A device and method for reducing the curing deformation of reinforced wall panels in a wet long stringer process

Abstract

This invention discloses an apparatus and method for reducing curing deformation of stiffened panel components during wet stringer processing. By setting a first allowance zone and a second allowance zone in the vertical stiffener area of ​​the wet stringer, the thermal uniformity and curing degree uniformity of the net dimensional area of ​​the wet stringer are increased during curing, reducing internal stress differences. Furthermore, during curing, no conformal devices are placed on both sides of the first allowance zone of the wet stringer, eliminating the interaction between the parts and the mold. The first allowance zone can freely expand, contract, and twist, releasing internal stress and reducing curing deformation of the stiffened panel assembly.

Description

Technical Field

[0001] This invention relates to the field of composite material component manufacturing, and in particular to an apparatus and method for reducing the curing deformation of stiffened wall panels in wet stringer processes. Background Technology

[0002] Stiffened panels are widely used in aircraft skin and other components. Under the combined influence of factors such as uneven heating, uneven curing, asymmetrical and uneven layup, and interactions between parts and molds, internal stress is generated during the curing process of composite materials. After demolding, driven by this internal stress, the parts exhibit varying degrees of curing deformation. Due to their complex cross-section with uneven surfaces and the coupling effect between the stringer and skin, the curing deformation of stiffened panels is more significant and difficult to eliminate. When using a wet stringer process to manufacture stiffened panels, the complex cross-section of the stringer and conformal fitting exacerbates various uneven states, further increasing the degree of curing deformation and affecting product quality. Existing methods mainly involve controlling curing parameters, such as reducing heating and cooling rates or adjusting the layup structure, to reduce curing deformation. However, reducing heating and cooling rates significantly prolongs curing time and reduces production efficiency. Adjusting the layup structure affects the load-bearing characteristics of the stiffened panel and may even reduce its mechanical properties.

[0003] Existing methods for manufacturing stiffened panels based on wet stringer processes typically leave no or only a small allowance in the height direction of the wet stringer ribs during assembly. Furthermore, the conformal fitting of the wet stringer is essentially the same height as the wet stringer ribs. While this method can manufacture stiffened panels, the conformal fitting affects the overall heat transfer efficiency of the stiffened panel and increases the interaction between the parts and molds, thereby increasing the curing deformation of the stiffened panel.

[0004] Therefore, there is an urgent need for a device and method that can effectively reduce the curing deformation of stiffened panels in wet stringer processes, without affecting the load-bearing characteristics, mechanical properties and production efficiency of the stiffened panels. Summary of the Invention

[0005] This invention discloses an apparatus and method for reducing curing deformation of stiffened panels in wet stringer manufacturing. This application breaks with the industry convention that wet stringer manufacturing should be done to net dimensions by setting a large allowance in the wet stringer stiffener area, improving the thermal uniformity and curing uniformity of the theoretical area of ​​the wet stringer stiffeners. No conformal device is placed in the first allowance area of ​​the wet stringer stiffeners, eliminating the interaction between the parts and the mold. Furthermore, the first allowance area of ​​the wet stringer stiffeners can freely expand, contract, and twist, releasing internal stress, thereby reducing the curing deformation of the stiffened panel.

[0006] A device for reducing the curing deformation of reinforced panels in a wet stringer process includes a wet stringer and wet stringer curing mandrels placed on both sides of the wet stringer. The device is characterized by a large allowance in the height direction for the wet stringer uprights. This allowance is divided into a first allowance zone and a second allowance zone from the edge. The height of the first allowance zone is not less than 2 / 3 of the maximum theoretical height of the wet stringer uprights, and the height of the second allowance zone is approximately 1mm to 3mm. The wet stringer curing mandrel is at the same height as the second allowance zone of the wet stringer uprights in its corresponding area. The length, thickness, ply angle, and material of the first and second allowance zones of the wet stringer uprights are the same as those of the theoretical zone of the wet stringer uprights.

[0007] A method for reducing the curing deformation of stiffened wall panels in wet stringer construction includes the following steps:

[0008] 1. Manufacture wet trusses;

[0009] 2. Pre-compact the wet stringers. During the pre-compaction, place conformal devices on both sides of the theoretical zone of the wet stringer reinforcement, the first allowance zone of the wet stringer reinforcement, and the second allowance zone of the wet stringer reinforcement.

[0010] 3. Combine the wet stringer with the skin, and place the wet stringer solidified core mold on both sides of the wet stringer;

[0011] 4. Make vacuum bags, and do not place shape-preserving devices on both sides of the first allowance zone of the wet long truss uprights;

[0012] 5. Curing;

[0013] 6. Remove the vacuum bag and demold the reinforced wall panel;

[0014] Mill the excess material at the top of the stringer in 7 layers until the desired shape and dimensions are achieved.

