Preforming method for complex crown-shaped stringers with large arch height

Abstract

This invention relates to a preforming method for cap-shaped stringers with complex, high arches. The preforming equipment can be designed in sections and includes straight section forming units and curvature section forming units. The curvature section forming units are designed with independently adjustable lifting frames. The forming method involves adjusting the height of the curvature sections to the same horizontal plane during the preforming process of a flat prepreg sheet. After heating, the curvature sections gradually descend, and the flat prepreg sheet is consistently supported by a forming mold during the conformal forming process. Preforming is then performed after the flat prepreg sheet is bonded to the forming mold, effectively avoiding quality problems such as wrinkles in cap-shaped stringer parts with complex, high arches.

Description

Technical Field

[0001] This invention relates to the field of composite material manufacturing technology, specifically to a preforming method for a large-arch, high-complex-structure hat-shaped stringer. Background Technology

[0002] Advanced resin-based composite materials possess characteristics such as lightweight, high strength, high modulus, fatigue resistance, corrosion resistance, good designability, and processability, making them ideal structural materials for aerospace applications. Currently, composite materials have become the main structural materials for the fuselage of next-generation aircraft. The large-arched, complex-configuration cap-shaped stringers of composite material fuselages are the main supporting structures, characterized by their large number and complex configuration.

[0003] Previously, stringer manufacturing relied on manual lamination and autoclave curing, which was inefficient, difficult to control fiber angles, and resulted in poor component quality stability. For the manufacture of complex, high-arched cap-shaped stringer components, automated manufacturing is necessary to meet the demands of mass production and large-scale applications. Hot molding preforming involves placing a pre-laid flat prepreg sheet in a specialized hot molding device, where it is heated, pressurized, shaped, and cooled to deform the prepreg sheet into a cap-shaped preform.

[0004] Currently, both domestically and internationally, the hot molding preforming of large-arch, high, complex-structure cap-shaped stringers requires specialized preforming molds tailored to the specific structure. The preforming of the stringer is achieved through variations in mold size and shape. Several related patents have been disclosed regarding hot molding preforming methods and molds. For example, CN110561786B describes a method for preforming by clamping and pressing a flat prepreg sheet using a mold. CN117799199A discloses a mold suitable for preforming large-arch, high, hyperbolic stringers.

[0005] However, existing technical solutions have significant drawbacks. Placing flat prepreg sheets on the mold results in some areas being suspended after placement. Heating the mold gradually softens the prepreg sheets, allowing them to conform to the mold's shape. However, for complex cap-shaped stringer parts with large curvature and high arches, wrinkles and other quality defects are easily generated during the conformation process. If curved sheet metal is used for preforming, separate tooling is required for laying the curved sheet, leading to high costs and insufficient manufacturing efficiency. Summary of the Invention

[0006] To address the aforementioned problems, the purpose of this invention is to provide a preforming method for a complex, high-arched, cap-shaped stringer. Through a segmented, adjustable preforming device, the height of the curvature segment can be adjusted and raised in segments during the preforming process using a flat prepreg sheet. After heating, the curvature segment descends, ensuring that the prepreg sheet is always supported by the forming mold during the shaping process, preventing the prepreg sheet from being suspended. Preforming is performed after the prepreg sheet is bonded to the forming mold, effectively avoiding quality problems such as wrinkles in the high-arched, complex cap-shaped stringer parts.

