A method for forming a composite C-rib for an inner belt honeycomb sandwich structure

Abstract

The present application relates to the technical field of aviation composite material manufacturing, in particular to a forming method for a C-shaped rib of a composite material with a honeycomb sandwich structure on the inner side. The forming method comprises the following steps: laying up an inner skin prepreg on a forming tool; covering a first adhesive film on the lower end surface of the honeycomb after cutting, and fixing the first adhesive film on the upper end surface of the inner skin prepreg; covering a second adhesive film on the upper end surface of the fixed honeycomb, and laying up an outer skin on the honeycomb and the inner skin prepreg; and finally, packaging into a tank for co-curing. The forming method for the C-shaped rib of the composite material with the honeycomb sandwich structure on the inner side aims to solve the problem of how to simultaneously improve the internal quality of the C-shaped rib, the positioning accuracy of the honeycomb, and the forming efficiency.

Description

Technical Field

[0001] This invention relates to the field of aerospace composite material manufacturing technology, and specifically to a molding method for C-ribs of composite materials with inner honeycomb sandwich structures. Background Technology

[0002] Composite materials, due to their high specific strength, high specific hardness, strong designability, good fatigue fracture resistance, corrosion resistance, good dimensional stability, and ease of large-area integral molding, have become one of the most important structural materials in modern aerospace. Honeycomb sandwich structures, in particular, are structural materials with an exceptionally high strength-to-weight ratio. Compared to solid materials, honeycomb sandwich composite materials use only 1%-5% of the material being replaced, making them a highly promising lightweight material that is economical in material usage and energy consumption. The C-ribs of honeycomb sandwich composite materials on the inner side are a highly stable rib structure used in aircraft flaps, ailerons, and other structures.

[0003] Currently, most aerospace composite material molding processes utilize autoclave molding. However, in the molding of C-ribs in composite materials with internal honeycomb sandwich structures, the honeycomb core material is difficult to accurately position on the inner surface of the C-rib, and it is prone to slippage during molding. If a male mold is used for co-curing, honeycomb pressure is difficult to apply, easily leading to defects under the honeycomb structure; if a female mold is used for co-curing, skin layering is difficult, easily causing porosity defects at the rib radius corners; and if step-by-step curing is used, it increases cost and part weight. How to ensure both the internal quality of the part and the honeycomb positioning accuracy while simplifying operations and improving molding efficiency remains a challenge.

[0004] Therefore, the inventors provide a method for molding C-ribs of composite materials with honeycomb sandwich structures on the inner side. Summary of the Invention

[0005] (1) Technical problems to be solved

[0006] This invention provides a molding method for C-ribs of composite materials with inner honeycomb sandwich structures, solving the technical problem of how to simultaneously improve the internal quality of C-ribs, honeycomb positioning accuracy, and molding efficiency.

[0007] (2) Technical solution

[0008] This invention provides a method for molding C-ribs in composite materials with an inner honeycomb core sandwich structure, comprising the following steps:

[0009] Lay the inner skin prepreg on the forming tooling;

[0010] A first adhesive film is covered on the lower end face of the slit honeycomb core and fixed to the upper end face of the inner skin prepreg.

[0011] A second adhesive film is covered on the upper surface of the fixed honeycomb core, and an outer skin is laid on the honeycomb core and the inner skin prepreg. Finally, the honeycomb core is sealed in a can for co-curing.

[0012] Furthermore, the honeycomb core is cut along the centerline of the honeycomb core in the W direction.

[0013] Furthermore, when the honeycomb core is a large rigid honeycomb core or a large-sized honeycomb core, it is cut at the chamfered edge of the honeycomb core.

[0014] Furthermore, after the honeycomb core is cut, a third adhesive film is placed at the cut position.

[0015] Furthermore, the thickness of the third adhesive film is 0.3-0.4 mm.

[0016] Furthermore, during the laying process of the outer skin, a vacuum is drawn after each layer of prepreg is laid, and a unidirectional strip of prepreg is used to compensate for the gaps in the splicing of the honeycomb core according to the flatness of the outer skin after vacuuming.

