A molding process for large-thickness torsion composite pipes with variable cross-section

Abstract

This invention discloses a molding process for variable cross-section, large thickness, torsional composite material pipe fittings. The key technical points are as follows: Step 1: Manufacturing a metal liner using a metal 3D printer, manufacturing in segments and then welding them together as a whole; Step 2: Material preparation: Preparing the required main and auxiliary materials before production and confirming the equipment status; Step 3: Tooling preparation: Cleaning and treating the mold surface to bring it to a usable state; The molding mold includes a mold body and three inserts, the dimensions of which correspond to the state after the metal liner is covered with 3mm, 6mm, and 9mm prepreg, respectively; The laying area in the middle of the three inserts is consistent with the surface of the part after the part is covered with 3mm, 6mm, and 9mm prepreg, respectively; Step 4: CNC blanking: Blanking according to the part's layup design; This invention solves the problem that traditional winding molding and pultrusion molding processes cannot mold variable cross-section, large thickness, torsional composite material pipe fittings.

Description

Technical Field

[0001] This invention relates to the field of pipe fitting processing, and in particular to a forming process for variable cross-section, large thickness torsional composite material pipe fittings. Background Technology

[0002] Carbon fiber, due to its excellent properties such as high specific strength and high specific modulus, is widely used in lightweight design and manufacturing processes. For simple, linear, non-torsional tubes with a uniform cross-section, processes such as filament winding and pultrusion can be used. However, for complex composite tubes with variable cross-sections, large thicknesses, and torsion, conventional composite molding processes are difficult to achieve.

[0003] Defects and shortcomings of existing technology:

[0004] The main challenges in forming composite pipe fittings with variable cross-section torsion are:

[0005] 1. The core mold inside the pipe cannot be extracted after forming. Due to this limitation, the forming of carbon fiber composite pipe variable cross-section pipes requires a better forming process.

[0006] 2. Thick composite materials cannot be laid solidly in one go, resulting in gaps between layers. After curing, the surface of the composite material may wrinkle or bend and deform.

[0007] 3. For composite parts with twisted shapes, internal stress exists during the curing process, which leads to twisting deformation of the parts after curing. Summary of the Invention

[0008] In view of the problems mentioned in the background art, the purpose of this invention is to provide a forming process for variable cross-section, large thickness torsional composite material pipes to solve the problems mentioned in the background art.

[0009] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0010] A forming process for a variable cross-section, large-thickness torsion composite material tube includes the following steps:

[0011] Step 1: Use a metal 3D printer to manufacture the metal lining, manufacture it in sections and then weld them together into a whole;

[0012] Step 2, Material Preparation: Prepare the main and auxiliary materials required before production, and confirm the equipment status;

[0013] Step 3, Tooling Preparation: Clean and treat the surface of the mold to bring it to a usable state; the forming mold includes the mold body and 3 inserts, the dimensions of the 3 inserts respectively correspond to the state after the metal liner is covered with 3mm, 6mm and 9mm prepreg; the laying area in the middle of the 3 inserts is consistent with the surface of the part after the part is covered with 3mm, 6mm and 9mm prepreg respectively.

[0014] Step 4, CNC blanking: Blank the part according to the layup design;

[0015] Step 5: Lay 3mm prepreg on the metal lining in the layup order. Lay the first layer and vacuum pre-extract for 5-10 minutes. Then, complete the layup of the fabric sheets in sequence according to the layup coordinate system and layup angle requirements. Vacuum pre-extract once every 4-5 layers. Control the layup angle. The deviation of the prepreg fabric should not exceed ±5°, and the deviation of the unidirectional prepreg should not exceed ±3°. Press the layup in the R-corner area firmly. If necessary, press it firmly with an electric iron.

[0016] Step 6, Bag making: Vacuum bag sealing components;

[0017] Step 7, Curing: At least two thermocouples are evenly distributed on the mold to monitor the curing temperature. The temperature is slowly increased according to the curing regime requirements, and the curing pressure is 0.3MPa-0.6MPa.

[0018] Step 8, Demolding and Post-processing: After curing, demold and check the surface of the parts for defects such as wrinkles and dents. Use sandpaper or pneumatic grinding tools to grind the surface of the parts, but do not damage the carbon fiber.

[0019] Step 9: Apply a layer of adhesive film to the surface of the part. If there is obvious deformation on the surface of the part, a local reinforcement layer can be applied as appropriate until the surface of the part is flat.

