A method for improving the surface quality of bonding between metal profiles and composite materials

Abstract

The present invention belongs to the technical field of aviation structure bonding, and discloses a method for improving the surface quality of bonding between metal profiles and composite materials. Before the vacuuming step of bonding between metal profiles and composite materials, a hard auxiliary tooling with a flat bottom surface and an acute angle between the inclined surface and the bottom surface is placed on the edge of the metal profile, and the vertical surface of the auxiliary tooling is tightly fitted with the edge of the metal profile, and the bottom surface of the auxiliary tooling is tightly fitted with the composite material, and then the vacuuming step is performed; the auxiliary tooling is taken out after the vacuuming is completed. The present invention ensures the uniform distribution and effective transmission of pressure on the entire pressure surface by adding a hard auxiliary tooling with an inclined angle of 15° to 30° to the side wall of the metal profile at the bending deformation position, solves the bending deformation at the bonding edge of the special metal profile and the composite skin, improves the surface quality of the bonding between the special metal profile and the composite skin, and guarantees the strength, skin integrity, and connection assembly accuracy requirements of the product.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation structure bonding, relates to a bonding method, and specifically to a method for improving the bonding surface quality of metal profiles and composite materials. Background Art

[0002] In order to meet the requirements of strength, skin integrity, connection and assembly accuracy of composite material wall panel parts of a special aircraft, the product design uses a composite material skin and a special metal profile bonding structure. At present, the manufacturing of this type of product usually adopts the method of secondary bonding or bonding + riveting. The composite component is first heated and cured in an autoclave to become a rigid component, and then bonded and positioned with the metal profile through a medium-temperature or high-temperature structural adhesive film, and then put into the autoclave for heating and pressurization curing. This method is prone to matching gaps or incoordination defects on the bonding surface, which affects the bonding strength. Therefore, in order to meet the requirements of the metal profile bonding strength, composite skin integrity, assembly accuracy, etc. of this product, the manufacturing of this product uses a method of co-bonding of metal profiles and composite skins, that is, after laying the skin prepreg, it is bonded and positioned with the metal profile and put into the autoclave for heating and pressurization curing. After the trial production of the first product, it was found that the composite skin layer at the edge of the special metal profile was buckled and deformed (see attached Figure 1 ), the surface quality does not meet the product manufacturing requirements.

[0003] In order to improve the surface quality of the product's bonding and solve the problem of buckling and deformation that occurs during the bonding process of special metal profiles and composite skins, after many improvements and tests, attempts were made to set auxiliary tooling at the location where the buckling and deformation occurs. First, common materials and structures such as silicone rubber sheets and rubber sealing strips were tried. During the packaging vacuum bag into the autoclave for heating and pressurizing curing, the problem of serious buckling and deformation of the metal profile side wall due to the vacuum bag bridging being unable to apply pressure at all was alleviated. However, since rubber materials will soften and flow during the heating process, the shape will be irregular and it is impossible to ensure that the pressure is fully and effectively transmitted, causing a difference in pressure between the metal profile side wall and the surrounding pressure, affecting the internal quality and surface flatness of this part; in addition, rubber materials flow freely after heating and softening, and it is difficult to control the shape, edge thickness, inclination angle, etc., resulting in secondary buckling and deformation at the edge of the rubber strip after heating and pressurizing curing, which is equivalent to transferring the buckling and deformation of the original metal side wall to the edge of the rubber strip, and the buckling and deformation problem cannot be effectively and thoroughly solved. In addition, through experiments we also found that the angle between the upper surface of the auxiliary tooling and the composite skin has a great influence on the effect of solving the bending deformation. It was found that the larger the angle, the worse the effect. The test tried to use an auxiliary tooling with an angle of 60°, and the buckling deformation basically did not change. When the auxiliary tooling with an angle of 45° was tried, the buckling deformation changed to a certain extent. Gradually reducing the angle, the improvement effect became more and more obvious. Comprehensive theoretical analysis of the test results shows that the smaller the angle, the better, but the smaller the angle means a larger auxiliary tooling, which will bring new problems (part size limitations, tooling costs, etc.). Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for improving the surface quality of bonding between metal profiles and composite materials, which can solve the problem of buckling deformation occurring during bonding between special metal profiles and composite material skins.

