Cap type stringer stiffened wallboard forming method

Abstract

The invention discloses a forming method of a cap-shaped stringer stiffened wall plate, and belongs to the technical field of composite material forming, and the cap-shaped stringer stiffened wall plate comprises a fixing tool and a skin; the supporting core mold is coated with two layers of isolating membranes, and the two ends of the isolating membranes extend out of the supporting core mold; the outermost isolating membrane is coated with a layer of inner side vacuum bag, and the two ends of the inner side vacuum bag extend out of the supporting core mold; the same end is pulled to insert the supporting core mold, the two layers of isolating membranes and the inner side vacuum bag into an annular stress application pad, the two ends of the supporting core mold extend out of the annular stress application pad, and then the annular stress application pad is fixed to the skin; paving fiber prepreg on the annular stress application pad; the vacuum bag on the inner side of one end of the annular stress application pad is fixed, the isolating membrane on the innermost layer and the supporting core mold wrapped by the isolating membrane are drawn out from the other end of the annular stress application pad, and then the isolating membrane on the outermost layer is drawn out; the inner side vacuum bag is sealed and vacuumized; and after curing, stripping the inner side vacuum bag and demolding, and finally drawing out the annular stress application pad. The forming quality is guaranteed, and fibers on the inner wall of the cap-shaped stringer stiffened wall plate cannot be damaged.

Description

Technical Field

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

[0002] Composite materials, with their advantages of low density, high specific strength, and corrosion resistance, have become core materials in the aerospace field. Among them, composite cap-shaped stringer stiffened panels, with their excellent buckling resistance and load-bearing efficiency, are widely used in key load-bearing components such as aircraft fuselage skin and wing panels. Their molding quality directly determines the reliability of the equipment structure. Due to the complex internal structure of the cap-shaped stringer, existing molding methods rely on specialized mandrels to provide internal support to ensure the dimensional accuracy and structural integrity of the stringer cross-section. The design and application of mandrels have become the core technical aspect of this type of panel molding method.

[0003] Currently, the mainstream molding method in the industry generally uses metal core molds as the support structure. This method uses high-strength metal materials such as aluminum alloys and titanium alloys to process and prepare integrated or segmented core molds. The core mold structure is customized according to the size and shape of the stringer cavity, providing rigid support during the cap-shaped stringer laying stage, and the core mold is removed after the wall panel has been cured as a whole. However, in this molding method, the metal core mold is rigid and lacks flexibility, which means that a large external force must be applied during the demolding process. This not only increases the difficulty of operation and reduces molding efficiency, but also easily scratches the surface of the wall panel cavity, causing fiber damage and affecting the molding quality.

[0004] Therefore, there is an urgent need to provide a method for forming hat-shaped stringer stiffened wall panels to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for forming a hat-shaped stringer stiffened panel, which can solve the problem of fiber damage to the inner wall of the hat-shaped stringer stiffened panel caused by traditional metal core molds while ensuring forming quality.

[0006] Based on the above concept, the technical solution adopted by this invention is as follows:

[0007] A method for forming a hat-shaped stiffened wall panel includes the following steps:

[0008] S1. Fix the tooling, and then fix the skin on the tooling;

[0009] S2. Cover the outer periphery of the support core mold with two layers of isolation film, and make both ends of the two layers of isolation film extend out of the support core mold along the length direction;

[0010] S3. Cover the outermost layer of the isolation membrane with an inner vacuum bag, and make the inner vacuum bag extend out of both ends along the length direction to support the core mold.

[0011] S4. Pull the two layers of isolation membrane and the inner vacuum bag to the same end, insert the support core mold, the two layers of isolation membrane and the inner vacuum bag into the annular force pad as a whole, so that both ends of the support core mold protrude from the annular force pad, and then fix the annular force pad on the skin. The annular force pad is made of rubber and has elasticity and support.

[0012] S5. Lay fiber prepreg on the annular reinforcement pad to form the uncured blank of the hat-shaped stringer;

[0013] S6. Fix the inner vacuum bag at one end of the annular force pad, pull out the innermost isolation film and the support core mold wrapped by the isolation film from the other end, and then pull out the outermost isolation film.

