A method for repairing damage to a composite T-stringer-stiffened panel stringer

Abstract

The application discloses a repairing method for T-shaped long string stiffened wallboard long string damage of a composite material, and relates to the technical field of aviation composite material repairing. The repairing method for T-shaped long string stiffened wallboard long string damage of the composite material comprises the following steps: removing a damage area of a skin and a long string to form an opening, and polishing edges of the opening to form a repairing window; bonding a skin repairing patch to the repairing window; bonding a bottom edge repairing patch to the skin repairing patch; bonding a T-shaped long string insert to the bottom edge repairing patch, the T-shaped long string insert filling the truncated long string; and symmetrically laying L-shaped long string repairing patches on two sides of the T-shaped long string insert. The repairing method for T-shaped long string stiffened wallboard long string damage of the composite material realizes uniform load transmission, smooth stiffness transition and excellent fatigue performance, and has the advantages of light weight, smooth aerodynamic shape, seamless sealing to prevent corrosion medium from entering, and avoidance of secondary damage caused by drilling on the original structure.

Description

Technical Field

[0001] This invention relates to the field of aerospace composite material repair technology, and in particular to a method for repairing damage to a composite material T-shaped stringer stiffened panel stringer. Background Technology

[0002] Composite materials, due to their superior properties such as high specific strength, high specific stiffness, strong designability, fatigue resistance, and corrosion resistance, are increasingly widely used in civil aircraft airframe structures, with their usage continuing to rise. T-shaped stringer stiffened panels, as a typical structural form of composite material airframes for civil aircraft, have become an important component of main load-bearing parts such as wings and fuselages.

[0003] Civil aircraft inevitably encounter unexpected damage such as impacts and overloads during their service life. To ensure flight safety and extend service life, effective repairs of damaged parts are necessary. Adhesive bonding repair technology is one of the main methods for repairing damage to composite material structures due to its mature process and uniform stress distribution. However, existing technologies are mainly applicable to skin damage that does not involve the stringer. In such cases, the adhesive bonding repair method for typical composite laminate structures can be used as a reference.

[0004] However, when damage extends to the girder, current repair methods still primarily rely on mechanical connections. This method requires drilling holes in the existing structure to install fasteners, which not only disrupts fiber continuity and causes stress concentration, significantly reducing structural strength and fatigue life, but also leads to a series of problems such as significant weight increase, disruption of aerodynamic shape, induction of galvanic corrosion of dissimilar materials, and seal failure. Summary of the Invention

[0005] The purpose of this invention is to provide a method for repairing damage to the stringers of a composite material T-shaped stiffened panel, so as to achieve uniform load transfer, smooth stiffness transition and excellent fatigue performance, while being lightweight, maintaining a smooth aerodynamic shape, providing a seamless seal to prevent the intrusion of corrosive media, and avoiding secondary damage caused by drilling holes in the original structure.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for repairing damage to a composite material T-shaped stiffened girder panel, the girder comprising a web and a bottom edge; comprising the following steps:

[0008] Remove damaged areas of the skin and stringers to create openings, and grind the edges of the openings to create repair windows;

[0009] A skin repair patch is bonded to the repair window;

[0010] A bottom edge repair patch is bonded to the skin repair patch;

[0011] A T-shaped stringer insert is bonded to the bottom edge repair patch, and the T-shaped stringer insert fills the truncated stringer.

[0012] L-shaped stringer repair patches are symmetrically applied to both sides of the T-shaped stringer insert.

[0013] As an alternative method for repairing damage to the T-shaped stiffened wall panel of the composite material, a method for grinding the edge of the opening to form a repair window includes:

[0014] On the non-stringer side of the skin, the skin at the edge of the opening is ground into a slope that slopes downward from the outside to the inside.

[0015] On the side of the skin stringer, the bottom edge of the opening edge is ground into a slope that slopes downward from the outside to the inside.

