Repair quality control method for wave-absorbing honeycomb sandwich structure

Abstract

The invention relates to the technical field of damage repair of wave-absorbing honeycomb sandwich structures, and particularly discloses a repair quality control method for a wave-absorbing honeycomb sandwich structure. Comprising the following steps of damage detection and evaluation, skin preliminary polishing removal, honeycomb core removal, honeycomb core repair, temporary skin panel preparation, panel-honeycomb core interface reinforcement, panel-honeycomb core interface inspection, wave absorbing performance pre-test, temporary skin panel removal, test result decision and wave absorbing performance final test. According to the method, a quality inspection node is moved forward, so that the repair process is changed into a closed loop from an open loop. On one hand, the problem of skin reworking caused by poor repairing effect of the wave-absorbing honeycomb is avoided, and on the other hand, when the final wave-absorbing performance does not meet the requirement, it can be determined that skin repairing does not reach the expectation, and the honeycomb core does not need to be repaired. According to the method, the repair cost is saved, the repair period is shortened, and the repair success rate and the long-term service reliability of the structure are improved.

Description

Technical Field

[0001] This invention relates to a quality control method, specifically a quality control method for repairing microwave absorbing honeycomb sandwich structures, belonging to the field of damage repair technology for microwave absorbing honeycomb sandwich structures. Background Technology

[0002] The microwave-absorbing honeycomb sandwich structure is a key component for realizing the electromagnetic functional characteristics of aircraft, typically composed of a transparent skin and a microwave-absorbing honeycomb core. This structure is susceptible to impact damage during service, leading to core collapse and breakage. The current mainstream repair process involves removing damage (including the skin and honeycomb core), replacing and curing the honeycomb core, repairing and curing the skin, and conducting a final microwave absorption performance test. Chinese patents CN115497584B, CN118829178A, and CN120682746A, all related to the repair of microwave-absorbing honeycomb sandwich structures, follow this process. However, it is worth noting that this process carries a significant systemic risk: the microwave absorption performance test is performed at the very end. If the test results are unsatisfactory, it indicates that the repair of the honeycomb core or skin panel has not met expectations. Since the skin is a composite laminate structure, the repair process is relatively mature, thus the possibility of non-compliance is low. However, the repair of the microwave-absorbing honeycomb requires precise matching of the electromagnetic parameters at the repair interface; even minute defects can become sources of electromagnetic scattering, affecting the final electromagnetic performance of the structure. Therefore, the repair of the honeycomb core is both a challenge and a key aspect of repairing microwave absorbing honeycomb sandwich structures. If the honeycomb core repair does not meet the requirements, the newly cured skin must be removed, and the honeycomb core must be repaired again. This repair process not only increases the repair cycle and cost but may also cause secondary damage to the surrounding intact skin during removal, greatly reducing the success rate and reliability of the repair. Therefore, how to verify the repair effect of the honeycomb core in advance without performing formal skin repair becomes a key issue in controlling the repair quality. Summary of the Invention

[0003] To address the problems in the existing technology, this invention provides a method for quality control of absorbing honeycomb sandwich structure repair. By introducing a pre-testing step of absorbing performance based on a temporary skin panel after the honeycomb core repair is cured and before the formal skin repair, an early and accurate diagnosis of the honeycomb core repair quality can be achieved.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for quality control in the repair of microwave absorbing honeycomb sandwich structures includes the following steps: Step 1: Damage Detection and Assessment: Use one or more of the following detection methods: visual inspection, ultrasound, and X-ray, to detect and determine the location of the damaged area in the honeycomb core and the size of the damage removal (the removal size should take into account the expansion of the potential hazard area). Step 2: Preliminary grinding and removal of the skin: The skin corresponding to the location of the damaged area of ​​the honeycomb core is initially ground into a regular shape (usually a circle) that is consistent with the projection of the damaged area of ​​the honeycomb core to be removed, and the size of the skin removal area after grinding is recorded. Step 3: Honeycomb core removal: Remove the damaged honeycomb core according to the dimensions determined in Step 1; Step 4: Honeycomb core repair: Repair and cure the honeycomb core; Step 5: Prepare a temporary skin panel: Using the same material system as the original skin, prepare a temporary skin panel with a diameter 0.3mm-1mm larger than the area where the skin was removed and a thickness consistent with the original skin. Step 6: Install temporary skin panel: Install the temporary skin panel with an interference fit in the repair area after the skin has been removed. The temporary skin panel should be flush with the surrounding skin and tightly spliced. Step 7: Panel-Cellular Core Interface Strengthening: Vacuum bag assembly is performed in the repair area. A uniform pressure of 0.1 MPa is applied to the installed temporary skin panel through the vacuum bag and the pressure is maintained for a preset time to ensure that the adhesive film fully contacts the repaired cell and removes interfacial air. Step 8: Panel-Cellular Core Interface Inspection: After the pressure holding is completed, the vacuum bag is removed, and non-destructive testing equipment such as ultrasonic A-scan is used to inspect and confirm that there is no gap between the temporary skin panel and the honeycomb core; Step 9: Pre-test of microwave absorption performance: With the temporary skin panel installed, the microwave absorption performance of the repaired microwave absorbing honeycomb sandwich structure is tested according to the preset test standards. Step 10: Remove the temporary skin panel: Remove the temporary skin panel using destructive or non-destructive methods. Since the skin in the repair area still needs to be polished later, slight damage to the skin area around the temporary skin panel is allowed to assist in the removal of the temporary skin panel. If you want to reuse the temporary skin panel, you can use non-destructive methods such as vacuum suction cups to remove the temporary skin panel. For example, if the absorption performance does not meet expectations in step 11 below, only the honeycomb core will be repaired. In this case, the temporary skin panel needs to be reused.

