A method of repairing delaminated damage in a composite material

Abstract

The application belongs to the field of composite material repair and discloses a composite material delamination damage repair method which adopts glue injection to repair the delamination damage of the composite material, specifically, first, the fastener hole edge of the composite material is visually inspected to locate the fastener space where delamination occurs; then, nondestructive testing is adopted to determine the damage area and depth of the delamination position; then, appropriate glue injection bolts are manufactured according to the hole diameter and depth of the fastener hole where delamination occurs, the glue injection blind hole and through hole are connected on the glue injection bolt, the glue injection bolt is installed in the damage area, then the prepared resin is injected into the damage area and solidified, after solidification, the glue is cleaned, the repaired composite material is subjected to nondestructive testing, and the repair is completed after the testing is qualified. Compared with the existing injection method and the patching method, the method is more convenient and effective for repairing the delamination damage of the composite material hole edge, has lower repair cost, has guaranteed reliability, causes little damage to the original structure, and has remarkable repair effect.

Description

Technical Field

[0001] This application belongs to the field of composite material repair, and specifically relates to a method for repairing delamination damage in composite materials. Background Technology

[0002] Composite materials are widely used in the aerospace field due to their superior performance, and currently, the amount of composite materials used in some aircraft models exceeds 50%. However, composite materials also have their obvious drawbacks - poor interlaminar mechanical properties. In aircraft composite material structures, such as covers in panels, bolt assembly is usually used, which requires a large number of holes in the composite material structure, causing initial damage and stress concentration at the hole edges. Moreover, some bolts are removable bolts, and frequent disassembly will exacerbate delamination damage of the composite material.

[0003] Currently, common methods for repairing delamination damage in composite materials include adhesive patching and resin injection repair. The adhesive patching method involves directly removing the area with large-area delamination damage and creating a bevel. Then, a composite laminate patch made of the same material as the original structure is bonded and cured to the original structure. However, this method is suitable for large, severe damage areas, but too costly for repairing small areas of composite material delamination damage. Traditional syringe resin injection repair involves drilling at least two small holes at the edge of the delamination damage, one for injection and one for ventilation (glue outlet), requiring the hole depth to precisely reach the delamination damage area. A specialized syringe is then used to inject the prepared resin into the delamination area through the injection holes to repair the delamination damage. However, for composite material delamination damage near bolt holes, it is generally not permissible to drill holes within a certain distance of the original hole, as this would significantly reduce the performance of the composite material. For field support of aircraft using a large number of composite materials, due to time and cost constraints, a rapid composite material delamination repair method that minimizes damage to the original structure, has low repair costs, and is simple to operate is needed. Summary of the Invention

[0004] The purpose of this application is to provide a method for repairing delamination damage in composite materials, so as to solve the problem of difficulty in repairing delamination damage at the hole edges of existing composite fasteners.

[0005] The technical solution of this application is: a method for repairing delamination damage in composite materials, comprising:

[0006] Visually inspect the edges of fastener holes in composite material structures to locate fastener holes with delamination, and then use non-destructive testing to scan a certain area around the fastener holes to determine the damaged area and depth of the delamination.

[0007] The bolt size is determined based on the hole diameter and depth of the fastener with delamination damage. Then, the appropriate bolt size is selected to make the glue-injecting bolt. A glue-injecting blind hole is made at the axial position of the glue-injecting bolt, and a through hole communicating with the glue-injecting blind hole is made at the radial position of the glue-injecting bolt.

[0008] Install injection bolts in the damaged area of ​​the composite material structure, and inject the prepared resin into the damaged area through the injection bolts;

[0009] The repaired structure is cured according to the curing requirements of the prepared resin-based material;

[0010] After curing, the sludge is cleaned up, and the repaired composite material structure is subjected to non-destructive testing. Once the test is passed, the repair is complete.