[0014] S7. Seal the inner vacuum bag circumferentially and draw a vacuum.

[0015] S8. Place the entire structure into an autoclave for curing. After curing, peel off the inner vacuum bag, demold the hat-shaped stringer stiffened wall panel composed of the hat-shaped stringer and skin from the tooling, and remove the annular reinforcing pad in the hat-shaped stringer.

[0016] Furthermore, in step S7, an outer vacuum bag is laid together on the cap-shaped stringer and the skin, and the outer vacuum bag is sealed and a vacuum is drawn.

[0017] Furthermore, in step S7, the inner vacuum bag and the outer vacuum bag are bonded together and connected to form an integral vacuum sealing system, and are simultaneously evacuated through the same vacuum pipeline.

[0018] Furthermore, in step S4, after the annular force-adding pad is fixed on the skin, the annular force-adding pad forms two chamfers with the skin on both sides along the width direction, and the two chamfers are filled with filler.

[0019] Furthermore, the filler is made of the same material as the annular reinforcing pad.

[0020] Further, in step S2, both ends of the two isolation membranes extend out of the support core mold along the length direction, and the length of one end of the isolation membrane extending out of the support core mold is greater than the length of the other end extending out of the support core mold; in step S4, the two isolation membranes are pulled to extend out of the longer end of the support core mold, and the support core mold, the two isolation membranes and the inner vacuum bag are inserted into the annular force pad as a whole.

[0021] Furthermore, in step S3, the length of the inner vacuum bag extending from both ends of the support core mold along the length direction is 100mm~150mm, which is less than the length of the separation membrane extending from the support core mold.

[0022] Furthermore, in step S2, the supporting core mold is made of rubber.

[0023] Furthermore, in step S2, a hollow cavity is opened inside the support core mold.

[0024] The beneficial effects of this invention are:

[0025] The proposed method for forming a hat-shaped stringer stiffened panel involves, in steps S2-S3, sequentially covering the supporting mandrel with two layers of isolation film and an inner vacuum bag, thus constructing a crucial multi-layered protective interface. In the demolding step S6, the inner vacuum bag at one end of the annular support pad is first fixed, forming an anchor point. Then, utilizing the low-friction characteristics between the two isolation films, the innermost isolation film and the supporting mandrel it encloses are extracted from the other end, followed by the extraction of the outermost isolation film separately. Using the isolation film as a lubricating medium, the extraction process of the supporting mandrel is completed within the two isolation film layers, completely avoiding direct friction between the supporting mandrel and the inner vacuum bag, thereby preventing scratches on the inner wall fiber layer of the hat-shaped stringer. Furthermore, since the supporting mandrel is removed before curing, the annular support pad can tightly adhere to the slightly deformed inner wall of the composite material during curing, uniformly transmitting the autoclave pressure to all areas, effectively avoiding bridging caused by rigid constraints and improving molding quality. Moreover, after the stiffened wall panel of the hat-shaped stringer is cured, the flexible nature of the annular reinforcement pad allows it to be easily extracted from the inner cavity of the hat-shaped stringer through elastic deformation, which further reduces the damage to the fiber layer of the inner wall of the hat-shaped stringer. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the first forming structure of the hat-shaped stringer reinforced wall panel provided in an embodiment of the present invention;

[0027] Figure 2 This is an assembly drawing of the supporting core mold provided in an embodiment of the present invention;

[0028] Figure 3 This is a cross-sectional view of the cap-shaped stringer being laid according to an embodiment of the present invention;

[0029] Figure 4 This is a cross-sectional view of the inner and outer vacuum bags during vacuuming, provided in an embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram of the second forming structure of the hat-shaped stringer reinforced wall panel provided in an embodiment of the present invention;

[0031] Figure 6 This is an exploded view of the forming process of the hat-shaped stringer stiffened wall panel provided in an embodiment of the present invention.

