A method of repairing a honeycomb sandwich structure

Abstract

A kind of honeycomb sandwich structure repair method, comprising the following steps: the posture of the end of each air guide strip is placed on the top surface of the repaired honeycomb core, the other end is placed on the top surface of the initial outer skin;Adhesive is arranged on the top surface of the repaired honeycomb core, the top surface of the part of the air guide strip stack located on the top surface of the repaired honeycomb core and the top surface of the part of the air guide strip stack located on the top surface of the initial outer skin;The repair outer skin is filled in the gap;Heat the adhesive, so that the adhesive is fully melted, and after the adhesive is solidified, the bottom surface of the repair outer skin is connected to the top surface of the repaired honeycomb core, and the edge of the repair outer skin is connected to the initial outer skin;The present application can prevent the defects such as hollowing and delamination of the outer skin after the repair is completed.

Description

Technical Field

[0001] This invention relates to the field of aircraft maintenance technology, and in particular to a method for repairing a honeycomb sandwich structure. Background Technology

[0002] To reduce weight while maintaining strength, many aircraft components feature honeycomb sandwich structures, such as flaps, elevators, and rudders on control surfaces, as well as radomes, landing gear doors, and fan covers on fuselage components. When a honeycomb sandwich structure is partially damaged, the general repair method involves removing the initial outer skin and initial honeycomb core in the repair area to create a gap in the initial outer skin. A spare honeycomb core is then placed in the corresponding position, and an adhesive film is laid on top of the initial outer skin and the spare honeycomb core, covering the gap and extending outwards. The spare outer skin is then placed over the gap and heated to bond it. However, because the honeycomb sandwich is a closed space with cavities inside, the air inside the honeycomb sandwich can easily expand during the heating process, leading to defects such as blistering and delamination of the outer skin, thus reducing the quality of the repair. Summary of the Invention

[0003] The purpose of this invention is to provide a repair method for honeycomb sandwich structures, in order to solve the technical problem that when honeycomb sandwich structures are repaired by thermal bonding, the air inside expands, causing defects such as hollowing and delamination of the outer skin, thereby reducing the repair quality.

[0004] To achieve the above objectives, the present invention provides a method for repairing a honeycomb sandwich structure, comprising the following steps: (S1) The initial outer skin is cut away at the location corresponding to the repair area to form a notch; (S2) Remove the initial honeycomb core at the location corresponding to the repair area; (S3) Place the repaired honeycomb core on the inner skin of the corresponding repair area; (S4) Connect the edge of the repaired honeycomb core to the initial honeycomb core, and connect the bottom surface of the repaired honeycomb core to the top surface of the inner skin; (S5) Place the air guide strip stack with one end of each air guide strip on the top surface of the repaired honeycomb core and the other end on the top surface of the initial outer skin. (S6) Apply adhesive to the top surface of the repaired honeycomb core, the top surface of the portion of the air guide strip stack located on the top surface of the repaired honeycomb core, and the top surface of the portion of the air guide strip stack located on the top surface of the initial outer skin; (S7) Fill the gap with the repaired outer skin; (S8) Heat the adhesive to fully melt it. After the adhesive solidifies, the bottom surface of the repaired outer skin is connected to the top surface of the repaired honeycomb core, and the edge of the repaired outer skin is connected to the initial outer skin. (S9) Remove the portion of the air guide bar that protrudes beyond the initial outer skin.

[0005] Optionally, in step (S5), the air guide strip stack is placed along the edge of the notch and completely covers the edge of the notch.

[0006] Optionally, in step (S5), the air guide bar stack is made of stacked glass fiber bundles.

[0007] Optionally, in step (S5), each air guide bar in the air guide bar stack has a length of 1 inch to 2 inches, and the weight of the air guide bar stack per square inch in the horizontal direction is less than 0.0025g.

[0008] Optionally, in step (S6), the adhesive is a structural adhesive film or an epoxy resin adhesive.

[0009] Optionally, in step (S6), the thickness of the adhesive is 0.5 mm to 1 mm, the temperature of heating the adhesive is 90°C to 180°C, and the duration of heating the adhesive is 0.5 hours to 4 hours.

[0010] Optionally, in step (S5), in the gas guide bar stack, each gas guide bar is perpendicular to the edge of the notch in the horizontal direction, and the midpoint of each gas guide bar is located on the notch in the horizontal direction.

[0011] Optionally, the following steps may also be included: Before step (S1), a protective film is used to cover the outer edge of the area corresponding to the initial outer skin repair area; After step (S9), the protective film is removed.

[0012] Optionally, the following steps are also included: after step (S2) and before step (S3), dehumidifying the location of the inner skin corresponding to the repair area, the location where the initial honeycomb core was removed, and the location where the initial outer skin was removed.

