A method and tooling for forming a reinforced wall panel with exposed ribs through co-curing and co-adhesion.

Abstract

This invention relates to the field of aerospace composite material component manufacturing technology, and discloses a method and tooling for forming a reinforced panel with exposed ribs through co-curing and co-bonding. By setting a positioning component at the opening position of the skin-laying tooling for fixing a filler block, after the corresponding opening position of the skin is completed, the stringer ribs and the skin with the opening are co-cured and co-bonded to form a reinforced panel. This invention utilizes a filler block fixed on the positioning component to fill the opening position of the skin. The surface structure of the filler block is consistent with the surface structure of the skin opening at the corresponding position, effectively avoiding the problem of glue accumulation caused by glue overflow during the curing process, while supporting the stringer ribs and preventing deformation. Furthermore, it solves the problem of ensuring the continuity of the ribs while opening the skin at the connection position in a reinforced panel with exposed ribs that cannot be mechanically cut, thus ensuring the development and mass production progress of the aircraft model.

Description

Technical Field

[0001] This invention relates to the field of aerospace composite material component manufacturing technology, and discloses a method and tooling for forming reinforced wall panels with exposed ribs through co-curing and co-bonding. Background Technology

[0002] Stiffened panels are a common structural form used in aviation, primarily for aircraft fuselage skin and wing structures. They improve structural stiffness, strength, and stability while maintaining low weight by arranging reinforcing ribs (usually longitudinal or transverse beams) on thin panels. Although the widely used metal stiffened panels have mature manufacturing processes, they are no longer sufficient to meet the high-performance, lightweight, and durability requirements of the aerospace industry.

[0003] Composite reinforced wall panels are lightweight structural components made by combining reinforcing materials such as carbon fiber and glass fiber with a resin matrix. Carbon fiber composites are an ideal choice for reinforced wall panels due to their high specific strength (a combination of high strength and low density), excellent corrosion resistance, and designability. Carbon fiber reinforced wall panels typically employ co-curing, co-bonding, and secondary bonding processes for the reinforcing ribs and skin. Co-curing involves curing the wet skin and wet stringer ribs together in a single process, resulting in excellent overall performance but high manufacturing difficulty and a high scrap rate. Secondary bonding involves bonding cured dry stringer ribs and cured dry skin together using an adhesive process, resulting in relatively poor overall performance and low strength, generally unsuitable for structural applications. Co-bonding involves bonding cured dry stringer ribs and wet skin (either cured dry skin and wet stringer ribs) together with an adhesive film and then curing, resulting in excellent overall performance and high strength, making it the preferred manufacturing method for reinforced wall panels. Typically, due to structural requirements, holes need to be made at the skin location, but to ensure the continuity of the ribs, it is necessary to manufacture reinforced wall panels with exposed ribs. Due to the characteristics of composite materials, precise cutting along the thickness direction can easily cause delamination, reducing the mechanical properties of the material. Summary of the Invention

[0004] The purpose of this invention is to provide a method and tooling for forming a reinforced wall panel with exposed ribs through co-curing and co-adhesion. This method avoids the problem of glue accumulation caused by glue overflow during the curing process at the hole location, while supporting the stringers and preventing deformation of the stringers. In addition, it solves the problem of ensuring the continuity of the ribs at the connection position between the skin and the ribs in a reinforced wall panel with exposed ribs that cannot be mechanically cut, while also opening holes at the skin.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows: A method for forming a reinforced wall panel with exposed ribs through co-curing and co-adhesion, the reinforced wall panel comprising a skin with openings, wherein a plurality of long stringers are fixed to one side of the skin, and the orthographic projection of some of the long stringers on the skin coincides with the openings; the forming method includes: A positioning component is set on the skin laying fixture, and the positioning component is located at the position corresponding to the opening of the skin; Based on the skin structure of the reinforced wall panel, a layup structure is set on the laying fixture to form an initial skin structure without the openings. Cut the initial skin structure and remove the ply at the opening location to form a skin with openings; A filling pad with a surface structure consistent with the perforated surface structure is installed on the positioning component. According to the relative positional relationship between the skin of the stiffened wall panel and the stringer, the corresponding stringer is glued to the skin with the perforation. A preset pressure molding process is used to glue and cure the skin and the stringer to form the stiffened wall panel structure. During the pressure molding process, the filling pad abuts against the stringer at the corresponding position.

[0006] Furthermore, the skin is a fiber prepreg. When cutting the opening position on the initial structure of the skin, the filling pad is installed on the positioning component. Using the filling pad as a template, the prepreg at the opening position is cut layer by layer until the excess prepreg at the opening is completely cut off.

