Composite material skin-metal web high-quality integrated manufacturing method

Abstract

The invention belongs to the technical field of composite material component manufacturing, and particularly relates to a composite material skin-metal web high-quality integrated manufacturing method. According to the method, residual stress caused by difference of thermal expansion coefficients is reduced through methods such as segmented machining, splicing forming and surface structure design of the metal web, the positioning precision of the metal web and the internal quality of the whole structure are improved through design and application of the positioning sample plate, and the machining precision is improved. Through process optimization, high-quality and high-efficiency integrated manufacturing of the composite material skin and the metal web is achieved, and a technical foundation is laid for manufacturing of a composite material-metal reinforced structural part made of dissimilar materials through a composite process.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material component manufacturing, and in particular relates to a high-quality integrated manufacturing method of a composite material skin-metal web. Background Art

[0002] With the development of composite material manufacturing technology and the increasing demand for aircraft weight reduction, carbon fiber composite reinforced structural parts are widely used in the main and secondary load-bearing structures in the aviation field, such as flat and vertical tail panels, wing panels, covers, doors, etc., due to their high specific strength, high specific modulus, corrosion resistance, strong structural designability, and integrated molding. Traditional carbon fiber composite reinforced structural parts are made of carbon fiber composite materials as a whole. The stiffeners and skins are autoclaved by co-curing, adhesive co-curing or secondary adhesive bonding. It is necessary to design and manufacture complex positioning assembly tooling to ensure the molding quality of the structural parts and the positioning accuracy of the stiffeners. The positioning assembly tooling has a complex structure, high design and manufacturing costs, cumbersome preparation processes, and low manufacturing efficiency. In addition, the stiffeners are difficult to position under high temperature and high pressure environments, and the positioning accuracy is difficult to ensure. The complex tooling structure also increases the difficulty of vacuum bag packaging during autoclave molding of parts. For example, a Chinese patent with publication number CN105346102B proposes a tooling and molding method for positioning and integrally molding composite reinforced wall panels, which can realize the integral molding of wall panel structural parts, but the positioning tooling needs to be repeatedly installed and removed during use, and the vacuum bag needs to be opened during curing and packaging, so that the bolts pass through the positioning beam through holes outside the vacuum bag and connect with the molding tooling inside the vacuum bag. The position where the bolts pass through the vacuum bag needs to be sealed with a sealing strip, and there is a risk of vacuum bag leakage during curing. In addition, the parts made by the co-curing and secondary bonding processes need to be put into the autoclave for curing and molding many times, which greatly increases the manufacturing cost. Therefore, some experts have proposed a method of using a hybrid process to manufacture reinforced wall panels with different materials, that is, after the composite skin and the metal web are integrally molded, a welding connection process is used to realize the connection between the reinforcing ribs and the web, and finally realize the integrated manufacturing of reinforced wall panel components with different materials. At present, there is little research on the integrated forming process of composite skin and metal web, and there are problems with connection quality and appearance quality during the integrated forming process due to the mismatch of thermal expansion coefficients. Therefore, achieving high-quality integrated forming of composite skin and metal web is an urgent problem to be solved. Summary of the invention

[0003] In view of the connection quality and appearance quality problems caused by the mismatch of thermal expansion coefficients during the integrated molding of the composite skin and the metal web mentioned above, a high-quality integrated molding method of the composite skin and the metal web is proposed. The present invention adopts pre-curing process parameters to optimize and control the stiffness of the skin to improve its appearance quality; the web is designed in a segmented form, and the size of the metal web is designed according to different curing temperatures to control the thermal expansion and reduce the residual stress of the connection surface; a special structure is designed and manufactured on the surface of the metal web connected to the composite skin to mechanically fit the connection surface between the two to improve the connection quality with the skin; the sample material and structure are optimized and designed to adjust its stiffness and positioning accuracy, thereby ensuring the accurate position of the web and the internal quality; through process flow design, high-efficiency, high-quality, integrated molding of the composite skin and the metal web is achieved.

