Composite material wallboard structure and forming method

Abstract

According to the composite material wallboard forming method, a wallboard structure comprises a skin and a plurality of stringers, the section of each stringer is in an inverted T shape, the stringers are connected to the inner surface of the skin, and the wallboard structure is decomposed into a plurality of assembly parts according to the theoretical appearance of the wallboard structure; the outer skin assembly part, the L-shaped assembly part and the semi-frame-shaped assembly part are respectively formed by paving composite material fiber prepreg; and according to the theoretical appearance of the wallboard structure, the assembly parts are pasted through adhesive films, hollow areas between the assembly parts are filled with foam cores, high-temperature co-curing is conducted in an autoclave, and the integrated composite wallboard structure is formed.

Description

Technical Field

[0001] The present application relates to the technical field of aircraft design, and in particular to a composite material wall panel structure and a molding method. Background Art

[0002] At present, with the rapid development of civil aviation, composite materials are widely used in aircraft, especially the wall panels of fuselage, wings and rudders. The traditional wall panel forming method is generally to stack the composite skin and the long stringer independently, solidify them separately, and then combine them through co-curing, co-bonding / secondary bonding technology, or use fasteners to mechanically connect them to form a whole. In this method, during curing, the skin and the long stringer are formed separately, and the quality requirements of their respective appearance are high. When secondary bonding is used, a certain degree of structural distortion will occur. In addition, the number of layers, curing temperature, material properties, etc. of the long stringer and the skin will be related to the bonding effect, and ultimately affect the connection strength of the wall panel. On the other hand, if fasteners are used for mechanical connection, holes need to be made on the skin and the long stringer respectively, and stress concentration will occur around the holes, reducing the connection efficiency. At the same time, in order to compensate for the impact of the decline in the performance of the composite material after the holes are made, the skin needs to be partially thickened, which will increase the weight. In addition, for the traditional wall panel forming method, there is a step in the connection area between the long stringer and the skin, which will cause uneven force on the entire wall panel and affect the load transfer efficiency. Therefore, it is hoped to design a composite wall panel structure that can not only reduce the structural distortion caused by the secondary bonding of the skin and the long stringer and enhance the bonding quality, but also reduce the stress concentration caused by hole making when the long stringer and the skin are fixedly connected and the resulting degradation of the fatigue performance of the composite material. Ultimately, the connection strength is increased and the performance of the aircraft is improved. Summary of the invention

[0003] The purpose of the present application is to provide a composite material wall panel structure and a forming method.

[0004] A composite wall panel forming method, the wall panel structure comprises a skin and a plurality of long stringers, the cross section of the long stringers is an inverted T-shape and connected to the inner surface of the skin, and is characterized in that it comprises the following contents: 1) according to the theoretical shape of the wall panel structure, the wall panel structure is decomposed into a plurality of assemblies; 2) composite fiber prepreg is used to lay and form each assembly separately; 3) according to the theoretical shape of the wall panel structure, the assemblies are pasted with adhesive film, the hollow areas between the assemblies are filled with foam cores, and then high-temperature co-curing is performed in an autoclave to form an integrated composite wall panel structure.

[0005] The composite material wall panel forming method is characterized in that: according to the theoretical shape of the wall panel structure, the overall outer skin of the wall panel is integrally formed into a wall panel outer skin assembly; 2) the outer side walls of the long stringers on both sides of the wall panel and the adjacent outer side wall panel inner skin layers are integrally formed into an L-shaped assembly; 3) the inner side walls of the adjacent long stringers in the middle of the wall panel and the adjacent wall panel inner skin layers are integrally formed into a semi-frame assembly.

[0006] A composite wall panel structure, the wall panel structure comprises a skin and a plurality of long stringers, the cross section of the long stringers is an inverted T-shape and connected to the inner surface of the skin, and is characterized in that the wall panel structure is formed by any of the above-mentioned composite wall panel forming methods, the wall panel structure comprises an outer skin assembly formed by paving composite fiber prepreg, an L-shaped assembly composed of the outer side walls of the long stringers on both sides of the wall panel and the inner skin layer of the adjacent outer wall panel, and a semi-frame assembly composed of the inner side walls of the adjacent long stringers in the middle of the wall panel and the inner skin layer of the adjacent wall panel, and the outer skin assembly, the L-shaped assembly and the semi-frame assembly are connected by a bonding film layer.

[0007] The composite wall panel structure is characterized in that the cavity between the L-shaped assembly, the semi-frame assembly and the outer skin assembly of the wall panel structure is filled with a foam core.