[0007] Furthermore, the positioning component and the filling pad slide together along the normal direction of the opening. After each layer of prepreg is cut, the filling pad is moved down to the next uncut layer of prepreg, and the next layer of prepreg is cut using the filling pad as a template.

[0008] Furthermore, before installing the stringer on the laying fixture, a layer of release cloth is pre-attached to the surface of the filling pad.

[0009] Furthermore, the normal thickness of the filling pad along the opening position is equal to the thickness of a single layer of prepreg × the number of layers × K1, where K1 is a coefficient with a value ranging from 0.9 to 1.1.

[0010] To achieve the above-mentioned technical effects, the present invention also provides a molding fixture for exposed ribs co-curing and co-bonding reinforced wall panels, used to implement the molding method, including: A laying fixture having the same molding surface as the skin structure is used to form an initial skin structure without the openings by laying a layer structure on the molding surface; A positioning component is fixed to the molding surface of the laying fixture, and the positioning component is located on the molding surface at a position corresponding to the opening of the skin; A filler block is installed on the positioning component. The surface structure of the filler block is consistent with the surface structure of the opening. It is used to pass through the perforation of the skin and abut against the corresponding long stringer during the pressure curing process of the stringer and skin, or as a cutting template for the opening when cutting the initial structure of the skin.

[0011] Furthermore, the positioning component is a limiting groove formed at the corresponding position of the paving tool.

[0012] Furthermore, the positioning component is a smooth rod or threaded rod fixed at the corresponding position of the laying fixture, and the filling pad is provided with a perforated structure that cooperates with the smooth rod or threaded rod.

[0013] Furthermore, it also includes a release liner, used to be placed between the filler pad and the stringer when the filler pad abuts against the stringer.

[0014] Compared with the prior art, the beneficial effects of this invention are: 1. The present invention utilizes a filling pad fixed on the positioning component to fill the opening position of the skin. The surface structure of the filling pad is consistent with the surface of the skin opening at the corresponding position, which effectively avoids the problem of glue accumulation caused by glue overflow during the curing process, and at the same time supports the stringer and prevents the stringer from deforming.

[0015] 2. This invention also solves the problem of ensuring the continuity of the ribs while opening holes at the skin connection position in stiffened panels where the ribs cannot be exposed by mechanical cutting, thus ensuring the progress of aircraft model development and mass production. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the reinforced wall panel structure in Example 1 or 2; Figure 2 This is a schematic diagram of the reinforcing wall panel forming tooling structure in Example 1 or 2; Among them, 1. opening; 2. skin; 3. stringer; 4. laying fixture; 5. positioning components; 6. filling pads. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0018] Example 1 See Figure 1 and Figure 2A method for forming a reinforced wall panel with exposed ribs through co-curing and co-bonding, wherein the reinforced wall panel includes a skin 2 with openings 1, and a plurality of long stringer ribs 3 are fixed to one side of the skin 2, with the orthographic projection of some of the long stringer ribs 3 on the skin 2 coinciding with the openings 1; the forming method includes: A positioning component 5 is set on the laying fixture 4 of the skin 2, and the positioning component 5 is located at the position corresponding to the opening 1 of the skin 2; Based on the skin 2 structure of the reinforced wall panel, a layup structure is set on the laying fixture 4 to form an initial skin 2 structure without the opening 1. Cut the initial structure of the skin 2 and remove the ply at the opening 1 position to form the skin 2 with the opening 1. A filling pad 6 with a surface structure consistent with that of the opening 1 is installed on the positioning component 5. According to the relative positional relationship between the skin 2 and the stringer 3 of the stiffened wall panel, the corresponding stringer 3 is glued to the skin 2 with the opening 1. The skin 2 and the stringer 3 are glued and cured by a preset pressure molding process to form the stiffened wall panel structure. During the pressure molding process, the filling pad 6 abuts against the stringer 3 at the corresponding position.

[0019] In this embodiment, a positioning component 5 for fixing a filling pad 6 is set at the opening 1 position of the skin 2 laying fixture 4. The cut-out layer structure is laid on the surface of the laying fixture 4 to lay the skin 2. After the opening 1 of the skin 2 is completed, during the process of co-curing and co-bonding the stringer 3 and the skin 2 with the opening 1 to form a stiffened wall panel, the filling pad 6 fixed on the positioning component 5 is used to fill the opening 1 position of the skin 2. The surface structure of the filling pad 6 is consistent with the surface of the opening 1 of the skin 2 at the corresponding position, which effectively avoids the problem of glue accumulation caused by glue overflow during the curing process. At the same time, it supports the stringer 3 and prevents the stringer 3 from deforming. In addition, it also solves the problem that the connection position between the skin 2 and the ribs in the stiffened wall panel where the ribs cannot be exposed by mechanical cutting of the opening 1 needs to ensure the continuity of the ribs while opening the opening 1 at the skin 2, thus ensuring the development and mass production progress of the model aircraft.