[0016] As an alternative method for repairing damage to the stiffened T-shaped stringer wall panel of the composite material, the slope of the ramp is 1:50 to 1:30.

[0017] As an alternative method for repairing damage to the T-shaped stiffened wall panel of the composite material, the method of bonding the skin repair patch includes:

[0018] A skin repair shim is provided, which is then bonded to the repair window from the skin stringer side, the skin repair shim covering the opening;

[0019] The skin repair patch is adhered to the repair window from the non-stringer side of the skin.

[0020] After the skin repair patch has been cured, the skin repair pad is removed.

[0021] As an alternative method for repairing damage to the T-shaped stiffened wall panel of the composite material, the skin repair pad is a metal plate or a non-metal plate, wherein the temperature resistance of the non-metal plate is higher than the curing temperature when the skin repair patch is bonded.

[0022] As an alternative method for repairing damage to the stiffened T-shaped stringer of the composite material, the T-shaped stringer insert is a pre-cured component.

[0023] As an optional method for repairing damage to the T-shaped stiffened wall panel of the composite material, along the extension direction of the stringer, the two sides of the L-shaped stringer repair patch extend beyond the damaged area, and the length extending beyond the damaged area is a preset length; along the direction perpendicular to the extension direction of the stringer, the L-shaped stringer repair patch extends beyond the width of the bottom edge, and the width extending beyond the bottom edge is a preset width.

[0024] As an alternative method for repairing damage to the T-shaped stiffened wall panel of the composite material, before the L-shaped stiffened repair patch is cured, twill strips are pre-filled at the steps formed between the two sides of the bottom edge and the skin.

[0025] As an alternative method for repairing damage to the stiffened T-shaped stringer panel of the composite material, the bonding and curing temperatures of the skin repair patch, the bottom edge repair patch, the T-shaped stringer insert, and the L-shaped stringer repair patch are lower than the bonding and curing temperatures during the production of the stiffened panel.

[0026] As an alternative method for repairing damage to the T-shaped stiffened wall panel of the composite material, the skin repair patch, the bottom edge repair patch, and the L-shaped stiffened wall panel are bonded with prepreg and adhesive film, or with dry fiber and resin wet lay-up layer.

[0027] The beneficial effects of this invention are:

[0028] This invention provides a method for repairing damaged T-shaped stiffened composite material panels. The method involves removing the skin and stringer in the damaged area to create an opening, preventing damage propagation. The edges of the opening are then ground to form a repair window, providing a bonding interface for subsequent patching. First, a skin repair patch is bonded to the repair window to restore skin continuity and provide a flat and stable base support surface for subsequent stringer repair, ensuring the integrity of the load transfer path and preventing skin deformation or secondary damage caused by repairing the stringer first. Next, a bottom edge repair patch is bonded to the skin repair patch to restore the connection interface between the stringer bottom edge and the skin. The stringer bottom edge is a critical area for the stringer to distribute loads to the skin; a separate bottom edge repair patch accurately restores the shear load transfer capacity of this area, avoiding direct load concentration to the skin repair patch and achieving gradual load diffusion. Finally, a T-shaped stringer insert is bonded to the bottom edge repair patch to fill the truncated stringer, allowing the stringer web and bottom edge to regain continuous support in the damaged area, restoring the stringer's bending stiffness and axial load-bearing capacity. By symmetrically applying L-shaped stringer repair patches to both sides of the T-shaped stringer insert, the T-shaped stringer insert is connected to the original stringer web as a whole. This ensures that the shrinkage stress during the adhesive curing process is balanced, preventing out-of-plane deformation or warping of the stringer web. The L-shaped stringer repair patches simultaneously wrap around the web and bottom edge, achieving a continuous load transfer path. This method for repairing damaged T-shaped stringer stiffened panels made of composite materials achieves uniform load transfer, a smooth stiffness transition, and excellent fatigue performance. It also features lightweight construction, maintains a smooth aerodynamic shape, provides a seamless seal to prevent the intrusion of corrosive media, and avoids secondary damage caused by drilling into the original structure. Attached Figure Description

