A method for co-curing forming of a special-shaped large-curvature composite cavity foam sandwich structure part

Abstract

The application discloses a kind of special-shaped large-curvature composite material cavity foam sandwich structure part co-curing forming method, method includes: installing composite material leading edge baffle at the leading edge of winglet;According to tooling line, in turn, paste mould face double-layer copper net, lower skin prepreg and foam lower surface adhesive film;Excess lower skin prepreg is placed on composite material baffle and is separated by thick isolation film prepreg;Place full height foam, and arrange internal vacuum bag in full height foam to realize cavity internal and external pressure balance;Paste foam upper surface adhesive film;Excess lower skin prepreg is turned back to full height foam upper surface, and then in turn, paste upper skin prepreg and paste bag face double-layer copper net;Finally, co-curing is carried out.The innovation of the application is to ensure internal and external pressure balance by arranging internal vacuum bag in cavity, double-layer copper net block staggered laying and leading edge composite material baffle setting, realize the integration of full height foam and composite material forming, ensure the surface quality of aircraft winglet.

Description

Technical Field

[0001] This invention belongs to the field of aerospace composite material aircraft winglet manufacturing technology, and specifically relates to a co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts. Background Technology

[0002] Aircraft winglets are key aerodynamic components located at the wingtips, effectively reducing drag and improving fuel economy. To reduce weight, modern aircraft winglets often employ composite sandwich structures, which are sandwich structures with lightweight foam or honeycomb as the core material and covered with composite skins on both the inside and outside.

[0003] Traditional manufacturing methods often employ secondary bonding, which involves curing the core material and skin separately before combining them. This method has drawbacks such as low interface strength and complex processes.

[0004] While co-curing technology can solve some problems, it faces significant challenges when manufacturing small wings with complex curved surfaces (especially the leading edge region) and internal cavities: First, the core material and skin are prone to deformation, wrinkling, or delamination during the curing process due to residual gas or uneven pressure. Second, the fiber orientation is easily disordered and the copper mesh lightning protection layer breaks due to material accumulation in transition areas such as the leading edge. Third, the laying of large-size copper mesh is prone to wrinkles, affecting surface quality and conductivity continuity.

[0005] Therefore, there is an urgent need for a manufacturing method that can achieve high-quality, integrated molding of complex aircraft winglets. Summary of the Invention

[0006] The purpose of this invention is to provide a co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts, which can avoid defects in the leading edge area of ​​aircraft winglets, ensure the quality of copper mesh laying, and thus ensure the structural strength of the parts.

[0007] To address the aforementioned technical problems, this invention provides a method for co-curing and molding irregularly shaped, high-curvature composite material cavity foam sandwich structure parts, comprising the following steps:

[0008] Step A: Setting the leading edge baffle: In the transition area of ​​the winglet's leading edge, place the composite material leading edge baffle according to the shape, and use locating pins to fix the leading edge baffle to the tooling;

[0009] Step B: Laying up the molding surface: According to the tooling markings, lay up the double-layer copper mesh, the lower skin prepreg layer and the foam underside adhesive film in sequence;

[0010] During installation, the portion of the lower skin prepreg layer that extends beyond the boundary is placed on the front edge baffle, and a release film is used to separate each layer of prepreg from the excess portion.

[0011] Step C: Positioning and film application of full-height foam: Position the full-height foam according to the tooling markings and auxiliary projection on the tooling, and place the heat-treated full-height foam. The full-height foam has a cavity structure and a foam thickness of about 15mm. Then apply the film to the upper surface of the full-height foam.

[0012] Step D: Prepreg folding and bag face laying: Fold the excess lower skin prepreg that was placed on the front edge baffle in step B onto the upper surface of the full-height foam surface film, and then lay the skin prepreg layer and the double-layer copper mesh of the bag face in sequence by butt joint method.

[0013] Step E: Co-curing molding: After all layers are laid up, the parts are encapsulated and cured in an autoclave; wherein, an independent internal vacuum bag is pre-placed in the internal cavity of the full-height foam, and the internal vacuum bag is connected to the external vacuum bag, so that the aircraft winglet parts can be subjected to uniform force both inside and outside during the curing process.

[0014] Preferably, the method for laying the double-layer copper mesh in steps S1 and S4 is as follows: the copper mesh is laid in sections, and pre-compacted after each section is laid; and the seams between the first layer of copper mesh and the second layer of copper mesh are staggered.