[0020] In this embodiment, the skin 2 is a fiber prepreg. When cutting the opening 1 position on the initial structure of the skin 2, the filling pad 6 is installed on the positioning component 5. Using the filling pad 6 as a template, the prepreg at the opening 1 position is cut layer by layer until the excess prepreg at the opening 1 position is completely cut off, thus ensuring the manufacturing accuracy of the opening 1 position.

[0021] In this embodiment, the positioning component 5 and the filling pad 6 slide together along the normal direction of the opening 1. After each layer of prepreg is cut, the filling pad 6 is moved down to the next uncut layer of prepreg. The filling pad 6 is used as a template to cut the next layer of prepreg, which further ensures the molding quality and precision of the opening 1 of the skin 2.

[0022] In this embodiment, before installing the stringer 3 on the laying fixture 4, a layer of release cloth is pre-attached to the surface of the filling pad 6. During the installation or curing process of the stringer 3 and the skin 2, the release cloth can prevent the stringer 3 from directly contacting the filling pad 6, avoiding adhesion between the two during the curing or bonding process. This ensures that the filling pad 6 can be smoothly separated from the stiffened wall panel in subsequent process steps without affecting the surface quality of the stiffened wall panel, and further improves the forming quality of the stiffened wall panel.

[0023] Based on the same inventive concept, this embodiment also provides a molding fixture for exposed ribs co-curing and co-bonding reinforced wall panels, used to implement the molding method, including: The laying fixture 4 has a molding surface that is the same as the structure of the skin 2, and is used to form an initial structure of the skin 2 without the opening 1 by laying a layer structure on the molding surface; The positioning component 5 is fixed on the molding surface of the laying fixture 4, and the positioning component 5 is located on the molding surface at a position corresponding to the opening 1 of the skin 2; A filling pad 6 is installed on the positioning component 5. The surface structure of the filling pad 6 is consistent with the surface structure of the opening 1. It is used to pass through the perforation of the skin 2 and abut against the corresponding long stringer 3 during the pressure curing process of the stringer 3 and the skin 2, or as a cutting template for the opening 1 when cutting the initial structure of the skin 2.

[0024] In this embodiment, the positioning component 5 is a smooth rod or threaded rod fixed at the corresponding position of the laying fixture 4. The filler block 6 is provided with a through-hole structure that cooperates with the smooth rod or threaded rod to achieve movable cooperation between the filler block 6 and the positioning component 5. This facilitates the movement of the filler block 6 during the cutting of the skin 2, allowing the filler block 6 to contact the cut layer skin 2 and function as a template. It should be noted that if the positioning component 5 is a smooth rod, the corresponding through-hole structure can be a guide hole that cooperates with the smooth rod, and a set bolt can also be provided on the filler block 6; if the positioning component 5 is a threaded rod, the through-hole structure is a threaded hole that cooperates with the threaded rod. Both of these combined structures can easily adjust the relative height of the filler block 6 to ensure that the filler block 6 abuts against the stringer 3, or serves as a template to contact the layup during cutting.

[0025] In some other embodiments, the positioning component 5 is a limiting groove opened at the corresponding position of the laying fixture 4, so as to realize the precise positioning and stable installation of the filling pad 6 on the laying fixture 4, and can ensure that during the pressure curing process of the stringer 3 and the skin 2, the filling pad 6 accurately passes through the perforation of the skin 2 and abuts against the corresponding stringer 3.

[0026] Example 2 See Figure 1 and Figure 2 This embodiment uses the co-bonding molding process of a certain type of machine's exposed stiffener wall panel as an example to describe in detail the process flow of the stiffener wall panel molding method of the present invention. The stiffener wall panel molding method of this embodiment mainly includes: prepreg cutting, laying of stringer 3, laying of wall panel skin 2, installation of filler blocks 6, bonding of stringer 3, sealing in vacuum bags, installation of positioning plates, autoclave molding, and parts inspection, etc. The specific steps and requirements are as follows: 1) Prepreg feeding: Cut the prepreg according to the drawings, including the stringer 3 and skin 2. Leave a margin at the opening 1 position of skin 2, extending at least 5mm beyond the part's outline. Mark the prepreg with information including, but not limited to, the material grade, layup angle, and layup number, and place it in a designated area for later use. This step can be omitted if an automatic fiber placement machine is used for automatic tape laying.

