Double curvature carbon fiber composite sandwich structure and method of forming same

Abstract

The application provides a double-curvature carbon fiber composite sandwich structure and a forming method thereof, and belongs to the field of carrying fairings. The composite structure described adopts a von Karman curve shape, and the forming method comprises the following steps: manufacturing a fairing negative mold; performing honeycomb shaping on the surface of the negative mold; and manufacturing a double-curvature carbon fiber composite fairing on the surface of the negative mold. The carbon fiber composite fairing is obtained through a co-curing forming method of an outer skin, a film, a honeycomb core material and an inner skin; through a process of precise layering design and temperature control curing, the integrated forming of the complex curved sandwich structure is realized, the forming precision, the apparent quality and the overall mechanical properties of the structure are significantly improved while the optimal shape of the structure is ensured, and the problems of structure deformation and layering difficulty are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of molding technology for composite material structural components, specifically relating to a double-curvature carbon fiber composite sandwich structure and its molding method. Background Technology

[0002] As a key aerodynamic protective structure of launch vehicles, satellite fairings primarily maintain the overall aerodynamic shape during flight, isolating the rocket from harsh environments such as aerodynamic heating and atmospheric thermal erosion, thus ensuring the safety and stability of high-precision components within the cabin. Currently, existing fairings mainly fall into two categories: metal riveted structures and resin-based composite materials. In recent years, with the iterative development of launch vehicles towards lightweight and high-performance designs, advanced resin-based composite materials, with their strong design capabilities and excellent specific strength and modulus, have gradually replaced traditional metal materials.

[0003] Patent document CN120620694A discloses a method and apparatus for integral molding of a large-size composite material fairing. The method includes the following steps: Step S1: Manufacturing a fairing molding mold; Step S2: Cutting pre-impregnated honeycomb and laying it sequentially on the mold surface for curing and shaping; Step S3: Processing the height of some of the shaped honeycomb; Step S4: Laying an outer skin on the mold surface and attaching a layer of adhesive film to the surface; Step S5: Laying the shaped honeycomb sequentially onto the surface of the outer skin; Step S6: Laying an inner skin on the surface of the already laid honeycomb core material.

[0004] However, technical challenges remain in the actual fabrication of composite fairings: on the one hand, to adapt to the load-bearing hyperbolic curved surface structure, the fiber angle changes continuously circumferentially during the non-woven fabric layup, making the fibers prone to twisting; on the other hand, the non-woven fabric needs to be cut or spliced, which disrupts fiber continuity and leads to a decrease in the mechanical properties of the composite material. If the layup wrinkles are eliminated by forcibly stretching the non-woven fabric, excessive pretension will be generated in the fibers, causing residual internal stress accumulation during curing, resulting in warping deformation of the structural components, which is detrimental to ensuring the dimensional accuracy and internal quality of the components. Therefore, developing a large-size variable curvature honeycomb sandwich molding method and determining the feasibility of large-size variable curvature surface non-woven fabric layup have significant theoretical and practical implications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a double-curvature carbon fiber composite sandwich structure and its molding method.

[0006] A method for molding a double-curvature carbon fiber composite sandwich structure according to the present invention includes: Step S1: Manufacture a mold for a double-curvature composite material cover. The mold is used for shaping the honeycomb core material and forming the double-curvature carbon fiber composite material cover. Step S2: Use process layup software for simulation design, and coordinate with laser positioning layup system and tooling mold to position the layup parting line; Step S3: Based on the positioning of the layup parting line, lay the outer skin on the mold surface. The layup process is performed with pre-compression as required. After the outer skin is laid up, apply a layer of adhesive film to the surface. Step S4: Place the honeycomb on the outer film for shaping, and lay it out in sequence after shaping as the core material of the composite material cover. Then, lay another layer of film on the inner surface of the honeycomb core material.