[0005] Step 11: Test result decision: If the absorption performance meets expectations, the skin is repaired; if the absorption performance does not meet expectations, only the honeycomb core is repaired until the absorption performance meets expectations before the skin is repaired. Step 12: Final absorption performance test: Conduct a final absorption performance test on the repaired absorbing honeycomb sandwich structure to ensure that the repaired absorbing honeycomb sandwich structure meets the usage requirements. If the absorption performance does not meet the requirements at this time, it is determined that the skin repair did not meet the expectations. Only the skin is repaired until the absorption performance test meets the requirements. There is no need to repair the honeycomb core to avoid expanding the scope of repair.

[0006] Optionally, in step 5, the temporary skin panel is prepared by autoclaving, and after preparation, it is tested by ultrasound to meet the preset usage requirements, that is, the temporary skin panel is in an undamaged state, so as to avoid the temporary skin panel affecting the test results of the wave absorption performance.

[0007] Optionally, during the installation of the temporary skin panel in step 6, an adhesive film of the same material system as the original absorbing honeycomb sandwich structure is pasted on its bottom surface to avoid the difference in adhesive film affecting the test results of the absorbing performance.

[0008] Optionally, if the honeycomb core repair effect in step 11 meets expectations, the skin of the repair area is polished and repaired according to the preset composite laminate repair process. A layer of isolation film is covered on the honeycomb core to prevent polishing dust from entering the honeycomb core cell. The skin is then polished into a stepped or sloping shape. After the skin is polished, the isolation film on the honeycomb core is removed. Then, the adhesive film and the prepreg to be used are laid layer by layer on the repair area and cured.

[0009] The beneficial effects of this invention are: This invention provides a method for controlling the repair quality of a microwave-absorbing honeycomb sandwich structure by preparing a temporary skin panel and conducting microwave absorption performance testing before skin repair. This method moves the quality inspection point forward, transforming the repair process from an "open-loop" to a "closed-loop" process. On the one hand, it avoids the problem of skin rework due to poor microwave-absorbing honeycomb repair results; on the other hand, if the final microwave absorption performance does not meet requirements, it can be clearly determined that the skin repair did not meet expectations, eliminating the need for rework of the honeycomb core and avoiding expanding the scope of rework. This method saves repair costs, shortens the repair cycle, improves the success rate of repair, and enhances the long-term reliability of the structure. Attached Figure Description

[0010] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0011] Figure 1 This is a schematic diagram of damage removal in the absorbing honeycomb sandwich structure of the present invention.

[0012] Figure 2 This is a schematic diagram of the microwave absorbing honeycomb sandwich structure with a temporary skin panel installed according to the present invention.

[0013] Figure 3 This is a schematic diagram illustrating the pre-test of the microwave absorption performance of a microwave-absorbing honeycomb sandwich structure with a temporary skin panel installed according to the present invention.

[0014] Figure 4 This is a schematic diagram of the repaired microwave absorbing honeycomb sandwich structure according to the present invention.

[0015] Figure 5This is a schematic diagram illustrating the pre-test of the absorption performance of the repaired absorbing honeycomb sandwich structure according to the present invention.