[0004] The technical means adopted by the present invention are:

[0005] A high-quality integrated manufacturing method of a composite material skin-metal web, comprising the following steps:

[0006] The method for integrally forming a composite material skin and a metal web is characterized in that the composite material skin is pre-cured after being laid up; the metal web is designed in sections to suppress residual stress caused by differences in thermal expansion coefficients, and grooves or V-grooves are processed on the surface, which are surface treated before being connected to the skin to improve the interface bonding strength between the composite material skin and the metal web; an integral or split structure positioning template is designed and manufactured, which has positioning, limiting and uniform pressure functions to prevent the metal plate from slipping during forming; the metal web is positioned and combined with the skin, the metal web is spliced ​​in sections, and a co-curing process is used to complete the integrated manufacturing of the composite material skin and the metal web.

[0007] The skin lay-up is characterized in that the skin material can be one or more of carbon fiber prepreg, glass fiber prepreg, quartz fiber prepreg or aramid fiber prepreg; after the lay-up is completed, it is packaged in an autoclave for pre-curing, the pre-curing temperature is 50-130°C, the pressure is 0.3MPa-0.6MPa, and the insulation time is 5-20min, the purpose is to make it close to the actual thickness after curing, and the hardness is close to the composite material skin after curing, to prevent the metal web from sinking too deeply into the skin during the curing process of the combination of the metal web and the skin, thereby affecting the surface quality.

[0008] The metal web size design is characterized in that the metal web is designed to be 2-4 mm thick and 20-65 mm wide, and the total length of the web is determined according to the skin length and design requirements. The same web can be designed in sections according to the total length and the different curing temperature conditions of the composite material and then spliced ​​for use. The splicing position can be designed as a vertical or beveled splicing structure. According to the different curing temperature ranges of the composite material, the web can be designed to be 300-1000 mm long to prevent the metal web from being too long. Due to the large difference in thermal expansion coefficient with the composite skin, residual stress is generated on the bonding surface during the integral molding, which affects the internal quality of the bonding surface.

[0009] The metal web surface structure design is characterized in that a concave groove or a V-shaped groove is machined by mechanical processing or laser processing on one side of the metal web bonded to the skin, the groove cavity depth ranges from 0.1 to 0.5 mm, the groove cavity width is 1 to 5 mm, the groove cavity length is the same as the web width, and the spacing between the grooves is 5 to 10 mm. According to the mechanical interlocking theory, the resin in the prepreg penetrates into the groove cavity of the metal web and removes the air adsorbed by it, thereby producing a good adhesion effect.

[0010] The design of the positioning template is characterized in that the positioning template can simultaneously achieve the functions of positioning, limiting and uniform pressure.

[0011] 1.1 Material selection: The positioning sample material can be one of glass fiber prepreg, carbon fiber prepreg, unvulcanized rubber and silicone rubber, or a combination of two. The hardness can be controlled and adjusted through the selection of material types and the design of the layer. Its Shore hardness D is between 38 and 90.

[0012] 1.2 Structural design: The positioning template can be designed as an integral structure, with a circular hole and an oblong hole designed at one end in the length direction and an oblong hole designed at the other end to achieve positioning between it and the skin; a metal web space is reserved at the corresponding position of the metal web of the positioning template. The width of the space needs to be 0.2 to 1 mm wider than the theoretical width of the metal web, and the length needs to be 1 to 15 mm longer than the theoretical length of the metal web; the positioning template can also be disconnected in the middle along the length direction of the web to form two matching comb-like structures. At this time, a circular hole and an oblong hole need to be designed at both ends in the length direction to position the template on the skin surface.

[0013] 1.3 Template manufacturing: The positioning template needs to be manufactured according to the shape of the upper surface of the skin, and the fitting gap with the skin should be in the range of 0 to 1 mm / m. When the fitting gap is greater than 1 mm / m, after external force is applied, the fitting gap at the force-applying point should not be greater than 0.2 mm.