[0029] Figure 1This is a structural schematic diagram of the T-shaped stringer reinforced wall panel provided in an embodiment of the present invention;

[0030] Figure 2 This is a flowchart of a method for repairing damage to a composite material T-shaped stringer reinforced wall panel provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure provided in an embodiment of the present invention, which shows the removal of damaged areas of the skin and stringer to form an opening, and the grinding of the opening to form a repair window;

[0032] Figure 4 This is a schematic diagram of the structure of the non-stringer side of the skin after forming the repair window, provided in an embodiment of the present invention;

[0033] Figure 5 yes Figure 3 A magnified view of a portion of point A in the middle;

[0034] Figure 6 This is a schematic diagram of the method for bonding repair pads to the skin provided in an embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of the method for bonding and repairing skin patches provided in an embodiment of the present invention;

[0036] Figure 8 This is a schematic diagram of the structure after the skin repair patch has been bonded, as provided in an embodiment of the present invention;

[0037] Figure 9 yes Figure 8 Sectional view along the BB direction;

[0038] Figure 10 This is a schematic diagram of the structure of the adhesive bottom edge repair patch provided in an embodiment of the present invention;

[0039] Figure 11 This is a schematic diagram of the structure after the T-shaped stringer insert is bonded according to an embodiment of the present invention;

[0040] Figure 12 This is a schematic diagram of a structure provided by an embodiment of the present invention, in which twist strips are pre-filled at the step between the bottom edge of the stringer and the skin;

[0041] Figure 13 This is a schematic diagram of the structure after L-shaped stringer repair patches are symmetrically laid on both sides of the T-shaped stringer insert provided in an embodiment of the present invention;

[0042] Figure 14 yes Figure 13 A magnified view of a portion of point C in the middle;

[0043] Figure 15This is a schematic diagram of the structure of the stringer side of the reinforced wall panel after repair using the repair method for stringer damage of the composite material T-shaped stringer stiffened wall panel provided in the embodiments of the present invention;

[0044] Figure 16 This is a schematic diagram of the non-stringer side of the reinforced wall panel after repair using the repair method for stringer damage of the composite material T-shaped stringer reinforced wall panel provided in the embodiments of the present invention;

[0045] Figure 17 This is a top view of the reinforced wall panel after repair using the repair method for damage to the composite material T-shaped stringer stiffened wall panel provided in the embodiments of the present invention.

[0046] Figure 18 yes Figure 17 The sectional view at point DD.

[0047] In the picture:

[0048] 1. Skin;

[0049] 2. Girder; 21. Bottom edge; 22. Web;

[0050] 3. Opening;

[0051] 4. Repair the window; 41. Slope;

[0052] 5. Skin repair patches;

[0053] 6. Repair patch for the bottom edge;

[0054] 7. T-shaped stringer insert;

[0055] 8. L-shaped stringer repair patch;

[0056] 9. Skin repair gaskets;