[0016] In the figure: 1. Honeycomb core; 2. Skin; 3. Temporary skin panel; 4. Wave absorption performance testing device; 5. Wave absorbing honeycomb sandwich structure. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0018] Please see Figure 1-5 As shown, this invention discloses a quality control method for repairing a microwave absorbing honeycomb sandwich structure. The following uses the repair of honeycomb core collapse damage in a certain type of aircraft microwave absorbing honeycomb sandwich structure as an example to further illustrate this invention.

[0019] 1. A certain type of aircraft's absorbing honeycomb sandwich structure experienced honeycomb core collapse damage. Visual inspection and ultrasonic A-scan determined the damaged dimensions of honeycomb core 1 to be 22mm × 21mm × 8mm (length × width × height). To standardize the repair dimensions and considering the influence of the damage boundary, the damage removal dimension was designed as a cylinder with a diameter of Ф30mm × 10mm.

[0020] 2. Use a pneumatic grinding tool to grind away the damaged skin 2 to create a circular opening with a diameter of 30mm.

[0021] 3. Using a milling machine, remove the damaged honeycomb core 1 according to the above-mentioned damage removal dimensions. The final removed absorbing honeycomb sandwich structure 5 is as follows. Figure 1 As shown.

[0022] 4. Replace and repair the SKuF absorbing honeycomb core 1, which is the same as the original absorbing honeycomb sandwich structure 5, and cure it according to the specified process.

[0023] 5. The temporary skin panel 3 was prepared using the original skin 2 material system QW280 / 5429 prepreg. To facilitate installation, the prepreg was cut into multiple circular plates with a diameter of 50mm using a cutting machine. These plates were then laid out according to the layering sequence of the original skin 2 and cured in an autoclave. The resulting thickness was 2mm. The patch formed by stacking multiple prepreg circular plates was then machined to control its diameter at 30.5mm (i.e., an interference fit of 0.5mm).

[0024] 6. Refer to "GJB 1038.1A-2024 Non-destructive testing methods for fiber reinforced composite materials: Part 1: Ultrasonic testing" to perform non-destructive testing on the prepared temporary skin panel 3 to ensure that there are no defects such as delamination or holes inside.

[0025] 7. Attach a layer of J-159 adhesive film (consistent with the original machine structure adhesive film) to the bottom surface of the temporary skin panel 3. Then align the temporary skin panel 3 with the repair area (i.e., the 30mm diameter circular opening after removing skin 2), and gently press it in. Utilize an interference fit to achieve a tight, flush installation with the surrounding skin 2. Figure 2 As shown.

[0026] 8. Assemble the vacuum bag, apply a vacuum pressure of 0.1 MPa, and maintain the pressure for 30 minutes to ensure that the film and the honeycomb core 1 are in complete contact and to remove interfacial air.

[0027] 9. Remove the vacuum bag and use ultrasonic A-scan to inspect the repair area to confirm that there are no gaps at the bonding surface between the temporary skin panel 3 and the honeycomb core 1, which will not affect the test of the absorption performance.

[0028] 10. Referring to "GJB 2038A-2011 Test Method for Reflectivity of Radar Absorbing Materials", the absorption performance of the repaired structure with the temporary skin panel 3 installed was tested using the absorption performance testing device 4. Figure 3 As shown in the figure. The test results are: the reflection loss of the repaired structure is only 1 dB higher than that of the intact structure, which meets the repair tolerance requirements.

[0029] 11. Since the repair effect of the honeycomb core 1 has reached the expected level, there is no need to use the temporary skin panel 3 again. Use an angle grinder to make a small amount of skin 2 on the edge of the temporary skin panel 3 with minor damage, and then use a pry tool to remove the temporary skin panel 3.

[0030] 12. Cover the honeycomb core 1 with a layer of isolation film, and grind the skin 2 again at a slope of 1:10 with a thickness-to-width ratio. Grind the opening after removing the skin 2 to a slope of 70mm on the outermost ring.

[0031] 13. After the skin 2 is sanded, remove the isolation film on the honeycomb core 1, then lay a layer of J-159 adhesive film on the repair interface, and then lay the cut QW280 / 5429 prepreg layer by layer according to the original structure's layering sequence, such as... Figure 4 As shown. The curing process was carried out using a heat-curing device in conjunction with a vacuum pump, following the curing procedure.

[0032] 14. The heating system was removed, and the final absorption performance test was conducted on the repaired absorbing honeycomb sandwich structure 5. The results showed that the reflection loss of the repaired absorbing honeycomb sandwich structure 5 increased by 1 dB compared with the intact absorbing honeycomb sandwich structure 5, indicating that the repair of the skin 2 also met the requirements, proving that the repair was successful.

