A method of forming a leading edge skin for an aircraft

Abstract

The application provides a kind of aircraft leading edge skin forming method, comprising the following steps: S1, making annular male die, the annular male die includes two male dies, the two male dies are symmetric about the center of rotation, and are connected by two connecting pieces between the two male dies;S2, sequentially lay inner skin layer, first adhesive film, honeycomb layer, second adhesive film and outer skin layer on the annular male die to form uncured leading edge skin product, then cured by curing equipment to obtain cured leading edge skin product;S3, sequentially lay third adhesive film and metal layer on the outer skin layer, then cure the metal layer by curing equipment;The curing temperature of the third adhesive film is lower than the curing temperature of the first adhesive film and the second adhesive film.The beneficial effects of the application are that by making an annular male die, two leading edge skin products can be formed at one time, the difficulty of laying is reduced, the existing problems in the forming process are improved, and the production efficiency and product quality are improved.

Description

Technical Field

[0001] This invention relates to the field of material forming technology, and in particular to a method for forming the leading edge skin of an aircraft. Background Technology

[0002] Bird strikes are a major contributing factor to aviation accidents, causing significant damage to aircraft and posing a serious threat to aircraft safety. Due to the severe consequences of bird strikes, airworthiness regulations in various countries explicitly stipulate that aircraft designers must incorporate corresponding bird strike protection measures during the design process. Specifically, Article 631 of Part 25 of the "Airworthiness Standards for Transport Category Aircraft" formulated by the Civil Aviation Administration of China (CAAC) clearly stipulates the bird strike damage requirements: the tail structure design must ensure that the aircraft can continue to fly and land safely after colliding with a bird weighing 3.6 kg (8 lb). Therefore, bird strike protection structural design has become a critical issue in the design of aircraft leading-edge structures.

[0003] Currently, the leading edge structure typically used is a honeycomb sandwich structure or laminated structure to enhance bird strike resistance. Traditional leading edge forming methods employ negative mold forming, where an outer skin, honeycomb layer, and inner skin are sequentially laid on the surface of the negative mold. After laying, the layers are transferred to a device with controlled temperature and pressure for curing. The difficulties of negative mold forming include the reliance on manual laying, the high difficulty of laying, and the ease with which gaps can form between layers. Summary of the Invention

[0004] To address the aforementioned shortcomings, the present invention aims to provide a method for forming aircraft leading edge skin, which can efficiently produce high-quality leading edge skin.

[0005] This invention provides a method for forming the leading edge skin of an aircraft, comprising the following steps:

[0006] S1. Make an annular male mold, the annular male mold comprising two male molds, the two male molds being symmetrical about the rotation center and connected to each other by two connecting pieces;

[0007] S2. An inner skin layer, a first adhesive film, a honeycomb layer, a second adhesive film, and an outer skin layer are sequentially laid on the annular male mold to form an uncured leading edge skin component. Then, the component is cured by a curing device to obtain a cured leading edge skin component.

[0008] S3. A third adhesive film and a metal layer are sequentially laid on the outer skin layer, and then the metal layer is cured by a curing device; the curing temperature of the third adhesive film is lower than the curing temperature of the first adhesive film and the second adhesive film.

[0009] Preferably, in step S1, the mold surface of the male mold is designed based on the inner surface of the existing leading edge skin part.

[0010] Preferably, in steps S2 and S3, the curing device is an autoclave.

[0011] Preferably, in step S2, the uncured leading edge skin component is cured using either of the following two methods:

[0012] Method 1: Transfer the annular male mold and the uncured leading edge skin part together to the curing equipment to complete the curing process;

[0013] Method 2: Cut off the two connecting parts to separate the two male molds in the annular male mold, then place the female mold on the outer skin layer, remove the male mold, transfer the uncured leading edge skin component to the female mold, and then transfer the female mold and the uncured leading edge skin component together to the curing device to complete the curing.

[0014] Preferably, if step S2 is selected as method two, then in step S3, the cured leading edge skin part is first transferred to the male mold, and then the third adhesive film and metal layer are laid and the metal layer is cured.

[0015] Preferably, in step S2, an automated laying device is used to lay the inner skin layer and the outer skin layer.