[0007] Step S5: Continue to lay the inner skin on the surface of the already laid honeycomb core material using a laser positioning and layering system. During the layering process, perform a pre-compression operation every 2 to 3 layers. After the layering is completed, cure it using co-curing molding technology.

[0008] Preferably, non-woven fabric is used as the reinforcing material, aluminum honeycomb is used as the core material, and a co-curing method is used to achieve integrated molding of complex curved sandwich structures.

[0009] Preferably, the mold adopts a single female mold structure, and the surface is formed by segmented rolling or pressing of steel plate, followed by welding, CNC milling and fine polishing to ensure a smooth aerodynamic surface after the fairing is formed; the mold as a whole is a thin-walled reinforced structure to ensure uniform temperature field during the curing process.

[0010] Preferably, in step S2: The layup reference for the double curvature composite material cover product is 0° circumferential direction at the large end of the product and 90° azimuth direction. The process layup software uses the angle between the large end of the mold in the circumferential direction and the center of the single prepreg fiber tape as the reference, and the principle of accurate fiber layup angle without twisting and fiber continuity as the basis to simulate and design the angle layup parting line. For non-large end positions, the angle between the center line of the hyperbolic surface and the center of the single prepreg fiber strip is used as a reference. The principle is to ensure that the fiber laying angle is accurate and not twisted, and that the fibers are continuous. The angle layup parting line is simulated and designed, and the prepreg is laid sequentially according to the generated projection program.

[0011] Preferably, step S2 includes: Step S2.1: Use process layup software to simulate and design the layup parting line, and generate projection program file and fabric cutting program file; Step S2.2: Input the projection program file into the laser positioning layup system; Step S2.3: Use a laser positioning layup system to locate the layup position on the surface of the tooling mold.

[0012] Preferably, in step S2: With the large end of the hyperbolic profile as the 0° direction and the heading as the 90° direction, the 0° layup is based on the angle between the circumferential direction of the large end of the mold and the center of the single prepreg fiber strip of 90±2°. The principle is to ensure accurate fiber laying angle without twisting and fiber continuity. The width is set at 180~230mm, while taking into account the prepreg utilization rate of ≥80%. The 0° layup parting line is designed using process layup software simulation.

[0013] Preferably, in step S2: Outside the large end of the mold, the angle between the center line of the mold surface and the center of the single prepreg fiber strip is 60±2° as the benchmark. The fiber is straight and continuous, and the width is set at 300~330mm. At the same time, the prepreg utilization rate is ≥80%. The process layup software simulation design + 60° layup parting line is used. The +60° layup is designed with the principle of accurate fiber layup angle without twisting and fiber continuity. The +60° layup parting line is designed using process layup software simulation. The reference is that the angle between the circumferential direction of the large end of the mold and the center of the fiber strip of a single prepreg is 60±2°. The principle is that the fibers are straight and continuous. The width is set at 300~330mm, while taking into account the prepreg utilization rate ≥80%. The +60° layup parting line is designed using process layup software simulation. For -60° layup, while ensuring the above-mentioned +60° parting principle, the -60° layup parting line is designed using process layup software simulation.

[0014] Preferably, in step S3: For double curvature surfaces, lay the +60°, -60°, and 0° layers. Based on the +60°, -60°, and 0° layer parting lines, align the edges of the prepreg with the projection lines to ensure that the product laying angle deviation is ≤1°. Start laying the layers from the middle part of the prepreg and compact them symmetrically to both sides.

[0015] Preferably, in step S4: The cut-out aluminum honeycomb segments are sequentially spliced ​​and placed on the negative mold surface. Because the segmented honeycomb core material has a small curvature, it matches the shape of the fairing after shaping, which can reduce the phenomenon of honeycomb collapse during the molding process of sandwich structure components.

[0016] In step S5: The sandwich structure was placed in an autoclave for curing. The curing parameters were: heating from room temperature to 150℃ at a heating rate of 0.3~1℃ / min, holding at 150±5℃ for 240min, maximum cooling rate of 1℃ / min, and pressure of 0.1~0.3MPa.

