Integrated molding method for composite fuselage fuel tank

Abstract

The present invention provides a method for integrally forming a composite fuselage fuel tank, comprising the following steps: forming a skin layup group on a skin layup die, and forming a fuel tank layup group on a fuel tank layup die; placing an isolation film on the surface of the fuel tank layup group, and positioning and assembling the fuel tank layup group, the fuel tank layup die, and the skin layup group on a positioning die; pre-pressing the fuel tank layup group and the skin layup group using an autoclave to form a fuel tank pre-press and a skin pre-press; positioning and assembling the fuel tank pre-press and the skin pre-press on a positioning die to form an assembly; placing an isolation film and auxiliary materials on the surface of the assembly, and integrally forming and curing the assembly using an autoclave to obtain a composite fuselage fuel tank. The present invention can achieve integrally forming a composite fuselage fuel tank, with low molding cost, light weight, and good sealing performance, which is conducive to achieving lightweight design of aircraft and meeting assembly requirements of fuselage fuel tanks.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material forming and processing, and more particularly to a method for integrally forming a composite material fuselage fuel tank. Background Art

[0002] The external composite fuselage skin and internal composite fuel tank bulkhead of a drone are often cured and molded as separate parts. To achieve a seal, two main methods are used. One is to mechanically connect the fuselage skin and fuel tank bulkhead with fasteners during the overall assembly of the drone, and then use resin glue to seal the gap. The other method is to place an adhesive film between the fuselage skin and fuel tank bulkhead, and connect the fuselage skin and fuel tank bulkhead through adhesive co-curing.

[0003] The above-mentioned fuselage and fuel tank molding methods have the following disadvantages: First, because the fuselage skin and fuel tank bulkhead are cured and molded separately, the multiple use of autoclaves for molding results in high costs. Second, when mechanically connecting and sealing the fuselage skin and fuel tank bulkhead of the drone using this method, due to the inevitable curing deformation problems that occur during the molding process of composite parts, the fitting clearance between the fuselage skin and the fuel tank bulkhead is difficult to meet the assembly requirements through manual adjustment. In addition, the resin glue used in the fitting clearance is prone to leakage when the fuel tank is fully loaded, affecting the sealing of the fuel tank and thus the operating state of the entire aircraft. For the co-curing molding method, the weight of the adhesive film used for co-curing in each aircraft is approximately (4-5) kg, which accounts for a high proportion of the total weight of the aircraft and is not conducive to the weight reduction design of the aircraft. Summary of the Invention

[0004] (1) Technical issues to be solved

[0005] The technical problem addressed by this invention is that existing fuselage and fuel tank molding methods require separate curing and molding of the fuselage skin and fuel tank bulkhead, resulting in high costs due to the multiple use of autoclaves. With mechanical joint sealing, the clearance between the fuselage skin and fuel tank bulkhead is difficult to manually adjust to meet assembly requirements. With adhesive co-curing molding, the introduction of adhesive film increases the aircraft's weight, making lightweight design difficult to achieve.

[0006] (2) Technical solution

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a method for integrally forming a composite material fuselage fuel tank, comprising the following steps:

[0009] The skin composite material lay-up is carried out on the skin lay-up mold to form a skin lay-up group, and the fuel tank composite material lay-up is carried out on the fuel tank lay-up mold to form a fuel tank lay-up group; the laying process of the composite material lay-up is as follows: a single layer of prepreg is laid on the corresponding lay-up mold (skin lay-up mold or fuel tank lay-up mold), and the single layer of prepreg is ironed with an electric iron to make the single layer of prepreg fit with the lay-up mold without bubbles and wrinkles, and then the next layer of prepreg is laid on the upper layer of prepreg, and ironed again to make the multiple layers of prepreg fit together to form a skin lay-up group or a fuel tank lay-up group.

[0010] Place an isolation film on the surface of the fuel tank layup group, and assemble the fuel tank layup group, the fuel tank layup mold, and the skin layup group on the positioning mold;

[0011] After assembly, auxiliary materials are placed and vacuum is drawn. When the vacuum degree meets the requirements, the tank layup group and the skin layup group are pre-pressed using an autoclave to form a tank pre-pressed part and a skin pre-pressed part. After pre-pressing, the tank layup group and the skin layup group can be discharged.

