Sandwich skin with gradient structure and preparation method thereof

Abstract

The invention discloses a sandwich skin with a gradient structure and a preparation method of the sandwich skin. The sandwich skin comprises a high-temperature layer, a low-temperature layer, a connecting layer and carbon fiber cloth, the low-temperature layer is arranged at the bottom of the high-temperature layer; the connecting layer is arranged at the bottom of the low-temperature layer; the high-temperature layer, the low-temperature layer and the connecting layer are sequentially brazed and connected; containing grooves are formed in the surfaces of the high-temperature layer and the low-temperature layer, and the carbon fibers are arranged in the containing grooves. The sandwich skin can serve for a long time in a high-temperature environment, through organic combination of different material properties, the overall performance of the skin can be improved, and the requirements for high-performance and light-weight skin in the fields of aerospace and the like are met.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material structures, and more specifically, to a sandwich skin with a gradient structure and a preparation method thereof. Background Art

[0002] With the rapid development of fields such as aerospace, rail transit, and automobile manufacturing, the demand for high-performance and lightweight skins is increasing day by day. As a key structural component, the performance of the skin directly affects the safety, stability, and service life of the overall system. Traditional skin structure materials mainly include metal materials and composite materials. Common materials for metal skins are titanium alloys, aluminum alloys, and stainless steels, etc. Although these materials have good strength and stiffness, their performance is prone to decay in high-temperature environments and it is difficult to meet the long-term stable use under high-temperature working conditions. Compared with traditional metal materials, carbon fiber composite materials have gradually become important materials for structural lightweight design due to their excellent specific strength, specific stiffness, and corrosion resistance. However, the mechanical properties of carbon fiber composite materials vary greatly in the stress direction, and fiber fracture, delamination, or surface damage are likely to occur, and at the same time, the impact resistance is poor. In addition, the interfacial bonding force between carbon fiber composite materials and metal materials is poor, resulting in the mechanical properties and service life of the overall structure being difficult to meet the requirements of high-performance applications.

[0003] To solve the above problems, gradient functional composite materials have gradually become a research hotspot in recent years. Gradient functional composite materials achieve a gradual spatial distribution of properties through continuous transitions in material composition or structure, thereby improving the overall mechanical properties, heat resistance, and service stability of the materials. However, the current design and manufacturing of gradient structure skins are still in the development stage. The invention patent CN 111680441A proposes a gradient lattice sandwich panel structure, but no specific implementable manufacturing scheme is given; the invention patent CN 206939036U designs a sandwich skin structure, which is formed by laminating three layers of composite material laminates and two layers of sandwich cores through gluing, but the composite material layer of this structure is located on the outside and the impact resistance is poor; the invention patent CN 118701124A realizes skin lightweight by filling foaming materials between the inner and outer aluminum alloy skins, but the foaming layer and the skin are bonded with glue, and the skin material uses aluminum alloy, resulting in poor high-temperature service performance.

[0004] Therefore, it is an urgent problem for those skilled in the art to research and develop a sandwich skin with a gradient structure and a preparation method thereof that can serve for a long time in a high-temperature environment. Summary of the Invention

[0005] In view of this, the present invention provides a sandwich skin with a gradient structure and a preparation method thereof that can serve for a long time in a high-temperature environment.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A sandwich skin with a gradient structure, comprising:

[0008] A high-temperature layer,

[0009] A low-temperature layer, and the low-temperature layer is placed at the bottom of the high-temperature layer;

[0010] A connection layer, the connection layer is placed at the bottom of the low-temperature layer, and the high-temperature layer, the low-temperature layer, and the connection layer are sequentially brazed and connected;

[0011] Carbon fiber cloth, accommodation grooves are formed on the surfaces of the high-temperature layer and the low-temperature layer, and the carbon fiber cloth is arranged in the accommodation grooves.

[0012] The beneficial effect of adopting the above technical solution is that through the sequential brazing connection of the high-temperature layer, the low-temperature layer, and the connection layer, and the design of arranging the carbon fiber cloth in the accommodation groove, the organic combination of different material properties is realized. This structure can serve for a long time in a high-temperature environment, and at the same time, by utilizing the high-strength characteristics of the carbon fiber cloth, the overall performance of the skin is improved, meeting the requirements for high-performance and lightweight skins in the fields of aerospace and the like.

[0013] Preferably, a brazing filler metal layer is provided between the high-temperature layer and the low-temperature layer, and between the low-temperature layer and the connection layer. Setting the brazing filler metal layer between the high-temperature layer and the low-temperature layer, and between the low-temperature layer and the connection layer can ensure the firm connection between each layer and improve the overall structural stability of the skin.