[0032] In the picture:

[0033] 1. Tooling;

[0034] 2. Supporting core mold; 20. Hollow cavity;

[0035] 3. Separating membrane;

[0036] 4. Inner vacuum bag;

[0037] 5. Circular reinforcement pad;

[0038] 6. Packing material;

[0039] 7. External vacuum bag;

[0040] 100. Skin;

[0041] 200. Hat-shaped stringer. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0043] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0045] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0047] See Figures 1-5 This invention provides a method for forming a hat-shaped stringer reinforced wall panel, comprising the following steps:

[0048] S1. Fix the fixture 1, and then fix the skin 100 on the fixture 1;

[0049] S2. Two layers of isolation film 3 are wrapped around the outer periphery of the support core mold 2, and both ends of the two layers of isolation film 3 extend out of the support core mold 2 along the length direction.

[0050] S3. Cover the outermost layer of the isolation membrane 3 with an inner vacuum bag 4, and make the inner vacuum bag 4 extend out of the support core mold 2 at both ends along the length direction.

[0051] S4. Pull the two layers of isolation film 3 and the inner vacuum bag 4 to the same end, insert the support core mold 2, the two layers of isolation film 3 and the inner vacuum bag 4 into the annular force pad 5 as a whole, so that both ends of the support core mold 2 extend out of the annular force pad 5, and then fix the annular force pad 5 on the skin 100, wherein the annular force pad 5 is made of rubber.

[0052] S5. Fiber prepreg is laid on the annular reinforcing pad 5 to form the uncured blank of the hat-shaped stringer (200);

[0053] S6. Fix the inner vacuum bag 4 at one end of the annular force pad 5, and pull out the innermost isolation film 3 and the support core mold 2 wrapped by the isolation film 3 from the other end, and then pull out the outermost isolation film 3.

[0054] S7. Seal the inner vacuum bag 4 circumferentially and draw a vacuum.

[0055] S8. Place the entire structure into an autoclave for curing. After curing, peel off the inner vacuum bag 4, demold the hat-shaped stringer reinforced wall panel composed of the hat-shaped stringer 200 and the skin 100 from the tooling 1, and pull out the annular reinforcing pad 5 in the hat-shaped stringer 200.

[0056] In steps S2-S3, two layers of release film 3 and an inner vacuum bag 4 are sequentially wrapped around the support mandrel 2, constructing a crucial multi-layered protective interface. In demolding step S6, the inner vacuum bag 4 at one end of the annular support pad 5 is first fixed to form an anchor point; then, utilizing the low friction characteristics between the two release films 3, the innermost release film 3 and the support mandrel 2 it wraps are first extracted from the other end, and then the outermost release film 3 is extracted separately. Using the release film 3 as a lubricating medium, the extraction process of the support mandrel 2 is completed entirely within the film layer, thereby completely avoiding direct friction between it and the inner vacuum bag 4, and thus avoiding scratching the inner wall fiber layer of the cap-shaped stringer 200. Furthermore, since the support mandrel 2 is removed before curing, during the curing process, the annular support pad 5 can closely adhere to the inner wall of the composite material, which changes slightly due to thermal expansion, and evenly transmit the autoclave pressure to all areas, effectively avoiding bridging caused by rigid constraints and improving molding quality. Moreover, after the stiffened wall panel of the hat-shaped stringer is cured, the flexible nature of the annular reinforcing pad 5 allows it to be easily extracted from the inner cavity of the hat-shaped stringer 200 through elastic deformation, which further reduces the damage to the fiber layer of the inner wall of the hat-shaped stringer 200.

[0057] In addition, the inner vacuum bag 4 is sealed and vacuumed before curing begins, which can pre-create a negative pressure environment in the inner cavity of the cap-shaped stringer 200, so that the inner vacuum bag 4 can tightly compress the annular pressure pad 5, providing uniform initial pressure for subsequent autoclave curing and eliminating interlayer gas.

[0058] In this embodiment, the tooling 1 includes an operating plate and four support legs fixed to the base plate of the operating plate.