[0014] The process design is characterized in that a pre-curing process is provided to improve the appearance quality of the integrated structure; the skin and the metal web are integrally formed at one time, and except for a short pre-curing, only one autoclave is required, which greatly reduces the production cost; a web surface groove or V-groove processing process and a surface treatment process are provided to improve the connection strength between the web and the skin; the web is processed in sections and spliced ​​to reduce the residual stress caused by the difference in thermal expansion coefficients; the specific process flow is as follows:

[0015] 2.1 Lay the prepreg on the surface of the skin forming tooling until the specified number of layers is reached, and then package it and send it into the autoclave for pre-curing to make it close to the actual thickness and hardness after curing;

[0016] 2.2 Fix the template on the positioning pins of the skin forming tooling according to the positioning holes on the positioning template, so that it fits with the upper surface of the skin;

[0017] 2.3 Process the metal web in sections and make grooves on the side where it is connected to the skin;

[0018] 2.4 Use sandblasting, pickling, anodizing or plasma treatment to treat the metal web surface to improve the connection strength;

[0019] 2.5 Place the metal web at the location of the positioning template placeholder and assemble it with the skin. The metal web is spliced ​​in sections, and 1-3mm expansion joints are reserved between sections to prevent residual stress from being generated at the interface between the composite skin and the metal web during curing due to the difference in thermal expansion coefficients;

[0020] 2.6 Fix the metal web to the surface of the positioning template with pressure-sensitive tape, assemble the whole and seal it in a vacuum bag;

[0021] 2.7 Curing and molding: After the skin and the metal belly are combined, they are packaged and sent into the autoclave for curing and molding. The curing temperature is 120-230℃, the curing pressure is 0.3MPa-0.6MPa, and the insulation time is 120-240min to complete the integrated manufacturing of the composite material skin and the metal belly.

[0022] Beneficial effects of the present invention:

[0023] The present invention proposes a method for the integrated manufacturing process of composite material skin and metal web. The residual stress caused by the difference in thermal expansion coefficient is reduced by methods such as segmented processing, splicing molding, and surface structure design of the metal web. The positioning template design and application improves the positioning accuracy of the metal web and the internal quality of the overall structure. Through process optimization, high-quality and high-efficiency integrated manufacturing of composite material skin and metal web is achieved, laying a technical foundation for the manufacture of heterogeneous materials and composite process composite-metal reinforced structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the integrated structure of fiber reinforced resin matrix composite skin and metal web;

[0025] Figure 2 It is a schematic diagram of the surface structure of the metal web;

[0026] Figure 3 It is a schematic diagram of the positioning template structure and the positioning combination of the skin and the metal web.

[0027] In the figure: 1 is the skin, 2 is the metal web, 2-1 is the vertical metal web segmented structure, 2-2 is the oblique metal web segmented structure, 2-3 is the integral metal web structure, 3 is the concave groove metal web surface structure, 4 is the V-groove metal web surface structure, 5 is the positioning template, 5-1 is the positioning circular hole A, 5-2 is the positioning circular hole B, 5-3 is the positioning oblong hole A, 5-4 is the positioning oblong hole B, and 6 is the metal web space. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings.

[0029] The heterogeneous material reinforced wall panels manufactured by hybrid process can replace the traditional composite material reinforced wall panels, but there is little research on the integrated forming process of composite material skin 1 and metal web 2, and its forming quality is difficult to control. Figure 1 As shown, the fiber reinforced resin-based composite material skin 1 and the metal web 2 are an integrated structure. Since the thermal expansion coefficients of the fiber reinforced resin-based composite material and the metal are quite different, when the two are integrally formed in an autoclave, there are connection quality and appearance quality problems caused by the mismatch of thermal expansion coefficients. Moreover, under high temperature and high pressure conditions, the metal web 2 is difficult to position and is easy to sink into the composite material skin 1, making it difficult to guarantee product quality.

[0030] Based on the connection quality and appearance quality issues during the integrated molding process of the composite skin 1 and the metal web 2, the present invention provides a high-quality integrated molding method for the composite skin 1 and the metal web 2. The metal web 2 is integrated with the skin 1 in a segmented manner and the surface of the metal web 2 is specially designed to ensure the connection quality and internal quality of the overall structure; the appearance quality and positioning accuracy of the integrated molding of the composite skin 1 and the metal web 2 are ensured by pre-curing the skin 1 and designing and using the positioning template 5, so as to achieve efficient, high-quality, integrated molding of the composite skin 1 and the metal web 2. The specific implementation process is as follows:

[0031] The first step is to lay up the skin 1: Use carbon fiber prepreg cured at 180℃ to lay up the skin 1 prepreg in sequence on the tooling surface. The length of skin 1 is 2000mm. After every 3 to 5 layers are laid up, vacuum compaction is performed at room temperature. After all the layers are laid up, the blank is packaged on the tooling surface and sent to the autoclave for pre-curing. The vacuum is not less than -0.092MPa throughout the process, the pressure is 0.6±0.035MPa, and the rate is 0.3MPa / min; the heating rate is not more than 1.5℃ / min, rising to 90℃, 90±5℃, and keeping warm for 15min; the temperature is reduced to 60℃ at a rate of no more than 1.5℃ / min, 60±5℃, and keeping warm for 2min, and then the pressure is released out of the tank.

[0032] The second step is the preparation and surface treatment of the metal web 2: the total length of a single web is 1800mm. Considering that the thermal expansion of the web is about 6.2mm at 180℃, the metal web 2 is designed as a segmented structure. The segmented form can be a vertical segmented structure or a beveled segmented structure, with each segment being 300mm. A 7B04 aluminum alloy sheet with a thickness of 2mm is selected to be processed into a web with a width of 50mm and a length of 300mm. A single web consists of 6 300mm long segmented webs; Figure 2 As shown, a concave groove structure metal web 3 or a V-groove structure metal web 4 is designed and manufactured, with a groove width of 2 mm, a depth of 0.2 mm, and a groove interval of 5 mm. Use acetone solvent to clean the oil stain on the surface of the aluminum alloy web; then use a mixed solution of sodium hydroxide and sodium carbonate to perform alkaline cleaning at 50-60°C for 0.5-1 min, and rinse in tap water for 2-5 min; use a deoxidized liquid to clean at room temperature for 2-5 min, and rinse in tap water for 5 min; put the aluminum alloy web into a phosphoric acid solution, connect a DC power supply at room temperature, and increase the DC voltage between the plates from 0V to 10±1V within 2 minutes. After anodizing for 20 minutes, take it out, rinse it, and dry it for use.

[0033] The third step is to coat the anti-electrochemical corrosion isolation layer: coat the surface of the metal web 2 with a layer of glass fiber prepreg to prevent electrochemical corrosion caused by direct contact between the composite skin 1 and the metal web 2. At the same time, the resin in this layer of prepreg can also act as a binder. The outline of the glass fiber prepreg needs to be larger than the ground of the metal web 2 and can cover the side of the metal web 2.

[0034] Step 4: Manufacturing of positioning template 5 and positioning assembly of metal web 2: Design and manufacture of split-flap positioning template 5 with a break in the middle, reserve space at the corresponding position of the web of positioning template 5, and reserve 10mm margin in the length direction of the space; each positioning template 5 contains two positioning holes, a round hole and an oblong hole; the first layer of positioning template 5 attached to the surface of skin 1 is made of unvulcanized rubber, and then 4 layers of carbon fiber tooling prepreg fabric are stacked on its surface to make it have a certain hardness and can evenly transmit pressure. Figure 3 As shown, the positioning template 5 is fitted with the surface of the skin 11, and the metal webs 2 are placed in the metal web space 6 in sequence, leaving a gap of 1 mm between the webs, and then fixed to the positioning template 5 with a pressure-sensitive tape.

[0035] The fifth step is curing and molding: the carbon fiber composite skin 1 and the aluminum alloy belly plate are combined and packaged and sent into the autoclave for curing and molding. The curing temperature is 180±5℃, the curing pressure is 0.6±0.035MPa, and the insulation time is 240min, thus completing the integrated manufacturing of the composite skin 1 and the metal belly plate 2.