[0057] 10. Twisted strips. Detailed Implementation

[0058] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0059] Unless otherwise expressly specified and limited, "above" or "below" a second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of a second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" of a second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0061] T-shaped stiffened stringer panels are a typical structural form for composite material fuselages of civil aircraft, and have become an important component of main load-bearing parts such as wings and fuselages. For example... Figure 1 As shown, the T-shaped stringer stiffened panel is a typical composite thin-walled stiffened structure, consisting of a skin 1 and several longitudinally arranged T-shaped stringers 2, which are co-cured or bonded together. The skin 1 serves as the basic shell unit of the panel, bearing in-plane tensile, compressive, shear, and aerodynamic loads, and transferring these loads to the stringers 2 and the internal frame. In civil aircraft structures, the skin 1 is typically a multi-layer carbon fiber and epoxy resin prepreg laminate, with the layup direction optimized based on the load spectrum. The T-shaped stringer is a slender, T-shaped reinforcing rib, comprising a web 22, a bottom edge 21, and a flange. The web 22 is the vertical portion perpendicular to the skin 1, bearing the axial tensile and compressive loads of the stringer 2 and providing bending stiffness. The bottom edge 21 is a horizontal flange bonded to the skin 1, responsible for distributing the load borne by the web 22 to the skin 1, and is the core area for load transfer at the stringer 2-skin 1 interface. The flange is the transition area between the web 22 and the bottom edge 21, typically using infilled twisted strips or rounded corners to avoid stress concentration at sharp corners. The T-shaped stringer increases the critical buckling stress of the skin 1, preventing instability of the thin-walled skin 1 under compressive and shear loads; it concentrates distributed loads such as fuselage airtight pressure difference and wing aerodynamic suction to the main load-bearing components such as frames and beams; and the stringer 2 acts as a crack arrestor, limiting the propagation path of cracks in the skin 1.

[0062] When civil aircraft suffer accidental damage such as impacts or overloads during service, affecting the stringer 2, the current repair solution still mainly relies on mechanical connections. This method requires drilling holes in the existing structure to install fasteners, which not only disrupts fiber continuity and causes stress concentration, significantly reducing structural strength and fatigue life, but also leads to a series of problems such as significant weight increase, damage to aerodynamic shape, induction of galvanic corrosion of dissimilar materials, and seal failure.

[0063] To solve the above technical problems, such as Figure 2As shown, this embodiment provides a method for repairing damage to the stiffened T-shaped stringer of a composite material wall panel, including the following steps:

[0064] S10. Remove the damaged areas of the skin 1 and stringer 2 to form an opening 3, and grind the edges of the opening 3 to form a repair window 4.

[0065] First, non-destructive testing methods such as ultrasonic scanning or impact testing were used to accurately detect the damaged areas of the T-shaped stringer stiffened panel, determining the boundary range of damages such as skin delamination 1, web crack 22, and bottom edge debonding 21. Then, based on the test results, the areas to be removed were marked on the outer side of skin 1 and web 22, completely removing all visible damage and potential damage propagation areas while preserving as much healthy parent material as possible.

[0066] Specifically, such as Figure 3 As shown, the excision range of skin 1 is: based on the damage boundary, extending outwards by at least 5mm to 10mm to ensure that the cut edge falls into a healthy laminate area without delamination or microcracks. The excision range of stringer 2 is: along the extension direction of stringer 2, based on the two ends where the web 22 cracks or the bottom edge 21 debonds, extending outwards by 10mm to 15mm to cut off stringer 2, ensuring that there is no residual damage at the ends of the remaining stringer 2. Typically, the cut-off length of the web 22 is greater than the cut-off length of the bottom edge 21 to leave a grinding area for the bottom edge 21, forming a bonding area.

[0067] In other embodiments, the specific length of the excision range of the skin 1 and the stringer 2 can be determined based on the determined damage boundary range, and is not limited to the excision length described above.

[0068] Using ultrasonic cutting equipment, the damaged area of ​​the skin 1 is cut off vertically along the marked line to form a rectangular or elliptical through opening 3; at the same time, the damaged section of the stringer 2 (including the web 22 and the bottom edge 21) is completely cut off and removed to expose the hole in the skin 1 to be repaired and the broken end of the stringer 2.

[0069] In one embodiment, such as Figure 4 and Figure 5 As shown, the method of grinding the edge of opening 3 to form repair window 4 includes: on the non-stringer side of the skin, grinding the skin 1 at the edge of opening 3 into a downward sloping slope 41 from the outside in; on the stringer side of the skin, grinding the bottom edge 21 of opening 3 into a downward sloping slope 41 from the outside in. The setting of grinding into slope 41 increases the bonding area, reduces the peak peel stress, ensures sealing, and prevents the intrusion of corrosive media.