[0007] Therefore, according to one aspect of the present invention, a preforming method for a cap-shaped stringer with a large arch height and complex configuration is provided, comprising: Flat prepreg sheets are prepared using manual or automated placement equipment. The preforming mold is installed on the preforming equipment, wherein the preforming mold includes an upper mold for a straight section, a lower mold for a straight section, an upper mold for multiple curvature sections, and a lower mold for multiple curvature sections; Adjust the lifting devices of the lower molds of multiple curvature sections respectively to raise the lower molds of multiple curvature sections to the same horizontal height as the lower mold of the straight section; The flat prepreg sheet is transferred to the straight section lower mold and the multiple curvature section lower molds and positioned thereon. The prepreg sheet located on the straight section lower mold and the multiple curvature section lower molds is heated by the heating device of the preforming equipment; Multiple lower molds with varying curvature segments are lowered sequentially at different rates using lifting devices, creating a continuously inclined configuration for the curvature segments. The lower molds consistently support the prepreg sheet. After this continuous inclined configuration is achieved, the flat prepreg sheet gradually conforms to and follows the shape of both the straight-segment lower mold and the multiple curvature-segment lower molds. The upper mold of the straight section and the upper mold of the multiple curved sections are lowered by lifting devices for the upper mold of the straight section and the upper mold of the multiple curved sections, respectively, thereby extruding the flat prepreg sheet located on the lower mold of the straight section and the lower mold of the multiple curved sections, thus completing the preforming of the large arch height complex structure hat-shaped stringer.

[0008] According to a further preferred embodiment of the present invention, the straight section upper mold is mounted on the heating plate of the upper mold beam, the straight section lower mold is mounted on the heating plate of the lower frame, the plurality of curvature section upper molds are respectively mounted on the plurality of heating plates of the plurality of curvature section upper mold lifting devices, and the plurality of curvature section lower molds are respectively mounted on the plurality of heating plates of the plurality of curvature section lower mold lifting devices.

[0009] According to a further preferred embodiment of the present invention, the straight section upper mold, the straight section lower mold, the plurality of curvature section upper molds, and the plurality of curvature section lower molds are respectively vacuum-adsorbed onto the heating plate.

[0010] According to a further preferred embodiment of the present invention, the positioning of the flat prepreg sheet on the straight section lower mold and the plurality of curved section lower molds is achieved by the engagement of a plurality of positioning grooves located on the flat prepreg sheet with limiting blocks on the straight section lower mold and the plurality of curved section lower molds.

[0011] According to a further preferred embodiment of the present invention, the straight section upper mold lifting device is configured to enable the upper mold beam to perform vertical lifting motion via its first servo motor, reducer, synchronous shaft and lifting mechanism.

[0012] According to a further preferred embodiment of the invention, after the flat prepreg sheet is positioned on the straight section lower mold and the plurality of curved section lower molds, the support rod of the support rod device is lowered to support the top crossbeam to reduce the flexural deformation of the top crossbeam.

[0013] According to a further preferred embodiment of the present invention, the plurality of curvature segment upper mold lifting devices are configured to enable the plurality of curvature segment upper molds to perform vertical lifting movements via their second servo motor, electric cylinder and upper mold lifting frame.

[0014] According to a further preferred embodiment of the present invention, the plurality of lower mold lifting devices for the curvature segments are configured to enable the plurality of lower molds for the curvature segments to perform vertical lifting and lowering movements via their third servo motor, electric cylinder, and linear guide rail.

[0015] According to a further preferred embodiment of the present invention, when heating the plurality of lower curvature sections of the mold and the flat prepreg sheet, the plurality of lower curvature sections of the mold and the flat prepreg sheet are gradually heated to a temperature that softens the flat prepreg sheet. Attached Figure Description

[0016] 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 reference numerals in the drawings refer to the same 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.

[0017] Figure 1 This is a side view of the preforming equipment according to the present invention.

[0018] Figure 2This is a structural schematic diagram of the straight section lifting device according to the present invention.

[0019] Figure 3 This is a structural schematic diagram of the support rod device according to the present invention.

[0020] Figure 4 This is a schematic diagram of the structure of the mold lifting device on the curvature section according to the present invention.

[0021] Figure 5 This is a schematic diagram of the structure of the lower mold lifting device of the curvature section according to the present invention.

[0022] Figure 6a This is a side view of a preforming apparatus according to the present invention, wherein flat prepreg sheets are placed and positioned.

[0023] Figure 6b This is a side view of a preforming apparatus according to the present invention, wherein preheating is performed.

[0024] Figure 6c This is a side view of a preforming apparatus according to the present invention, wherein extrusion preforming is performed.

[0025] Figure 7a This is a side view of the complex, high-arched, hat-shaped stringer after it has been formed according to the present invention.