[0005] The technical solution of the present invention is as follows:

[0006] A method for improving the surface quality of bonding between a metal profile and a composite material. Before the vacuuming step of bonding between the metal profile and the composite material, a hard auxiliary tooling with a flat bottom and an acute angle between the inclined surface and the bottom surface is placed on the edge of the metal profile, the vertical surface of the auxiliary tooling is tightly fitted with the edge of the metal profile, and the bottom surface of the auxiliary tooling is tightly fitted with the composite material, and then the vacuuming step is performed; the auxiliary tooling is taken out after the vacuuming is completed.

[0007] Furthermore, the number of the auxiliary tooling is the same as the number of types of the vertical surfaces of the metal profile, and the height of the auxiliary tooling is consistent with the height of the vertical surface of the metal profile.

[0008] Furthermore, the angle between the inclined surface and the bottom surface of the auxiliary tooling is 15 to 30 degrees.

[0009] Furthermore, the auxiliary tooling is made of a high temperature resistant hard material.

[0010] Furthermore, the material of the auxiliary tooling is a combination of one or more of high temperature resistant metal, high temperature resistant hard plastic, and laminated cloth board.

[0011] Furthermore, after the auxiliary tooling is placed, the positions of the auxiliary tooling and the metal profile are fixed using pressure-sensitive tape.

[0012] Further, the method specifically includes the following steps:

[0013] Step 1: prepare auxiliary tooling according to the height and length of the side wall of the special metal profile;

[0014] Step 2: Use adhesive film to stick to the bonding surface of the special metal profile, and the adhesive film is slightly larger than the bonding surface of the metal profile;

[0015] Step 3: Lay and cut the peeling cloth on the composite material skin according to the bonding surface shape of the special metal profile, and then attach the special metal profile to the notch of the peeling cloth on the composite material skin;

[0016] Step 4: Place the auxiliary tooling close to the special metal profile and fix it to the special metal profile;

[0017] Step 5: Vacuum cure and remove the auxiliary tooling after curing.

[0018] Furthermore, after removing the auxiliary tooling, check the surface quality of the glued components and polish and remove excess glue accumulation on the surface.

[0019] Beneficial effects:

[0020] 1. The process method provided by the present invention adds a hard auxiliary tooling with an angle of 15° to 30° to the side wall of the metal profile at the bending and deformation position, places it close to the metal profile and fixes it with a pressure-sensitive tape, and then seals the vacuum bag into an autoclave for heating and pressurization curing. Due to the slope of the auxiliary tooling, the bridging problem between the profile at this position and the composite skin vacuum bag is effectively solved, the uniform distribution and effective transmission of pressure on the entire pressure surface are ensured, the bending and deformation at the bonding edge of the special metal profile and the composite skin is solved, the bonding surface quality of the special metal profile and the composite skin is improved, and the strength, skin integrity, and connection and assembly accuracy requirements of the product are guaranteed.

[0021] 2. The selection of hard materials is the key. The tooling of hard materials can effectively ensure the shape of the auxiliary tooling, especially the bevel, and can effectively transfer the vacuum bag, tank pressure, etc. to the composite skin through the hard auxiliary tooling, and keep it consistent with the surface pressure of the metal material, avoiding pressure differences, etc., which affect the internal quality of the composite material or cause secondary buckling deformation.

[0022] 3. Through experimental verification, the larger the bevel angle, that is, the angle between the upper surface of the auxiliary tooling and the composite material skin, the worse the effect of solving the buckling deformation defect, and the smaller the bevel angle, the better the effect. Taking into account the influence of part size, manufacturing quality requirements, auxiliary tooling cost, etc., the selection of an angle of 15° to 30° can not only meet the product manufacturing surface quality requirements, but also control costs, and meet the requirements of part size and processing platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the deformation defect diagram before improvement;

[0024] Figure 2 This is the improved effect diagram;

[0025] Figure 3 It is an auxiliary tooling drawing;

[0026] Figure 4 To assist in the placement and positioning of tooling;

[0027] Figure 5 This is a vacuum bag packaging diagram.