[0013] Optionally, the following step is also included: between step (S2) and step (S3), a base coat is applied to the top surface of the inner skin located in the repair area; Step (S3) is: Place the repaired honeycomb core on the base adhesive; The repair method further includes the following step: between step (S3) and step (S4), filling adhesive is applied to the gap between the repaired honeycomb core and the surrounding initial honeycomb core; Step (S4) is as follows: heat the primer and filler adhesive to fully melt them. After the primer and filler adhesive solidify, connect the edge of the repaired honeycomb core to the initial honeycomb core and connect the bottom surface of the repaired honeycomb core to the top surface of the inner skin.

[0014] Compared with the prior art, the repair method for a honeycomb sandwich structure according to an embodiment of the present invention has the following advantages: This invention creates a notch at the location corresponding to the repair area of ​​the initial outer skin. After replacing the damaged pull-out honeycomb core with a repair honeycomb core, the air guide strip stack is positioned with one end of each air guide strip on the top surface of the repair honeycomb core and the other end on the top surface of the initial outer skin. The repair outer skin is then placed over the notch, and the bottom surface of the initial outer skin is connected to the repair honeycomb core and the edge of the initial outer skin is connected to the initial outer skin via thermal bonding. The air guide strip stack is made of multiple stacked air guide strips, with air guide gaps between each strip to allow the cavities inside the honeycomb core to communicate with the outside. This is achieved by heating the adhesive... During the process, the air that expands and heats up inside the cavity can be promptly discharged through the aforementioned air guide gap. After heating for a certain period of time, a considerable amount of gas has been discharged through the air guide gap, which can prevent defects such as hollowing and delamination from occurring on the outer skin after the repair is completed. Furthermore, after heating for a period of time, the adhesive completely melts and permeates the air guide strip stack, filling the air guide gaps between the air guide strips. The adhesive passes through the air guide strip stack and fully contacts the initial outer skin. After heating ends and the adhesive solidifies, the bottom surface of the repaired outer skin is connected to the top surface of the repaired honeycomb core, and the edge of the repaired outer skin is connected to the initial outer skin. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of the exploded view of the present invention.

[0016] Figure 2 This is a view of the air guide bar stack of the present invention perpendicular to the length direction of the air guide bar.

[0017] Reference numerals: 1. Initial honeycomb core; 2. Repaired honeycomb core; 3. Initial outer skin; 4. Repaired outer skin; 5. Adhesive; 6. Air guide strip stack; 61. Air guide gap; 7. Inner skin. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] In the description of this invention, it should be understood that the terms "top", "bottom", "inner", "outer", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0021] like Figure 1 and Figure 2 As shown, a method for repairing a honeycomb sandwich structure according to the present invention includes the following steps: (S1) cutting off the position of the initial outer skin 3 corresponding to the repair area to form a notch; (S2) cutting off the position of the initial honeycomb core 1 corresponding to the repair area; (S3) placing the repair honeycomb core 2 on the inner skin 7 corresponding to the repair area; (S4) connecting the edge of the repair honeycomb core 2 to the initial honeycomb core 1, and connecting the bottom surface of the repair honeycomb core 2 to the top surface of the inner skin 7; (S5) placing the air guide strip stack 6 with one end located on the top surface of the repair honeycomb core 2 and the other end located on the initial outer skin 3. (S6) Position the top surface of the repaired honeycomb core 2; (S7) Place the adhesive 5 on the top surface of the portion of the air guide strip stack 6 located on the top surface of the repaired honeycomb core 2 and the top surface of the portion of the air guide strip stack 6 located on the top surface of the initial outer skin 3; (S8) Fill the gap with the repaired outer skin 4; (S9) Heat the adhesive 5 to fully melt it. After the adhesive 5 solidifies, the bottom surface of the repaired outer skin 4 is connected to the top surface of the repaired honeycomb core 2, and the edge of the repaired outer skin 4 is connected to the initial outer skin 3; (S10) Cut off the portion of the air guide strip stack 6 that protrudes from the initial outer skin 3.

[0022] In the above technical solution, the air guide strip stack 6 is made of multiple air guide strip stacks 6, and there is an air guide gap 61 between each air guide strip so that the cavity inside the honeycomb core is connected to the outside. During the heating of the adhesive 5, the air in the cavity that has heated and expanded can be discharged to the outside in time through the aforementioned air guide gap 61. After heating for a certain period of time, the air guide gap 61 has discharged a considerable amount of gas, which can prevent defects such as hollowing and delamination from occurring in the outer skin after the repair is completed. Furthermore, after heating for a period of time, the adhesive 5 completely melts and permeates the air guide strip stack 6, filling the air guide gap 61 between the air guide strips. The adhesive 5 passes through the air guide strip stack 6 and fully contacts the initial outer skin 3. After the heating is completed and the adhesive 5 solidifies, the bottom surface of the repaired outer skin 4 is connected to the top surface of the repaired honeycomb core 2, and the edge of the repaired outer skin 4 is connected to the initial outer skin 3. The air guide strip can be solid or open-core.