[0020] Step 10: Remove the insert corresponding to the 3mm prepreg-thick composite carbon tube laid in the metal liner and replace it with the insert corresponding to the 6mm thick composite carbon tube.

[0021] Step 11: Repeat steps 5 to 9 to complete the laying, curing, demolding and post-treatment of 6mm prepreg composite carbon tubes for metal lining;

[0022] Step 12: Remove the insert corresponding to the 6mm prepreg composite carbon tube laid in the metal liner and replace it with the insert corresponding to the 9mm thick composite carbon tube.

[0023] Step 13: Repeat steps 5 to 9 to complete the laying, curing, demolding and post-treatment of 9mm prepreg composite carbon tubes for metal lining;

[0024] Step 14: Machin the parts according to the drawings;

[0025] Step 15: Conduct quality inspection on composite pipe fittings in accordance with manufacturing and acceptance technical requirements.

[0026] Preferably, the mold treatment in step 3 includes sealing agent treatment and release agent treatment.

[0027] Preferably, after step 14, the composite material pipe is composed of a metal liner and a carbon fiber composite pipe, with a pipe length of 1000mm and a wall thickness of 10mm; the metal liner is made of aerospace aluminum alloy or titanium alloy with a wall thickness of 1mm; the carbon fiber composite pipe has a thickness of 9mm and is formed by laying and curing epoxy resin carbon fiber fabric prepreg or unidirectional tape prepreg according to the design.

[0028] Preferably, in step 3, the forming mold body includes a first bolt hole, a first positioning pin hole, a weight reduction hole, and a bag-making area necessary for the forming process.

[0029] Preferably, in step 3, the three inserts are provided with a second bolt hole and a second positioning pin hole.

[0030] Preferably, in step 5, if the material size is insufficient, overlap or butt joints shall be made according to design requirements, and the overlap distance between adjacent plies shall not be less than 25mm.

[0031] In summary, the present invention has the following main beneficial effects:

[0032] 1. This invention proposes a molding process for carbon fiber composite tubes with variable cross-section and large thickness torsion structure, solving the problem that traditional winding molding and pultrusion molding processes cannot form variable cross-section torsion composite tubes;

[0033] 2. For thick carbon fiber composite pipes, a step-by-step laying and curing method is adopted to solve the problem of insufficient curing pressure in composite parts, which may lead to defects such as delamination and wrinkles, caused by sequential laying and curing.

[0034] 3. Different sized inserts are designed for carbon fiber composite pipes that are cured in stages. The inserts and the mold body are easy to replace, reducing mold costs and making them easy to operate.

[0035] 4. The inserts play a supporting and shaping role in the curing process of carbon fiber composite materials, avoiding the problem of deformation of composite parts due to internal stress during the curing process. Attached Figure Description

[0036] Figure 1 This is a diagram of a variable cross-section, large-thickness torsional composite material pipe fitting;

[0037] Figure 2 This is a diagram of the metal lining of a variable cross-section, large-thickness torsion composite pipe fitting;

[0038] Figure 3 This is a drawing of the molding die body;

[0039] Figure 4 This is a schematic diagram of the inlay;

[0040] Figure 5 This is a schematic diagram of a variable cross-section, large-thickness torsional composite material pipe structure;

[0041] Figure 6 yes Figure 5 Enlarged view of point A;

[0042] Figure 7 yes Figure 5 Enlarged view of point B.

[0043] Reference numerals: 1. Metal liner; 2. Carbon fiber composite tube; 31. First bolt hole; 32. First locating pin hole; 41. Second bolt hole; 42. Second locating pin hole. Detailed Implementation

[0044] 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.

[0045] refer to Figures 1-7 A typical structure of a variable cross-section, large thickness torsion composite material pipe fitting is as follows: Figure 1 As shown, it consists of a metal liner 1 and a carbon fiber composite tube 2. The tube is approximately 1000 mm long and has a wall thickness of approximately 10 mm.

[0046] The metal liner 1 is made of aerospace-grade aluminum alloy or titanium alloy. The wall thickness is approximately 1 mm, and the structural form is as follows: Figure 1 As shown;

[0047] The carbon fiber composite tube 2 is approximately 9mm thick. It is formed by laying and curing epoxy resin carbon fiber fabric prepreg or unidirectional tape prepreg according to the design.