[0016] The advantages of this invention are:

[0017] 1. By making a ring-shaped positive mold, two front edge skin parts can be laid out and formed at one time, reducing the difficulty of laying out, improving the problems existing in the forming process, and improving production efficiency and finished product quality;

[0018] 2. Automated laying equipment is used to lay the inner and outer skin layers, reducing labor costs and further improving production efficiency;

[0019] 3. After the leading edge skin component has cured, a film with a lower curing temperature is used to bond the metal layer, which effectively reduces the deformation of the leading edge skin component, further improves the quality of the finished product, and enhances the bird strike protection performance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the layers in the process of laying the leading edge skin component on the surface of the annular male mold;

[0021] Figure 2 This is a schematic diagram of the inner skin layer, honeycomb layer, and outer skin layer being cured on the surface of the negative mold.

[0022] Component designation explanation:

[0023] 1. Circular male mold

[0024] 11 Positive molds

[0025] 12 Connectors

[0026] 13 Center of Rotation

[0027] 2. Inner cortex

[0028] 3. Honeycomb layer

[0029] 4. Outer cortex

[0030] 5 Metal Layers

[0031] 6. Female mold Detailed Implementation

[0032] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0033] In the description of this invention, it should be noted that the terms "center", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, 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 limiting this invention.

[0034] like Figure 1 As shown, the present invention provides a specific embodiment of an aircraft leading edge skin forming method, including the following steps:

[0035] S1. Fabricate an annular male mold 1, which includes two male molds 11. The two male molds 11 are symmetrical about the rotation center 13 and are connected by two connecting parts 12. The mold surface of the male mold 11 is designed based on the inner surface of the existing leading edge skin part to ensure that the leading edge skin part obtained after demolding from the male mold 11 is an arc-shaped cover that can be connected to the aircraft wing or tail structure. Using the annular male mold 1, two leading edge skin parts can be obtained in one step, effectively improving production efficiency. The connecting parts 12 serve as a reserved process allowance, facilitating subsequent cutting, transfer, or demolding; their specific length and shape can be adjusted as needed.

[0036] S2. Lay the inner skin layer 2 on the annular male mold 1. The inner skin layer 2 is specifically made of prepreg. The laying method can be manual or machine laying as used in this embodiment, using a hot molding press and automatic laying equipment (such as an automatic tape laying machine or an automatic yarn laying machine) to ensure that the laying thickness of the inner skin layer 2 is symmetrical about the center line of the male mold 11 and evenly distributed on the mold surface of the annular male mold 1. After laying, place a breathable felt and a vacuum bag on the surface of the inner skin layer 2 in sequence. Seal and fix the vacuum bag with sealant around its perimeter to seal the inner skin layer 2 on the annular male mold 1. Use a vacuum device to expel the gas inside the bag, keeping the vacuum bag in a vacuum state, and press the inner skin layer 2 firmly onto the annular male mold 1. Placing the breathable felt helps to evenly and thoroughly expel the gas from the vacuum bag. Then open the vacuum bag, remove the breathable felt, and check the surface quality of the inner skin layer 2. Next, a first adhesive film, a honeycomb layer 3, a second adhesive film, and an outer skin layer 4 are sequentially laid on the surface of the inner skin layer 2 to form an uncured leading edge skin component. Specifically, the honeycomb layer 3 is an aramid honeycomb layer, machined. The outer skin layer 4 is made of prepreg, and can be laid manually or by machine, ensuring that the thickness of the outer skin layer 4 is symmetrical about the centerline of the male mold 11. Through proper layering, subsequent curing deformation can be reduced.

[0037] After the outer skin layer 4 is laid, either of the following two curing methods can be used to cure the uncured leading edge skin component, so that the inner skin layer 2, honeycomb layer 3 and outer skin layer 4 are bonded together without relative displacement between the three, thus obtaining a cured leading edge skin component:

[0038] Method 1: A breathable felt and a vacuum bag are sequentially laid on the outer skin layer 4. The vacuum bag is sealed and fixed with sealant. The uncured leading edge skin component is then sealed onto the annular male mold 1. Gas is expelled from the bag using a vacuum device, maintaining a vacuum state inside the bag. Next, the annular male mold 1 and the uncured leading edge skin component are placed together in a curing device. Curing is completed by applying pressure and curing temperature in the curing device.

