A method for repairing cracks of an airplane by using a composite material based on VIMP-microwave process

Abstract

This invention relates to the field of adhesive bonding and repair of aircraft structural composite materials, specifically a method for rapid repair of aircraft cracks based on VIMP-microwave technology. The specific steps are as follows: S1, determine the solution; S2, grind; S3, prepare and cut materials; S4, prevent potential corrosion; S5, connect to vacuum; S6, water bath heating; S7, bond; S8, fill the mold; S9, absorb microwaves; S10, cure; S11, secondary grinding. This invention combines the VIMP process with microwave curing technology. By readjusting the adhesive formulation, it shortens the repair operation time and adhesive curing time. Simultaneously, the repair platform can be integrated into a field repair kit for easy transport during emergency repairs.

Description

Technical Field

[0001] This invention relates to the field of adhesive bonding and repair of aircraft structural composite materials, specifically a method for rapid repair of aircraft cracks using composite materials based on the VIMP-microwave process. Background Technology

[0002] Existing research indicates that composite material bonding repair mainly includes pre-cured patch bonding repair, wet bonding repair, and dry bonding repair. It is worth noting that in actual aircraft airframe structural repair, due to the complexity of the repair structure, pre-cured patch bonding repair sometimes cannot achieve complete adhesion to the aircraft structural surface; wet bonding repair requires the fabrication of wet patches, resulting in a long repair time; dry bonding repair requires obtaining prepreg within its service life, and in most cases, the prepreg needs to be heated to increase its adhesion before application. Therefore, all of these traditional composite material bonding repair processes suffer from long repair cycles and cumbersome procedures. Furthermore, considering the long curing time of the adhesive, completing one curing cycle requires at least 3 hours. Therefore, to meet the needs of emergency repairs in aircraft field operations, this invention proposes a metal crack repair method based on the vacuum injection molding process (VIMP) and microwave curing, building upon existing composite material bonding repair methods. This method uses the metal part to be repaired as a rigid mold and a flexible vacuum bag as a soft mold. Gas is expelled from the mold cavity through vacuum negative pressure, and a microwave-curable adhesive is injected, utilizing its penetration and flow to impregnate the fibrous fabric. After mold filling, the adhesive is cured using microwave curing equipment, thus shortening the repair time in terms of both operation and curing time.

[0003] Chinese patent application number 112356467A discloses a microwave repair device and method for composite materials in the field of aircraft. Although the invention shortens the curing time of the adhesive, it still requires the fabrication of wet patch for application and repair, and the repair operation time is still relatively long, which cannot fully meet the needs of emergency repair in the field. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology.

[0005] A method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology, the specific steps of which are as follows:

[0006] S1. Determine the solution: Based on the structural damage, design a repair plan and determine the patch thickness and layup angle;

[0007] S2. Grinding: Use 80# sandpaper to grind the area to be repaired, then clean the surface with acetone and wait for it to dry.

[0008] S3. Prepare cutting materials: Cut carbon fiber fabric 5, release cloth 6, flow guiding medium 9, isolation film 8, vacuum bag film 10 types of materials according to repair needs;

[0009] S4. Prevent electrochemical corrosion:

[0010] a. First, lay a layer of alkali-free glass cloth in the repair area, and then lay carbon fiber fabric 5 according to the design angle and number of layers;

[0011] b. Lay out the release cloth, flow guiding medium, porous isolation film, vacuum bag film and other auxiliary materials layer by layer, and stick vacuum tape to the edge of the area to be repaired;

[0012] c. Connect a rubber tube with a valve to the adhesive injection port and the adhesive outlet respectively, which are called adhesive outlet tube one and adhesive outlet tube two. Then seal the repair area with a vacuum sealant strip.

[0013] S5. Connect to vacuum: Connect to vacuum equipment, open the valve at the glue outlet, observe the vacuum gauge on the adhesive collection tank 12, and check the airtightness of the vacuum bag.