[0014] Preferably, the included angle between the laying directions of the carbon fiber cloth in the high-temperature layer and the low-temperature layer is between 30° and 90°. By reasonably adjusting the laying angle, the stress can be dispersed in different directions, enhancing the tensile strength and impact resistance of the skin, and further improving its service performance under complex working conditions.

[0015] Preferably, reinforcing ribs and weight-reducing holes are provided on the surface of the connecting plate. The reinforcing ribs can effectively enhance the bearing capacity of the connection layer and improve the overall structural strength of the skin; the weight-reducing holes help to reduce the weight of the skin, realizing lightweight design while ensuring strength, which is of great significance for weight-sensitive application scenarios such as aerospace.

[0016] A preparation method of a sandwich skin with a gradient structure, comprising the following preparation methods:

[0017] S1, cutting the high-temperature layer, the low-temperature layer, the connection layer, and the brazing filler metal layer that meet the size requirements, and processing an accommodation groove structure on the surfaces of the high-temperature layer and the low-temperature layer;

[0018] S2. Polish the parts on the surfaces of the high-temperature layer, low-temperature layer, and connection layer that need to be brazed to ensure that the surface roughness is less than Ra1.6;

[0019] S3. Lay carbon fiber cloth in the receiving grooves of the high-temperature layer and the low-temperature layer;

[0020] S4. Stack the high-temperature layer, low-temperature layer, and connection layer in sequence, and place a brazing filler metal layer between adjacent layers to assemble and form a skin;

[0021] S5. Put the assembled skin into a brazing furnace for welding;

[0022] S6. After brazing is completed, take out the skin after the temperature in the brazing furnace drops to room temperature.

[0023] Preferably, during the brazing process, the skin is placed in the brazing furnace, the interlayer gap is less than 0.1 mm, and the vacuum degree in the furnace is less than 5×10 -3 Pa. When heating up, raise the temperature to 600 °C at a rate of 5-10 °C / min, then raise the temperature to 850 °C - 900 °C at a rate of 5 °C / min and keep it warm for 20 min, and finally cool down to 500 °C at a rate of 10 °C / min, and then cool down with the furnace.

[0024] Preferably, the material of the high-temperature layer is a nickel-based superalloy; the material of the low-temperature layer is a titanium alloy; the material of the connection layer is an aluminum alloy or a magnesium alloy. Nickel-based superalloys have excellent high-temperature performance, titanium alloys have good strength and corrosion resistance, and aluminum alloys or magnesium alloys have the characteristics of light weight. This combination not only meets the use requirements of the skin in a high-temperature environment but also realizes lightweight design and improves the comprehensive performance of the skin.

[0025] Preferably, the brazing filler metal layer is a sheet-like titanium-based brazing filler metal or an aluminum-based brazing filler metal, and the thickness is 0.02 mm - 0.05 mm.

[0026] Preferably, the depth and width of the receiving groove are equal to the thickness and width of the carbon fiber cloth. This design can ensure that the carbon fiber cloth fits tightly in the receiving groove, avoiding voids or looseness. This not only helps to improve the fixing effect of the carbon fiber cloth but also ensures that it can fully exert its mechanical properties in the skin, further enhancing the overall strength and stability of the skin.

[0027] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a sandwich skin with a gradient structure and a preparation method thereof, and its beneficial effects are:

[0028] (1) Give full play to the respective performance advantages of nickel-based superalloys, titanium alloys, aluminum alloys / magnesium alloys, and carbon fiber cloth. The nickel-based alloy in the high-temperature layer ensures the service performance of the skin in high-temperature environments, the carbon fiber cloth provides high strength and high modulus, and the connecting layer of aluminum alloy or magnesium alloy realizes lightweight design; this skin with a gradient structure not only meets the requirements of high-temperature service but also reduces weight, and is suitable for the high-performance and lightweight needs in fields such as aerospace and rail transit.

[0029] (2) Compared with brazing connection used in other processing methods, the process flow is simpler, the welding quality is stable, the product qualification rate and production efficiency are high, and mass production can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0031] Figure 1 It is a schematic structural diagram of the sandwich skin provided by the present invention;

[0032] Figure 2 It is a flowchart of the preparation process of the sandwich skin provided by the present invention;

[0033] Figure 3 It is a schematic structural diagram of the connecting layer provided by the present invention.

