Molding method for curved frame member of aircraft made of thermoplastic composite material

Abstract

The invention provides a forming method for a curved frame component of an aircraft made of a thermoplastic composite material, which comprises the following steps: S1, based on a mathematical model of the curved frame component, laying the thermoplastic composite material through an automatic fiber laying process to form a preformed body flat plate; s2, the preformed body flat plate is cut to the preformed body size required by mold pressing along the laid positioning tows; and S3, the preformed body flat plate is subjected to mold pressing through a hot mold pressing process to form the curved frame component in a preset shape. According to the scheme, the thermoplastic composite material preform flat plate is prepared by adopting an automatic fiber placement process, so that automatic and accurate positioning of fibers can be realized, and interlayer bonding stability can be realized through high-energy laser heating. In addition, the material sheets can be accurately positioned through the hot mold pressing process, and therefore rapid mold pressing forming of parts with complex characteristics is achieved.

Description

Technical Field

[0001] This invention relates to the field of automated manufacturing of composite material parts, and more particularly to a molding method for curved frame components of aircraft made of thermoplastic composite materials. Background Technology

[0002] Continuous carbon fiber reinforced thermoplastic resin matrix composites possess advantages such as wear resistance, corrosion resistance, good impact resistance, long shelf life at room temperature, short molding time, and recyclability. Currently, thermoplastic composites are mainly used in aircraft flooring, corner plates, leading edges, and beam ribs.

[0003] Aircraft fuselage panel structures typically employ cap-shaped stringer-reinforced panels connected to curved frames. The curved frame structure is complex, and preforms of thermoplastic composite parts are usually fabricated using a manual lay-up method. Manual lay-up requires ultrasonic spot welding to achieve interlayer bonding and is suitable for lay-ups at fixed angles such as 0°, ±45°, and 90°. However, the spot welding density affects the interlayer positioning accuracy, potentially leading to uncontrollable interlayer slippage during sheet bending, causing fiber angle deviations. Furthermore, manual lay-up cannot achieve precise control of the curve.

[0004] Therefore, there is a need to provide a molding method for curved frame components of aircraft made of thermoplastic composite materials, in order to at least partially solve the above-mentioned problems. Summary of the Invention

[0005] The molding method for curved frame components of aircraft made of thermoplastic composite materials proposed in this invention includes the following steps:

[0006] S1. Based on the digital model of the curved frame component, the thermoplastic composite material is laid using an automated wire laying process to form a preformed flat plate;

[0007] S2. Cut the preform plate along the laid positioning wire bundle to the preform size required for molding; and

[0008] S3. The preformed flat plate is molded into a curved frame component with a predetermined shape by hot molding process.

[0009] Preferably, step S1 includes: laying multiple thermoplastic composite material layups layer by layer on an automatic filament placement die, wherein the multiple thermoplastic composite material layups include curved layups and / or fixed angle layups.

[0010] Preferably, the fixed angle ply includes 0° ply, 90° ply, and ±45° ply.

[0011] Preferably, the curved frame component includes an arc-shaped web, and the forming method further includes:

[0012] The web midline is set as a reference curve, and multiple parallel curve laying trajectories are generated based on the reference curve; and

[0013] The thermoplastic composite material is laid along the multiple parallel curved layup paths to form the curved layup.

[0014] Preferably, for the curved layup, the thermoplastic composite material is laid out in a segmented curved manner.

[0015] Preferably, step S2 further includes: laying four positioning wire bundles on the preform plate as positioning references, and cutting the preform plate to the preform size along the positioning wire bundles, wherein the four positioning wire bundles are arranged perpendicular to each other.

[0016] Preferably, the molding method further includes: after performing hot molding, using a part drawing tool to draw a cutting line on the surface of the curved frame component as a cutting reference, and performing edge trimming on the curved frame component along the cutting line.

[0017] Preferably, the forming method further includes: based on the digital model of the curved frame component, using wire layup design software to unfold the model to obtain the net dimensions of the preformed flat plate of the curved frame component;

[0018] Based on the net dimensions, the size of the transition zone at the edge of the sheet, the hot molding process allowance, and the machining allowance are considered to estimate the first layer laying dimensions.