[0014] S6. Water bath heating: Weigh appropriate amounts of resin and curing agent according to the size of the repair area and place them in the two tubes of the online mixing intelligent metering and delivery system. Turn on the water bath heating switch and set the heating temperature to 50℃. Set the online delivery parameters according to the resin and curing agent mixing ratio.

[0015] S7. Bonding: After the resin and curing agent have been fully heated, connect the glue outlet tube to the adhesive preparation tube outlet.

[0016] S8, Mold Filling:

[0017] a. Turn on the online hybrid intelligent metering and delivery system switch, and open the valve at the glue injection port. The adhesive will flow into the repair area and impregnate the fiber fabric under atmospheric pressure.

[0018] b. When the adhesive completely fills the repair area of ​​the structure to be repaired, and there is adhesive flowing out of the outlet without any air bubbles overflowing, close the injection port, the valve at the outlet, the online mixing intelligent metering and dispensing system switch, and the water bath heating switch in sequence to end the mold filling process.

[0019] S9. Wave Absorption: Place a wave-absorbing pad on the vacuum bag to improve the wave absorption effect in the repair area;

[0020] S10. Curing: Place a microwave radiation hood in the repair area and turn on the microwave generator to cure the radiation.

[0021] S11. Secondary polishing: After the vacuum pump has finished curing, remove the vacuum bag and pipeline, and polish the remaining adhesive.

[0022] In step S4, the width dimension of the release fabric is 20mm-30mm larger than that of the fiber fabric.

[0023] In step S4, the rubber tubes at both locations are wrapped with vacuum adhesive strips.

[0024] In step S4c, the adhesive uses bisphenol A epoxy resin, and bisphenol F epoxy resin is used in combination to adjust the viscosity of the resin. Glycidyl ester epoxy resin and multifunctional epoxy resin are used to improve the microwave absorption capacity and high temperature resistance of the resin matrix.

[0025] In step S5, the vacuum device is a vacuum pump, and the vacuum level of the vacuum bag must not be lower than 90 kPa.

[0026] In step S6, if a new low-viscosity microwave repair adhesive is developed, the water bath heating process can be eliminated.

[0027] In the implementation step S10, the power and radiation time of the microwave generator need to be determined based on the actual repair situation.

[0028] The beneficial effects of this invention are: this invention combines the VIMP process with the microwave curing process, and by readjusting the adhesive formula, it shortens the repair operation time and adhesive curing time. At the same time, the repair platform can be integrated into an emergency repair kit, which is convenient for emergency repairs. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Figure 1 This is a schematic diagram of the main structure of the present invention.

[0031] In the diagram: 1. Online hybrid intelligent metering and distribution system; 2. Glue dispensing conduit one; 3. Structure to be repaired; 4. Vacuum adhesive strip; 5. Carbon fiber fabric; 6. Release cloth; 7. Microwave radiator; 8. Isolation membrane; 9. Flow guiding medium; 10. Vacuum bag film; 11. Glue dispensing conduit two; 12. Adhesive collection tank; 13. Vacuum pump. Detailed Implementation

[0032] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below.

[0033] like Figure 1 As shown, a method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology is described, and its specific steps are as follows:

[0034] S1. Determine the solution: Based on the structural damage, design a repair plan and determine the patch thickness and layup angle;

[0035] S2. Grinding: Use 80# sandpaper to grind the area to be repaired, then clean the surface with acetone and wait for it to dry.

[0036] S3. Prepare cutting materials: Cut carbon fiber fabric 5, release cloth 6, flow guiding medium 9, isolation film 8, vacuum bag film 10 types of materials according to repair needs;

[0037] S4. Prevent electrochemical corrosion:

[0038] a. To prevent the carbon fiber fabric 5 from undergoing potential corrosion with the metal substrate, first lay a layer of alkali-free glass cloth in the repair area, and then lay the carbon fiber fabric 5 according to the design angle and number of layers.