[0015] In step 7, after the wet stringer is manufactured, the pre-compacting pressure is not less than the curing pressure of the stiffened wall panel.

[0016] In step 4, the encapsulation scheme of the theoretical area of ​​the wet stringer reinforcement is consistent with the first and second allowance areas of the wet stringer reinforcement.

[0017] The apparatus and method of the present invention have the following advantages: 1) The height of the first allowance zone of the wet stringer is close to the theoretical height of the wet stringer. The curing deformation of the first allowance zone can effectively affect the overall curing deformation of the reinforced wall panel. Internal stress is released through the first allowance zone, thereby reducing the curing deformation of the reinforced wall panel; 2) The first and second allowance zones of the wet stringer act as a transition zone between uneven temperature and curing degree, resulting in better thermal uniformity and curing degree uniformity in the theoretical region of the wet stringer, and lower internal stress; 3) No conforming devices are placed on both sides of the first allowance zone of the wet stringer, allowing full utilization of the free end function. During curing, the first allowance zone of the wet stringer can freely expand, contract, and twist, releasing internal stress; 4) The encapsulation scheme of the first allowance zone of the wet stringer is consistent with the theoretical region of the wet stringer, ensuring a consistent external thermal environment for the entire wet stringer. However, the conforming devices on both sides of the theoretical region of the wet stringer hinder heat escape. The curing of the prepreg is an exothermic reaction initiated by heat. Therefore, during curing, the first allowance zone of the wet stringer reinforcement begins to cure first, but the theoretical area of ​​the wet stringer reinforcement completes curing first, thereby transferring internal stress to the not-yet-fully-cured first allowance zone of the wet stringer reinforcement. This drives the first allowance zone of the wet stringer reinforcement to change its shape in real time, releasing internal stress and reducing the curing deformation of the stiffened panel; 5) The second allowance zone of the wet stringer reinforcement acts as a buffer. The theoretical area of ​​the wet stringer reinforcement does not directly contact the first allowance zone, resulting in less internal residual stress and improving the shape accuracy of the theoretical area of ​​the wet stringer reinforcement. Conformance devices are placed on both sides of the theoretical area of ​​the wet stringer reinforcement, but not on both sides of the first allowance zone, while conformance devices are placed on both sides of the second allowance zone. Therefore, the expansion, contraction, and torsion of the first allowance zone of the wet stringer under internal stress is transmitted to the second allowance zone of the wet stringer. Due to the constraint of the solidified core mold on both sides of the wet stringer, it cannot expand, contract, or torsion freely, thus generating residual internal stress. After curing, the second allowance zone of the wet stringer is milled off, and the residual internal stress disappears; 6) No additional adjustment of process parameters, ply structure, and other important design and process parameters is required, and there is no additional impact on the overall performance of the part. Attached Figure Description

[0018] Figure 1 Schematic diagram of a device to reduce curing deformation of stiffened wall panels in wet stringer process.

[0019] Figure 2 Cross-sectional view of a device for reducing curing deformation of stiffened wall panels in wet stringer process

[0020] The numbers in the diagram are explained as follows: 1 - Skin, 2 - First allowance zone of wet stringer reinforcement, 3 - Second allowance zone of wet stringer reinforcement, 4 - Wet stringer solidified core mold, 5 - Wet stringer. Detailed Implementation

[0021] Example 1

[0022] like Figures 1-2 This invention takes the manufacturing of T-shaped stiffened wall panels using a co-curing process as an example. The maximum theoretical height of the wet stringer vertical reinforcement is 30mm. A device for reducing curing deformation of stiffened wall panels using the wet stringer process includes a wet stringer 5 and wet stringer curing mandrels 4 placed on both sides of the wet stringer. The wet stringer vertical reinforcement has a large allowance in the height direction. The allowance is divided into a first allowance area 2 and a second allowance area 3 from the edge. The height of the first allowance area 2 is about 20mm, and the height of the second allowance area 3 is about 1mm. The wet stringer curing mandrel 4 is at the same height as the second allowance area 3 in the vertical reinforcement height direction. The length, thickness, layup angle, and material of the first and second allowance areas of the wet stringer vertical reinforcement are the same as those of the theoretical area of ​​the wet stringer vertical reinforcement.