Claims

1. A high-quality integrated manufacturing method for composite skin-metal web, characterized in that: The steps are as follows: pre-curing the composite material skin (1) after it is laid up; The metal web (2) is designed in sections to suppress residual stress caused by differences in thermal expansion coefficients, and grooves or V-shaped grooves are processed on the surface. The surface is treated before being connected to the skin (1) to improve the interface bonding strength between the composite material skin (1) and the metal web (2); Designing and manufacturing a positioning template (5) of an integral or split structure, which has the functions of positioning, limiting and equalizing pressure, so as to prevent the metal plate from slipping during forming; The metal web (2) and the skin (1) are positioned and assembled, the metal web (2) is spliced ​​in sections, and a co-curing process is used to complete the integrated manufacturing of the composite material skin (1) and the metal web (2); The skin (1) is stacked and after stacking is completed, it is packaged in an autoclave for pre-curing, the pre-curing temperature is 50-130° C., the pressure is 0.3 MPa-0.6 MPa, and the insulation time is 5-20 minutes; The size design of the metal web (2) is as follows: the metal web (2) is designed to be 2 to 4 mm thick and 20 to 65 mm wide, and the total length of the web is determined according to the length of the skin (1) and design requirements; the same web can be designed in sections according to the total length and the curing temperature conditions of the composite material and then spliced ​​for use. The splicing position can be designed as a vertical or beveled splicing structure. According to the different curing temperature ranges of the composite material, the web can be designed to be 300 to 1000 mm long to prevent the metal web (2) from being too long. Due to the large difference in thermal expansion coefficient with the composite material skin (1), residual stress is generated on the bonding surface during the integral molding, thereby affecting the internal quality at the bonding surface.

2. A high-quality integrated manufacturing method of composite skin-metal web according to claim 1, characterized in that: The design of the positioning template (5) is as follows: 1.1 Material selection: The positioning sample (5) can be made of one or a combination of glass fiber prepreg, carbon fiber prepreg, unvulcanized rubber and silicone rubber. The hardness can be adjusted by selecting the material type and designing the layer. Its Shore hardness D is between 38 and 90. 1.2 Structural design: The positioning template (5) can be designed as an integral structure, with a circular hole and an oblong hole designed at one end in the length direction and an oblong hole designed at the other end to achieve positioning between it and the skin (1); a metal web (2) space is reserved at the corresponding position of the metal web (2) of the positioning template (5), and the width of the space needs to be 0.2 to 1 mm wider than the theoretical width of the metal web (2), and the length needs to be 1 to 15 mm longer than the theoretical length of the metal web (2); the positioning template (5) can also be disconnected in the middle along the length direction of the web to form two interlocking comb-like structures, in which case a circular hole and an oblong hole need to be designed at both ends in the length direction respectively to position the template on the surface of the skin (1); 1.3 Template manufacturing: The positioning template (5) needs to be manufactured according to the upper surface shape of the skin (1), and the fitting gap with the skin (1) should be in the range of 0 to 1 mm / m. When the fitting gap is greater than 1 mm / m, after external force is applied, the fitting gap at the force application point should not be greater than 0.2 mm.

3. A high-quality integrated manufacturing method of composite skin-metal web according to claim 1 or 2, characterized in that: The surface structure design of the metal web (2) is as follows: a concave groove or a V-shaped groove is machined on one side of the metal web (2) bonded to the skin (1) by mechanical processing or laser processing, the groove cavity depth ranges from 0.1 to 0.5 mm, the groove cavity width is 1 to 5 mm, the groove cavity length is the same as the web width, and the spacing between the grooves is 5 to 10 mm.

4. A high-quality integrated manufacturing method of composite skin-metal web according to claim 1 or 2, characterized in that: The skin (1) material is one or more of carbon fiber prepreg, glass fiber prepreg, quartz fiber prepreg or aramid fiber prepreg.

5. A high-quality integrated manufacturing method of composite skin-metal web as claimed in claim 3, characterized in that: The skin (1) material is one or more of carbon fiber prepreg, glass fiber prepreg, quartz fiber prepreg or aramid fiber prepreg.