[0019] Preferably, the size of the edge transition zone is related to the thickness of the single-layer material and / or the number of layups.

[0020] Preferably, the size of the first layer is larger than the size of the subsequent layers.

[0021] Preferably, step S3 includes: preheating the preform plate using an infrared heating device to accelerate the softening of the preform plate.

[0022] Preferably, thermocouples are provided in the upper and lower molds of the hot molding tooling, and step S3 further includes: controlling the heating power of the hot press in response to the temperature detected by the thermocouples.

[0023] Preferably, the surface of the automatic filament placement mold is covered with a high-temperature resistant film, and the high-temperature resistant film is tightly adhered to the surface of the automatic filament placement mold by vacuuming.

[0024] Preferably, the mold surfaces of the upper and lower molds of the hot molding tooling are provided with a high-temperature resistant release agent.

[0025] Preferably, the cross-sectional shape of the curved frame component is L-shaped, C-shaped, or Z-shaped.

[0026] Preferably, the thermoplastic composite material is a continuous carbon fiber reinforced thermoplastic resin matrix composite material.

[0027] The molding method described above has the following technical advantages:

[0028] (1) The molding method uses automatic fiber placement technology to prepare preformed flat plates, which can realize the placement of fibers at fixed angles and curved fibers. It has the advantages of strong fiber direction designability and high control precision. In addition, this scheme can solve the problem that manual placement cannot achieve curve control and meet the fiber direction requirements of curved frame web.

[0029] (2) The thermoplastic composite material is laid out using an automatic fiber placement technology that combines high-energy laser heating with high pressure, which makes the interlayer bonding of the sheet stable. As a result, the preformed sheet is not easy to slip between layers when it is bent.

[0030] (3) Special tooling for hot molding can be designed based on the specific structure of the part to be molded, and the hot molding process can achieve fiber direction control and part thickness control. In addition, hot molding technology can realize the manufacturing of complex structural parts such as curved frames, solving the problem of difficult molding of complex structures such as Z-shaped curved frames.

[0031] (4) The segmented curve layup in the curve layup can solve the wrinkles and warping problems caused by the small turning radius of the curve layup of complex parts. Attached Figure Description

[0032] To better understand the above and other objects, features, advantages, and functions of the present invention, reference can be made to the preferred embodiments shown in the accompanying drawings. The same or similar reference numerals in the drawings refer to the same or similar parts. Those skilled in the art should understand that the drawings are intended to schematically illustrate preferred embodiments of the invention and do not limit the scope of the invention in any way; the parts in the drawings are not drawn to scale.

[0033] Figure 1 This is a schematic diagram of a curved frame component according to a preferred embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of determining the layup boundary in a molding method according to a preferred embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the laying trajectory of multiple parallel curves in a molding method according to a preferred embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of laying positioning filament bundles on a preform plate in a molding method according to a preferred embodiment of the present invention.

[0037] Figure 5 This is a flowchart of the automatic filament placement process in a molding method according to a preferred embodiment of the present invention.

[0038] Figure 6 A flowchart of the hot molding process in a molding method according to a preferred embodiment of the present invention.

[0039] Figure 7 This is a flowchart of a molding method for a curved frame component for an aircraft according to a preferred embodiment of the present invention. Detailed Implementation

[0040] The molding method according to a preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the following description is merely a preferred embodiment of the present invention, and those skilled in the art can conceive of other ways to implement the present invention based on the preferred embodiments; such other ways also fall within the scope of the present invention.

[0041] First, it should be noted that the directional and positional terms used in this invention should be understood as relative directions and positions, rather than absolute directions and positions.

[0042] The following will refer to Figures 1 to 7 A method for molding a curved frame component according to a preferred embodiment of the present invention will be described in detail. The curved frame component is used in aircraft, primarily in the panel structure of the aircraft fuselage. The curved frame component can have a predetermined shape, for example, its cross-section can be L-shaped, C-shaped, Z-shaped, etc., and is made of thermoplastic composite material, preferably a continuous carbon fiber reinforced thermoplastic resin-based composite material. Figure 1 In the exemplary embodiment shown, the cross-section of the curved frame member 100 is approximately Z-shaped and includes a web 110 and flanges 120 located on both sides of the web, both of which are arc-shaped.