[0017] Furthermore, during the encapsulation process, a fiberglass cover plate is used to apply pressure evenly to the outer skin.

[0018] Furthermore, the thickness of the fiberglass cover plate is 1.5-2.5mm.

[0019] Furthermore, after the outer skin is laid on the honeycomb core and the inner skin prepreg, the method further includes: sequentially placing a release material, a separating material, a breathable material, the fiberglass cover plate, and a vacuum bag on the upper surface of the outer skin.

[0020] Furthermore, before laying the inner skin prepreg on the molding fixture, the process further includes: cleaning the molding fixture and applying a release agent to its upper surface.

[0021] (3) Beneficial effects

[0022] In summary, this invention, through the design of honeycomb core slicing, provides better local pressure on the inner skin after slicing, effectively improving the positioning accuracy of the honeycomb core. Furthermore, the molding tooling controls the slippage of the honeycomb core material during the molding process, ensuring the internal quality and surface accuracy of the parts. At the same time, it is simple to operate and has high production efficiency. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of a molding method for a composite material C-rib with an inner honeycomb core sandwich structure provided by an embodiment of the present invention;

[0025] Figure 2(a) is a schematic diagram of a small-sized honeycomb core cutting structure provided in an embodiment of the present invention;

[0026] Figure 2(b) is a schematic diagram of a large-size honeycomb core slicing structure provided in an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of a molding tooling and C-rib assembly provided in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure of a composite material with an inner honeycomb core sandwich structure after C-rib molding, provided by an embodiment of the present invention.

[0029] In the picture:

[0030] 1-Outer skin; 2-Honeycomb core; 3-Inner skin prepreg; 4-Molding tooling; 5-Fiberglass cover plate; A-First slitting line; B-Second slitting line. Detailed Implementation

[0031] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to 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 this invention.

[0034] Figure 1 This is a schematic flowchart of a molding method for C-ribs of a composite material with an inner honeycomb core sandwich structure provided by an embodiment of the present invention, as shown below. Figure 1 As shown, the method may include the following steps:

[0035] S100, Lay the inner skin prepreg 3 on the molding fixture 4;

[0036] S200. Cover the lower end face of the slit honeycomb core 2 with a first adhesive film and fix it to the upper end face of the inner skin prepreg 3.

[0037] S300. Cover the upper surface of the fixed honeycomb core 2 with a second adhesive film, and lay the outer skin 1 on the honeycomb core 2 and the inner skin prepreg. Finally, seal it in a can for co-curing.

[0038] In the above embodiment, the molding fixture 4 is CNC machined from Q235 material, the honeycomb core 2 is inside the C-shaped rib, and the working surface of the molding fixture 4 is consistent with the inner surface of the C-shaped rib.

[0039] Through the design of honeycomb core slicing, the slicing honeycomb core 2 can be fully and completely fitted with the inner surface of the C-shaped rib to position the inner surface of the C-shaped rib. The whole honeycomb core is rigid to the inner skin and is not conducive to local pressure on the inner skin. However, the slicing honeycomb core is more conducive to local pressure on the inner skin, thus effectively ensuring the pressure of the inner skin prepreg 3 under the honeycomb. The slippage of the honeycomb core material during the molding process is controlled by the molding tooling, ensuring the internal quality and surface accuracy of the parts. At the same time, the operation is simple and the production efficiency is high.

[0040] As an optional implementation, as shown in Figure 2(a), the honeycomb core 2 is evenly divided along the centerline of the honeycomb core (i.e., the first slicing line A) in the W direction. It should be noted that the specific location of the slicing line is not limited, as long as it satisfies the purpose of dividing the honeycomb core 2. Of course, cutting along the W direction (the direction of cell expansion) reduces the overall stiffness of the honeycomb in the L direction.

[0041] As an optional implementation, as shown in Figure 2(b), when the honeycomb core 2 is a large rigid honeycomb core or a large-sized honeycomb core, in addition to cutting the honeycomb core 2 along the direction parallel to the honeycomb core W (the direction shown in the figure) and the center line of the honeycomb core (i.e., the first cutting line A), it is also necessary to cut the honeycomb core 2 at the chamfered edge (i.e., the second cutting line B).