[0033] The present invention has the following main advantages: The two-step process for skin repair is as follows: First, the area to be removed from the skin 2 is ground into a regular shape, usually a circle, so as to facilitate the pre-test of the wave absorption performance according to the temporary skin panel 3; Second, after confirming that the repair of the honeycomb core 1 meets the requirements, the skin 2 is ground into the final required shape (stepped / sloping).

[0034] Application of temporary skin panel 3: Temporary skin panel 3 must be prepared using a material system completely identical to the original skin 2 to minimize its impact on pre-testing. Furthermore, the preparation of temporary skin panel 3 is simple and rapid. Using temporary skin panel 3 instead of the original skin 2 to test the repaired honeycomb core 1 improves overall efficiency and reduces costs.

[0035] Micro-interference fit installation structure: The diameter of the temporary skin panel 3 is designed to be larger than the area removed by skin 2 by a specific range (0.3mm-1mm), forming a micro-interference fit, thereby achieving a tight splicing without fasteners or gaps, eliminating the interference of assembly gaps on test results.

[0036] The closed-loop control logic of the entire repair process: The process of "repairing the honeycomb core 1 - installing temporary skin panel 3 for pre-testing - making decisions based on the pre-test results - repairing skin 2 / returning the honeycomb core 1 - final testing" forms a complete quality control closed loop, which is more comprehensive and thorough.

[0037] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for quality control in the repair of a microwave absorbing honeycomb sandwich structure, characterized in that, Includes the following steps: Step 1: Detect and determine the location of the damaged area in the honeycomb core and the size of the damage removal; Step 2: Initially grind the skin corresponding to the location of the damaged area of ​​the honeycomb core into a regular shape consistent with the projection of the damaged area of ​​the honeycomb core to be removed, and record the size of the skin removal area after grinding; Step 3: Remove the damaged honeycomb core according to the dimensions determined in Step 1; Step 4: Repair and cure the honeycomb core; Step 5: Using the same material system as the original skin, prepare a temporary skin panel with a diameter 0.3mm-1mm larger than the area where the skin was removed and a thickness consistent with the original skin. Step 6: Install the temporary skin panel with an interference fit in the repair area after the skin has been removed; Step 7: Apply uniform pressure to the installed temporary skin panel using a vacuum bag and maintain the pressure for a preset time; Step 8: After the pressure holding is completed, remove the vacuum bag and check and confirm that there is no gap between the temporary skin panel and the honeycomb core; Step 9: With the temporary skin panel installed, conduct a microwave absorption performance test on the repaired microwave absorbing honeycomb sandwich structure according to the preset test standards; Step 10: Remove the temporary skin panel using destructive or non-destructive methods; Step 11: If the absorption performance meets expectations, repair the skin; if the absorption performance does not meet expectations, only repair the honeycomb core until the absorption performance meets expectations before repairing the skin. Step 12: Conduct a final absorption performance test on the repaired absorbing honeycomb sandwich structure. If the absorption performance does not meet the requirements at this time, it is determined that the skin repair did not meet the expectations. Only the skin needs to be repaired again until the absorption performance test meets the requirements.

2. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, In step 1, one or more detection methods, including visual inspection, ultrasound, and X-ray, are used for detection.

3. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, In step 2, the projection of the damaged area in the honeycomb core is a regular circle.

4. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, In step 5, the temporary skin panel is prepared by autoclaving, and after preparation, it is tested by ultrasound to ensure it meets the preset usage requirements.

5. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, In step 6, when installing the temporary skin panel, the bottom surface of the temporary skin panel is pasted with an adhesive film of the same material system as the original absorbing honeycomb sandwich structure. After the temporary skin panel is installed, it is flush with the surrounding skin and tightly spliced.

6. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, The pressure applied in step 7 is 0.1 MPa.

7. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, In step 8, ultrasonic testing is used to detect whether there is a gap between the temporary skin panel and the honeycomb core.

8. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, In step 10, if the temporary skin panel needs to be reused, a vacuum suction cup can be used to remove the temporary skin panel without damage. If it does not need to be reused, it can be disassembled in a destructive manner.

9. The method for quality control of absorbing honeycomb sandwich structure repair according to claim 1, characterized in that, If the honeycomb core repair effect meets expectations in step 11, the skin of the repair area is polished and repaired, a layer of isolation film is covered on the honeycomb core, and the skin is further polished into a stepped or sloping shape. After the skin is polished, the isolation film on the honeycomb core is removed, and then the adhesive film and the prepreg to be used are laid layer by layer on the repair area and cured.

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