A fiber continuous longitudinal and transverse reinforced integral composite material skin structure and forming method

Abstract

This invention relates to a fiber-continuous longitudinally and transversely reinforced integral composite material skin structure, which is formed by bonding an upper skin (3), a lower skin (1), and longitudinally and transversely reinforcing structures (2). It also relates to a method for forming the fiber-continuous longitudinally and transversely reinforced integral composite material skin structure, including the forming of the longitudinally and transversely reinforcing structures (2); skin laying and positioning of the longitudinally and transversely reinforcing structures (2); curing the laid fiber-continuous longitudinally and transversely reinforced integral composite material skin structure; and machining a circular opening on each of the left and right sides of the longitudinally and transversely reinforcing structures (2), thus completing the entire process of forming the fiber-continuous longitudinally and transversely reinforced integral composite material skin structure. The skin structure of this invention is lightweight, has continuous fibers, and the integral structure is bonded and co-cured, effectively enhancing structural strength and resulting in superior overall structural rigidity and strength performance. Furthermore, the embedded longitudinally and transversely reinforcing structures have high dimensional and positional accuracy.

Description

Technical Field

[0001] This invention relates to the field of composite materials, and in particular to a fiber-reinforced integral composite material skin structure and its molding method. Background Technology

[0002] Continuous fiber-reinforced composite materials (CFRPs) possess outstanding mechanical properties and designability, making them widely used in the aerospace field. In particular, the composite material cabin structures of aircraft are relatively thin, requiring stiffeners to enhance their load-bearing capacity and increase the strength, stiffness, and stability of the thin-walled structure. Longitudinal and transverse stiffeners, as the main load-bearing components of thin-walled structures, can effectively enhance the overall mechanical properties of the structure. Currently, most composite material longitudinal and transverse stiffener structures select continuous longitudinal / transverse ribs based on the main load-bearing direction, requiring the removal of ribs perpendicular to the load. This method fails to leverage the advantages of fiber-reinforced composite materials, and the mechanical properties of the stiffener structure are not particularly outstanding. Especially for thin-walled composite material structures with large openings, local reinforcement near the openings is necessary. However, using conventional methods, the structural reinforcement effect is limited within the confined reinforcement space. Therefore, it is necessary to develop a continuous fiber longitudinal and transverse stiffened integral composite material skin structure. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned technical problems by providing a fiber-continuous longitudinal and transverse reinforced integral composite material skin structure and molding method. The structure is lightweight, the fibers are continuous, and the integral structure is bonded and co-cured to effectively enhance the structural strength.

[0004] The technical solution of this invention is:

[0005] A fiber-continuous longitudinal and transverse reinforced integral composite material skin structure is formed by bonding an upper skin 3, a lower skin 1 and a longitudinal and transverse reinforcing structure 2 together.

[0006] The longitudinal and transverse reinforcing structure 2 includes two transverse reinforcing ribs and one longitudinal reinforcing rib. The upper skin 3 and the lower skin 1 cover the longitudinal and transverse reinforcing structure 2 on the upper and lower surfaces, respectively. The upper skin 3 and the lower skin 1 are both rounded rectangles of the same size. The middle part is the longitudinal and transverse reinforcing structure 2. The longitudinal and transverse reinforcing structure 2 has a circular opening on the left and right sides.

[0007] A method for molding a fiber-reinforced integral composite skin structure includes the following steps:

[0008] 1) Forming of longitudinal and transverse reinforcing structure 2: The longitudinal and transverse reinforcing structure paving surface 4 is formed by making a mold. Seven ply groups are laid on the seven longitudinal and transverse reinforcing structure paving surfaces 4 respectively. The seven longitudinal and transverse reinforcing structure paving surfaces 4 include one longitudinal paving surface, four "L" shaped paving surfaces, and two "U" shaped paving surfaces. The longitudinal paving surface is ply group four 5, which includes five layers of prepreg. The four "L" shaped paving surfaces and the two "U" shaped paving surfaces are ply group three 6, which includes ten layers of prepreg. After the plying is completed, the longitudinal and transverse reinforcing structure 2 is cured and formed, and then machined to the required thickness.

[0009] 2) Skin installation and positioning of longitudinal and transverse reinforcing structures 2: The skin installation surface 7 is formed by making a mold. The lower skin 1 is laid on the skin installation surface 7. After wrapping the transverse reinforcing structure 3 with the adhesive film, the transverse reinforcing structure 3 is laid in the center of the lower skin 1. Positioning is performed on the skin 2 to ensure the positional accuracy of the transverse reinforcing structure 3. Finally, the upper skin 3 is laid on top of the transverse reinforcing structure 3 and the lower skin 1 to complete the skin installation.

[0010] 3) The fiber-reinforced composite material skin structure after laying is cured. A circular opening is machined on each side of the longitudinal and transverse reinforcement structure 2 to complete the whole process of forming the fiber-reinforced composite material skin structure.