[0042] As an optional implementation, after the honeycomb core is cut, a third adhesive film with a thickness of 0.3-0.4 mm is placed at the cut location. This ensures the adhesion of the honeycomb core during the part curing process.

[0043] As an optional implementation, during the laying process of the outer skin 1, a vacuum is applied after each layer of prepreg is laid. Based on the flatness of the outer skin 1 after vacuuming, a unidirectional prepreg tape is used to compensate for the gaps at the honeycomb core splicing. Specifically, this process is repeated until there are no gaps at the honeycomb core splicing after vacuuming.

[0044] In addition, during the encapsulation process, a fiberglass cover plate 5 is used to apply uniform pressure to the outer skin. The fiberglass cover plate 5 is made of fiberglass prepreg, which is laid up and cured, and its outer surface is consistent with the C-shaped rib of the inner honeycomb core sandwich structure composite material, with a thickness of 1.5-2.5mm.

[0045] As an optional implementation method, such as Figure 3 As shown, after the outer skin 1 is laid on the honeycomb core 2 and the inner skin prepreg 3, the method further includes: placing a release material, a separating material, a breathable material, a fiberglass cover plate 5 and a vacuum bag on the upper surface of the outer skin 1 in sequence.

[0046] As an optional implementation, before step S100, where the inner skin prepreg is laid on the molding fixture, the following steps are also included: cleaning the molding fixture and applying a release agent to its upper surface. Additionally, after co-curing, the fiberglass cover plate 5 and other encapsulation materials are first removed from the part, and then the part is removed from the molding fixture 4 to complete the demolding process. The resulting structure, with the inner honeycomb core sandwich composite material C-ribs, is as follows: Figure 4 As shown.

[0047] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0048] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method for molding C-ribs in composite materials with an inner honeycomb core sandwich structure, characterized in that, The method includes the following steps: Lay the inner skin prepreg on the forming tooling; A first adhesive film is covered on the lower end face of the slit honeycomb core and fixed to the upper end face of the inner skin prepreg. A second adhesive film is covered on the upper surface of the fixed honeycomb core, and an outer skin is laid on the honeycomb core and the inner skin prepreg. Finally, the honeycomb core is sealed in a can for co-curing. During the encapsulation process, a fiberglass cover plate is used to apply pressure evenly to the outer skin; The honeycomb core is cut along the center line of the honeycomb core in the W direction. When the honeycomb core is a large rigid honeycomb core or a large-sized honeycomb core, it is cut at the chamfered edge of the honeycomb core.

2. The molding method for C-shaped ribs of composite materials with inner honeycomb core sandwich structures according to claim 1, characterized in that, After the honeycomb core is cut, a third adhesive film is placed at the cut position.

3. The molding method for C-ribs of composite materials with inner honeycomb core sandwich structures according to claim 2, characterized in that, The thickness of the third adhesive film is 0.3-0.4 mm.

4. The molding method for C-ribs of composite materials with inner honeycomb core sandwich structures according to claim 1, characterized in that, During the laying process of the outer skin, a vacuum is drawn after each layer of prepreg is laid. Based on the flatness of the outer skin after vacuuming, a unidirectional prepreg tape is used to compensate for the gaps in the splicing of the honeycomb core.

5. The molding method for C-ribs of composite materials with inner honeycomb core sandwich structures according to claim 1, characterized in that, The thickness of the fiberglass cover plate is 1.5-2.5mm.

6. The molding method for C-ribs of composite materials with inner honeycomb core sandwich structures according to claim 5, characterized in that, After the outer skin is laid on the honeycomb core and the inner skin prepreg, the process further includes: Release material, isolation material, breathable material, fiberglass cover plate, and vacuum bag are placed sequentially on the upper surface of the outer skin.

7. The molding method for C-ribs of composite materials with inner honeycomb core sandwich structures according to claim 1, characterized in that, Before laying the inner skin prepreg on the molding fixture, the process further includes: cleaning the molding fixture and applying a release agent to its upper surface.

Images