[0070] Specifically, an annular band radiating outward from the edge of opening 3 with a width of 20mm to 30mm is formed using alumina sandpaper or diamond grinding head to avoid fiber fuzzing or overheating damage to the resin.

[0071] The slope of ramp 41 is 1:50 to 1:30. For example, the slope of ramp 41 can be 1:50, 1:40, or 1:30.

[0072] If the slope of ramp 41 is 1:30, that is, for every 1mm decrease in thickness, the horizontal extension is 30mm, it ensures a smooth stress transfer. Of course, in other embodiments, the slope of ramp 41 can be flexibly varied according to the actual repair conditions, and is not limited to the slope range mentioned above.

[0073] S20. Attach the skin repair patch 5 to the repair window 4 (refer to...) Figure 7 ).

[0074] In one embodiment, such as Figure 6 As shown, the method for bonding the skin repair patch 5 includes:

[0075] S21. Provide a skin repair pad 9, and attach the skin repair pad 9 to the repair window 4 from the side of the skin stringer, with the skin repair pad 9 covering the opening 3.

[0076] Based on the size of the repair window 4, if the opening 3 is a rectangular opening, the repair window 4 is a rectangular opening with a relatively larger area than the opening 3. The size of the skin repair pad 9 matches the size of the repair window 4, while avoiding the bottom edge 21 of the outer edge of the opening 3, so that it completely covers the opening 3 after bonding.

[0077] In one embodiment, the skin repair pad 9 is a metal plate or a non-metal plate, wherein the non-metal plate has a higher temperature resistance than the curing temperature during the bonding of the skin repair patch 5. The skin repair pad 9 not only provides support for the laying and curing of the skin repair patch 5, but also controls the quality of the repair curing interface and optimizes the bonding quality of the bottom edge repair patch 6.

[0078] When the skin repair shim 9 is a metal plate, the metal plate has sufficient hardness to provide effective support and can withstand the curing temperature during the bonding of the skin repair shim 9. When the skin repair shim 9 is a non-metallic plate, it must be ensured that its temperature resistance is higher than the curing temperature during the bonding of the skin repair patch 5 to prevent it from melting during the curing process. The non-metallic plate can be a plastic plate or a composite material plate.

[0079] S22. Attach the skin repair patch 5 to the repair window 4 from the non-stringer side of the skin.

[0080] like Figures 7-9 As shown, the ply configuration of the skin repair patch 5 is determined based on the ply sequence, ply angle, single-layer thickness, and material system of the original skin 1 structure, and meets the requirements for the geometric dimensions, load transfer path, and stiffness matching of the repair window 4. After the skin repair patch 5 is laid, it completely fills the opening 3 on the skin 1 and is flush with the side surface of the skin stringer.

[0081] S23. After curing the skin repair patch 5, remove the skin repair pad 9.

[0082] S30. Attach the bottom edge repair patch 6 to the skin repair patch 5.

[0083] like Figure 10 As shown, the bottom edge repair patch 6 is laid and cured from the side of the girder. The layup angle and sequence of the bottom edge repair patch 6 are consistent with the layup design of the corresponding area of ​​the original girder bottom edge 21 to ensure axial stiffness matching. The thickness of the cured bottom edge repair patch 6 is equal to the remaining thickness of the ground girder bottom edge 21, or slightly thicker by 0.1mm to 0.2mm to allow for finishing after curing.

[0084] The bottom edge repair patch 6 has a rectangular shape, with the same width as the bottom edge 21 of the original stringer 2. Its length extends to both sides along the extension direction of the stringer 2, and each side extends beyond the edge of the opening 3 to the slope 41 covering the bottom edge 21.

[0085] S40. Attach T-shaped stringer insert 7 to the bottom edge repair patch 6. The T-shaped stringer insert 7 fills the cut stringer 2.