[0011] The feature is that the lower skin 1 is laid up in 8 layers with different layup angles, the bottommost prepreg is glass cloth prepreg, and the inner side is carbon fiber prepreg.

[0012] The feature is that the upper skin 3 is laid up in three layers with different layup angles, the uppermost prepreg is a glass cloth prepreg, and the inner layer is a carbon fiber prepreg.

[0013] Its characteristic is that the third layer 6 is laid up with 10 layers using different layup angles, and the layup material is carbon fiber fabric prepreg.

[0014] Its characteristic is that the four-layer layup group 5 uses different layup angles to lay up 5 layers, and the layup material is carbon fiber fabric prepreg.

[0015] The feature is that, during the molding of the longitudinal and transverse reinforcing structure 2, the triangular areas formed between different layup groups are filled with unidirectional tape prepreg 8.

[0016] The feature is that the bottom corners of the longitudinal and transverse reinforcing structure 2 are covered with unidirectional prepreg 8 to prevent the formation of cavities in the right-angle transition area between the upper skin 3 and the longitudinal and transverse reinforcing structure 2 during the laying process.

[0017] Its characteristic feature is that lines are drawn on the skin 2 or positioning plates are made to ensure the positional accuracy of the horizontal reinforcing structure 3.

[0018] The advantages of this invention are:

[0019] The fiber-reinforced integral composite skin structure of this invention utilizes continuous fiber layups in both longitudinal and transverse reinforcement, fully leveraging the mechanical properties of continuous fiber-reinforced composites. The longitudinal and transverse reinforcement structure is divided into multiple layup groups, allowing for precise design based on working conditions and dimensional requirements. The longitudinal and transverse reinforcement structure is first cured and formed, then unidirectional prepreg is filled around the reinforcement structure, and an adhesive film is adhered to the contact surface with the skin. Finally, the structure is pre-embedded between the skin layups and bonded together for co-curing to form the integral structure. The overall structure exhibits superior strength and stiffness, and the dimensional and positional accuracy of the pre-embedded longitudinal and transverse reinforcement structure is high. This fiber-reinforced integral composite skin structure is lightweight, features continuous fibers, and the co-curing and bonding of the integral structure effectively enhances structural strength. Attached Figure Description

[0020] Figure 1 Composite material longitudinal and transverse stiffened integral skin structure

[0021] Figure 2 Horizontal and vertical reinforced structure tiling diagram

[0022] Figure 3 Tile breakdown diagram Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0024] See appendix Figure 1 This composite material longitudinally and transversely reinforced integral skin structure is formed by bonding and curing skin 2, skin 5, and longitudinally and transversely reinforcing structure 2 together. Positional accuracy of the longitudinally and transversely reinforcing structure 2 can be ensured by marking lines on skin 2 or creating positioning clips. All fibers in the longitudinally and transversely reinforcing structure 2 are continuous in their main directions. The triangular areas formed at the corners of different laying groups are filled with unidirectional prepreg tape. Unidirectional prepreg tape 8 is attached to the bottom corners of the longitudinally and transversely reinforcing structure 2 to transition in right-angle areas and prevent bridging and the formation of resin-rich areas during skin 5 laying. See appendix. Figure 2 The longitudinal and transverse reinforcement structure consists of 7 paving groups (6-12) and 7 paving surfaces (13). The triangular mating areas of different paving groups are filled with unidirectional prepreg tape. The required thickness for machining is determined after the longitudinal and transverse reinforcement structure 2 has cured and hardened; see appendix. Figure 3 After the overall structure has solidified, a large circular opening is machined to complete the entire process of manufacturing composite material parts.

[0025] The present invention relates to a fiber-reinforced integral composite skin structure with longitudinal and transverse reinforcement. This structure is formed by bonding and co-curing a cured longitudinal and transverse reinforcement structure with a thin-walled skin. The longitudinal and transverse reinforcement structure ensures fiber continuity in all directions through multiple application surfaces, with more fibers along the main load-bearing direction. After curing, the longitudinal and transverse reinforcement structure needs to be machined to a specified rib height. The form of the longitudinal and transverse reinforcement structure can be adjusted according to the structural force transmission characteristics and large opening features, adjusting the number and position of longitudinal / transverse ribs to ensure that each longitudinal / transverse interlacing form is an open form, thus ensuring fiber continuity by increasing the application surfaces. During skin application, the longitudinal and transverse reinforcement structure is pre-embedded in the middle layer of the skin application. Adhesive films are applied to the upper and lower contact surfaces between the longitudinal and transverse reinforcement structure and adjacent skin application layers. Unidirectional prepreg tape is filled at the bottom corners of the longitudinal and transverse reinforcement structure to prevent subsequent skin application from bridging and creating resin-rich areas that affect structural quality. After pre-embedding and application, co-curing is completed, and the required openings are machined to complete the preparation of the composite material part. The application groups in Tables 1 and 2 are used as examples.