[0023] A method for reducing the curing deformation of stiffened wall panels in wet stringer construction includes the following steps:

[0024] 1. Manufacture wet long trusses 5;

[0025] 2. Manufacturing wet skin 1;

[0026] 3. Pre-compact the wet stringer 5. During pre-compaction, shape-conserving devices are placed on both sides of the theoretical zone of the wet stringer reinforcement, the first allowance zone 2 of the wet stringer reinforcement, and the second allowance zone 3 of the wet stringer reinforcement. The pre-compaction pressure is 0.6 MPa.

[0027] 4. Combine the wet stringer 5 with the skin 1, and place the wet stringer solidified core mold 4 on both sides of the wet stringer 5.

[0028] 5. Construct vacuum bags, without placing conformal devices on both sides of the first allowance zone 2 of the wet stringer uprights. The sealing scheme for the theoretical zone of the wet stringer uprights is consistent with that for the first and second allowance zones of the wet stringer uprights;

[0029] 6. Curing. The curing pressure is 0.6 MPa;

[0030] 7. Remove the vacuum bag and demold the reinforced wall panel;

[0031] Mill the excess material at the top of the stringer in 8 layers until the desired shape and dimensions are achieved.

[0032] Using the above method, the curing deformation of the reinforced wall panel is reduced by approximately 40%.

[0033] Example 2

[0034] like Figures 1-2This invention takes the manufacturing of T-shaped stiffened wall panels using a co-bonding process as an example. The maximum theoretical height of the wet stringer vertical reinforcement is 50mm. A device for reducing the curing deformation of stiffened wall panels manufactured using the wet stringer process includes a wet stringer 5 and a wet stringer curing mandrel 4 placed on both sides of the wet stringer. The wet stringer vertical reinforcement has a large allowance in the height direction. The allowance is divided into a first allowance area 2 and a second allowance area 3 from the edge. The height of the first allowance area 2 is 60mm, and the height of the second allowance area 3 is about 3mm. The wet stringer curing mandrel 4 is at the same height as the second allowance area 3 of the wet stringer vertical reinforcement in the vertical reinforcement height direction. The length, thickness, layup angle, and material of the first and second allowance areas of the wet stringer vertical reinforcement are the same as those of the theoretical area of ​​the wet stringer vertical reinforcement.

[0035] A method for reducing the curing deformation of stiffened wall panels in wet stringer construction includes the following steps:

[0036] 1. Manufacturing wet skin 1;

[0037] 2. Wet skin, 1. Curing;

[0038] 3. Manufacture wet stringers 5;

[0039] 4. Pre-compact the wet stringer 5. During pre-compaction, shape-conserving devices are placed on both sides of the theoretical zone of the wet stringer reinforcement, the first allowance zone 2 of the wet stringer reinforcement, and the second allowance zone 3 of the wet stringer reinforcement. The pre-compaction pressure is 0.65 MPa.

[0040] 5. Combine the wet stringer 5 with the skin 1, and place the wet stringer solidified core mold 4 on both sides of the wet stringer 5.

[0041] 6. Fabricate vacuum bags, without placing conformal devices on both sides of the first allowance zone 2 of the wet stringer. The theoretical area of ​​the wet stringer is consistent with the sealing scheme of the first and second allowance zones of the wet stringer;

[0042] 7. Curing. The curing pressure is 0.5 MPa;

[0043] 8. Remove the vacuum bag and demold the reinforced wall panel;

[0044] Mill the excess material at the top of the stringer ribs in 9 layers until the desired shape and dimensions are achieved.

[0045] Using the above method, the curing deformation of the reinforced wall panel is reduced by approximately 60%.

[0046] It should be noted that this application only illustrates a trapezoidal structure wet stringer cured core mold. The structure of the wet stringer cured core mold can be adjusted according to the actual situation, and can be rectangular, trapezoidal, L-shaped, or other structures.

[0047] In this application, the first and second allowance zones of the wet stringer reinforcement serve different purposes. The main functions of the first allowance zone of the wet stringer reinforcement are threefold: (1) It exerts the free end effect, allowing for free shape changes and releasing internal stress; (2) It plays a regulating role, making the theoretical area of ​​the wet stringer reinforcement the core area, resulting in better thermal uniformity and curing uniformity; (3) It releases internal stress. The first allowance zone of the wet stringer reinforcement completes the curing reaction last, and the internal stress of other cured areas is ultimately transferred to this zone and released, reducing the residual internal stress of the reinforced wall panel and thus reducing the curing deformation of the reinforced wall panel.

[0048] For the reasons mentioned above, commonly used evaluation indicators for composite material parts, such as surface quality and porosity, are not applicable to the first allowance zone of wet stringer ribs. Unconstrained on both sides, consistent with the encapsulation scheme of the theoretical zone of wet stringer ribs, and successful completion of the curing reaction are the indicators that need to be considered. In principle, the larger the first allowance zone of the wet stringer ribs, the better its effect in reducing curing deformation.