[0086] In one embodiment, such as Figure 11 As shown, the T-shaped stringer insert 7 is a pre-cured component. The T-shaped stringer insert 7 is pre-cured using an independent mold to ensure sufficient structural rigidity and dimensional stability, facilitating direct placement and bonding during repair operations.

[0087] The layup sequence, layup angle, and layup ratio in each direction of the T-shaped stringer insert 7 completely replicate the design layup of the cut stringer segment, ensuring that the axial stiffness, bending stiffness, and coefficient of thermal expansion match the original stringer 2. The total thickness of the T-shaped stringer insert 7 and the thickness of each layer after curing are consistent with the original stringer 2. After molding, the height of the web 22, the width of the bottom edge 21, and the thickness of the bottom edge 21 strictly meet the tolerance requirements of the original engineering drawings.

[0088] Apply a layer of adhesive to the entire surface of the bottom edge repair patch 6, covering the projection area of ​​the bottom edge 21 of the T-shaped stringer insert 7. Place the T-shaped stringer insert 7 accurately on the bottom edge repair patch 6 according to the alignment line, and the lower surface of the bottom edge 21 of the T-shaped stringer insert 7 is completely adhered to the adhesive film.

[0089] Using the T-shaped stringer insert 7 can accurately restore structural stiffness and force transmission path, optimize stress distribution, simplify the process and ensure quality, and effectively improve repair efficiency and long-term reliability.

[0090] S50. Apply L-shaped stringer repair patches 8 symmetrically on both sides of the T-shaped stringer insert 7.

[0091] like Figures 12-14As shown, L-shaped stringer repair patches 8 are symmetrically laid on both sides of the T-shaped stringer insert 7. Before the L-shaped stringer repair patches 8 are cured, tack strips 10 need to be pre-filled at the steps formed between the bottom edge 21 and the skin 1 to ensure the internal quality after curing.

[0092] The L-shaped stringer repair patch 8 is symmetrically laid on both sides. While restoring the axisymmetric load-bearing characteristics of stringer 2, it can simultaneously offset peeling stress, eliminate eccentric load, and effectively restore the symmetrical load-bearing characteristics and overall stability of the stringer 2-skin 1 interface.

[0093] In one embodiment, along the extension direction of the stringer 2, the two sides of the L-shaped stringer repair patch 8 extend beyond the damaged area, with the length exceeding the damaged area being a preset length; along the extension direction perpendicular to the stringer 2, the L-shaped stringer repair patch 8 extends beyond the width of the bottom edge 21, with the width exceeding the bottom edge 21 being a preset width. The L-shaped stringer repair patch 8 extending beyond the damaged area along the extension direction of the stringer 2 overlaps with the original stringer 2, and the L-shaped stringer repair patch 8 extending beyond the damaged area along the extension direction perpendicular to the stringer 2 overlaps with the skin 1, increasing the bonding area, which can homogenize boundary stress, reduce the risk of debonding, improve sealing performance and fatigue life, and ensure the reliability of the repair boundary.

[0094] In this embodiment, the preset length and preset width are not specifically limited. The preset length can be one-fifth of the length of the damaged area, and the preset width can be equal to one-half of the width of the bottom edge 21, and does not cover the bottom edge 21 of the stringer 2 adjacent to the damaged stringer 2.

[0095] The bonding and curing temperatures of the aforementioned skin repair patch 5, bottom edge repair patch 6, T-shaped stringer insert 7, and L-shaped stringer repair patch 8 are lower than the bonding and curing temperatures during the production of the stiffened wall panel, in order to avoid thermal aging, thermal stress cracking, or dimensional instability of the original structural composite material matrix and adhesive interface caused by high temperature.

[0096] The curing equipment uses a composite material bonding and repair heat repair instrument for heating and curing, combined with a local vacuum bag system for heating and pressurization. No autoclave is required throughout the process, making it suitable for field and repair station environments.