6. A high-quality integrated manufacturing method of composite skin-metal web as claimed in claim 1, 2 or 5, characterized in that: The process flow of the manufacturing method is as follows: 2.1 Laying prepreg on the surface of the skin (1) molding tool until the specified number of layers is reached, packaging and sending it into an autoclave for pre-curing to make it close to the actual thickness and hardness after curing; 2.2 Fix the template (5) on the positioning pins of the skin (1) forming tool according to the positioning holes on the positioning template (5) so that it fits with the upper surface of the skin (1); 2.3 Processing the metal web (2) in sections, and processing a groove on the side thereof connected to the skin (1); 2.4 The metal web (2) is surface treated by sandblasting, pickling, anodizing or plasma treatment to improve the connection strength; 2.5 Place the metal web (2) at the position of the positioning template (5) and position it with the skin (1). The metal web (2) is spliced ​​in sections, and a 1-3 mm expansion joint is reserved between the sections to prevent residual stress from being generated at the interface between the composite skin (1) and the metal web (2) during curing due to the difference in thermal expansion coefficients; 2.6 Fix the metal web (2) to the surface of the positioning template (5) with a pressure-sensitive tape, assemble the whole and seal it in a vacuum bag; 2.7 Curing and molding: After the skin (1) and the metal belly plate (2) are combined, they are packaged and sent into a hot autoclave for curing and molding. The curing temperature is 120-230°C, the curing pressure is 0.3MPa-0.6MPa, and the insulation time is 120-240min, thereby completing the integrated manufacturing of the composite material skin (1) and the metal belly plate (2).

7. A high-quality integrated manufacturing method of composite skin-metal web as claimed in claim 3, characterized in that: The process flow of the manufacturing method is as follows: 2.1 Laying prepreg on the surface of the skin (1) molding tool until the specified number of layers is reached, packaging and sending it into an autoclave for pre-curing to make it close to the actual thickness and hardness after curing; 2.2 Fix the template (5) on the positioning pins of the skin (1) forming tool according to the positioning holes on the positioning template (5) so that it fits with the upper surface of the skin (1); 2.3 Processing the metal web (2) in sections, and processing a groove on the side thereof connected to the skin (1); 2.4 The metal web (2) is surface treated by sandblasting, pickling, anodizing or plasma treatment to improve the connection strength; 2.5 Place the metal web (2) at the position of the positioning template (5) and position it with the skin (1). The metal web (2) is spliced ​​in sections, and a 1-3 mm expansion joint is reserved between the sections to prevent residual stress from being generated at the interface between the composite skin (1) and the metal web (2) during curing due to the difference in thermal expansion coefficients; 2.6 Fix the metal web (2) to the surface of the positioning template (5) with a pressure-sensitive tape, assemble the whole and seal it in a vacuum bag; 2.7 Curing and molding: After the skin (1) and the metal belly plate (2) are combined, they are packaged and sent into a hot autoclave for curing and molding. The curing temperature is 120-230°C, the curing pressure is 0.3MPa-0.6MPa, and the insulation time is 120-240min, thereby completing the integrated manufacturing of the composite material skin (1) and the metal belly plate (2).

8. A high-quality integrated manufacturing method of composite skin-metal web as claimed in claim 4, characterized in that: The process flow of the manufacturing method is as follows: 2.1 Laying prepreg on the surface of the skin (1) molding tool until the specified number of layers is reached, packaging and sending it into an autoclave for pre-curing to make it close to the actual thickness and hardness after curing; 2.2 Fix the template (5) on the positioning pins of the skin (1) forming tool according to the positioning holes on the positioning template (5) so that it fits with the upper surface of the skin (1); 2.3 Processing the metal web (2) in sections, and processing a groove on the side thereof connected to the skin (1); 2.4 The metal web (2) is surface treated by sandblasting, pickling, anodizing or plasma treatment to improve the connection strength; 2.5 Place the metal web (2) at the position of the positioning template (5) and position it with the skin (1). The metal web (2) is spliced ​​in sections, and a 1-3 mm expansion joint is reserved between the sections to prevent residual stress from being generated at the interface between the composite skin (1) and the metal web (2) during curing due to the difference in thermal expansion coefficients; 2.6 Fix the metal web (2) to the surface of the positioning template (5) with a pressure-sensitive tape, assemble the whole and seal it in a vacuum bag; 2.7 Curing and molding: After the skin (1) and the metal belly plate (2) are combined, they are packaged and sent into a hot autoclave for curing and molding. The curing temperature is 120-230°C, the curing pressure is 0.3MPa-0.6MPa, and the insulation time is 120-240min, thereby completing the integrated manufacturing of the composite material skin (1) and the metal belly plate (2).

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