[0012] Taking out the fuel tank pre-pressed parts and the skin pre-pressed parts, positioning and assembling the fuel tank pre-pressed parts and the skin pre-pressed parts on the positioning mold to form an assembly;

[0013] An isolation film and auxiliary materials are placed on the surface of the assembly, and vacuum is applied. After the vacuum degree meets the requirements, the assembly is integrally molded and cured using an autoclave to obtain a composite fuselage fuel tank.

[0014] Preferably, the oil tank pre-compression member includes an oil tank periphery and an edge connected to the top of the oil tank periphery, the oil tank periphery is surrounded to form an oil storage cavity, and an opening is provided in the edge.

[0015] Preferably, after the isolation film and auxiliary materials are placed on the surface of the assembly, a support plate is placed in the oil storage cavity, and the support plate is used to support the edge.

[0016] Preferably, the positioning mold includes two baffles, there are multiple tank pre-pressed parts, and the multiple tank pre-pressed parts are installed on the skin pre-pressed parts in sequence. The two baffles are arranged on opposite sides of the multiple tank pre-pressed parts to position and fix the multiple tank pre-pressed parts.

[0017] Preferably, the positioning mold further includes a skin laying mold, and the skin laying mold and two baffles together form a cavity, and the skin layup group and the fuel tank layup group are molded on the inner wall of the cavity.

[0018] Preferably, the number of layers of the skin composite material layup and the number of layers of the fuel tank composite material layup are both 7 layers.

[0019] Preferably, the auxiliary materials include breathable felt and vacuum bags.

[0020] Preferably, the method further comprises the following steps:

[0021] The composite fuselage fuel tank is machined to obtain a composite fuselage fuel tank with preset dimensions.

[0022] (3) Beneficial effects

[0023] The above technical solution of the present invention has at least the following advantages:

[0024] In this invention, the skin and fuel tank layup groups are pre-pressed to form fuel tank and skin pre-presses. These are then assembled using a positioning mold to form a composite assembly, achieving high-precision assembly of the fuel tank and skin. The assembly is then integrally cured to form the composite fuselage fuel tank. The entire manufacturing process eliminates the need for multiple autoclave curing cycles, effectively reducing component costs. It also eliminates the need for adhesive film, significantly reducing aircraft weight and avoiding the difficulty in achieving satisfactory sealing when the fuselage and fuel tank are separately formed and then assembled, ensuring that the fuselage and fuel tank meet assembly requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 It is a schematic diagram of the three-dimensional structure of a composite material fuselage fuel tank provided by an embodiment of the present invention.

[0027] Figure 2 yes Figure 1 Cross-sectional view at AA in the middle.

[0028] Figure 3 This is one of the molding flow charts of the composite fuselage fuel tank provided by the embodiment of the present invention.

[0029] Figure 4 This is the second forming flow chart of the composite fuselage fuel tank provided by the embodiment of the present invention.

[0030] The reference numerals in the figures are:

[0031] 200. Fuel tank laying mold; 10. Skin pre-press; 20. Fuel tank pre-press; 30. Composite fuselage fuel tank; 1. Skin layup group; 2. Fuel tank layup group; 3. Isolation membrane; 4. Positioning mold; 5. Auxiliary materials; 6. Support plate; 7. Sealing strip; 21. Fuel tank side; 22. Edge; 23. Oil storage cavity; 221. Opening; 41. Baffle; 42. Skin laying mold; 51. Breathable felt; 52. Vacuum bag. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that when an element is referred to as being “fixed to” or “disposed on” another element, it may be directly located on the other element or indirectly located on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0034] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate that the device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating relative importance or the number of technical features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. The following is a more detailed description of the specific implementation of the present invention in conjunction with specific embodiments:

[0036] The structure of the composite material fuselage fuel tank required for forming in this embodiment is as follows Figure 1 and Figure 2 As shown, a fuel tank 201 is connected to the inner side of the skin 101 .

[0037] like Figure 3 and Figure 4 As shown ( Figure 3 and Figure 4 Both Figure 1 An embodiment of the present invention provides a method for integrally forming a composite fuselage fuel tank, comprising the following steps:

[0038] The skin composite material layup is laid on the skin laying mold 42 to form the skin laying group 1, and the fuel tank composite material layup is laid on the fuel tank laying mold 200 to form the fuel tank laying group 2; specifically, the skin laying mold 42 is a forming female mold, and the fuel tank laying mold 200 is a forming male mold.