[0026] Figure 7b This is a schematic diagram of the positioning groove of the flat prepreg sheet according to the present invention. Detailed Implementation

[0027] Now, referring to the accompanying drawings, specific embodiments of the present invention will be described in detail. The embodiments described herein are merely preferred embodiments of the invention, and those skilled in the art can conceive of other ways to implement the invention based on these preferred embodiments, which also fall within the scope of the invention. In the following detailed description, directional terms such as "left," "right," "up," "down," "inner," and "outer" are used with reference to the directions described in the accompanying drawings, where "longitudinal" refers to the length direction of the aircraft. Components of embodiments of the invention can be placed in various different orientations; directional terms are for illustrative purposes and not restrictive. Specifically, "inner side" as used herein refers to a side located within the fuselage structure of the aircraft. "Outer side" as used herein refers to a side located outside the fuselage structure of the aircraft.

[0028] This invention provides a preforming method for cap-shaped stringers with complex, high arch structures. The preforming equipment is designed in sections, including straight section forming units and curved section forming units. The curved section is designed as a device with a segmented, independently lifting frame. During the preforming process using flat prepreg sheets, the height of the curved section can be adjusted and raised to the same horizontal plane in sections. After heating, the curved section gradually descends, ensuring that the sheet is always supported by the mold during the shaping process. Preforming is performed after the sheet adheres to the mold, effectively avoiding quality problems such as wrinkles in cap-shaped stringer parts with complex, high arch structures.

[0029] Figure 1 A side view of the preforming equipment according to the present invention is shown. The preforming equipment mainly includes a frame column 1, a straight section lower frame 2, an upper mold crossbeam 3, a top crossbeam 4, a straight section upper mold lifting device 5, a support rod device 6, multiple curvature section upper mold lifting devices 7, multiple curvature section upper molds 8, multiple curvature section lower mold lifting devices 9, multiple curvature section lower molds 10, a straight section upper mold 11, and a straight section lower mold 12.

[0030] In the segmented design of the preforming equipment of the present invention, the straight section upper mold lifting device 5, the straight section upper mold 11, the straight section lower mold 12, and the straight section lower frame 2 together constitute a straight section forming unit, while multiple curvature section upper mold lifting devices 7 and multiple curvature section upper molds 8, multiple curvature section lower mold lifting devices 9, and multiple curvature section lower molds 10 respectively constitute multiple curvature section forming units.

[0031] Based on the structural characteristics of the large arch height complex configuration hat-shaped stringer, the preforming device has straight section forming units and curvature section forming units. Each unit is a segmented design of 1m / segment. Each segment of the curvature section forming unit can be raised and lowered by an electric cylinder driven by a servo motor to achieve different height adjustments.

[0032] like Figure 1 As shown, the straight section upper mold 11 is installed on the upper mold beam 3, the straight section lower mold 12 is installed on the straight section lower frame 2, the multiple curvature section upper molds 8 are respectively installed on the multiple curvature section upper mold lifting devices 7, in particular on the heating plate 704 of the multiple curvature section upper mold lifting devices 7, and the multiple curvature section lower molds 10 are respectively installed on the multiple curvature section lower mold lifting devices 9, in particular on the heating plate 905 of the multiple curvature section lower mold lifting devices 9.

[0033] Further as Figure 1 As shown, the frame columns 1 located on both sides of the preforming equipment of the present invention support the top crossbeam 4 and serve as a guide for the upper mold crossbeam 3 in the vertical direction, ensuring the support strength of the overall frame.

[0034] like Figure 2As shown, the straight section upper mold lifting device 5 includes a first servo motor 501, a reducer 502, a synchronous shaft 503, and a lifting machine 504, so that the upper mold beam 3 and the straight section upper mold 11 installed on the upper mold beam 3 can be lifted and lowered together in the vertical direction.

[0035] like Figure 3 As shown, the support rod device 6 includes a cylinder 601 and a support rod 602. The support rod 602 can be pushed in the vertical direction so that the middle section of the top crossbeam 4 can be supported, thereby reducing the deflection deformation of the top crossbeam 4.