[0039] b. Lay out the following auxiliary materials in layers: 6. Release cloth, 9. Flow guiding medium, 8. Porous isolation film, 10. Vacuum bag film, and 4. Adhere vacuum tape to the edge of the area to be repaired.

[0040] c. Connect a rubber tube with a valve to the adhesive injection port and the adhesive outlet respectively, namely adhesive outlet tube 12 and adhesive outlet tube 21, and then seal the repair area with vacuum adhesive strip 4;

[0041] S5. Connect to vacuum: Connect to vacuum equipment, open the valve at the glue outlet, observe the vacuum gauge on the adhesive collection tank 12, and check the airtightness of the vacuum bag.

[0042] S6. Water bath heating: Weigh appropriate amounts of resin and curing agent according to the size of the repair area and place them in the two tubes of the online mixing intelligent metering and delivery system 1. Turn on the water bath heating switch and set the heating temperature to 50℃. Set the online delivery parameters according to the resin and curing agent mixing ratio.

[0043] S7. Bonding: After the resin and curing agent have been fully heated, connect the dispensing conduit 2 at the dispensing port to the outlet of the adhesive preparation tube;

[0044] S8, Mold Filling:

[0045] a. Turn on the online hybrid intelligent metering and delivery system switch, and open the valve at the glue injection port. The adhesive will flow into the repair area and impregnate the fiber fabric under atmospheric pressure.

[0046] b. When the adhesive completely fills the repair area of ​​the structure to be repaired 3, and there is adhesive flowing out of the outlet without any air bubbles overflowing, close the injection port, the valve at the outlet, the switch of the online mixing intelligent metering and dispensing system 1, and the water bath heating switch in sequence to end the mold filling process.

[0047] S9. Wave Absorption: Considering the wave absorption properties of the repair area, a wave-absorbing pad can be placed on the vacuum bag to improve the wave absorption effect of the repair area.

[0048] S10. Curing: Place the microwave radiation cover 7 in the repair area and turn on the microwave generator to cure;

[0049] S11. Secondary polishing: After the curing process is completed by vacuum pump 13, remove the vacuum bag and pipeline, and polish the remaining adhesive.

[0050] In step S4, to facilitate demolding after curing, the width dimension of the demolding cloth 6 is 20mm-30mm larger than that of the fiber fabric.

[0051] In step S4, to ensure the sealing of the injection port and the outlet port, a vacuum strip 4 can be used to wrap the rubber tubes at both locations once.

[0052] In step S4c, the resin matrix of the adhesive is selected from bisphenol A type epoxy resin, and bisphenol F epoxy resin is used in combination to adjust the viscosity of the resin matrix. Glycidyl ester type epoxy resin and multifunctional epoxy resin are used to improve the microwave absorption capacity and high temperature resistance of the resin matrix. The curing agent in the adhesive is a mixed amine curing agent with high reactivity and good flexibility modified by Mannich.

[0053] This invention combines the VIMP process with microwave curing technology. By readjusting the adhesive formulation, the repair operation time and adhesive curing time are shortened. At the same time, the repair platform can be integrated into an emergency repair kit for easy transport during emergency repairs.

[0054] In step S5, the vacuum equipment is a vacuum pump 13. In order to ensure that the adhesive is discharged smoothly and to ensure the repair quality, the vacuum degree of the vacuum bag must not be lower than 90 kPa.

[0055] In step S6, if a new low-viscosity microwave repair adhesive is developed, the water bath heating process can be eliminated.

[0056] In step S6, considering the high viscosity of the microwave-cured repair adhesive at room temperature, making vacuum introduction difficult, a water bath heating method is used to reduce the adhesive viscosity. However, because the resin-curing agent mixture reacts within 10 minutes under water bath heating conditions, the resin viscosity increases. Therefore, an online resin mixing and intelligent metering and dispensing system is used to heat the resin and curing agent separately, then mix and heat them thoroughly through a spiral tube, and finally introduce them into the mold cavity under vacuum pressure to impregnate the carbon fiber fabric.