[0034] Among them, in the figure,

[0035] 1 - High-temperature layer; 2 - Low-temperature layer;

[0036] 3 - Connecting layer;

[0037] 31 - Reinforcing rib; 32 - Weight-reducing hole;

[0038] 4 - Carbon fiber cloth; 5 - Brazing layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0040] Embodiment 1:

[0041] An embodiment of the present invention discloses a sandwich skin with a gradient structure, including:

[0042] A high-temperature layer 1,

[0043] A low-temperature layer 2, and the low-temperature layer 2 is placed at the bottom of the high-temperature layer 1;

[0044] A connection layer 3, the connection layer 3 is placed at the bottom of the low-temperature layer 2, and the high-temperature layer 1, the low-temperature layer 2, and the connection layer 3 are sequentially brazed and connected;

[0045] A carbon fiber cloth 4, accommodation grooves are formed on the surfaces of the high-temperature layer 1 and the low-temperature layer 2, and the carbon fiber cloth 4 is placed in the accommodation grooves.

[0046] To further optimize the above technical solution, a brazing filler metal layer 5 is provided between the high-temperature layer 1 and the low-temperature layer 2, and between the low-temperature layer 2 and the connection layer 3.

[0047] To further optimize the above technical solution, the included angle between the laying directions of the carbon fiber cloth 4 in the high-temperature layer 1 and the low-temperature layer 2 is between 30° and 90°.

[0048] To further optimize the above technical solution, reinforcing ribs 31 and weight-reducing holes 32 are provided on the surface of the connection plate 3.

[0049] To further optimize the above technical solution, the skin includes at least one layer of high-temperature layer 1, one layer of low-temperature layer 2, and one layer of connection layer 3.

[0050] A preparation method of a sandwich skin with a gradient structure includes the following preparation methods:

[0051] S1, cutting the high-temperature layer 1, the low-temperature layer 2, the connection layer 3, and the brazing filler metal layer 5 that meet the size requirements, and processing an accommodation groove structure on the surfaces of the high-temperature layer 1 and the low-temperature layer 2;

[0052] S2, polishing the parts on the surfaces of the high-temperature layer 1, the low-temperature layer 2, and the connection layer 3 that need to be brazed and connected to ensure that the surface roughness is less than Ra1.6;

[0053] S3, laying the carbon fiber cloth 4 in the accommodation grooves of the high-temperature layer 1 and the low-temperature layer 2;

[0054] S4, stacking the high-temperature layer 1, the low-temperature layer 2, and the connection layer 3 in sequence, and placing the brazing filler metal layer 5 between adjacent layers to assemble and form a skin;

[0055] S5, putting the assembled skin into a brazing furnace for welding;

[0056] S6, after brazing is completed, taking out the skin after the temperature in the brazing furnace drops to room temperature.

[0057] To further optimize the above technical solution, during the brazing process, the skin is placed in a brazing furnace with an interlayer gap less than 0.1 mm and a furnace vacuum less than 5×10 -3 Pa. When heating up, it is heated to 600 °C at a rate of 5 - 10 °C / min, then heated to 850 - 900 °C at a rate of 5 °C / min and held for 20 min, and finally cooled to 500 °C at a rate of 10 °C / min, and then cooled in the furnace.

[0058] To further optimize the above technical solution, the material of the high-temperature layer 1 is a nickel-based superalloy; the high-temperature layer 1 is located on the outermost side of the skin, with a maximum working temperature not lower than 1000 °C, a minimum size of 10 mm × 10 mm, and a maximum size of 1000 mm × 1000 mm.

[0059] To further optimize the above technical solution, the material of the low-temperature layer 2 is a titanium alloy; the low-temperature layer 2 is located in the middle of the skin, with a maximum working temperature not lower than 600 °C, a minimum size of 10 mm × 10 mm, and a maximum size of 1000 mm × 1000 mm.

[0060] To further optimize the above technical solution, the material of the connecting layer 3 is an aluminum alloy or a magnesium alloy. The connecting layer 3 is located inside the skin, with a maximum working temperature not lower than 300 °C, a minimum size of 10 mm × 10 mm, and a maximum size of 1000 mm × 1000 mm.

[0061] To further optimize the above technical solution, the maximum working temperature of the carbon fiber cloth 4 is not lower than 1000 °C, and the tensile strength is not less than 3000 MPa.

[0062] To further optimize the above technical solution, the filler metal layer 5 is a sheet-like titanium-based filler metal or an aluminum-based filler metal, and the coating thickness is 0.02 mm - 0.05 mm.

[0063] To further optimize the above technical solution, the depth and width of the receiving groove are equal to the thickness and width of the carbon fiber cloth 4 respectively.