[0097] The curing process is as follows: T-type thermocouples are placed at the edge of the patch, the bonding interface, and the heat-sensitive areas of the original structure (such as the root of web 22) to monitor the curing temperature in real time; then, a vacuum bag is used for sealing, and the heating blanket of the composite material bonding repair heat repair instrument is directly attached to the top of the vacuum bag, with the edges fixed with high-temperature resistant tape; the curing temperature is lower than the curing temperature of the original structure, completely eliminating the risk of thermal damage and ensuring the mechanical integrity of the original stringer 2 and skin 1; the closed-loop temperature control of the composite material bonding repair heat repair instrument combined with the pressure equalization of the vacuum bag meets the standards for repairing aerospace bonded structures.

[0098] In one embodiment, the skin repair patch 5, the bottom edge repair patch 6, and the L-shaped stringer repair patch 8 are bonded with prepreg and adhesive film, or with dry fiber and resin wet lay-up layer.

[0099] When using prepreg and epoxy film co-curing bonding, the patch material is selected from carbon fiber and epoxy resin prepreg of the same system as the base material; a medium-temperature curing epoxy film is laid at the bonding interface. The prepreg is laid on the activated repair area according to the designed layup sequence, the epoxy film is placed at the bonding interface, a vacuum bag is sealed in one go, and a composite material bonding repair heat patching instrument is used for heating and co-curing.

[0100] When using a wet-lay bonding method with dry fibers and resin, the patch material is selected as carbon fiber dry fiber (fabric or unidirectional tape), which is impregnated on-site with a two-component epoxy repair resin (such as epoxy resin and amine curing agent, mixed and degassed according to the supplier's specified ratio). Layers are laid and compacted using rollers, ensuring accurate fiber orientation and uniform resin impregnation for each layer. Finally, the layers are sealed in vacuum bags and cured at a medium temperature. For example, the medium temperature is 90℃~120℃.

[0101] like Figures 15-18As shown in this embodiment, the method for repairing damage to the composite material T-shaped stiffened panel stringer involves removing the skin 1 and stringer 2 in the damaged area to form an opening 3, preventing damage propagation. The edges of the opening 3 are then ground to form a repair window 4, providing a bonding interface for subsequent patches. First, a skin repair patch 5 is bonded to the repair window 4 to restore the continuity of the skin 1 and provide a flat and stable base support surface for subsequent stringer 2 repair, ensuring the integrity of the load transfer path and preventing deformation or secondary damage to the skin 1 caused by repairing the stringer 2 first. Next, a bottom edge repair patch 6 is bonded to the skin repair patch 5 to restore the connection interface between the bottom edge 21 of the stringer 2 and the skin 1. The bottom edge 21 of the stringer 2 is a critical area for the stringer 2 to diffuse the load to the skin 1. Separately setting the bottom edge repair patch 6 can accurately restore the shear load transfer capacity of this area, avoiding direct concentrated transfer of the stringer 2 load to the skin repair patch 5, and achieving gradual load diffusion. By bonding T-shaped stringer inserts 7 to the bottom edge repair patch 6 to fill the truss 2 that was cut off, the web 22 and bottom edge 21 of the stringer 2 regain continuous support in the damaged area, restoring the bending stiffness and axial load-bearing capacity of the stringer 2. By symmetrically attaching L-shaped stringer repair patches 8 to both sides of the T-shaped stringer insert 7, the T-shaped stringer insert 7 is connected to the original web 22 of the stringer 2 as a whole. This ensures that the shrinkage stress during the adhesive curing process is balanced, preventing out-of-plane deformation or warping of the web 22 of the stringer 2. The L-shaped stringer repair patches 8 simultaneously wrap around the web 22 and bottom edge 21, achieving a continuous load transfer path. This method for repairing damaged T-shaped stringer stiffened wall panels made of composite materials achieves uniform load transfer, a smooth stiffness transition, and excellent fatigue performance. It also features lightweight construction, maintains a smooth aerodynamic shape, provides a seamless seal to prevent the intrusion of corrosive media, and avoids secondary damage caused by drilling into the original structure.