[0008] The beneficial effects of the present application are as follows: 1) The skin and the long stringer are formed in an integrated manner, which weakens the influence caused by the different thermal expansion coefficients, reduces the structural distortion caused by the separate curing, greatly improves the connection efficiency, improves the structural strength and rigidity of the composite wall panel, and improves the performance of the aircraft. 2) The skin and the long stringer are formed in an integrated manner by using a film, which avoids the stress concentration around the hole caused by the mechanical connection of the fasteners, improves the fatigue performance of the composite structure, and extends the service life of the wall panel structure. 3) In this molding method, the connection area between the long stringer and the skin has no steps and is of equal thickness. The entire wall panel is evenly stressed and has good load-transmitting performance, which improves the reliability during flight. 4) In this molding method, there is no need to cure the long stringer and the skin separately, the manufacturing process is simple, and there is no need to use fasteners to connect, which reduces the assembly and maintenance costs. 5) In this molding method, the thickness of the skin in the reinforced area and the non-reinforced area is the same, and there is no need to locally thicken the connection area, which greatly reduces the weight of the wall panel, thereby reducing the total weight of the entire composite body structure.

[0009] The present application is further described in detail below in conjunction with the accompanying drawings of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Schematic diagram of the integrated composite material wall panel structure.

[0011] Figure 2 Schematic diagram of the integrated composite material wall panel forming method.

[0012] Figure 3 Schematic diagram of the relationship between the inner fillet radius and thickness of the long stringer side wall and the inner skin of the wall panel.

[0013] Explanation of numbers in the figure: 1 skin, 2 long stringer, 3 outer skin assembly, 4 L-shaped assembly, 5 semi-frame assembly, 6 film, 7 foam core. DETAILED DESCRIPTION

[0014] Referring to the accompanying drawings, the composite wall panel structure of the present application is composed of a skin 1, a long stringer 2, a foam core 7 and an adhesive film 6. Figure 1 As shown. During manufacturing, the outer surface of the aircraft wall panel is used as the mold surface, that is, the negative mold is laid. First, several layers of carbon fiber or glass fiber prepreg are laid at room temperature as the outer skin assembly 3. Then, the L-shaped assembly 4 and the semi-frame assembly 5 are pre-made according to the spacing and height of the long stringer 2. Then, a layer of adhesive film 6 is applied between the outer skin assembly 3 and the L-shaped assembly 4 and the semi-frame assembly 5. The cavity position between the outer skin assembly 3 and the L-shaped assembly 4 and the semi-frame assembly 5 is filled with a matching foam core 7. The outer skin assembly 3 and the L-shaped assembly 4 and the semi-frame assembly 5 are spliced ​​together and put into an autoclave for high-temperature co-curing to form an integrated composite wall panel structure.

[0015] In specific implementation, according to the theoretical shape of the wall panel structure, the wall panel structure is decomposed into multiple assemblies, including an outer skin assembly 3, two L-shaped assemblies 4 and multiple semi-frame assemblies. The outer skin assembly 3 has the same curvature as the outer skin of the wall panel; the two L-shaped assemblies 4 are respectively composed of the outer side walls of the long stringers on the outermost sides of the wall panel and the inner skin layers of the adjacent outer wall panels; the semi-frame assembly is composed of the inner side walls of the adjacent long stringers in the middle of the wall panel and the adjacent inner skin layers of the wall panel. The number of semi-frame assemblies is related to the number of long stringers. When the wall panel structure contains two long stringers, there is a semi-frame assembly between the two adjacent long stringers. When the wall panel structure contains three long stringers, there will be two semi-frame assemblies between the inner side walls of the adjacent long stringers in the middle of the wall panel and the adjacent inner skin layers of the wall panel, and so on. Each assembly is formed by laying out composite fiber prepreg separately. In the L-shaped assembly 4 and the semi-frame assembly 5, the composite fiber prepreg of the long stringer side wall and the inner skin layer of the wall panel is laid in a continuous layer without missing layers.

[0016] In practice, in the L-shaped assembly 4 and the semi-frame assembly 5, the inner fillet radius r of the long stringer side wall and the inner skin layer of the wall panel should be greater than 0.5 times the thickness of the assembly wall t (r≥0.5t), and the outer fillet radius is R=r+t, therefore, R≥1.5t should be ensured. Figure 3 shown.