[0015] Preferably, the leading edge baffle mentioned in step A is disposed in the leading edge region of the aircraft winglet, that is, the geometric transition area between the lower skin and the upper skin, and the interface between the leading edge baffle and the tooling is at an angle to prevent step difference from occurring.

[0016] Preferably, the separator described in step B is placed between two adjacent layers of prepreg, and the separator thickness is at least 0.18 mm.

[0017] Preferably, the full-height foam that has undergone heat treatment in step C is heat-treated in an autoclave or oven to dry the full-height foam.

[0018] Preferably, the full-height foam is placed in an autoclave or oven, heated from 55°C to 130°C ± 6°C at a heating rate of no more than 3°C / min and held for at least 180 min, and then cooled to below 60°C at a rate of no more than 3°C / min before being removed and dried.

[0019] Preferably, the step E, which involves placing an independent internal vacuum bag inside the cavity of the full-height foam, specifically involves placing the internal vacuum bag inside the cavity before placing the full-height foam, and the opening of the internal vacuum bag must extend beyond the full-height foam.

[0020] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0021] 1. The molding method of the present invention can manufacture irregularly shaped, high-curvature aircraft winglets that are integrally molded with double-layer copper mesh and full-height foam co-curing;

[0022] 2. This invention provides a buffer space for excess copper mesh and prepreg by conformally setting a composite material leading edge baffle in the transition area of ​​the winglet leading edge, which solves the problem of fiber wrinkles and copper mesh stress concentration and fracture caused by material accumulation in this area, and ensures the accuracy of the key aerodynamic shape.

[0023] 3. The present invention uses a method of laying double-layer copper mesh in sections, pre-pressing each section, and laying with staggered joints, which effectively eliminates wrinkles and bulges when laying large-size copper mesh, ensures the flatness and conductivity continuity of the copper mesh layer, and improves lightning protection performance and surface quality.

[0024] 4. By setting an independent internal vacuum bag inside the full-height foam, the present invention keeps the internal and external pressures of the aircraft winglet balanced during the curing process, which greatly reduces defects such as core material crushing and skin deformation caused by pressure difference, and ensures the structural stability of the full-height foam cavity. Attached Figure Description

[0025] Figure 1 A schematic diagram of the overall structure of the co-curing molding tooling for aircraft winglets provided by the present invention;

[0026] Figure 2 A layout diagram of the leading edge baffle and tooling provided for this invention;

[0027] Figure 3 A pressure diagram of the vacuum bag provided by the present invention.

[0028] The meanings of the markings in the attached diagram are as follows:

[0029] In the diagram: 1. Full-height foam; 2. Leading edge baffle; 3. Internal vacuum bag; 4. Tooling markings; 5. Tooling. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0031] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "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 limitations on this invention.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Example

[0034] This invention provides a method for co-curing and molding irregularly shaped, high-curvature composite material cavity foam sandwich structure parts. Please refer to [link / reference]. Figure 1-3 It includes the following steps:

[0035] 1. Preparation stage: Clean the tooling and ensure that the tooling markings 4 are clear. Place the full-height foam 1 into an autoclave or oven, and heat it from 55°C to 130°C ± 6°C at a rate not exceeding 3°C / min and hold for at least 180 min. Then, cool it down to below 60°C at a rate not exceeding 3°C / min and remove the full-height foam. Dry the full-height foam.

[0036] 2. Leading edge treatment: On the tooling in the leading edge transition area of ​​the winglet, a composite material leading edge baffle 2 is placed. Since the interface between the leading edge baffle 2 and the tooling 5 is at an angle, the leading edge baffle 2 is fixed to the tooling 5 using a locating pin; this can effectively prevent step difference from occurring.

[0037] 3. Laying up the molding surface: Along the tooling etched line 4, first lay the first layer of copper mesh for the molding surface. This layer of copper mesh is divided into several pieces and laid in sequence. After each piece is laid, pre-pressing is performed. Then lay the second layer of copper mesh for the molding surface, ensuring that its seam is staggered from the first layer by 20mm. Next, lay the lower skin carbon fiber prepreg, and finally lay the foam lower surface adhesive film. Fold the excess part of the lower skin prepreg onto the front edge baffle 2. And place a release film with a thickness of at least 0.18mm on each layer of prepreg to separate each layer of prepreg.