[0027] 2) Laying the reinforcing bars 3: The stringer 3 includes, but is not limited to, T-shaped stringer 3, I-shaped stringer 3, C-shaped stringer 3, and I-shaped stringer 3. This embodiment uses the T-shaped stringer 3 as an example, employing left and right L-shaped fixtures for installation. To ensure the compatibility between the T-shaped stringer 3 and the adhesive surface of the skin 2, a pre-formed pressure-equalizing plate can be placed on the surface of the base plate when sealing the stringer 3 in a vacuum bag. After sealing, the stringer 3 is cured. Once curing is complete, the parts are cut to their net dimensions for later use.

[0028] 3) Installing wall panel covering 2: A directional optical axis is installed as a positioning component 5 at the opening 1 of the skin 2 laying fixture 4 to fix the filler block 6. The prepreg is laid on the surface of the fixture, and the size of the opening 1 of the prepreg should allow the directional optical axis to pass through. After the skin 2 is laid, the perforated structure of the filler block 6 is fitted onto the outer wall of the directional optical axis. Using the filler block 6 as a template, the prepreg at the opening 1 is cut. As the cutting deepens, the position of the filler block 6 is adjusted in time to ensure that the filler block 6 contacts the layup to be cut until the excess prepreg at the opening 1 is completely cut off.

[0029] 4) Installation of filler block 6: Remove the filler block 6, attach a layer of release cloth to the surface of the block, and then place the filler block 6 at the opening 1. At this time, the relative position of the optical axis and the filler block 6 can be adjusted by using the set bolts and then fixed to ensure that the filler block 6 is in contact with the stringer 3. If the opening 1 and the filler block 6 interfere, the prepreg at the opening 1 can be manually trimmed according to the actual situation until the filler block 6 is completely placed in the hole of the skin 2. Vacuum bag the skin 2 and cold-pump it for no less than 40 minutes. Place the skin 2 after cold-pumping in the fixed area and wait for the stringer 3 to be bonded.

[0030] In this embodiment, the function of the release cloth is to prevent resin overflow during the curing process of the skin 2, which would cause the pad to stick to the skin 2 and make it difficult to remove the pad; the surface height of the filling pad 6 after it is engaged with the positioning component 5 is generally consistent with the theoretical thickness of the part. The selection of the actual thickness is ultimately based on the manufacturing tolerance of the composite part, but should not be greater than the manufacturing tolerance of the composite part; when the gap between the hole of the skin 2 and the filling pad 6 is greater than 1mm, the gap can be filled with short chopped resin fibers of the same as the prepreg.

[0031] The cured thickness of a single layer of prepreg has inherent tolerances, typically controlled within ±8%. As the number of material layers increases, the product thickness also increases. With a fixed pressure, a thickness exceeding 3mm will result in reduced compaction, leading to an actual product thickness greater than the theoretical thickness. Therefore, in this embodiment, the normal thickness of the filling pad 6 along the opening 1 is calculated as: single-layer prepreg thickness × number of layers × K1, where K1 is a coefficient ranging from 0.9 to 1.1. This ensures that when the molding pressure is high, the cured thickness of the skin 2 is closer to the theoretical thickness, thus guaranteeing the co-curing and co-bonding molding accuracy of the stiffened wall panel.

[0032] 5) Bonding of truss reinforcement bars 3: Before bonding the stringer 3, the bonding surface needs to be sanded to remove surface grease and increase surface friction. After sanding, wipe the bonding surface with a cleaning solvent and let it air dry for at least 20 minutes. After drying, paste the cut adhesive film onto the bonding surface of the stringer 3. Keep the backing paper of the adhesive film and the skin 2 bonding surface intact, and perform a trial positioning of the stringer 3, marking the installation position of the stringer 3 on the surface of the skin 2. If the stringer 3 is positioned using a laser positioning device, the trial positioning step can be omitted. After the installation position of the stringer 3 is determined, peel off the backing paper of the adhesive film and bond it to the skin 2. After bonding, vacuum-seal the wall panel to be cured and perform cold extraction. During cold extraction, selectively install positioning clips according to the length of the wall panel to ensure that the axis of the stringer 3 does not shift.

[0033] 6) Vacuum bag sealing: Before the reinforced wall panel is put into the autoclave for curing, it is resealed in a vacuum bag. Then, a release cloth, a non-porous release film, a pressure equalizing plate (as needed), and a breathable felt are laid on the surface of the wall panel in sequence (the position where the card plate is placed should be removed and a layer of glass cloth should be laid). Finally, it is sealed in a vacuum bag.