[0059] Specifically, in step S2, the support core mold 2 is made of rubber. Not only is it low-cost, but during the installation stage, the rubber support core mold 2, with its certain rigidity, can provide sufficient rigid support for the external annular reinforcing pad 5.

[0060] Specifically, such as Figure 3 As shown, in step S2, a hollow cavity 20 is formed inside the support core mold 2. The hollow cavity 20 ensures that the support core mold 2 has the necessary support rigidity while reducing its own weight and improving the ease of operation.

[0061] Specifically, in step S2, both ends of the two isolation films 3 extend beyond the support core mold 2 along the length direction, with one end of the isolation film 3 extending beyond the support core mold 2 by a greater length than the other end. In step S4, the longer end of the two isolation films 3 is pulled, and the support core mold 2, the two isolation films 3, and the inner vacuum bag 4 are inserted into the annular support pad 5 as a whole. In step S2, the isolation films 3 extend beyond the support core mold 2 at both ends along the length direction, and one end is intentionally set to extend longer than the other, providing significant convenience and reliability for subsequent assembly operations. In step S4, the operator pulls the longer end, easily obtaining sufficient gripping space, thus allowing for a more effortless and stable insertion of the assembly of the support core mold 2, isolation films 3, and inner vacuum bag 4 into the inner cavity of the annular support pad 5.

[0062] Specifically, in step S3, the inner vacuum bag 4 extends 100mm to 150mm beyond the supporting core mold 2 at both ends along its length, which is less than the length of the separator 3 extending beyond the supporting core mold 2. The longer separator 3 ensures that the hand only contacts the membrane layer when gripping and pulling, avoiding contamination or damage to the inner vacuum bag 4; while the 100mm to 150mm extended section of the vacuum bag provides sufficient overlap area for reliable sealing and fixing in step S6, ensuring the effectiveness of the seal, and also avoids excessive material waste or entanglement due to excessive length, thus improving process reliability and operational efficiency.

[0063] Specifically, such as Figure 3 As shown, in step S4, after the annular reinforcing pad 5 is fixed to the skin 100, the annular reinforcing pad 5 forms two chamfers with the skin 100 on both sides along the width direction, and the two chamfers are filled with filler 6. If the sharp corners for bonding with the skin are directly formed when manufacturing the annular reinforcing pad 5, these sharp corners are prone to defects, rounding, or uneven quality due to stress concentration during processing and subsequent treatment, making it difficult to guarantee dimensional accuracy and structural integrity. Therefore, by actively designing them as chamfers that are easier to manufacture and ensure quality, and by using special filler 6 to fill these two chamfers during assembly, a continuous and smooth transition surface that perfectly matches the contour of the final product can be formed before installation.

[0064] More specifically, the filler 6 and the annular reinforcing pad 5 are made of the same material. During the heating and cooling process, the two will expand and contract synchronously at the same rate, thus forming a uniform support interface without relative displacement and stress concentration.

[0065] Specifically, such as Figure 4 and Figure 6As shown, in step S7, an outer vacuum bag 7 is applied to both the cap-shaped stringer 200 and the skin 100, and then sealed and vacuumed. The outer vacuum bag 7 applies uniform curing pressure from above to the contours of the skin 100 and the cap-shaped stringer 200, ensuring a tight and gapless co-bonding interface between the skin 100 and the cap-shaped stringer 200. Simultaneously, the inner vacuum bag 4 continuously provides adaptive support pressure to the inner wall of the cap-shaped stringer 200 from the inside through the annular reinforcing pad 5. The balancing effect of the internal and external pressures suppresses deformation or delamination that may occur during the curing process.

[0066] More specifically, in step S7, the inner vacuum bag 4 and the outer vacuum bag 7 are bonded together and connected to form an integrated vacuum-sealed system, and are simultaneously evacuated through the same vacuum pipeline. This setup ensures the immediate balance of pressure states inside and outside the cap-shaped stringer 200, reduces the risk of component deformation caused by pressure differences, and ensures uniform and coordinated compaction at the bonding interface between the skin 100 and the cap-shaped stringer 200, as well as between fiber layers. Simultaneously, by simplifying the complex multi-channel vacuum system into a single reliable loop, process efficiency is improved.