[0017] In the implementation, in order to ensure that the long stringer 2 has a symmetrical cross-section after the splicing is completed, the L-shaped assembly 4 and the semi-frame assembly 5 have the same thickness. At this time, due to the existence of the paving fillet, a hollow area will appear at the docking position of the L-shaped assembly 4 and the semi-frame assembly 5 with the outer skin assembly 3, and the foam core 7 is filled therein so that the outer skin assembly 3 and the L-shaped assembly 4 and the semi-frame assembly 5 form a complete structure. At the same time, in order to ensure that the void ratio of the filling area is small, the foam core 7 can be processed into smaller particles. In the implementation, in order to ensure that the adhesive layer is more uniform during autoclave molding and the thickness of the adhesive layer is easy to control, the integrated molded composite material siding structure of the present application, its adhesive film 6 adopts a composite material special adhesive film, which can more effectively improve the peel strength of the adhesive layer and improve the performance of the entire siding structure compared to paste glue. In practice, the integrated composite material wall panel structure of the present application is continuous layering, without layer loss, and does not need to be locally thickened in the connection area. The inner skin layer of the final part after curing has no steps. Therefore, the wall panel structure is particularly suitable for connection with ribs, partitions and other transverse parts, without avoiding the layer loss transition area, increasing the width of the connection area, and improving the connection performance between the wall panel and the transverse part. At the same time, in order to facilitate the removal of the L-shaped assembly 4 and the semi-frame assembly 5 from the mold and prevent them from being damaged, the demoulding slope is 1° to 3°.

[0018] In the implementation, the outer skin assembly 3, the L-shaped assembly 4 and the semi-frame assembly 5 are laid at room temperature, avoiding structural distortion caused by medium and high temperature curing respectively. The wall panel finally only needs to be co-cured and autoclaved once, which weakens the influence of temperature change on it. In addition, in order to minimize the influence of different thermal expansion coefficients of materials on the performance of the present structure, the outer skin assembly 3, the L-shaped assembly 4 and the semi-frame assembly 5 are preferably made of carbon fiber or glass fiber prepreg with similar expansion coefficients. In addition, in the implementation, considering the connection between the wall panel and the metal frame, a layer of glass cloth can be laid on the contact surface of the outer skin assembly 3, the L-shaped assembly 4 and the semi-frame assembly 5 when laying them, so as to prevent the electrochemical reaction between the composite material and the metal from causing frame corrosion.

[0019] In practice, the adjacent plies of the outer skin assembly 3 and the L-shaped assembly 4 and the semi-frame assembly 5 and the adhesive film 6 should be set to a 45° ply to prevent peeling at the interface and affect the performance of the wall panel after molding.

Claims

1. A composite wall panel forming method, wherein the wall panel structure comprises a skin and a plurality of long stringers, wherein the cross section of the long stringers is an inverted T-shape and connected to the inner surface of the skin, characterized in that The method comprises the following contents: 1) decomposing the wall panel structure into a plurality of assemblies according to the theoretical shape of the wall panel structure; 2) using composite fiber prepreg to lay out and form each assembly; 3) According to the theoretical shape of the siding structure, the assembled parts are pasted with adhesive film, the hollow areas between the assembled parts are filled with foam cores, and then high-temperature co-curing is carried out in an autoclave to form an integrated composite siding structure.

2. The composite material wallboard forming method according to claim 1, characterized in that: According to the theoretical shape of the wall panel structure, the overall outer skin of the wall panel is integrally formed into a wall panel outer skin assembly; 2) the outer side walls of the long stringers on both sides of the wall panel and the adjacent outer side wall panel inner skin layers are integrally formed into an L-shaped assembly; 3) the inner side walls of the adjacent long stringers in the middle of the wall panel and the adjacent wall panel inner skin layers are integrally formed into a semi-frame assembly.

3. The composite material wallboard forming method according to claim 1, characterized in that: In the L-shaped assembly and the semi-frame assembly, the inner fillet radius of the long stringer side wall and the inner skin layer of the wall panel should be greater than 0.5 times the thickness of the assembly wall.

4. The composite material wallboard forming method according to claim 1, characterized in that: In the L-shaped assembly and the semi-frame assembly, the composite fiber prepreg of the long stringer side wall and the inner skin layer of the wall panel is laid in a continuous layer.

5. A composite wall panel structure, comprising a skin and a plurality of long stringers, wherein the cross-section of the long stringers is an inverted T-shape and connected to the inner surface of the skin, characterized in that: The wall panel structure is formed by any composite wall panel forming method as described in claims 1-4, and the wall panel structure contains an outer skin assembly formed by laying out composite fiber prepreg, an L-shaped assembly composed of the outer side walls of the long stringers on both sides of the wall panel and the inner skin layers of the adjacent outer wall panels, and a semi-frame assembly composed of the inner side walls of the adjacent long stringers in the middle of the wall panel and the inner skin layers of the adjacent wall panels, and the outer skin assembly, the L-shaped assembly and the semi-frame assembly are connected by an adhesive film layer.

6. The composite wall panel structure according to claim 5, characterized in that: The cavities among the L-shaped assemblies, the half-frame assemblies and the outer skin assemblies of the wall panel structure are filled with foam cores.

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