[0064] Example 2:

[0065] To further optimize the above technical solution, the high-temperature layer 1 of the skin selects a 0.3-mm-thick GH4169 thin plate with a size of 200 mm × 200 mm, on which there are two receiving grooves with a depth of 0.15 mm, a width of 6 mm, and a spacing of 4 mm. The low-temperature layer 2 selects a 0.3-mm-thick TC4 thin plate with a size of 200 mm × 200 mm, on which there are two receiving grooves with a depth of 0.15 mm, a width of 6 mm, and a spacing of 4 mm. The connecting layer 3 selects a 0.2-mm-thick 2A12 aluminum alloy thin plate, on which there are stiffening ribs 31 and weight-reducing holes 32, as Figure 3As shown. The carbon fiber cloth 4 is selected with a tensile strength of 3400 MPa, a thickness of 0.16 mm, and a size of 200 mm × 6 mm, and it is laid inside the accommodation grooves of the high-temperature layer 1 and the low-temperature layer 2. A sheet-like titanium-based filler metal is used between the high-temperature layer 1 and the low-temperature layer 2, and a sheet-like aluminum-based filler metal is used between the low-temperature layer 2 and the connection layer 3. Assemble each layer according to Figure 1 the positions shown, and then put it into a brazing furnace, evacuate it, and when the vacuum degree in the furnace is less than 5×10 -3 Pa, heat it up to 600 °C at a rate of 10 °C / min, then heat it up to 870 °C at a rate of 5 °C / min and hold for 20 min, and finally cool it down to 500 °C at a rate of 10 °C / min, and then cool it in the furnace. After cooling to room temperature, take out the specimen.

[0066] In this embodiment, other technical solutions are the same as those in Embodiment 1, and will not be elaborated one by one here.

[0067] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same and similar parts between each embodiment, reference can be made to each other.

[0068] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sandwich skin with a gradient structure, characterized in that, It includes: A high-temperature layer, A low-temperature layer which is placed at the bottom of the high-temperature layer; A connection layer which is placed at the bottom of the low-temperature layer, and the high-temperature layer, the low-temperature layer and the connection layer are sequentially brazed and connected; Carbon fiber cloth, and accommodation grooves are formed on the surfaces of the high-temperature layer and the low-temperature layer, and the carbon fiber cloth is arranged in the accommodation grooves.

2. The sandwich skin with a gradient structure according to claim 1, wherein, A brazing filler metal layer is provided between the high-temperature layer and the low-temperature layer, and between the low-temperature layer and the connection layer.

3. The sandwich skin with a gradient structure according to claim 1, characterized in that, The included angle between the laying directions of the carbon fiber cloth in the high-temperature layer and the low-temperature layer is between 30° and 90°.

4. The sandwich skin with a gradient structure according to claim 1, characterized in that, Reinforcing ribs and weight-reducing holes are provided on the surface of the connection plate.

5. The preparation method of a sandwich skin with a gradient structure according to any one of claims 1-4, characterized in that, It includes the following preparation method: S1. Cut the high-temperature layer, the low-temperature layer, the connection layer and the brazing filler metal layer that meet the dimensional requirements, and process an accommodation groove structure on the surfaces of the high-temperature layer and the low-temperature layer; S2. Polish the parts of the surfaces of the high-temperature layer, the low-temperature layer and the connection layer that need to be brazed and connected to ensure that the surface roughness is less than Ra1.6; S3. Lay carbon fiber cloth in the accommodation grooves of the high-temperature layer and the low-temperature layer; S4. Stack the high-temperature layer, the low-temperature layer and the connection layer in sequence, and place a brazing filler metal layer between adjacent two layers to assemble and form a skin; S5. Put the assembled skin into a brazing furnace for welding; S6. After brazing is completed, take out the skin after the temperature in the brazing furnace drops to room temperature.

6. The preparation method of a sandwich skin with a gradient structure according to claim 5, characterized in that, During the brazing process, the skin is placed in a brazing furnace, the interlayer gap is less than 0.1 mm, the vacuum degree in the furnace is less than 5×10 -3 Pa. When heating up, it is heated to 600℃ at a rate of 5 - 10℃ / min, then heated to 850℃ - 900℃ at a rate of 5℃ / min and held for 20 min. Finally, it is cooled to 500℃ at a rate of 10℃ / min and then cooled in the furnace.

7. The preparation method of a sandwich skin with a gradient structure according to claim 5, characterized in that, The material of the high-temperature layer is a nickel-based superalloy; the material of the low-temperature layer is a titanium alloy; the material of the connection layer is an aluminum alloy or a magnesium alloy.

8. The preparation method of a sandwich skin with a gradient structure according to claim 5, characterized in that, The brazing filler metal layer is a sheet-like titanium-based brazing filler metal or an aluminum-based brazing filler metal, and the thickness is 0.02 mm - 0.05 mm.

9. The preparation method of a sandwich skin with a gradient structure according to claim 5, characterized in that, The depth and width of the accommodation groove are equal to the thickness and width of the carbon fiber cloth.

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