[0011] Preferably, the specific method for injecting resin into the injection bolt is as follows:

[0012] A first rubber pad and a second rubber pad are respectively set on the upper and lower sides of the composite material structure. A first shim is set on the outside of the first rubber pad, and a second shim is set on the outside of the second rubber pad. The glue injection bolt is installed to the delamination damage position of the fastener hole of the composite material structure and connected to the first rubber pad, the second rubber pad, the first shim and the second shim respectively, until the top of the glue injection bolt protrudes from the inside of the second shim. The first shim and the second shim are adjusted so that the through hole is aligned with the delamination damage position. Then, a nut is screwed on the bottom of the glue injection bolt to fix it.

[0013] Inject the resin into the blind injection hole, and then let it flow through the through hole to the delamination position of the composite material. Apply appropriate pressure during injection to ensure that air bubbles in the cavity are expelled. After the resin injection is completed, remove the injection bolt and press the delamination position tightly.

[0014] Preferably, the first and second shims are threadedly fitted to the glue injection bolts.

[0015] Preferably, the resin is injected into the injection blind hole under pressure using a syringe, and the pressure is maintained for 2-3 minutes after injection.

[0016] Preferably, the layered areas are pressed together using a fish-shaped clamp and a pressure plate.

[0017] Preferably, the standard for fixing the resin is to maintain it at 66℃±5℃ for more than 65 minutes.

[0018] This application discloses a method for repairing delamination damage in composite materials. The method employs a resin injection technique. Specifically, it involves first visually inspecting the edges of fastener holes in the composite material to locate the gaps where delamination has occurred. Then, non-destructive testing (NDT) is used to determine the damaged area and depth of the delamination. Next, a suitable bolt is selected based on the hole diameter and depth of the delamination-damaged fastener to manufacture a resin injection bolt. Connected blind and through holes are made on the resin injection bolt. The bolt is then installed in the damaged area. Finally, the prepared resin is injected into the damaged area and cured. After curing, the resin residue is cleaned, and the repaired composite material undergoes NDT. If the test is successful, the repair is complete. Compared to existing injection and patching methods, this method is more convenient and effective for repairing delamination damage at the edges of composite material holes, with lower repair costs, guaranteed reliability, minimal damage to the original structure, and significant repair results. Attached Figure Description

[0019] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0020] Figure 1 This is a sectional view of the overall structure of the glue-injecting bolt in this application;

[0021] Figure 2 This is an exploded view of the assembly structure of the glue-injected bolts and composite material structure in this application.

[0022] 1. Glue-injecting bolt; 2. First shim; 3. First rubber pad; 4. Composite material structure; 5. Second shim; 6. Second rubber pad; 7. Self-locking nut; 8. Glue-injecting blind hole; 9. Through hole. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] A method for repairing delamination damage in composite materials, comprising:

[0025] Step S100: Visually inspect the edges of fastener holes in the composite material structure to initially identify fastener holes with delamination. Then, use non-destructive testing to scan a certain area around the fastener hole edges to determine the damaged area and depth of the delamination location.

[0026] Step S200: Obtain the hole diameter and depth of the fastener with delamination damage, select a suitable bolt, determine the bolt size, and then use a bolt of the corresponding size to manufacture the glue-injecting bolt 1. The structure of the glue-injecting bolt 1 is as follows: Figure 1 As shown, a blind hole 8 for injecting glue is opened at the axial position of the glue injection bolt 1, and a through hole 9 communicating with the blind hole 8 is opened at the radial position of the glue injection bolt 1.

[0027] The diameters of the blind hole 8 and through hole 9 for resin injection should be determined according to the actual situation to ensure that the resin can be injected smoothly. The distance between the center of through hole 9 and the nut position needs to be determined according to the actual delamination damage location to ensure that the delamination damage area is accessible.

[0028] Step S300, combined Figure 2 Injection bolt 1 is installed in the damaged area of ​​composite material structure 4, and the prepared resin is injected into the damaged area through injection bolt 1.