[0028] Among them: 1-1 special metal profiles, 1-2 composite skin, 1-3 bending deformation defects, 2-1 auxiliary tooling, 2-2 improved surface condition, 3-1 left auxiliary tooling, 3-2 left auxiliary tooling bevel, 3-3 right auxiliary tooling, 3-4 right auxiliary tooling bevel, 4-1 molding mold, 4-2 special metal profiles, 4-3 composite skin ply, 4-4 glass cloth, 4-5 left auxiliary tooling positioning, 4-6 right auxiliary tooling positioning, 5-1 isolation film, 5-2 breathable felt, 5-3 sealing tape, 5-4 vacuum bag film. DETAILED DESCRIPTION

[0029] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships as given in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0032] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0033] In order to improve the surface quality of the bonding of the product and solve the problem of bending and deformation during the bonding process of the special metal profile and the composite skin. After many improvements and tests, an auxiliary tooling with a slope of 15° to 30° is added to the side wall of the metal profile where the bending and deformation occurs. High-temperature resistant hard plastics, laminated cloth panels, hard metals, etc. are placed close to the metal profile and fixed with pressure-sensitive tape, and then the vacuum bag is sealed and put into the autoclave for heating and pressurization curing. Due to the slope of the auxiliary tooling, the problem of bridging the vacuum bag between the profile and the composite skin in this part is effectively solved, ensuring the uniform distribution of pressure on the entire pressure surface, avoiding the bending and deformation of the composite skin and the metal profile in this part due to the pressure difference, improving the bonding surface quality of the special metal profile and the composite skin, and ensuring the strength of the product, skin integrity, and connection assembly accuracy requirements. See attached Figure 2 .

[0034] The method of the present invention mainly includes the steps of auxiliary tooling preparation, special metal profile bonding surface preparation, molding tooling preparation, composite skin prepreg laying, special metal profile positioning and bonding, glass cloth laying, auxiliary tooling positioning, vacuum bag packaging, bonding component inspection and surface finishing, etc. The specific steps and requirements are as follows:

[0035] 1) Auxiliary tooling preparation: According to the height, length and other dimensions of the side wall of the special metal profile, epoxy phenolic laminated glass cloth plate is used for CNC machining. Figure 3 Shape, the bevel angle of auxiliary tooling should be controlled at 15° to 30°, and the surface should be flat, smooth and streamlined;

[0036] 2) Preparation of special metal profile bonding surface: First, use 180# aviation washing gasoline to clean and degrease the bonding surface of the special metal profile, let it stand for 30 minutes, then use 120# sandpaper to polish the bonding surface of the special metal profile, wipe it with fine white cotton cloth and then clean it with alcohol, let it stand for 15 minutes before use;

[0037] 3) Preparation of molding tooling: clean the surface glue and debris of the molding tooling and wipe it with fine white cotton cloth, then use fine white cotton cloth dipped in alcohol to clean the molding surface of the mold, let it dry for 15 minutes, and then apply Frekote55NC release agent twice, with an interval of 10 minutes each time;

[0038] 4) Laying of composite skin prepreg: Lay the prepreg on the surface of the prepared molding die according to the layer material, angle composition and quantity required by the composite skin drawing. After the laying is completed, the vacuum bag is packaged for vacuum pre-compaction (a porous isolation film and a breathable material are laid on the prepreg in sequence). The vacuum pressure is not less than -0.08MPa, and the time is 2h to 4h;

