A method for forming a square tubular torsion type composite structural member

Abstract

The application discloses a forming method of a square-cylinder torsion type composite material structural member and relates to the technical field of composite material forming. The method comprises the following steps: S1, tooling pretreatment; S2, composite material forming; and S3, demolding forming. Through the combined split tooling and the sequential centripetal collapse demolding mode, the forming method solves the problems of the large curvature change of the square-cylinder torsion type structural member and the demolding difficulty, uses the putty to fill the joints to ensure the smooth continuity of the forming surface, ensures the good quality of the inner surface of the part, has the simple process flow and the strong operability, and reduces the manufacturing cost.

Description

Technical Field

[0001] This invention relates to the field of composite material molding technology, specifically a molding method for a square-tube torsion composite material structural component. Background Technology

[0002] Resin-based composite materials, due to their lightweight, high strength, and excellent designability, can maintain structural integrity and performance stability in a variety of complex shapes. They have been widely used in aerospace, rail transportation, and high-performance structural components. In particular, in aerospace cylindrical structural components, the use of composite molding can not only achieve significant structural weight reduction, but also meet the service requirements under complex load conditions through layup optimization.

[0003] However, existing technologies still have process problems such as easy wrinkling, bridging, and difficulty in demolding when manufacturing cylindrical parts with complex molding structures and large curvature changes. In order to improve product quality and production efficiency, and reduce demolding difficulty and production cost, this invention provides a molding method for square cylindrical torsion composite material structural parts, which realizes convenient demolding of square cylindrical torsion composite material structural parts, while taking into account efficiency and cost. Summary of the Invention

[0004] The purpose of this invention is to provide a molding method for a square-tube torsion composite material structure to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for molding a square-tube torsion composite material structural component, comprising the following steps:

[0006] S1. Tooling pretreatment: Before use, the segmented tooling needs to be assembled and fixed into a forming tooling. After assembly, the surface of the forming tooling is coated with putty to fill the gaps in the mold until the surface is flat and continuous. Then the forming tooling is cured. After curing, the forming tooling is cleaned with acetone.

[0007] S2. Composite molding: The material sheets are laid on the cleaned molding fixture. For areas with large curvature changes, the material sheets are cut and segmented before laying. During the laying process, pre-compacting is performed every 1-2 layers. Each layer is checked to avoid wrinkles and bridging. After all the material sheets are laid, release film, breathable felt, and vacuum bag are placed in sequence for sealing and vacuuming. The sealed parts are then sent to an autoclave for curing and molding.

[0008] S3. Demolding and molding: After the part has cured, remove the surface vacuum bag, breathable felt and isolation film in sequence. Then remove the No. 1 segment tooling first. The tooling collapses inward. Remove the No. 1 segment tooling from the small end to the large end. Then remove the No. 2 and No. 3 segment tooling in sequence. They collapse inward respectively. Finally, remove the No. 4 segment tooling. After all the tooling is completely removed, a complete square cylindrical torsion composite material structure is obtained.

[0009] As a preferred technical solution, the molding fixture in step S1 is a combined male mold fixture, composed of segmented fixtures. These segmented fixtures are designated as segmented fixture No. 1, segmented fixture No. 2, segmented fixture No. 3, and segmented fixture No. 4. The segmented fixtures are fastened together using pins and bolts. Furthermore, the parting surfaces of the segmented fixtures are designed with bevels to ensure that the segmented fixtures do not interfere with each other, allowing them to move towards the center and successfully complete demolding.

[0010] As a preferred technical solution, the curing in step S1 is to cure at room temperature for 12h~24h or to cure in an oven at 80℃~100℃ for 1~2h to ensure that the inner surface of the molded part is smooth.

[0011] As a preferred technical solution, the pre-compaction parameters in step S2 are: vacuum degree ≥ -90 kPa, time ≥ 15 min.

[0012] As a preferred technical solution, the leak test vacuum after encapsulation in step S2 is -80kpa to -95kpa; the curing pressure of the autoclave is 300kpa to 600kpa, the curing temperature is 120℃ to 180℃, and the heat preservation time is 90min to 180min.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] 1. This invention adopts a positive mold forming method, in which the inner surface of the part is in direct contact with the forming surface of the tooling. After curing, the inner surface is smooth and flat, requiring no secondary trimming. At the same time, the positive mold tooling has a modular segmented structure, which has good openness of the laying operation surface, higher operability, improved production efficiency, reduced operation difficulty and dependence on the skill level of the operator.

[0015] 2. This invention addresses the characteristics of large curvature variations and complex torsion angles in square-shaped torsion structural components. During the laying of the material sheets, slits and block treatments are performed in areas with large curvature variations. This effectively releases local stress concentrations generated during the laying process, avoids wrinkles and bridging defects caused by fiber bending and accumulation, effectively improves the product quality of variable curvature and flanged positions, and ensures that the shape, contour, thickness, and key dimensions of the parts are controllable, meeting the overall high-strength design requirements.

[0016] 3. This invention addresses the problem of limited demolding space and difficulty in demolding of cylindrical torsion-type structural parts. It designs segmented fixtures (numbers 1 to 4) that collapse and demold sequentially in a specific order. This demolding method allows each segmented fixture to automatically retract inward after the fasteners are removed, disengaging from the inner wall of the part and creating a demolding gap. This allows for smooth extraction from the part's cavity with minimal operating force. Compared to forced demolding with integral fixtures or destructive demolding, this invention effectively avoids scratches and delamination on the inner surface of the part, significantly improving the demolding success rate and product qualification rate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the forming tooling in this invention.