[0023] Furthermore, in step (S5), the gas guide strip stack 6 is placed along the edge of the notch and completely covers the edge of the notch to uniformly guide the gas outward and improve the gas guiding efficiency. Moreover, the gas guide strip is uniformly filled between the repaired outer skin 4 and the initial outer skin 3, so that the strength of each connection between the repaired outer skin 4 and the initial outer skin 3 tends to be the same.

[0024] Furthermore, in step (S5), the air guide strip stack 6 is made of stacked glass fiber bundles to obtain better air permeability, lighter weight and better strength.

[0025] Furthermore, in step (S5), in the air guide strip stack 6, each air guide strip is 1 to 2 inches long, and in the horizontal direction, the weight of each square inch of the air guide strip stack 6 is less than 0.0025g, in order to prevent the air guide strips from being too numerous, resulting in a small amount of adhesive 5 between the repaired outer skin 4 and the initial outer skin 3, which in turn leads to a serious decrease in the connection strength between the repaired outer skin 4 and the initial outer skin 3, making the connection strength unable to meet the usage requirements.

[0026] Furthermore, in step (S6), the adhesive 5 is a structural adhesive film or an epoxy resin adhesive; specifically, the adhesive 5 can be a structural adhesive film such as AF163-2 or EA9658, or an epoxy resin adhesive such as EA9390 or EA9321.

[0027] Furthermore, in step (S6), the thickness of the adhesive 5 is 0.5 mm to 1 mm, the temperature of the adhesive 5 is heated to 90°C to 180°C, and the duration of heating the adhesive 5 is 0.5 hours to 4 hours, so that the adhesive 5 can be completely melted and fully penetrate and contact the components.

[0028] Furthermore, in step (S5), in the air guide bar stack 6, each air guide bar is perpendicular to the edge of the notch in the horizontal direction, and the midpoint of each air guide bar is located on the notch in the horizontal direction, so that the air guide bar stack 6 is evenly distributed, so that the repair area obtains a more uniform weight and strength, and facilitates subsequent processes to be operated with the position of the air guide bar as an identifier.

[0029] Furthermore, the procedure includes the following steps: before step (S1), a protective film is used to cover the outer edge of the position corresponding to the repair area of ​​the initial outer skin 3 to prevent the process related to the adhesive 5 and the air guide strip stack 6 from affecting the top surface of the initial outer skin 3; after step (S9), the protective film is removed, at which time the surface of the protective film has solidified adhesive 5.

[0030] Furthermore, the procedure also includes the following steps: after step (S2) and before step (S3), the positions of the inner skin 7 corresponding to the repair area, the positions where the initial honeycomb core 1 is cut off, and the positions where the initial outer skin 3 is cut off are dehumidified to ensure the reliability of the connection in subsequent processes.

[0031] Furthermore, the procedure also includes the following steps: between steps (S2) and (S3), a base coat is applied to the top surface of the inner skin 7 located in the repair area; Step (S3) is as follows: Place the repaired honeycomb core 2 on the base adhesive; The repair method further includes the following step: between step (S3) and step (S4), filling adhesive is applied to the gap between the repaired honeycomb core 2 and the surrounding initial honeycomb core 1; Step (S4) is as follows: Heat the primer and filler adhesive to fully melt them. After the primer and filler adhesive solidify, connect the edge of the repaired honeycomb core 2 to the initial honeycomb core 1 and connect the bottom surface of the repaired honeycomb core 2 to the top surface of the inner skin 7. The primer can be an epoxy resin adhesive with a thickness of 0.5mm to 1mm, such as EA9390 or EA9321. The filler adhesive can be a structural bonding foam, such as FM410-1 or FM490A.

[0032] Furthermore, the specific connection methods of fixed setting and fixed connection refer to the methods that can fix the relative positional relationship of two connected components, including fixing by connectors, fixing by welding, fixing by adhesive, fixing by integral molding, and fixing by snap-fit ​​connection.