[0017] According to the present invention, a double-curvature carbon fiber composite sandwich structure is prepared by the molding method of the double-curvature carbon fiber composite sandwich structure.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention effectively eliminates problems such as fiber wrinkling, bridging, and resin enrichment caused by significant fiber angle deflection due to changes in surface curvature. By precisely positioning the layup reference and controlling fiber orientation, it significantly improves layup processability. It enhances the molding accuracy of double-curvature sandwich structures, reduces structural deformation, and ensures effective transfer of interlayer loads.

[0019] 2. This invention employs a carbon fiber aluminum honeycomb integrated molding scheme, combined with co-curing molding technology. This significantly improves manufacturing efficiency and reduces production costs while ensuring structural strength and rigidity. Furthermore, the molded structural components exhibit clear carbon fiber texture, consistent gloss, good overall appearance consistency, and stable molding quality. This provides a viable solution for molding large-size double-curvature carbon fiber sandwich structure fairings. Attached Figure Description

[0020] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a hyperbolic carbon fiber composite structure. Figure 2 This is a cross-sectional view of a hyperbolic carbon fiber composite structural component. Figure 3 A female mold for a double-curvature carbon fiber composite material cover; Figure 4 A schematic diagram of a 0° layup method for a double-curvature surface of a structural component, simulated using software for process layup; Figure 5 A schematic diagram of the layup method for the double curvature surface of the structural component with a +60° large end region, simulated by the software for the process layup; Figure 6 A schematic diagram of the layup method for the double curvature surface of the structural component with a +60° non-large end area, as simulated by the software.

[0021] The diagram shows: Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0023] To address the shortcomings of existing technologies, the present invention aims to provide a double-curvature carbon fiber composite sandwich structure and its molding method. By optimizing the layup design and molding process, problems such as fiber continuity damage, curing internal stress, and difficulties in co-curing molding are overcome, achieving a synergistic improvement in lightweight and high performance.

[0024] This invention belongs to the field of vehicle fairings. The described composite material structural component adopts a von Kármán curve shape, and the molding method includes: manufacturing a fairing die; performing honeycomb shaping on the die surface; and manufacturing a double-curvature carbon fiber composite material fairing on the die surface. The carbon fiber composite material fairing is obtained by co-curing molding of an outer skin, a film, a honeycomb core material, and an inner skin; through a process combining precise layup design and temperature-controlled curing, the integrated molding of complex curved sandwich structures is achieved. While ensuring the optimal shape of the structural component, the molding accuracy, appearance quality, and overall mechanical properties of the structural component are significantly improved, effectively solving the problems of structural deformation and layup difficulties.

[0025] The present invention will now be described in more detail.

[0026] This embodiment provides a double-curvature carbon fiber sandwich structure, which is manufactured using a molding and preparation method for double-curvature carbon fiber composite sandwich structures. A schematic diagram of the structure can be found in the attached diagram. Figure 1 , Figure 2 .

[0027] A method for molding and preparing a double-curvature carbon fiber composite sandwich structure according to the present invention includes the following steps: Step 1: Manufacture a double-curvature composite material cover female mold. The mold is used for shaping the honeycomb core material and forming the composite material cover. The mold is made of Q235 steel, and its surface is manufactured through welding, CNC milling, and precision polishing to ensure a smooth aerodynamic surface after the fairing is formed. The mold as a whole has a thin-walled and reinforced structure to ensure a uniform temperature field during the curing process.