[0039] An isolation film 3 is placed on the surface of the tank layup group 2, and the tank layup group 2, tank layup mold 200, and skin layup group 1 are positioned and assembled on the positioning mold 4. Positioning can be achieved by, for example, making measurement marks on the skin layup group 1. If there are multiple tank layup groups 2, an isolation film 3 is placed on the surface of each tank layup group 2. This isolation film 3 separates adjacent tank layup groups 2, as well as separates the tank layup group 2 from the skin layup group 1 and auxiliary materials to prevent adhesion, thereby ensuring that each tank layup group 2 and skin layup group 1 is adequately preloaded.

[0040] After assembly, auxiliary materials 5 are placed and vacuum is applied. When the vacuum degree meets the requirements, the fuel tank ply group 2 and the skin ply group 1 are pre-pressed using an autoclave to form a fuel tank pre-pressed part 20 and a skin pre-pressed part 10. The purpose of pre-pressing is to expel the air between the plies to make the structure tighter.

[0041] Take out the fuel tank pre-pressed part 20 and the skin pre-pressed part 10, and assemble the fuel tank pre-pressed part 20 and the skin pre-pressed part 10 on the positioning mold 4 to form an assembly;

[0042] An isolation film 3 and auxiliary materials 5 are placed on the surface of the assembly and vacuumed. After the vacuum level meets the requirements, the assembly is integrally molded and cured in an autoclave to obtain a composite fuselage fuel tank 30. In this step, the isolation film 3 is only used to isolate the assembly and the auxiliary materials.

[0043] In one embodiment, the fuel tank pre-pressed member 20 includes a fuel tank periphery 21 and a rim 22 connected to the top of the fuel tank periphery 21. The fuel tank periphery 21 encloses an oil storage cavity 23, and the rim 22 has an opening 221. After pre-pressing, the fuel tank pre-pressed member 20 is still uncured and relatively soft. The fuel tank paving mold 200 can be removed from the oil storage cavity 23 by folding over the rim 22.

[0044] In one embodiment, after the isolation film 3 and auxiliary materials are placed on the assembly surface, a support plate 6 is placed within the oil reservoir 23 to support the edge 22. Since the tank paving mold 200 has been removed from the oil reservoir 23, the support plate 6 is provided to prevent deformation of the edge 22 during the curing process. The auxiliary materials include a vacuum bag 52, which, when expanded, secures the support plate 6 within the oil reservoir 23.

[0045] In one embodiment, the positioning mold 4 includes two baffles 41. There are multiple fuel tank preforms 20, which are sequentially mounted on the skin preform 10. The two baffles 41 are disposed on opposite sides of the multiple fuel tank preforms 20 to position and secure the multiple fuel tank preforms 20. The two baffles 41 serve as positioning components to position the fuel tank preforms 20 on the skin preform 10. Furthermore, the two baffles 41 limit deformation of the outermost portions of the fuel tank preforms 20 during the prepressing and curing processes.

[0046] In one embodiment, the positioning mold 4 further includes a skin laying mold 42. The skin laying mold 42 and two baffles 41 together form a cavity, and the skin laying group 1 and the fuel tank laying group 2 are molded on the inner wall of the cavity.

[0047] In one embodiment, the number of layers of the skin composite material layup and the number of layers of the fuel tank composite material layup are both 7 layers.

[0048] In one embodiment, the auxiliary material 5 includes an air-permeable felt 51 and a vacuum bag 52 .

[0049] In one embodiment, the following steps are also included:

[0050] The composite fuselage fuel tank 30 is machined to obtain a composite fuselage fuel tank having a preset size.

[0051] The following is a specific embodiment provided by this application: the one-piece fuselage fuel tank parts to be produced are as follows: Figure 1 and Figure 2 As shown in the figure, the one-piece fuselage fuel tank component consists of a skin and a fuel tank box section, where the fuel tank box section consists of three fuel tanks. The thickness of the skin and fuel tanks is 1.5mm.

[0052] The molding steps are as follows:

[0053] Layer laying: Use the forming female mold (skin laying mold 42) to lay the skin composite material layer, and lay the fuel tank according to the layer laying on the fuel tank laying male mold (fuel tank laying mold 200). The skin and fuel tank have 7 layers of layers each, forming skin layer group 1 and fuel tank layer group 2.