[0033] In summary, the embodiments of the present invention provide a method for repairing a honeycomb sandwich structure, the technical effects of which are as follows: In this invention, a notch is created at the location corresponding to the repair area of ​​the initial outer skin 3. After replacing the damaged pull-out honeycomb core with the repair honeycomb core 2, the air guide strip stack 6 is placed with one end of each air guide strip on the top surface of the repair honeycomb core 2 and the other end on the top surface of the initial outer skin 3. The repair outer skin 4 is then placed over the notch. The bottom surface of the initial outer skin 3 is connected to the repair honeycomb core, and the edge of the initial outer skin 3 is connected to the initial outer skin 3 by thermal bonding. The air guide strip stack 6 is composed of multiple stacks of air guide strips 6, with air guide gaps 61 between each air guide strip to allow the cavity inside the honeycomb core to communicate with the outside. During the heating and bonding process of the adhesive 5... In the process, the air that expands due to heating in the cavity can be promptly discharged out through the aforementioned air guide gap 61. After heating for a certain period of time, a considerable portion of the gas has been discharged through the air guide gap 61, which can prevent defects such as hollowing and delamination from occurring in the outer skin after the repair is completed. Furthermore, after heating for a period of time, the adhesive 5 completely melts and permeates the air guide strip stack 6, filling the air guide gap 61 between the air guide strips. The adhesive 5 passes through the air guide strip stack 6 and fully contacts the initial outer skin 3. After the heating ends and the adhesive 5 solidifies, the bottom surface of the repaired outer skin 4 is connected to the top surface of the repaired honeycomb core 2, and the edge of the repaired outer skin 4 is connected to the initial outer skin 3.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for repairing a honeycomb sandwich structure, characterized in that, Includes the following steps: (S1) The initial outer skin is cut away at the location corresponding to the repair area to form a notch; (S2) Remove the initial honeycomb core at the location corresponding to the repair area; (S3) Place the repaired honeycomb core on the inner skin of the corresponding repair area; (S4) Connect the edge of the repaired honeycomb core to the initial honeycomb core, and connect the bottom surface of the repaired honeycomb core to the top surface of the inner skin; (S5) Place the air guide strip stack with one end of each air guide strip on the top surface of the repaired honeycomb core and the other end on the top surface of the initial outer skin. (S6) Apply adhesive to the top surface of the repaired honeycomb core, the top surface of the portion of the air guide strip stack located on the top surface of the repaired honeycomb core, and the top surface of the portion of the air guide strip stack located on the top surface of the initial outer skin; (S7) Fill the gap with the repaired outer skin; (S8) Heat the adhesive to fully melt it. After the adhesive solidifies, the bottom surface of the repaired outer skin is connected to the top surface of the repaired honeycomb core, and the edge of the repaired outer skin is connected to the initial outer skin. (S9) Remove the portion of the air guide bar that protrudes beyond the initial outer skin.

2. The repair method for the honeycomb sandwich structure according to claim 1, characterized in that, In step (S5), the air guide strip stack is placed along the edge of the notch and completely covers the edge of the notch.

3. The method for repairing a honeycomb sandwich structure according to claim 1, characterized in that, In step (S5), the air guide bar stack is made of stacked glass fiber bundles.

4. The repair method for the honeycomb sandwich structure according to claim 3, characterized in that, In step (S5), each air guide bar in the air guide bar stack is 1 to 2 inches long, and the weight of each square inch of the air guide bar stack is less than 0.0025g in the horizontal direction.

5. The method for repairing a honeycomb sandwich structure according to claim 1 or 4, characterized in that, In step (S6), the adhesive is a structural adhesive film or an epoxy resin adhesive.

6. The repair method for the honeycomb sandwich structure according to claim 5, characterized in that, In step (S6), the thickness of the adhesive is 0.5 mm to 1 mm, the temperature of the adhesive is heated to 90°C to 180°C, and the duration of heating the adhesive is 0.5 hours to 4 hours.

7. The method for repairing a honeycomb sandwich structure according to claim 1, characterized in that, In step (S5), in the gas guide bar stack, each gas guide bar is perpendicular to the edge of the notch in the horizontal direction, and the midpoint of each gas guide bar is located on the notch in the horizontal direction.

8. The method for repairing a honeycomb sandwich structure according to claim 1, characterized in that, It also includes the following steps: Before step (S1), a protective film is used to cover the outer edge of the area corresponding to the initial outer skin repair area; After step (S9), the protective film is removed.

9. The method for repairing a honeycomb sandwich structure according to claim 1, characterized in that, It also includes the following steps: After step (S2) and before step (S3), the locations of the inner skin corresponding to the repair area, the locations where the initial honeycomb core was cut off, and the locations where the initial outer skin was cut off are dehumidified.

10. The method for repairing a honeycomb sandwich structure according to claim 1, characterized in that, It also includes the following steps: Between steps (S2) and (S3), the primer is applied to the top surface of the inner skin located in the repair area; Step (S3) is: Place the repaired honeycomb core on the base adhesive; The repair method further includes the following step: between step (S3) and step (S4), filling adhesive is applied to the gap between the repaired honeycomb core and the surrounding initial honeycomb core; Step (S4) is as follows: heat the primer and filler adhesive to fully melt them. After the primer and filler adhesive solidify, connect the edge of the repaired honeycomb core to the initial honeycomb core and connect the bottom surface of the repaired honeycomb core to the top surface of the inner skin.

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