[0028] Step 2: For composite material structural components, the circumferential direction of the large end of the product is 0°, and the heading direction is 90°. Using the process layup software, with a 60±2° angle between the circumferential direction and the center of the single prepreg fiber strip at the large end of the mold as the reference, and a width of 300~330mm set, while ensuring a prepreg utilization rate of ≥80%, simulate and design +60° and -60° layup parting lines. At non-large end positions, with a 60±2° angle between the center line of the mold surface and the center of the single prepreg fiber strip as the reference, and a width of 300~330mm set, while ensuring a prepreg utilization rate of ≥80%, simulate and design +60° and -60° layup parting lines. With a 90±2° angle between the circumferential direction and the center of the single prepreg fiber strip at the large end as the reference, and a width of 180~230mm set, while ensuring a prepreg utilization rate of ≥80%, simulate and design a 0° layup parting line. Generate inner and outer skin projection program files and fabric cutting program files respectively. Input the projection program files into the laser positioning layup system. The fabric width is set at 300-330mm. This is to improve the prepreg cutting and utilization rate. On the other hand, if the width is too large, fiber twisting and deformation will occur in the simulation design. Step 3: Based on the laser positioning layup system, locate the outer skin's +60° / 0° / -60° / -60° / 0° / +60° layup parting positions on the tooling mold surface and lay the prepreg sequentially, ensuring the edges of each prepreg piece are aligned with the projected lines. After each layer is laid, compact the prepreg to ensure a smooth and conforming surface. Perform a pre-compression operation every 2-3 layers. After laying the outer skin, apply a layer of adhesive film to the surface; splicing of the adhesive film is permitted. Step 4: Place the honeycomb core on the outer film for shaping. After shaping, lay them out sequentially as the core material of the composite material cover. Then, lay another layer of film on the inner surface of the honeycomb core. Arrange the cut and segmented aluminum honeycomb pieces sequentially on the hyperboloid surface. Because the segmented honeycomb core has a small curvature, it matches the shape of the fairing after shaping, which can reduce the phenomenon of honeycomb collapse during the molding of sandwich structure components.

[0029] Step 5: Lay the aluminum honeycomb on the surface of the outer skin, and apply a layer of adhesive film to the inner surface of the honeycomb core material; Step 6: Lay the inner skin on the aluminum honeycomb surface, performing a pre-compression operation every 2-3 layers. Using a laser-guided layup system, lay the +60° / 0° / -60° / -60° / 0° / +60° prepreg sequentially. The layup sequence of the inner and outer skins exhibits mirror symmetry, which maximizes the optimal performance of the sandwich structure. After the inner skin is laid, lay a breathable material and create a vacuum bag. Place the sandwich structure in an autoclave for curing.

[0030] Step 7: Remove the autoclave, dismantle the positioning fixtures and auxiliary layers in sequence, demold the structural components, and obtain the double-curvature carbon fiber composite sandwich structure cover.

[0031] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "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 application 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 application.

[0032] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for forming a double-curvature carbon fiber composite sandwich structure, characterized in that, include: Step S1: Manufacture a mold for a double-curvature composite material cover. The mold is used for shaping the honeycomb core material and forming the double-curvature carbon fiber composite material cover. Step S2: Use process layup software for simulation design, and coordinate with laser positioning layup system and tooling mold to position the layup parting line; Step S3: Based on the positioning of the layup parting line, lay the outer skin on the mold surface. The layup process is performed with pre-compression as required. After the outer skin is laid up, apply a layer of adhesive film to the surface. Step S4: Place the honeycomb on the outer film for shaping, and lay it out in sequence after shaping as the core material of the composite material cover. Then, lay another layer of film on the inner surface of the honeycomb core material. Step S5: Continue to lay the inner skin on the surface of the already laid honeycomb core material using a laser positioning and layering system. During the layering process, perform a pre-compression operation every 2 to 3 layers. After the layering is completed, cure it using co-curing molding technology.

2. The molding method of the double-curvature carbon fiber composite sandwich structure according to claim 1, characterized in that, Using non-woven fabric as the reinforcing material and aluminum honeycomb as the core material, combined with a co-curing method, an integrated molding of complex curved sandwich structures is achieved.

3. The molding method for the double-curvature carbon fiber composite sandwich structure according to claim 1, characterized in that, The mold adopts a single female mold structure. The surface is formed by rolling or pressing steel plates in sections, and then welded, CNC milled and polished. The mold as a whole is a thin-walled and reinforced structure.