[0039] Method 2: For example Figure 1 and Figure 2As shown, the two connecting pieces 12 are cut to separate the two male molds 11 in the annular male mold 1. Then, the female mold 6 is placed on the outer skin layer 4, and the male molds 11 are removed, transferring the uncured leading edge skin component to the female mold 6. Next, a breathable felt and a vacuum bag are laid sequentially on the outer skin layer 4. The vacuum bag is sealed and fixed with sealant to seal the uncured leading edge skin component onto the female mold 6. The gas inside the bag is discharged through a vacuum device to maintain a vacuum state inside the vacuum bag. Then, the female mold 6 and the uncured leading edge skin component are placed together in a curing device. Curing is completed in the curing device by applying pressure and curing temperature. Transferring the uncured leading edge skin component to the female mold 6 to complete the curing process can make the outer surface of the leading edge skin component smoother.

[0040] After obtaining the cured leading edge skin component using method one in steps S3 and S2, a third adhesive film and a metal layer 5 are sequentially laid on the outer skin layer 4. Then, the annular male mold 1 and the leading edge skin component with the metal layer 5 are placed together in a curing device to cure the metal layer 5. Due to the difference in thermal expansion coefficients between the metal layer 5 and the leading edge skin component, a well-designed composite laminate structure helps reduce deformation. Specifically, the curing temperature of the third adhesive film is lower than that of the first and second adhesive films. This setting avoids excessive temperature changes during the curing of the metal layer 5, preventing significant deformation of the cured leading edge skin component and ensuring a high-quality finished product. Finally, the two connectors 12 are cut off, the male mold 11 is removed, and the leading edge skin component with the bonded metal layer 5 is obtained.

[0041] After obtaining the cured leading edge skin part using method two in S2, the cured leading edge skin part is first transferred to the male mold 11. Then, a third adhesive film and a metal layer 5 are sequentially laid on the outer skin layer 4. The male mold 11 and the leading edge skin part with the metal layer 5 are then placed together in a curing device to cure the metal layer 5. Similarly, the curing temperature of the third adhesive film is lower than that of the first and second adhesive films. Finally, the male mold 11 is removed to obtain the final leading edge skin part with the metal layer 5 bonded to it.

[0042] The curing equipment used in the aforementioned steps S2 and S3 is specifically an autoclave.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for forming an aircraft leading edge skin, characterized in that, Includes the following steps: S1. Make an annular male mold, the annular male mold comprising two male molds, the two male molds being symmetrical about the rotation center and connected to each other by two connecting pieces; S2. An inner skin layer, a first adhesive film, a honeycomb layer, a second adhesive film, and an outer skin layer are sequentially laid on the annular male mold to form an uncured leading edge skin component. Then, the component is cured by a curing device to obtain a cured leading edge skin component. S3. A third adhesive film and a metal layer are sequentially laid on the outer skin layer, and then the metal layer is cured by a curing device; the curing temperature of the third adhesive film is lower than the curing temperature of the first adhesive film and the second adhesive film.

2. The method for forming the leading edge skin of an aircraft according to claim 1, characterized in that, In step S1, the mold surface of the male mold is designed based on the inner surface of the existing leading edge skin part.

3. The method for forming the leading edge skin of an aircraft according to claim 1, characterized in that, In steps S2 and S3, the curing device is an autoclave.

4. The method for forming the leading edge skin of an aircraft according to claim 1, characterized in that, In step S2, the uncured leading edge skin component is cured using either of the following two methods: Method 1: Transfer the annular male mold and the uncured leading edge skin part together to the curing equipment to complete the curing process; Method 2: Cut off the two connecting parts to separate the two male molds in the annular male mold, then place the female mold on the outer skin layer, remove the male mold, transfer the uncured leading edge skin component to the female mold, and then transfer the female mold and the uncured leading edge skin component together to the curing device to complete the curing.

5. The method for forming the leading edge skin of an aircraft according to claim 4, characterized in that, If step S2 is selected as method two, then in step S3, the cured leading edge skin part is first transferred to the male mold, and then the third adhesive film and metal layer are laid and the metal layer is cured.

6. The method for forming the leading edge skin of an aircraft according to claim 1, characterized in that, In step S2, an automated laying device is used to lay the inner skin layer and the outer skin layer.

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