[0036] like Figure 4 As shown, the multiple curvature segment mold lifting devices 7 are driven by the second servo motor 701 and the electric cylinder 702 respectively, and have an upper heating plate 704 at the bottom. In addition, the multiple curvature segment molds 8 can be fixed to the upper heating plate 704 by vacuum adsorption, so that the multiple curvature segment molds 8 can be lifted and lowered in the vertical direction.

[0037] like Figure 5 As shown, the multiple curvature segment lower mold lifting devices 9 are driven by a third servo motor 901 and an electric cylinder 902, guided by a linear guide rail 904, and have a lower heating plate 905 on top. In addition, the multiple curvature segment lower molds 10 can be fixed to the lower heating plate 905 by vacuum adsorption, so that the curvature segment lower molds 10 can be lifted and lowered in the vertical direction.

[0038] Similarly, the upper mold 11 and the lower mold 12 of the straight section can also be vacuum-adsorbed onto their respective heating plates.

[0039] The following is for reference. Figures 6a-6c The present invention describes a method for preforming cap-shaped stringers with complex, high arch configurations, comprising: Flat prepreg sheets are prepared using manual or automated placement equipment. The preforming mold is installed on the preforming equipment, wherein the preforming mold includes an upper mold for a straight section, a lower mold for a straight section, an upper mold for multiple curvature sections, and a lower mold for multiple curvature sections; Adjust the lifting devices of the lower molds in multiple curvature sections respectively to raise the lower molds in multiple curvature sections to the same horizontal height as the lower mold in the straight section; The flat prepreg sheet is transferred to the straight section lower mold and multiple curvature section lower molds and positioned. The prepreg sheet located on the straight section lower mold and multiple curvature section lower molds is heated by the heating device of the preforming equipment; Multiple lower molds of different curvature sections are lowered sequentially at different rates using lifting devices, creating a continuously inclined configuration. The lower molds consistently support the prepreg sheet. After this continuous inclined configuration, the flat prepreg sheet gradually conforms to the straight section lower mold and the multiple lower curvature sections, following their shape. The straight section upper mold and the multiple upper curvature sections are then lowered by lifting devices, compressing the flat prepreg sheet on top of the straight section lower mold and the multiple lower curvature sections, thus completing the preforming of the complex, high-arch, cap-shaped stringer.

[0040] Specifically, such as Figure 6a As shown, before the preforming equipment of this invention is put into operation, the flat prepreg sheet is laid out by manual / automatic laying equipment to complete the preparation of the flat prepreg sheet. Next, the straight section upper mold lifting device 5 is connected to the reducer 502 through the first servo motor 501 and driven by the synchronous shaft 503 to lift the upper mold beam 3 and the straight section upper mold 11 together to a certain height. The curvature section upper mold lifting device 7 and the curvature section lower mold lifting device 9 are driven by the electric cylinders 702 and 902 through the second servo motor 701 and the third servo motor 901 respectively to the designated position. Then, the molds 8 and 10 are installed manually or by a robotic arm. The molds are installed in sections onto the heating plate 905 of the straight section lower frame 2 and the curvature section lower mold lifting device 9 platform. The upper mold beam 3 is lowered into place. After the device is fixedly connected to the upper mold 8, the upper mold beam 3 is lifted to a certain height. The installation of the molds into the preforming device is completed. In particular, the straight section upper mold 11 is installed on the upper mold beam 3, the straight section lower mold 12 is installed on the straight section lower frame 2, the multiple curvature section upper molds 8 are respectively installed on the multiple curvature section upper mold lifting devices 7, especially on the heating plate 704 of the multiple curvature section upper mold lifting devices 7, and the multiple curvature section lower molds 10 are respectively installed on the multiple curvature section lower mold lifting devices 9, especially on the heating plate 905 of the multiple curvature section lower mold lifting devices 9.

[0041] Before the flat prepreg sheet is placed, the lifting device 9 of the multiple curvature section lower molds is raised, raising the multiple curvature section lower molds 10 to the same horizontal height as the straight section lower mold 12, such as Figure 6a As shown.