[0039] 5) Positioning and bonding of special metal profiles: Cut J-271 structural adhesive film according to the bonding surface size of the metal profile. The film should be 0.5mm to 1mm larger than the bonding surface of the metal profile. Tear off the release paper on one side of the cut film sheet and paste it on the bonding surface of the metal profile. The film should be laid flat when pasting, and wrinkles, film pulling and deformation, etc. are not allowed. Then, according to the laser projection positioning edge line, the special metal profile and the composite skin are precisely positioned, and then the vacuum bag is encapsulated for vacuum pre-compaction (a porous isolation film and a breathable material are laid on the prepreg in turn). The vacuum pressure is not less than -0.08MPa, and the time is 2h to 4h;

[0040] 6) Laying the stripping cloth: Lay a layer of Release Ply B stripping cloth on the composite skin, cut and remove the stripping cloth along the edge where the metal profile and the skin are glued, lay the entire stripping cloth and the cut edge flat and firmly, and then simply fix the stripping cloth with tape;

[0041] 7) Positioning of auxiliary tooling: Position the auxiliary tooling close to the metal profile. During the positioning process, care should be taken to avoid causing deformation and wrinkles in the peeling cloth. Then use GS-213 pressure-sensitive tape to connect and fix the two components through the auxiliary tooling and the upper surface of the metal profile to prevent slippage during the heating and curing process. See attached Figure 4 ;

[0042] 8) Packaging vacuum bag: Lay a layer of A4000 non-porous isolation film, AIRWEAVE N10 breathable felt, WN1500 vacuum bag (sealed with sealing tape on all sides) on the assembly that has been glued and positioned, then evacuate the bag and adjust the vacuum bag where bridges appear, especially the slope of the auxiliary tooling, to ensure that the vacuum bag is firmly attached, see attached Figure 5 Then it is sent into the autoclave for heating and pressurizing curing according to the curing parameters of the composite material skin and the film;

[0043] 9) Inspection and surface finishing of bonded components: After curing is completed, remove the vacuum bag, check the surface quality of the bonded components, and polish to remove excess glue on the surface.

Claims

1. A method for improving the surface quality of bonding between metal profiles and composite materials, characterized in that: Before the vacuuming step of gluing the metal profile and the composite material, a hard auxiliary tooling with a flat bottom and an acute angle between the inclined surface and the bottom surface is placed on the edge of the metal profile, the vertical surface of the auxiliary tooling is tightly fitted with the edge of the metal profile, and the bottom surface of the auxiliary tooling is tightly fitted with the composite material, and then the vacuuming step is performed; the auxiliary tooling is taken out after the vacuuming is completed; the number of auxiliary tooling is the same as the number of types of vertical surfaces of the metal profile, and the height of the auxiliary tooling is consistent with the height of the vertical surface of the metal profile; The angle between the inclined surface and the bottom surface of the auxiliary tooling is 15 to 30 degrees; The specific steps include: Step 1: Prepare auxiliary tooling according to the height and length of the side wall of the metal profile; Step 2: Use adhesive film to stick to the bonding surface of the metal profile, and the adhesive film is slightly larger than the bonding surface of the metal profile; Step 3: Lay and cut the peeling cloth on the composite material skin according to the shape of the bonding surface of the metal profile, and then attach the metal profile to the notch of the peeling cloth on the composite material skin; Step 4: Place the auxiliary tooling close to the metal profile and fix it to the metal profile; Step 5: Vacuum cure and remove the auxiliary tooling after curing.

2. A method for improving the surface quality of bonding between metal profiles and composite materials according to claim 1, characterized in that: The material of the auxiliary tooling is a high temperature resistant hard material.

3. A method for improving the surface quality of bonding between metal profiles and composite materials according to claim 2, characterized in that: The material of the auxiliary tooling is a combination of one or more of high temperature resistant metal, high temperature resistant hard plastic, and laminated cloth board.

4. The method for improving the surface quality of bonding between metal profiles and composite materials according to claim 1, characterized in that: After placing the auxiliary tooling, use pressure-sensitive tape to fix the position of the auxiliary tooling and the metal profile.

5. The method for improving the surface quality of bonding between metal profiles and composite materials according to claim 1, characterized in that: After removing the auxiliary tooling, check the surface quality of the bonded components and polish and remove excess glue on the surface.

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