[0043] This invention proposes a molding method combining automated wire placement and hot molding processes for curved frame components of aircraft with complex structures, specifically including the following steps:

[0044] S1. Based on the digital model of the curved frame component, the thermoplastic composite material is laid up using an automated fiber placement process to form a preformed flat plate. In this step, according to the structure of the curved frame component and the layup requirements of its product, a digital model of the component is used. Based on this digital model, multiple layers of thermoplastic composite material are laid up layer by layer on an automated fiber placement mold using laser heating automated fiber placement technology to obtain a preformed flat plate.

[0045] Preferably, in step S1, the automatic fiber placement can design trajectories in layers and regions. A preformed flat plate can simultaneously have fixed-angle layups and curved layups. That is, during placement, the fiber direction can be designed to include both fixed-angle and curved directions, with the fixed-angle direction being a linear direction, thereby meeting the diverse fiber direction requirements of complex curved frame parts. For curved layups, the bending direction and curvature of the curve are consistent with the bending direction and curvature of the centerline of the curved web of the curved frame component. In actual manufacturing, the web centerline can be set as a reference curve using fiber placement programming software, and multiple parallel curved placement trajectories (such as...) can be generated based on this reference curve. Figure 3 (As shown), thermoplastic composite materials are laid along multiple parallel curved layup paths to form curved layups. Fixed angle layups can include 0° layups, 90° layups, and ±45° layups.

[0046] The programming software allows for setting parameters such as layup reference points, fiber bundle gaps, fiber initiation direction, pressure, and heating methods. The generated program then lays up the fiber sheet, enabling better control over the fiber placement process. By employing automated fiber placement technology, fiber orientation can be accurately controlled, and curved layups and fixed-angle layups can be placed as needed, thereby enhancing the design flexibility of the layup.

[0047] In actual manufacturing, when fibers are laid along a curved path, the inner turning radius of the fibers is smaller than the outer turning radius. This causes the outer fibers to be under tension, which may result in curling and lifting, while the inner fibers are compressed, potentially forming wrinkles. The smaller the turning radius, the more severe the wrinkles and warping defects. To avoid these issues affecting the layup implementation, it is preferable to use segmented curved layup for curved layers to ensure both the layup effect and feasibility.

[0048] Since bonding thermoplastic composite materials to automatic fiber placement molds is difficult, a high-temperature resistant film can preferably be laid on the mold surface as a base layer. For example, a vacuum method can be used to ensure that the high-temperature resistant film adheres tightly to the mold surface, thereby preventing wrinkles from forming on the high-pressure layup.

[0049] In a preferred embodiment, such as Figure 2 and Figure 5 As shown, the forming method further includes step S0 before step S1: Based on the digital model of the curved frame component, the net dimensions of the preformed flat plate of the curved frame component are obtained by unfolding the model using wire layup design software; based on the net dimensions, considering the size of the transition zone at the edge of the sheet layup, the hot molding process allowance, and the machining allowance, the first layer layup size is estimated, and the layup boundary is determined. For details, please refer to... Figure 2In other words, the layup boundary is determined based on the net dimensions of the preform plate plus allowances for the molding, machining, and edge transition areas. The allowances for the hot molding and machining areas are estimated based on the larger area to meet process quality requirements. The edge transition area is designed to address the issue of accumulated layup edge thickness forming stepped surfaces, which is detrimental to layup edge quality control. In a preferred embodiment, the size of the edge transition area is related to the single-layer material thickness and the number of layups. The thicker the single-layer material or the greater the number of layups, the larger the size of the edge transition area.

[0050] After the layup boundary is determined, the thermoplastic composite material is laid according to the layup boundary in step S1, and the actual size of the resulting preform plate is larger than the net size. Preferably, the size of the first layer of thermoplastic composite material is larger than the size of the subsequent layers of thermoplastic composite material.