[0042] Furthermore, such as Figure 6b As shown, after the support rod device 6 lifts the support rod 602, the flat prepreg sheet is transferred by manual labor or a transfer robot to the upper part of the straight section lower mold 12 and the multiple curvature section lower molds 10 for positioning.

[0043] Figure 7aThe side view of the large arch height complex configuration hat-shaped truss 21 after its formation is shown.

[0044] Figure 7b A plan view of the flat prepreg sheet 22 before molding is shown. The flat prepreg sheet 22 includes a main positioning groove 23 located at the junction of the straight section and the curved section, a positioning groove 24 located in the middle of the straight section, a straight section end positioning groove 25 located at the end of the straight section, and a curved section end positioning groove 26 located at the end of the curved section. These positioning grooves can engage with corresponding limiting blocks (not shown) on the straight section lower mold 12 and multiple curved section lower molds 10. The positioning grooves 23, 24, 25, and 26 on the flat prepreg sheet 22 are positioned on the straight section lower mold 12 and the curved section lower mold 10 as follows: Figure 7b As shown, unlike traditional positioning methods, the allowance areas on both sides of the straight section end serve as the main positioning, working in conjunction with the positioning grooves in the middle and end allowance areas of the straight section to achieve precise positioning and limiting of the flat prepreg sheet within the straight section. Since the curvature section needs to change during heating, no limiting is applied when the flat prepreg sheet is placed initially. The curvature section end mold limiting block is then installed after heating and shaping.

[0045] Subsequently, the support rod 602 of the support rod device 6 descends, and the support rod 602 supports the top crossbeam 4, thereby completing the placement of the flat prepreg sheet.

[0046] After the flat prepreg sheet is placed, the curvature segment forming unit with a 1m interval in the curvature segment provides effective support for the flat prepreg sheet, thus eliminating the problem of the sheet being suspended in the air as in previous technical solutions.

[0047] After the flat prepreg sheet is placed and positioned, the preforming mold is heated, gradually heating both the mold and the prepreg sheet to a temperature that softens the sheet, such as 50°C. Then, the lower mold lifting device 9 descends, with each section individually controllable and the descent rate set proportionally to ensure the flat prepreg sheet bends smoothly downwards. The final state is as follows. Figure 6b As shown. At this time, the sheet gradually conforms to the molding mold, and hot molding preforming can be carried out to preheat the flat prepreg sheet to the specified temperature. That is, through the lifting device 9 of multiple curvature segments of the lower mold, multiple curvature segment lower molds 10 are lowered in sequence to form a continuously inclined configuration. At this time, the flat prepreg sheet gradually conforms to the straight segment lower mold 12 and the multiple curvature segment lower molds 10 and conforms to them.

[0048] Subsequently, as Figure 6cAs shown, the intermediate crossbeam 3 descends to a designated height, clamping the flat prepreg sheet through the gap between the upper mold 8 and the lower mold 10 of the curvature section. Pressure is applied downwards along the vertical direction to the middle of the flat prepreg sheet for a certain distance before stopping, and heat preservation continues. Specifically, the upper mold 11 of the straight section and the upper molds 8 of multiple curvature sections are lowered by the lifting device 5 of the straight section and the lifting devices 7 of multiple curvature sections, thereby compressing the flat prepreg sheet located on the lower mold 12 of the straight section and the lower molds 10 of multiple curvature sections. After heat preservation, the molds are cooled, the intermediate crossbeam 3 is raised to a certain height, the support rod device 6 opens the support rod, and the preform is removed manually or by a transfer robot, thus completing the preforming of the large-arch, complex-structured hat-shaped stringer.

[0049] The advantages of this invention are: Compared with existing technologies, this invention solves the problem of wrinkling defects that easily occur when preforming complex, high-arched, hat-shaped stringers from flat prepreg sheets. The curvature section can be raised to the same horizontal level for placing the sheet, and the curvature section is gradually lowered after the sheet is heated, allowing the sheet to slowly conform to the shape. While solving the quality problem, the solution effectively avoids the use of complex molds, reducing mold costs. Simultaneously, it boasts high heating efficiency and a fast forming process, reducing energy consumption and manufacturing costs.