[0018] The meanings of the markings in the diagram are as follows: 1, No. 1 petal splitting fixture; 2, No. 2 petal splitting fixture; 3, No. 3 petal splitting fixture; 4, No. 4 petal splitting fixture. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1

[0021] This embodiment provides a molding method for a square-tube torsion composite material structural component, specifically including the following steps:

[0022] S1. Tooling pretreatment: Before use, the No. 1 segmented tooling, No. 2 segmented tooling, No. 3 segmented tooling, and No. 4 segmented tooling need to be combined and fixed together with pins and fastening bolts to form a molding tooling. In this embodiment, the parting surface is an inclined surface. After the combination is completed, putty is applied to the surface of the molding tooling to fill the gaps in the mold joint until the surface of the tooling is flat and continuous. Then, the molding tooling is cured in an oven at 80°C for 2 hours. After curing, the molding tooling is cleaned with acetone.

[0023] S2. Composite Molding: Carbon fiber prepreg is laid on the cleaned molding fixture. For areas with large curvature changes, the carbon fiber prepreg is cut and segmented. The cutting and segmentation are determined according to the Fibersim software design. After the design is completed, the fabric cutting machine will automatically cut according to the drawings and then lay the prepreg. In this embodiment, a total of 20 layers are laid. During the laying process, pre-compaction is performed every other layer. The pre-compression vacuum degree is -100kPa and the time is 20min. Each layer is checked during laying to avoid wrinkles and bridging. After all the sheets are laid, the release film, breathable felt, and vacuum bag are placed in sequence for sealing and vacuuming. The leak test vacuum is -90kPa. The sealed parts are sent to the autoclave for curing at a curing pressure of 600kPa, a curing temperature of 150℃, and a holding time of 120min.

[0024] S3. Demolding and Molding: After the part has cured, remove the surface vacuum bag, breathable felt and isolation film in sequence. Then remove No. 1 segmentation tooling 1 first. At this time, No. 2 segmentation tooling 2, No. 3 segmentation tooling 3 and No. 4 segmentation tooling 4 are not removed. The molding tooling collapses inward. After No. 1 segmentation tooling 1 is removed from the small end to the large end, No. 2 segmentation tooling 2 and No. 3 segmentation tooling 3 are removed in sequence. They collapse inward respectively. When removing No. 2 segmentation tooling 2 and No. 3 segmentation tooling 3, care should be taken to prevent the part from being bumped. Finally, No. 4 segmentation tooling 4 is removed. After all the tooling is completely removed, a complete square cylindrical torsion composite material structure is obtained.

[0025] The square-tube torsion composite material structural parts obtained by this method have a smooth and flat inner surface after curing, requiring no secondary trimming. They can be demolded in one go without damaging the parts. To address the problems of limited demolding space and difficult demolding in existing technologies, we designed segmented tooling No. 1 to No. 4 and demolded them in a specific order, which overcomes the forced demolding or destructive demolding of existing integral tooling. This effectively avoids damage such as scratches and delamination on the inner surface of the parts, and significantly improves the demolding success rate and product qualification rate.

[0026] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for molding a square-tube-shaped torsion composite material structural component, characterized in that, Includes the following steps: S1. Tooling pretreatment: Before use, the segmented tooling needs to be assembled and fixed into a forming tooling by fasteners. After assembly, the surface of the forming tooling is coated with putty to fill the gaps in the mold until the surface is flat and continuous. Then the forming tooling is cured. After curing, the forming tooling is cleaned with acetone. S2. Composite molding: The material sheets are laid on the cleaned molding fixture. For areas with large curvature changes, the material sheets are cut and segmented before laying. During the laying process, pre-compacting is performed every 1-2 layers. Each layer is checked to avoid wrinkles and bridging. After all the material sheets are laid, release film, breathable felt, and vacuum bag are placed in sequence for sealing and vacuuming. The sealed parts are then sent to the autoclave for curing. S3. Demolding and molding: After the part has cured, remove the surface vacuum bag, breathable felt and isolation film in sequence. Then, remove the fixing parts on No. 1 segment tooling. The tooling collapses inward. After No. 1 segment tooling is removed from the small end to the large end, remove No. 2 and No. 3 segment tooling in sequence. They collapse inward respectively. Finally, remove No. 4 segment tooling. After all the tooling is completely removed, a complete square cylindrical torsion composite material structure is obtained.

2. The molding method for a square-tube torsion composite material structural component according to claim 1, characterized in that, The molding fixture mentioned in step S1 is a combined male mold fixture, which is composed of segmented fixtures. The segmented fixtures are divided into segmented fixture No. 1, segmented fixture No. 2, segmented fixture No. 3 and segmented fixture No.

4. The fixing parts when the segmented fixtures are combined are pins and fastening bolts.

3. The molding method for a square-tube torsion composite material structural component according to claim 1, characterized in that, The curing process described in step S1 is either room temperature curing for 12-24 hours or oven curing at 80-100°C for 1-2 hours to ensure a smooth inner surface of the molded part.

4. The molding method for a square-tube torsion composite material structural component according to claim 1, characterized in that, The pre-compaction parameters in step S2 are: vacuum degree ≥ -90 kPa, time ≥ 15 min.

5. The molding method for a square-tube torsion composite material structural component according to claim 1, characterized in that, The leak test vacuum after encapsulation in step S2 is -80kpa to -95kpa; the curing pressure of the autoclave is 300kpa to 600kpa, the curing temperature is 120℃ to 180℃, and the holding time is 90min to 180min.

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