[0054] Pre-pressing: After the layup is complete, a barrier film 3 is placed on the surface of the tank layup group 2. The three tank layup groups 2 and the tank layup mold 200 are sequentially placed on the skin layup group 1 to form a tank box segment. After confirming that the tank box segment length matches the digital mold, baffles 41 are placed and fixed on both sides of the tank box segment on the skin layup mold 42. After assembly, a breathable felt 51 and a vacuum bag 52 are sequentially placed on the mold surface, and vacuum is applied. Once the vacuum level meets the requirements, the skin layup group 1 and the tank layup group 2 are pre-pressed in an autoclave to form the tank pre-press 20 and the skin pre-press 10.

[0055] Process combination: remove the pre-pressed tank pre-pressed part 20 from the tank paving mold 200, and place it in sequence on the corresponding positions of the skin pre-pressed part 10, place and fix the baffle 41 on both sides of the tank box section on the skin paving mold 42, and assemble to form an assembly. Place the isolation film 3, breathable felt 51 and vacuum bag 52 on the surface of the assembly in sequence, and stick the vacuum bag 52 to the mold surface with sealing strips 7 around it, and evacuate.

[0056] Curing: After the vacuum level meets the requirements, the fuel tank preform 20 and the skin preform 10 are integrally molded and cured in an autoclave according to the corresponding process to form the composite fuselage fuel tank. After demolding, the composite fuselage fuel tank is machined to obtain the integrally molded fuselage fuel tank component.

[0057] The above description is only a preferred embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A composite material fuselage fuel tank integral molding method, characterized in that: The following steps are involved: Laying out the skin composite material layup on the skin laying mold to form a skin layup group, and laying out the fuel tank composite material layup on the fuel tank laying mold to form a fuel tank layup group; Place an isolation film on the surface of the fuel tank layup group, and assemble the fuel tank layup group, the fuel tank layup mold, and the skin layup group on the positioning mold; After assembly, auxiliary materials are placed and vacuum is applied. When the vacuum degree meets the requirements, the fuel tank layup group and the skin layup group are pre-pressed using an autoclave to form a fuel tank pre-pressed part and a skin pre-pressed part. Taking out the fuel tank pre-pressed parts and the skin pre-pressed parts, positioning and assembling the fuel tank pre-pressed parts and the skin pre-pressed parts on the positioning mold to form an assembly; An isolation film and auxiliary materials are placed on the surface of the assembly, and vacuum is applied. After the vacuum degree meets the requirements, the assembly is integrally molded and cured using an autoclave to obtain a composite fuselage fuel tank.

2. The method for integrally forming a composite material fuselage fuel tank according to claim 1, characterized in that: The oil tank pre-pressing member includes an oil tank periphery and an edge connected to the top of the oil tank periphery. The oil tank periphery is surrounded by an oil storage cavity, and an opening is provided in the edge.

3. The method for integrally forming a composite material fuselage fuel tank according to claim 2, characterized in that: After the isolation film and auxiliary materials are placed on the surface of the assembly, a support plate is placed in the oil storage cavity, and the support plate is used to support the edge.

4. The method for integrally forming a composite material fuselage fuel tank according to claim 1, characterized in that: The positioning mold includes two baffles. There are multiple fuel tank pre-pressed parts. The multiple fuel tank pre-pressed parts are installed on the skin pre-pressed parts in sequence. The two baffles are arranged on opposite sides of the multiple fuel tank pre-pressed parts to position and fix the multiple fuel tank pre-pressed parts.

5. The method for integrally forming a composite material fuselage fuel tank according to claim 4, characterized in that: The positioning mold also includes a skin laying mold, which is combined with two baffles to form a cavity, and the skin laying group and the fuel tank laying group are molded on the inner wall of the cavity.

6. The method for integrally forming a composite material fuselage fuel tank according to claim 1, characterized in that: The number of layers of the skin composite material layup and the number of layers of the fuel tank composite material layup are both 7 layers.

7. The method for integrally forming a composite material fuselage fuel tank according to claim 1, characterized in that: The auxiliary materials include breathable felt and vacuum bags.

8. The method for integrally forming a composite material fuselage fuel tank according to claim 1, wherein: The following steps are also included: The composite fuselage fuel tank is machined to obtain a composite fuselage fuel tank with preset dimensions.

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