[0049] The main functions of the second allowance zone of the wet stringer are twofold: (1) to act as a buffer. The expansion and contraction of the first allowance zone of the wet stringer will not directly affect the shape accuracy of the theoretical zone of the wet stringer. (2) to act as a normal allowance zone. Since the surface quality, porosity and other internal and external quality indicators are not controlled in the first allowance zone of the wet stringer, the second allowance zone of the wet stringer can eliminate the edge effect of the composite material, similar to the function of the conventional allowance zone.

[0050] For the reasons mentioned above, the enclosure scheme for the conformal device in the second allowance zone of the wet stringer should be consistent with the theoretical zone of the wet stringer. In principle, the smaller the second allowance zone of the wet stringer, the better.

[0051] It should be emphasized that leaving margins at the edges is a common method in the manufacturing of composite parts, but: (1) the goal of this method is to eliminate edge effects. That is, the thickness, resin content, mechanical properties and other indicators of the edge area of ​​the composite part are significantly different from those of the middle area. (2) the size of the margin area is much smaller than the theoretical size of the part. (3) the tooling structure of the margin area is consistent with that of the theoretical area of ​​the part.

[0052] In this application, the height of the first allowance zone of the wet stringer is close to or even greater than the theoretical zone of the wet stringer. The first allowance zone of the wet stringer is sufficient to affect the overall curing deformation of the reinforced wall panel.

[0053] In this application, the first allowance zone of the wet stringer vertical reinforcement is completely different from the allowance zone for eliminating edge effects. Therefore, it is not necessary to consider the surface quality, internal quality, thickness, weight, and other indicators of the first allowance zone of the wet stringer vertical reinforcement.

[0054] For the reasons mentioned above, no conformal devices are placed on either side of the first allowance zone of the wet stringer reinforcement. Under these conditions, the first allowance zone of the wet stringer reinforcement can deform under the drive of internal stress, thereby reducing the curing deformation of the stiffened wall panel.

Claims

1. A device for reducing the curing deformation of stiffened wall panels in wet stringer process, comprising a wet stringer and wet stringer curing mandrels placed on both sides of the wet stringer, characterized in that... The wet stringer has a large allowance in the height direction. The allowance is divided into the first allowance zone and the second allowance zone from the edge. The height of the first allowance zone is not less than 2 / 3 of the maximum theoretical height of the wet stringer. The height of the second allowance zone is about 1mm to 3mm. The solidified core mold of the wet stringer is not at the same height as the wet stringer in the height direction. It is higher than the theoretical height of the wet stringer in the area, but lower than the actual height of the wet stringer in the area.

2. The device for reducing the curing deformation of reinforced wall panels in wet stringer process according to claim 1, characterized in that... The solidified core mold of the wet stringer is at the same height as the second allowance zone of the wet stringer in the area where the vertical reinforcement is located.

3. The device for reducing the curing deformation of reinforced wall panels in wet stringer process according to claim 1, characterized in that... The first and second allowance zones of the wet stringer reinforcement have the same length, thickness, ply angle, and material as the theoretical zone of the wet stringer reinforcement.

4. A method for reducing the curing deformation of stiffened wall panels in wet stringer construction, characterized by the following steps: 4-1 Manufacturing wet stringers; 4-2 Pre-compact the wet stringer. During pre-compaction, place conformal devices on both sides of the theoretical zone of the wet stringer reinforcement, the first allowance zone of the wet stringer reinforcement, and the second allowance zone of the wet stringer reinforcement. 4-3 Combine the wet stringer with the skin, and place the wet stringer solidified core mold on both sides of the wet stringer; 4-4 Make vacuum bags, and do not place conformal devices on both sides of the first allowance zone of the wet stringer. 4-5 minutes to cure; 4-6 Remove the vacuum bag and demold the reinforced wall panel; Mill the excess material at the top of the stringer reinforcement in 4-7 layers until the desired shape and dimensions are achieved.

5. The method for reducing the curing deformation of reinforced wall panels in wet stringer process according to claim 4, characterized in that... After the wet stringer is manufactured, the pre-compacting pressure shall not be less than the curing pressure of the stiffened wall panel.

6. The method for reducing the curing deformation of reinforced wall panels in wet stringer process according to claim 4, characterized in that... In step 4-4, the encapsulation scheme of the theoretical area of ​​the wet stringer reinforcement is consistent with the first and second allowance areas of the wet stringer reinforcement.

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