[0026] The longitudinal and transverse reinforcement structure has continuous fibers in all major directions, and the triangular areas formed at the corners of different layup groups should be filled with unidirectional tape prepreg. The longitudinal and transverse reinforcement structure has 7 longitudinal and transverse reinforcement layup surfaces and 7 layup groups, as shown in Table 1. All layup materials are carbon fiber fabric prepreg.

[0027] Table 1 Reinforcing bar layer group

[0028]

[0029]

[0030] The thin-walled skin consists of one film-coated surface and one layup assembly, as shown in Table 2. The outermost prepreg of the skin is always glass cloth fabric prepreg. After the longitudinal and transverse reinforcing structures have cured, they are laid between C-P080 and C-P090.

[0031] Table 2 Skin Layup Group

[0032]

Claims

1. A molding method for a fiber-continuous longitudinal and transverse reinforced integral composite material skin structure, wherein the fiber-continuous longitudinal and transverse reinforced integral composite material skin structure is formed by bonding an upper skin (3), a lower skin (1), and a longitudinal and transverse reinforcing structure (2); the longitudinal and transverse reinforcing structure (2) includes two transverse reinforcing ribs and one longitudinal reinforcing rib, the upper skin (3) and the lower skin (1) respectively cover the longitudinal and transverse reinforcing structure (2) on the upper and lower surfaces, the upper skin (3) and the lower skin (1) are both rounded rectangles of the same size, the middle part is the longitudinal and transverse reinforcing structure (2), and the longitudinal and transverse reinforcing structure (2) has a circular opening on the left and right sides; Its features are, The method includes the following steps: 1) Forming of longitudinal and transverse reinforcing structure (2): The longitudinal and transverse reinforcing structure paving surface (4) is formed by making a mold. Seven ply groups are laid on the seven longitudinal and transverse reinforcing structure paving surfaces (4). The seven longitudinal and transverse reinforcing structure paving surfaces (4) include one longitudinal paving surface, four "L" shaped paving surfaces, and two "U" shaped paving surfaces. The longitudinal paving surface is ply group four (5), which includes five layers of prepreg. The four "L" shaped paving surfaces and the two "U" shaped paving surfaces are ply group three (6), which includes ten layers of prepreg. After the plying is completed, the longitudinal and transverse reinforcing structure (2) is cured and formed, and then machined to the required thickness. 2) Skin laying and positioning of longitudinal and transverse reinforcement structure (2): The skin laying surface (7) is formed by making a mold. The lower skin (1) is laid on the skin laying surface (7). After wrapping the transverse reinforcement structure (2) with the laying film, the longitudinal and transverse reinforcement structure (2) is laid in the center of the lower skin (1). Positioning is performed on the lower skin (1) to ensure the positional accuracy of the longitudinal and transverse reinforcement structure (2). Finally, the upper skin (3) is laid on top of the longitudinal and transverse reinforcement structure (2) and the lower skin (1) to complete the skin laying. 3) The fiber-reinforced composite material skin structure after laying is cured. A circular opening is machined on both sides of the longitudinal and transverse reinforcement structure (2) to complete the whole process of forming the fiber-reinforced composite material skin structure.

2. The molding method as described in claim 1, characterized in that, The lower skin (1) is laid up in 8 layers with different layup angles. The bottom prepreg is made of glass cloth fabric prepreg and the inner layer is made of carbon fiber fabric prepreg.

3. The molding method as described in claim 2, characterized in that, The upper skin (3) is laid up in three layers with different layup angles. The uppermost prepreg is made of glass cloth fabric prepreg, and the inner layer is made of carbon fiber fabric prepreg.

4. The molding method as described in claim 3, characterized in that, Ply group 3 (6) uses different ply angles to lay 10 layers, and the ply material is carbon fiber fabric prepreg.

5. The molding method as described in claim 4, characterized in that, Ply group four (5) uses different ply angles to lay up 5 layers, and the ply material is carbon fiber fabric prepreg.

6. The molding method as described in claim 5, characterized in that, When the longitudinal and transverse reinforcing structure (2) is formed, the triangular area formed between different ply groups is filled with unidirectional strip prepreg (8).

7. The molding method as described in claim 6, characterized in that, The perimeter corners of the longitudinal and transverse reinforcing structure (2) are covered with unidirectional prepreg (8) to prevent the formation of cavities in the right-angle transition area between the upper skin (3) and the longitudinal and transverse reinforcing structure (2) during the laying process.

8. The molding method as described in claim 7, characterized in that, Draw lines or make positioning plates on the lower skin (1) to ensure the positional accuracy of the horizontal reinforcing structure (2).

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