4. The molding method of the hyperbolic carbon fiber composite sandwich structure according to claim 1, characterized in that, In step S2: The layup reference for the double curvature composite material cover product is 0° circumferential direction at the large end of the product and 90° azimuth direction. The process layup software uses the angle between the large end of the mold in the circumferential direction and the center of the single prepreg fiber tape as the reference, and the principle of accurate fiber layup angle without twisting and fiber continuity as the basis to simulate and design the angle layup parting line. For non-large end positions, the angle between the center line of the hyperbolic surface and the center of the single prepreg fiber strip is used as a reference. The principle is to ensure that the fiber laying angle is accurate and not twisted, and that the fibers are continuous. The angle layup parting line is simulated and designed, and the prepreg is laid sequentially according to the generated projection program.

5. The molding method for the double-curvature carbon fiber composite sandwich structure according to claim 1, characterized in that, Step S2 includes: Step S2.1: Use process layup software to simulate and design the layup parting line, and generate projection program file and fabric cutting program file; Step S2.2: Input the projection program file into the laser positioning layup system; Step S2.3: Use a laser positioning layup system to locate the layup position on the surface of the tooling mold.

6. The molding method of the double-curvature carbon fiber composite sandwich structure according to claim 4, characterized in that, In step S2: With the large end of the hyperbolic profile as the 0° direction and the heading as the 90° direction, the 0° layup is based on the angle between the circumferential direction of the large end of the mold and the center of the single prepreg fiber strip of 90±2°. The principle is to ensure accurate fiber laying angle without twisting and fiber continuity. The width is set at 180~230mm, while taking into account the prepreg utilization rate of ≥80%. The 0° layup parting line is designed using process layup software simulation.

7. The molding method of the double-curvature carbon fiber composite sandwich structure according to claim 4, characterized in that, In step S2: Outside the large end of the mold, the angle between the center line of the mold surface and the center of the single prepreg fiber strip is 60±2° as the benchmark. The fiber is straight and continuous, and the width is set at 300~330mm. At the same time, the prepreg utilization rate is ≥80%. The process layup software simulation design + 60° layup parting line is used. The +60° layup is designed using process layup software simulation to simulate and design the +60° layup parting line, based on the principles of accurate fiber layup angle without twisting and fiber continuity. Based on a 60±2° angle between the circumferential direction of the large end of the mold and the center of the fiber strip of a single prepreg, and with the principle of straight and continuous fibers, the width is set at 300~330mm, while taking into account the prepreg utilization rate of ≥80%, and using process layup software simulation design + 60° layup parting line. For -60° layup, while ensuring the above-mentioned +60° parting principle, the -60° layup parting line is designed using process layup software simulation.

8. The molding method of the double-curvature carbon fiber composite sandwich structure according to claim 4, characterized in that, In step S3: For double curvature surfaces, lay the +60°, -60°, and 0° layers. Based on the +60°, -60°, and 0° layer parting lines, align the edges of the prepreg with the projection lines to ensure that the product laying angle deviation is ≤1°. Start laying the layers from the middle part of the prepreg and compact them symmetrically to both sides.

9. The molding method of the double-curvature carbon fiber composite sandwich structure according to claim 1, characterized in that, In step S4: The cut and segmented aluminum honeycomb pieces are sequentially assembled and placed on the negative model surface; In step S5: The sandwich structure was placed in an autoclave for curing. The curing parameters were: heating from room temperature to 150℃ at a heating rate of 0.3~1℃ / min, holding at 150±5℃ for 240min, maximum cooling rate of 1℃ / min, and pressure of 0.1~0.3MPa.

10. A double-curvature carbon fiber composite sandwich structure, characterized in that, The structure was prepared using the molding method of any one of claims 1 to 9 for a double-curvature carbon fiber composite sandwich structure.

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