[0029] Preferably, the specific method for injecting resin into the injection bolt 1 is as follows:

[0030] In step S310, a first rubber pad 3 and a second rubber pad 6 are respectively installed on the upper and lower sides of the composite material structure 4. A first adjusting shim 2 is installed on the outside of the first rubber pad 3, and a second adjusting shim 5 is installed on the outside of the second rubber pad 6. The resin injection bolt 1 is inserted into the damaged position of the composite material structure 4 and connected to the first rubber pad 3, the second rubber pad 6, the first adjusting shim 2, and the second adjusting shim 5 respectively, until the top of the injection bolt 1 protrudes from the inside of the second adjusting shim 5. The first adjusting shim 2 and the second adjusting shim 5 are adjusted so that the through hole 9 corresponds to the delamination position. Then, the self-locking nut 7 is screwed on the bottom of the injection bolt 1. The first rubber pad 3 and the second rubber pad 6 can seal the glue to prevent the glue from flowing out during injection. The first adjusting shim 2 and the second adjusting shim 5 can adjust the upper and lower positions of the through hole 9 so that the through hole 9 is aligned with the delamination position, ensuring that the repair efficiency of the delamination area is as high as possible.

[0031] Preferably, the first adjusting shim 2 and the second adjusting shim 5 are both threadedly engaged with the glue injection bolt 1. The position of the through hole 9 can be adjusted up and down by rotating the first adjusting shim 2, the second adjusting shim 5, or the glue injection bolt 1.

[0032] In step S320, resin is injected into the injection blind hole 8, and then flows through the through hole 9 to the delamination position of the composite material. After injection, pressure is maintained for 2-3 minutes to allow the resin to flow fully into the delamination damage area and to expel air bubbles from the cavity. After the resin injection is completed, the injection bolt 1 is removed and the delamination position is tightened.

[0033] Preferably, the layered area is pressed tightly by a fish-shaped clamp and a pressure plate to prevent air from entering and to prevent the layered area from expanding again after repair, which would introduce air bubbles and reduce repair efficiency.

[0034] Step S400: Curing the resin according to the required fixation of the resin base material in the prepared resin. After curing, a small amount of resin residue should remain inside and around the injection hole after repair, with no visible delamination.

[0035] Step S500: After cleaning the sludge, perform non-destructive testing on the repaired composite material. If the test is passed, the repair is complete. Non-destructive testing ensures the reliability of the repair.

[0036] Compared to existing patching and traditional injection methods, patching causes significant structural damage and incurs higher repair costs. Like traditional injection methods, it also causes secondary damage, which is unacceptable. This application employs a resin injection method for repairing delamination damage in composite materials. Specifically, the process involves first visually inspecting the fastener hole edges of the composite material to locate the gaps in the fasteners where delamination has occurred. Then, non-destructive testing is used to determine the damaged area and depth of the delamination. Next, suitable bolts are selected based on the hole diameter and depth of the delamination-damaged fasteners to manufacture resin injection bolts. Connected blind and through holes are made on the resin injection bolts, which are then installed in the damaged area. The prepared resin is then injected into the damaged area and cured. After curing, the resin residue is cleaned, and the repaired composite material undergoes non-destructive testing. Once the test is passed, the repair is complete. Compared to existing injection and patching methods, this method is more convenient and effective for repairing delamination damage at the hole edges of composite materials, with lower repair costs, guaranteed reliability, minimal damage to the original structure, and significant repair results.

[0037] As a specific implementation method, the following example is used to repair delamination damage at the leading edge of a fastener hole on a certain type of aircraft. After repair, non-destructive testing confirmed that the delamination at the fastener hole edge has been successfully repaired.

[0038] 1. In a certain type of aircraft, the area around the fasteners connecting the leading edge of the composite material and the upper wall panel (connecting strip) of the box section exhibits fraying, paint peeling, and detachment of the lightning protection mesh. Non-destructive testing scanned an area within 50mm of the hole edge, confirming delamination damage at the hole edge, with the damage location approximately 2.9mm from the outer surface of the skin.