[0034] 7) Install the positioning plate: Place all the card plates in sequence, making sure that the card plate limit slots correspond exactly to the positions in "6) sealing the vacuum bag" after removing the breathable felt, to avoid getting stuck on the breathable felt and affecting the axial accuracy of the stringer 3 axis. Then, use positioning pins and screws to fix all the card plate bases at once.

[0035] 8) Autoclave forming: After completing step 6) of sealing, perform a leak check on the wall panel. If no leaks are found, proceed with curing according to the lamination structure curing parameters. Once curing is complete, remove the panel from the can, remove the vacuum bag, and clean the exposed areas of the reinforcing ribs and the adhesive residue at the joint between the stringer ribs 3 and the skin 2.

[0036] 9) Parts inspection: After the surface adhesive is cleaned, check the outer surface for defects, and then send it to a testing unit for ultrasonic testing.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for forming a reinforced wall panel with exposed ribs through co-curing and co-bonding, the reinforced wall panel comprising a skin (2) having an opening (1), wherein a plurality of long stringers (3) are fixed to one side of the skin (2), and the orthographic projection of some of the long stringers (3) on the skin (2) coincides with the opening (1); characterized in that, The molding method includes: A positioning component (5) is set on the laying fixture (4) of the skin (2), and the positioning component (5) is located at the position corresponding to the opening (1) of the skin (2); Based on the skin (2) structure of the reinforced wall panel, a layup structure is set on the laying fixture (4) to form an initial skin (2) structure without the opening (1); Cut the initial structure of the skin (2) and remove the ply at the opening (1) position to form a skin (2) with opening (1); A filling pad (6) with the same surface structure as the opening (1) is installed on the positioning component (5). According to the relative positional relationship between the skin (2) of the stiffened wall panel and the stringer (3), the corresponding stringer (3) is glued to the skin (2) with the opening (1). The skin (2) and the stringer (3) are glued and cured by a preset pressure molding process to form the stiffened wall panel structure. During the pressure molding process, the filling pad (6) abuts against the corresponding stringer (3).

2. The method for forming a reinforced wall panel according to claim 1, characterized in that, The skin (2) is a fiber prepreg. When cutting the opening (1) position on the initial structure of the skin (2), the filling pad (6) is installed on the positioning component (5). Using the filling pad (6) as a template, the prepreg at the opening (1) position is cut layer by layer until the excess prepreg at the opening (1) is completely cut off.

3. The method for forming a reinforced wall panel according to claim 1, characterized in that, The positioning component (5) and the filling pad (6) slide together along the normal direction of the opening (1). After each layer of prepreg is cut, the filling pad (6) is moved down to the next uncut layer of prepreg and the next layer of prepreg is cut using the filling pad (6) as a template.

4. The method for forming a reinforced wall panel according to claim 1, characterized in that, Before installing the stringer (3) on the laying fixture (4), a layer of release cloth is pasted on the surface of the filling pad (6).

5. The method for forming a reinforced wall panel according to claim 1, characterized in that, The normal thickness of the filling pad (6) along the position of the opening (1) is = thickness of a single layer of prepreg × number of layers × K1, where K1 is a coefficient with a value range of 0.9 to 1.

1.

6. A molding fixture for a reinforced wall panel with exposed ribs, co-cured and co-bonded, used to implement the molding method according to any one of claims 1-5, characterized in that, include: The laying fixture (4) has a molding surface that is the same as the structure of the skin (2) and is used to form an initial structure of the skin (2) without the opening (1) by laying a layered structure on the molding surface; The positioning component (5) is fixed on the molding surface of the laying fixture (4), and the positioning component (5) is located on the molding surface at a position corresponding to the opening (1) of the skin (2); A filling pad (6) is installed on the positioning component (5). The surface structure of the filling pad (6) is consistent with the surface structure of the opening (1). It is used to pass through the perforation of the skin (2) and abut against the corresponding long stringer (3) during the pressure curing process of the stringer (3) and the skin (2), or as a cutting template for the opening (1) when cutting on the initial structure of the skin (2).

7. The stiffened wall panel forming fixture according to claim 6, characterized in that, The positioning component (5) is a limiting groove opened at the corresponding position of the paving fixture (4).

8. The reinforcing panel forming fixture according to claim 6, characterized in that, The positioning component (5) is a smooth rod or threaded rod fixed at the corresponding position of the paving fixture (4), and the filling pad (6) is provided with a perforated structure that cooperates with the smooth rod or threaded rod.

9. The reinforcing panel forming fixture according to claim 6, characterized in that, It also includes a release cloth, which is placed between the filler block (6) and the stringer (3) when the filler block (6) abuts against the stringer (3).

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