[0050] The above description of various embodiments of the present invention is provided for illustrative purposes to a person of ordinary skill in the art. It is not intended to exclude or limit the invention to a single disclosed embodiment. As described above, those of ordinary skill in the art will understand various alternatives and variations of the invention. Therefore, although some alternative embodiments have been specifically described, those of ordinary skill 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 preforming method for a cap-shaped stringer with a large arch height and complex configuration, comprising: Flat prepreg sheets are prepared using manual or automated placement equipment. The preforming mold is installed on the preforming equipment, wherein the preforming mold includes an upper mold for a straight section, a lower mold for a straight section, an upper mold for multiple curvature sections, and a lower mold for multiple curvature sections; Adjust the lifting devices of the lower molds of multiple curvature sections respectively to raise the lower molds of multiple curvature sections to the same horizontal height as the lower mold of the straight section; The flat prepreg sheet is transferred to the straight section lower mold and the multiple curvature section lower molds and positioned thereon. The prepreg sheet located on the straight section lower mold and the multiple curvature section lower molds is heated by the heating device of the preforming equipment; Multiple lower molds with varying curvature segments are lowered sequentially at different rates using lifting devices, creating a continuously inclined configuration for the curvature segments. The lower molds consistently support the prepreg sheet. After the continuous inclined configuration is achieved, the flat prepreg sheet gradually conforms to and follows the shape of both the straight-segment lower mold and the multiple curvature-segment lower molds. The upper mold of the straight section and the upper mold of the multiple curved sections are lowered by lifting devices for the upper mold of the straight section and the upper mold of the multiple curved sections, respectively, to compress the flat prepreg sheet located on the lower mold of the straight section and the lower mold of the multiple curved sections, thereby completing the preforming of the large arch height complex structure hat-shaped stringer.

2. The preforming method according to claim 1, wherein, The upper mold of the straight section is installed on the heating plate of the upper mold beam of the preforming equipment, the lower mold of the straight section is installed on the heating plate of the lower frame of the straight section of the preforming equipment, the upper molds of the multiple curvature sections are respectively installed on the multiple heating plates of the upper mold lifting device of the multiple curvature sections, and the lower molds of the multiple curvature sections are respectively installed on the multiple heating plates of the lower mold lifting device of the multiple curvature sections.

3. The preforming method according to claim 2, wherein, The upper mold of the straight section, the lower mold of the straight section, the upper molds of the plurality of curvature sections, and the lower molds of the plurality of curvature sections are respectively vacuum-adsorbed onto the heating plate.

4. The preforming method according to claim 1, wherein, The positioning of the flat prepreg sheet on the straight section lower mold and the plurality of curved section lower molds is achieved by the engagement of a plurality of positioning grooves on the flat prepreg sheet with limiting blocks on the straight section lower mold and the plurality of curved section lower molds.

5. The preforming method according to claim 2, wherein, The straight section upper mold lifting device is configured to enable the upper mold beam to perform vertical lifting motion via a first servo motor, a reducer, a synchronous shaft, and a lifting machine.

6. The preforming method according to claim 1, wherein, After the flat prepreg sheet is positioned on the straight section lower mold and the plurality of curved section lower molds, the support rods of the support rod assembly are lowered to support the top crossbeam in order to reduce the flexural deformation of the top crossbeam.

7. The preforming method according to claim 1, wherein, The upper mold lifting device of the multiple curvature segments is configured to enable the upper mold of the multiple curvature segments to perform vertical lifting and lowering movements through the second servo motor, electric cylinder and upper mold lifting frame.

8. The preforming method according to claim 1, wherein, The multiple curvature segment lower mold lifting device is configured to enable the multiple curvature segment lower molds to perform vertical lifting and lowering movements via a third servo motor, electric cylinder, and linear guide rail.

9. The preforming method according to claim 1, wherein, When heating the multiple curvature sections of the lower mold and the flat prepreg sheet, the multiple curvature sections of the lower mold and the flat prepreg sheet are gradually heated to a temperature that softens the flat prepreg sheet.

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