[0039] 2. Select a titanium alloy bolt with a rod diameter of Φ5mm and a rod length of about 10mm according to the fastener diameter to make glue injection bolt 1. The diameter of glue injection blind hole 8 and through hole 9 is Φ2mm. The glue injection blind hole 8 is located at the bolt axis, and the center of the through hole 9 is about 3mm away from the nut.

[0040] 3. Inject the prepared resin into the damaged area through injection bolt 1.

[0041] (1) Use self-locking nut 7 to install glue injection bolt 1 on skin 4, and place Airpad rubber pads 3 and 6 above and below the delamination damage area of ​​composite material structure for sealing to prevent glue from flowing out during glue injection; adjust the position of glue injection through hole 9 by adding or removing shims 2 and 5 so that through hole 9 is aligned with the delamination position.

[0042] (2) Prepare a certain type of resin, use a syringe to inject the resin under pressure from the injection blind hole 8, maintain the pressure for 2-3 minutes, remove the injection bolt 1, remove excess sludge, and use fish clips and pressure plates to press the delaminated area.

[0043] 4. Cured and repaired structure: According to the curing requirements of a certain type of resin, it is maintained at 66℃±5℃ for more than 65 minutes. After repair, there is a small amount of glue sludge in the injection hole and around the hole, and no visible delamination.

[0044] 5. Non-destructive testing was performed on the repaired composite material structure. The reflected wave was consistent with the undelaminated area, indicating that the repair was effective.

[0045] Finally, it should be noted that the accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0046] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of repairing delaminated damage in a composite material, characterized in that, include: Visually inspect the edges of fastener holes in composite material structures to locate fastener holes with delamination, and then use non-destructive testing to scan a certain area around the fastener holes to determine the damaged area and depth of the delamination. The bolt size is determined based on the hole diameter and hole depth of the fastener with delamination damage. Then, the appropriate size bolt is selected to make the glue injection bolt (1). A glue injection blind hole (8) is opened at the axial position of the glue injection bolt (1), and a through hole (9) communicating with the glue injection blind hole (8) is opened at the radial position of the glue injection bolt (1). Install injection bolts (1) in the damaged area of ​​the composite material structure (4) and inject the prepared resin into the damaged area through the injection bolts (1); The repaired structure is cured according to the curing requirements of the prepared resin-based material; After curing, the sludge is cleaned up, and the repaired composite material structure is subjected to non-destructive testing. Once the test is passed, the repair is complete. The specific method for injecting resin into the glue-filled bolt (1) is as follows: A first rubber pad (3) and a second rubber pad (6) are respectively set on the upper and lower sides of the composite material structure (4). A first shim (2) is set on the outside of the first rubber pad (3), and a second shim (5) is set on the outside of the second rubber pad (6). The glue injection bolt (1) is installed to the delamination (4) damage position of the fastener hole of the composite material structure and connected to the first rubber pad (3), the second rubber pad (6), the first shim (2) and the second shim (5) respectively, until the top of the glue injection bolt (1) extends out from the inside of the second shim (5). The first shim (2) and the second shim (5) are adjusted so that the through hole (9) is aligned with the delamination damage position. Then, a nut (7) is screwed on the bottom of the glue injection bolt (1) to fix it. Resin is injected into the injection blind hole (8) and then flows through the through hole (9) to the delamination position of the composite material. Appropriate pressure is applied during injection to ensure that air bubbles in the cavity are discharged. After the resin injection is completed, the injection bolt (1) is removed and the delamination position is pressed tightly. The first and second shims (2) and the glue injection bolt (1) are threaded together.

2. The composite material delamination damage repair method as described in claim 1, characterized in that: The resin is injected into the injection blind hole (8) under pressure using a syringe, and the pressure is maintained for 2-3 minutes after injection.

3. The composite material delamination damage repair method as described in claim 1, characterized in that: The layers are pressed together using fish-shaped clamps and pressure plates.

4. The composite material delamination damage repair method as described in claim 1, characterized in that: The standard for fixing the resin is to maintain it at 66℃±5℃ for at least 65 minutes.

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