[0102] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for repairing damage to a composite material T-shaped stiffened girder panel, wherein the girder (2) comprises a web (22) and a bottom edge (21); characterized in that, Includes the following steps: Remove the damaged areas of the skin (1) and stringer (2) to form an opening (3), and grind the edges of the opening (3) to form a repair window (4); A skin repair patch (5) is bonded to the repair window (4); A bottom edge repair patch (6) is bonded to the skin repair patch (5); A T-shaped stringer insert (7) is bonded to the bottom edge repair patch (6), and the T-shaped stringer insert (7) fills the truncated stringer (2); L-shaped stringer repair patches (8) are symmetrically applied to both sides of the T-shaped stringer insert (7).

2. The method for repairing damage to the composite material T-shaped stringer reinforced panel stringer according to claim 1, characterized in that, The method of grinding the edge of the opening (3) to form the repair window (4) includes: On the non-stringer side of the skin, the skin (1) at the edge of the opening (3) is ground into a slope (41) that slopes downward from the outside to the inside; On the side of the skin stringer, the bottom edge (21) of the opening (3) is ground into a slope (41) that slopes downward from the outside to the inside.

3. The method for repairing damage to the composite material T-shaped stringer reinforced wall panel stringer according to claim 2, characterized in that, The slope of the ramp (41) is 1:50 to 1:

30.

4. The method for repairing damage to the composite material T-shaped stringer reinforced wall panel stringer according to claim 1, characterized in that, The method of bonding the skin repair patch (5) includes: A skin repair pad (9) is provided and is bonded to the repair window (4) from the side of the skin stringer, the skin repair pad (9) covering the opening (3); The skin repair patch (5) is bonded to the repair window (4) from the non-stringer side of the skin. After the skin repair patch (5) is cured, the skin repair pad (9) is removed.

5. The method for repairing damage to the composite material T-shaped stringer reinforced wall panel stringer according to claim 4, characterized in that, The skin repair pad (9) is a metal plate or a non-metal plate, wherein the temperature resistance of the non-metal plate is higher than the curing temperature of the skin repair patch (5) during bonding.

6. The method for repairing damage to the composite material T-shaped stringer reinforced panel stringer according to claim 1, characterized in that, The T-shaped stringer insert (7) is a pre-cured component.

7. The method for repairing damage to the composite material T-shaped stringer reinforced panel stringer according to claim 1, characterized in that, Along the extension direction of the stringer (2), the two sides of the L-shaped stringer repair patch (8) extend beyond the damaged area, and the length beyond the damaged area is a preset length; along the extension direction perpendicular to the stringer (2), the L-shaped stringer repair patch (8) extends beyond the width of the bottom edge (21), and the width beyond the bottom edge (21) is a preset width.

8. The method for repairing damage to the composite material T-shaped stringer reinforced panel stringer according to claim 1, characterized in that, Before the L-shaped stringer repair patch (8) is cured, twist strips (10) are prefilled at the steps formed between the two sides of the bottom edge (21) and the skin (1).

9. The method for repairing damage to the composite material T-shaped stringer reinforced panel stringer according to any one of claims 1-8, characterized in that, The bonding and curing temperatures of the skin repair patch (5), the bottom edge repair patch (6), the T-shaped stringer insert (7), and the L-shaped stringer repair patch (8) are lower than the bonding and curing temperatures during the production of the stiffened wall panel.

10. The method for repairing damage to the composite material T-shaped stringer reinforced panel stringer according to any one of claims 1-8, characterized in that, The skin repair patch (5), the bottom edge repair patch (6), and the L-shaped stringer repair patch (8) are bonded with prepreg and adhesive film, or with dry fiber and resin wet-lay layer.

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