and carbon cloth. The glass cloth and carbon cloth are cut 5 mm to 10 mm beyond the repair boundary, and the 0° fiber direction is required to be consistent with the flight direction. The patch thickness is designed based on a repair stiffness ratio s of 1 to 1.

2. s= ； In the formula: E is the elastic modulus of the material, T is the material thickness, patch represents a patch, and plate represents the aluminum alloy plate being repaired; Step 3: Prepare the adhesive solution and apply it to the bonding surface of the metal to be repaired before it hardens. Step 4: Apply adhesive to the surface of the patch prepared in Step 2, and then attach the patch to the adhesive surface of the metal to be repaired. Specifically, first, apply adhesive evenly to the surface of the glass cloth and lay the glass cloth as the first layer in the area to be bonded. After laying it, use a roller to remove air bubbles and compact the glass cloth so that it is completely adhered to the surface to be repaired. Then, lay the carbon cloth, apply adhesive evenly to the surface of the carbon cloth, and lay the cut carbon cloth on the glass cloth layer by layer. Each layer must be laid and checked. Step 5: Sealing. Vacuum seal the pasted patch. Step 6: Curing at 21℃~25℃. After curing, remove the encapsulation material, trim and polish the patch edges to complete the repair.

2. The method for repairing surface damage of aircraft metal materials according to claim 1, characterized in that, In step one, before cleaning the damaged metal area, the surface paint layer near the damaged metal area is polished and the dirt near the damaged area is cleaned. Then, damage detection and evaluation are carried out, and the damage boundary and repair boundary are drawn. The outline of the repair boundary is drawn by extending 20 mm to 30 mm outward from the cutting outline of the damaged area as a reference.

3. The method for repairing surface damage of aircraft metal materials according to claim 1, characterized in that, In step one, after sanding and cleaning the adhesive surface, adhesive release cloth is laid on the non-repair area.

4. The method for repairing surface damage of aircraft metal materials according to claim 1, characterized in that, In step three, the adhesive is either SY-49 adhesive or SY-37 adhesive. The components A and B of SY-49 adhesive are prepared in a mass ratio of 5:2, and the components A and B of SY-37 adhesive are prepared in a mass ratio of 10:

9.

5. The method for repairing surface damage of aircraft metal materials according to claim 1, characterized in that, The amount of adhesive applied to the glass cloth and carbon cloth is 280 g / m². 2 ~340 g / m 2 .

6. The method for repairing surface damage of aircraft metal materials according to claim 1, characterized in that, In step five, the vacuum sealing operation for the pasted patch is as follows: a layer of perforated isolation film is laid on top of the patch, requiring the perforated isolation film to extend beyond the repair area, and then a breathable felt and a vacuum bag film are laid in sequence. Sealing putty is applied around the vacuum bag film, and then the vacuum bag film is vacuumed and compacted.

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