[0067] In this embodiment, the inner vacuum bag 4 and the outer vacuum bag 7 can be bonded together with sealant.

[0068] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for forming a hat-shaped stringer reinforced wall panel, characterized in that, Includes the following steps: S1. Fix the fixture (1), and then fix the skin (100) on the fixture (1). S2. Two layers of isolation film (3) are wrapped around the outer periphery of the support core mold (2), and both ends of the two layers of isolation film (3) extend out of the support core mold (2) along the length direction. S3. Cover the outermost isolation membrane (3) with an inner vacuum bag (4) and make the inner vacuum bag (4) extend out of the support core mold (2) at both ends along the length direction. S4. Pull the two layers of isolation film (3) and the inner vacuum bag (4) to the same end, insert the support core mold (2), the two layers of isolation film (3) and the inner vacuum bag (4) into the annular force pad (5) as a whole, and make both ends of the support core mold (2) extend out of the annular force pad (5). Then fix the annular force pad (5) on the skin (100). The annular force pad (5) is made of rubber and has elasticity and support. S5. Fiber prepreg is laid on the annular reinforcing pad (5) to form the uncured blank of the hat-shaped stringer (200); S6. Fix the inner vacuum bag (4) at one end of the annular force pad (5), and pull out the innermost isolation film (3) and the support core mold (2) wrapped by the isolation film (3) from the other end, and then pull out the outermost isolation film (3). S7. Seal the inner vacuum bag (4) circumferentially and draw a vacuum; S8. Place the overall structure into a hot autoclave for curing. After curing, peel off the inner vacuum bag (4), demold the hat-shaped stringer stiffened wall panel composed of the hat-shaped stringer (200) and the skin (100) from the tooling (1), and pull out the annular reinforcing pad (5) in the hat-shaped stringer (200).

2. The method for forming a hat-shaped stringer reinforced wall panel according to claim 1, characterized in that, In step S7, an outer vacuum bag (7) is laid on the hat-shaped stringer (200) and the skin (100), and the outer vacuum bag (7) is sealed and vacuumed.

3. The method for forming a hat-shaped stringer reinforced wall panel according to claim 2, characterized in that, In step S7, the inner vacuum bag (4) and the outer vacuum bag (7) are glued together and connected to form an integral vacuum sealing system, and are simultaneously evacuated through the same vacuum pipeline.

4. The method for forming a hat-shaped stringer reinforced wall panel according to claim 1, characterized in that, In step S4, after the annular force pad (5) is fixed on the skin (100), the annular force pad (5) forms two chamfers with the skin (100) on both sides along the width direction, and the two chamfers are filled with filler (6).

5. The method for forming a hat-shaped stringer reinforced wall panel according to claim 4, characterized in that, The filler (6) is made of the same material as the annular reinforcing pad (5).

6. The method for forming a hat-shaped stringer reinforced wall panel according to claim 1, characterized in that, In step S2, both ends of the two isolation membranes (3) extend out of the support core mold (2) along the length direction, and the length of one end of the isolation membrane (3) extending out of the support core mold (2) is greater than the length of the other end extending out of the support core mold (2); in step S4, the two isolation membranes (3) are pulled to extend out of the longer end of the support core mold (2), and the support core mold (2), the two isolation membranes (3) and the inner vacuum bag (4) are inserted into the annular force pad (5) as a whole.

7. The method for forming a hat-shaped stringer reinforced wall panel according to claim 1, characterized in that, In step S3, the length of the inner vacuum bag (4) extending from both ends of the support core mold (2) along the length direction is 100mm~150mm, which is less than the length of the separation membrane (3) extending from the support core mold (2).

8. The method for forming a hat-shaped stringer reinforced wall panel according to any one of claims 1-7, characterized in that, In step S2, the support core mold (2) is made of rubber.

9. The method for forming a hat-shaped stringer reinforced wall panel according to any one of claims 1-7, characterized in that, In step S2, a hollow cavity (20) is opened inside the support core mold (2).

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