[0038] 4. Placement of full-height foam 1: Use a laser projector to project the outline of full-height foam 1 onto the layup to assist in precise positioning, and place the heated full-height foam 1 in place; place an inner vacuum bag 3 inside the cavity of full-height foam 1; and finally apply a surface adhesive film to full-height foam 1.

[0039] 5. Prepreg folding and bag surface laying: Fold back the excess lower skin prepreg folded over the front edge baffle 2 in the above steps together with the release film and lay it on the upper surface film; then, lay the skin carbon fiber prepreg; finally, lay the double-layer copper mesh on the bag surface using a segmented and staggered stitching process.

[0040] 6. Co-curing and molding: After the installation is completed, the outer vacuum bag is sealed, and the inner vacuum bag 3 of the full-height foam 1 cavity is connected to the outer vacuum bag; finally, the entire fixture 5 is sent into the autoclave and co-cured and molded according to the required curing curve.

[0041] 7. Post-demolding treatment: After curing, the part is demolded to obtain the final irregularly shaped, high-curvature aircraft winglet, which is integrally cured with double-layer copper mesh and full-height foam. Inspection revealed that the part has a precise shape, excellent internal quality, and no fiber wrinkles or copper mesh damage in the leading edge area.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for co-curing and molding irregularly shaped, high-curvature composite material cavity foam sandwich structure parts, characterized in that, The steps include the following: Step A: Setting of leading edge baffle (2): In the transition area of ​​the leading edge of the winglet, place the composite material leading edge baffle (2) according to the shape, and use positioning pins to fix the leading edge baffle (2) to the tooling (5); Step B: Laying up the molding surface: According to the tooling markings (4), lay up the double-layer copper mesh, the lower skin prepreg layer and the foam underside adhesive film in sequence; During installation, the portion of the lower skin prepreg layer that extends beyond the boundary is placed on the front edge baffle (2), and a release film is used to separate each layer of prepreg from the excess portion. Step C: Positioning and film application of full-height foam (1): Position the full-height foam (1) according to the tooling markings (4) and auxiliary projection on the tooling (5), place the heat-treated full-height foam (1), the full-height foam (1) has a cavity structure and a foam thickness of about 15mm, and then apply the film to the upper surface of the full-height foam (1). Step D: Prepreg folding and bag face laying: Fold the excess lower skin prepreg that was placed on the front edge baffle (2) in step B to the upper surface of the full height foam (1) surface film, and then lay the skin prepreg layer and the double-layer copper mesh of the bag face in sequence by butt joint method. Step E: Co-curing molding: After all the layers are laid up, the parts are encapsulated and cured in an autoclave; wherein, an independent internal vacuum bag (3) is pre-placed in the internal cavity of the full-height foam (1), and the internal vacuum bag (3) is connected to the external vacuum bag, so that the internal and external parts of the aircraft wing parts can be subjected to uniform force at the same time during the curing process.

2. The co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts according to claim 1, characterized in that, The specific method for laying the double-layer copper mesh in steps S1 and S4 is as follows: the copper mesh is laid in sections, and pre-compacted after each section is laid; and the seams between the first layer of copper mesh and the second layer of copper mesh are staggered.

3. The co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts according to claim 1, characterized in that, The leading edge baffle (2) mentioned in step A is set in the leading edge region of the aircraft winglet, that is, the geometric transition area between the lower skin and the upper skin, and the interface between the leading edge baffle (2) and the tooling (5) is at an angle to prevent step difference from occurring.

4. The co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts according to claim 1, characterized in that, The separator described in step B is placed between two adjacent layers of prepreg, and the separator thickness is at least 0.18 mm.

5. The co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts according to claim 1, characterized in that, The full-height foam (1) described in step C is heat-dried in an autoclave or oven to dry the full-height foam (1).

6. The co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts according to claim 5, characterized in that, Place the full-height foam (1) in an autoclave or oven, heat it from 55°C to 130°C ± 6°C at a heating rate of no more than 3°C / min and hold it for at least 180 min, then cool it down to below 60°C at a rate of no more than 3°C / min and remove the full-height foam (1), and dry the full-height foam (1).

7. The co-curing molding method for irregularly shaped, high-curvature composite material cavity foam sandwich structure parts according to claim 1, characterized in that, The specific operation of placing an independent internal vacuum bag (3) in the internal cavity of the full-height foam (1) in step E is as follows: before placing the full-height foam (1), the internal vacuum bag (3) is placed in the cavity, and the opening of the internal vacuum bag (3) must extend beyond the full-height foam (1).

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