[0057] In the implementation step S10, the power and radiation time of the microwave generator need to be determined based on the actual repair situation.

[0058] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology, characterized in that: The specific steps are as follows: S1. Determine the solution: Based on the structural damage, design a repair plan and determine the patch thickness and layup angle; S2. Grinding: Use 80# sandpaper to grind the area to be repaired, then clean the surface with acetone and wait for it to dry. S3. Prepare cutting materials: Cut carbon fiber fabric (5), release cloth (6), flow guiding medium (9), isolation membrane (8), vacuum bag film (10) and other materials according to repair needs; S4. Prevent potential corrosion; S5. Connect to vacuum: Connect to vacuum equipment, open the valve at the glue outlet, observe the vacuum gauge on the adhesive collection tank (12), and check the airtightness of the vacuum bag; S6, Water bath heating: Weigh appropriate amounts of resin and curing agent according to the size of the repair area and place them in the two tubes of the online mixing intelligent metering and distribution system (1). Turn on the water bath heating switch and set the heating temperature to 50℃. Set the online distribution parameters according to the resin and curing agent preparation ratio. S7, Bonding: After the resin and curing agent are fully heated, connect the glue outlet tube 1 (2) at the glue outlet to the adhesive preparation tube outlet; S8, mold filling; S9. Wave Absorption: Place a wave-absorbing pad on the vacuum bag to improve the curing efficiency of the adhesive; S10. Curing: Place a microwave radiation shield (7) in the repair area and turn on the microwave generator power to cure; S11, Secondary polishing: After the curing is completed by vacuum pump (13), remove the vacuum bag and pipeline, and polish the remaining adhesive.

2. The method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology according to claim 1, characterized in that: The specific content of step S4 is as follows: a. First, lay a layer of alkali-free glass cloth in the repair area, and then lay carbon fiber fabric according to the design angle and number of layers (5). b. Lay out the following auxiliary materials in layers: release cloth (6), flow guiding medium (9), porous isolation membrane (8), and vacuum bag film (10). Adhere vacuum adhesive strips (4) to the edge of the area to be repaired. c. Connect a rubber tube with a valve to the glue injection port and the glue outlet respectively, namely glue outlet tube one (2) and glue outlet tube two (11), and then seal the repair area with a vacuum strip (4).

3. The method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology according to claim 2, characterized in that: In step S4, the width dimension of the release fabric (6) is 20mm-30mm larger than that of the fiber fabric.

4. The method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology according to claim 2, characterized in that: In step S4, the rubber tubes at both locations are wrapped with a vacuum adhesive strip (4).

5. The method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology according to claim 2, characterized in that: In step S4c, the adhesive uses bisphenol A epoxy resin, and bisphenol F epoxy resin is used in combination to adjust the viscosity of the resin. Glycidyl ester epoxy resin and multifunctional epoxy resin are used to improve the microwave absorption capacity and high temperature resistance of the resin matrix.

6. The method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology according to claim 1, characterized in that: In step S5, the vacuum device is a vacuum pump (13), and the vacuum degree of the vacuum bag cannot be lower than 90 kPa.

7. The method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology according to claim 1, characterized in that: The specific content of step S8 is as follows: a. Turn on the online hybrid intelligent metering and delivery system switch, and open the valve at the glue injection port. The adhesive will flow into the repair area and impregnate the fiber fabric under atmospheric pressure. b. When the adhesive completely fills the repair area of ​​the structure to be repaired (3), and there is adhesive flowing out of the outlet without any bubbles overflowing, close the injection port, the valve at the outlet, the switch of the online mixing intelligent metering and distribution system (1), and the water bath heating switch in sequence to end the mold filling process.

8. The method for rapid repair of aircraft cracks using composite materials based on VIMP-microwave technology according to claim 1, characterized in that: In step S10, the power and radiation time of the microwave generator need to be determined based on the actual repair situation.

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