[0051] If local reinforcement is considered in the assembly area, a layer-dropping design can be introduced. The selection of reference points must ensure precise control of the layer-dropping position. Based on the minimum wire feeding length requirement of the equipment, the sequence of the starting ends of the wire bundles should be adjusted to leave excess wire bundles outside the net dimension area.

[0052] S2. Cut the preform plate along the laid positioning wire bundle to the preform size required for molding.

[0053] Positioning wire bundles 130 are laid on the preform plate as positioning references, and the preform plate is precisely cut to the preform size along the positioning wire bundles 130. For example... Figure 4 As shown, four positioning wire bundles 130 can be used, and the four positioning wire bundles 130 can be laid perpendicularly in pairs on the surface of the preform plate. Then, ultrasonic cutting can be used to cut the preform plate along the positioning wire bundles 130 to the preform size required for hot molding.

[0054] S3. The preformed flat plate is molded into a curved frame component with a predetermined shape by hot molding process.

[0055] In this step, a special tooling for hot molding of the part can be designed according to the actual shape of the curved frame component. This solution enables precise positioning of the sheet metal and the tooling, and rapid molding of the part is achieved through the closing of the upper and lower molds. For complex parts such as curved frames, the hot molding tooling can consider functions such as forming surface placement, sheet metal positioning, and part thickness control, thereby facilitating the control of the hot molding deformation process of the part. Preferably, a high-temperature resistant release agent can be applied to the surfaces of the upper and lower molds of the hot molding tooling that contact the sheet metal to facilitate demolding of the molded part.

[0056] Since thermoplastic composite resins have a high softening temperature, it is preferable to use a heating device such as an infrared lamp to preheat the sheet so that the sheet softens quickly during the molding process.

[0057] During the hot pressing process, the lower mold can be placed in the designated position on the hot press, and the upper mold can be connected to the upper table of the hot press to ensure alignment of the upper and lower molds and facilitate rapid mold closing. Then, the heating rate of the hot press can be set according to actual needs to raise the temperature of the mold forming surface. Once the surface temperature of the mold forming surface reaches the required level, automated equipment quickly moves the preform plate to the predetermined position on the lower mold. Infrared lamps are used to preheat the preform plate as needed; once the plate reaches the resin softening temperature, the infrared lamp preheating function is turned off. The upper mold moves downward with the hot press, completing the hot molding mold closing. After the mold closes, the hot press slowly applies pressure through the upper mold, and the preform flat plate bends along the forming surface of the mold until the specified pressure is reached. When the temperature rises to the curing temperature, heat preservation and pressure holding begin for a certain period of time. While maintaining the pressure, cooling begins at a certain rate. Once the temperature has cooled below the resin softening temperature, pressure is released. When the mold temperature drops to about 60°C or below, the mold is removed from the hot press as a whole. After the mold temperature drops to room temperature, the upper mold is removed, allowing the part to be demolded.

[0058] In a preferred embodiment, thermocouples are pre-embedded in the upper and lower molds of the hot molding tooling. Preferably, the heating power of the hot press can be controlled in response to the temperature detected by the thermocouples, thereby enabling precise control of the heating rate, holding temperature, cooling rate, etc.

[0059] Preferably, the bending and deformation process of the sheet material during the hot molding process of the curved frame component can be simulated and analyzed in advance to obtain the correspondence between the flat sheet material and each area of ​​the curved frame component, down to the change of fiber angle of each layer of fiber during the bending process. This is beneficial for the design of the sheet material layup direction and the control of the fiber direction of the part after the sheet material is molded.

[0060] After hot molding, a part drawing tool can be used to draw cutting lines on the surface of the curved frame component as a cutting reference. The curved frame component can be cut manually or by using a CNC machine tool to trim the edges along the cutting lines. In this way, a curved frame component of the desired shape can be obtained.

[0061] This molding method utilizes automated fiber placement technology to prepare preformed flat sheets, enabling the placement of fibers at fixed angles and curved fibers. It offers advantages such as high design flexibility in fiber orientation and high control precision. Furthermore, this method solves the problem of uncontrollable curves in manual fiber placement, meeting the fiber orientation requirements of curved frame webs. In addition, the automated fiber placement technology, combining high-energy laser heating and high pressure, lays up thermoplastic composite materials, resulting in stable interlayer bonding. This prevents interlayer slippage during bending of the preformed sheet. Moreover, hot molding technology enables the manufacture of complex structural parts such as curved frames, solving the problem of difficult molding of complex structures like Z-shaped curved frames.

[0062] The above description of various embodiments of the present invention is provided for illustrative purposes to a person skilled in the art. It is not intended to limit the invention to a single disclosed embodiment. As taught above, those skilled in the art will understand various alternatives and variations of the invention. Therefore, although some alternative embodiments have been specifically described, those skilled in the art will understand or relatively easily develop other embodiments. The present invention is intended to include all alternatives, modifications, and variations of the invention described herein, as well as other embodiments falling within the spirit and scope of the invention described above.

Claims

1. A molding method for a curved frame component of an aircraft made of thermoplastic composite material, comprising the following steps: S1. Based on the digital model of the curved frame component, the thermoplastic composite material is laid using an automated wire laying process to form a preformed flat plate; S2. Cut the preform plate along the laid positioning wire bundle to the preform size required for molding; as well as S3. The preformed flat plate is molded into a curved frame component with a predetermined shape by hot molding process.

2. The molding method according to claim 1, characterized in that, Step S1 includes: laying multiple thermoplastic composite material layups layer by layer on an automatic filament laying die, wherein the multiple thermoplastic composite material layups include curved layups and / or fixed angle layups.

3. The molding method according to claim 2, characterized in that, The fixed angle ply includes 0° ply, 90° ply, and ±45° ply.

4. The molding method according to claim 2, characterized in that, The curved frame component includes an arc-shaped web, and the forming method further includes: The web midline is set as a reference curve, and multiple parallel curve laying trajectories are generated based on the reference curve; and The thermoplastic composite material is laid along the multiple parallel curved layup paths to form the curved layup.

5. The molding method according to claim 4, characterized in that, For the aforementioned curved layup, the thermoplastic composite material is laid out using a segmented curved layup method.

6. The molding method according to claim 1, characterized in that, Step S2 further includes: laying four positioning wire bundles on the preform plate as positioning references, and cutting the preform plate to the preform size along the positioning wire bundles, wherein the four positioning wire bundles are arranged perpendicular to each other.

7. The molding method according to claim 1, characterized in that, The molding method further includes: after performing hot molding, using a part drawing tool to draw a cutting line on the surface of the curved frame component as a cutting reference, and performing edge trimming on the curved frame component along the cutting line.

8. The molding method according to claim 1, characterized in that, The forming method further includes: based on the digital model of the curved frame component, using wire layup design software to unfold the model to obtain the net dimensions of the preformed flat plate of the curved frame component; Based on the net dimensions, the size of the transition zone at the edge of the sheet, the hot molding process allowance, and the machining allowance are considered to estimate the first layer laying dimensions.

9. The molding method according to claim 8, characterized in that, The size of the edge transition zone is related to the thickness of the single-layer material and / or the number of layups.

10. The molding method according to claim 8, characterized in that, The dimensions of the first layer are larger than those of the subsequent layers.

11. The molding method according to claim 1, characterized in that, Step S3 includes: preheating the preform plate using an infrared heating device to accelerate the softening of the preform plate.

12. The molding method according to claim 1, characterized in that, The upper and lower molds of the hot molding tooling are equipped with thermocouples. Step S3 further includes controlling the heating power of the hot press in response to the temperature detected by the thermocouples.

13. The molding method according to claim 2, characterized in that, The surface of the automatic filament placement mold is covered with a high-temperature resistant film, and the high-temperature resistant film is tightly adhered to the surface of the automatic filament placement mold by vacuuming.

14. The molding method according to claim 1, characterized in that, The surfaces of the upper and lower molds of the hot molding tooling are coated with a high-temperature resistant release agent.

15. The molding method according to claim 1, characterized in that, The cross-sectional shape of the curved frame component is L-shaped, C-shaped, or Z-shaped.

16. The molding method according to claim 1, characterized in that, The thermoplastic composite material is a continuous carbon fiber reinforced thermoplastic resin-based composite material.

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