[0048] refer to Figures 1-6 The specific implementation plan is as follows:

[0049] Step 1: Use a metal 3D printer to manufacture the metal liner 1. Since the size of the part exceeds the processing range of a conventional 3D printer, it can be manufactured in sections and then welded into a whole.

[0050] Step 2, Material Preparation: Prepare the main and auxiliary materials required before production, and confirm the equipment status.

[0051] Step 3, Tooling preparation: Clean and treat the surface of the mold (using sealing agent and release agent) to bring the mold to a usable state.

[0052] The forming mold includes a mold body and three inserts, with the insert sizes corresponding to the metal lining 1 being laid in 3mm, 6mm, and 9mm states, respectively.

[0053] The molding die body includes a first bolt hole 31, a first positioning pin hole 32, a weight reduction hole, and a bag-making area necessary for the molding process.

[0054] A typical schematic diagram of a patch structure is shown below. Figure 4 As shown, the inserts are provided with a second bolt hole 41 and a second locating pin hole 42. The padding areas in the middle of the three inserts are consistent with the surfaces of the parts after being padded with 3mm, 6mm, and 9mm of prepreg, respectively.

[0055] Step 4, CNC blanking: Blank the part according to the layup design.

[0056] Step 5: As Figure 5 As shown, lay 3mm prepreg on the metal lining 1 according to the layup sequence. Apply the first layer and vacuum pre-extract for 5-10 minutes, then complete the layup sequentially according to the layup coordinate system and layup angle requirements. Vacuum pre-extract every 4-5 layers. Control the layup angle; the prepreg deviation should not exceed ±5°, and the unidirectional prepreg deviation should not exceed ±3°. Compact the layup in the radius (R-angle) area, pressing it firmly with an iron if necessary. If the material size is insufficient, overlap or butt joint according to design requirements; the overlap distance between adjacent layups should not be less than 25mm.

[0057] Step 6, Bag Making: Vacuum bag sealing component, bag making diagram as shown. Figure 6 As shown;

[0058] Step 7: Evenly distribute at least two thermocouples on the mold to monitor the curing temperature. Slowly increase the temperature and cure according to the curing regime requirements. The curing pressure is 0.3MPa-0.6MPa.

[0059] Step 8: Demolding and Post-processing. Demold after curing. Inspect the surface of the part for defects such as wrinkles and dents. Use sandpaper or pneumatic sanding tools to sand the surface of the part, but be careful not to damage the carbon fiber.

[0060] Step 9: Apply a layer of adhesive film to the surface of the part. If there is obvious deformation on the surface of the part, a local reinforcement layer can be applied until the surface of the part is flat.

[0061] Step 10: Remove the insert corresponding to the 3mm thick composite carbon nanotube and replace it with the insert corresponding to the 6mm thick composite carbon nanotube.

[0062] Step 11: Repeat steps 5 to 9 to complete the laying, curing, demolding and post-processing of the 6mm thick composite carbon nanotube.

[0063] Step 12: Remove the insert corresponding to the 6mm thick composite carbon nanotube and replace it with the insert corresponding to the 9mm thick composite carbon nanotube.

[0064] Step 13: Repeat steps 5 to 9 to complete the laying, curing, demolding and post-processing of the 9mm thick composite carbon tube.

[0065] Step 14: Machin the parts according to the drawings.

[0066] Step 15: Conduct quality inspection on composite pipe fittings in accordance with manufacturing and acceptance technical requirements.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A variable cross-section, large thickness, torsion composite pipe forming process, characterized by: Includes the following steps: Step 1: Use a metal 3D printer to manufacture a metal liner (1), manufacture it in sections and then weld them together into a whole; Step 2, Material Preparation: Prepare the main and auxiliary materials required before production, and confirm the equipment status; Step 3, Tooling preparation: Clean and process the surface of the mold to make it ready for use; the forming mold includes the mold body and 3 inserts, the dimensions of the 3 inserts correspond to the state after the metal liner (1) is covered with 3mm, 6mm and 9mm prepreg; the laying area in the middle of the 3 inserts is consistent with the surface of the part after the part is covered with 3mm, 6mm and 9mm prepreg; Step 4, CNC blanking: Blank the part according to the layup design; Step 5: Lay 3mm prepreg on the metal lining (1) in the layup sequence. Lay the first layer and vacuum pre-extract for 5-10 minutes. Then, lay the material sheets in sequence according to the layup coordinate system and layup angle requirements. Vacuum pre-extract once every 3-5 layers. Control the layup angle. The deviation of the fabric prepreg should not exceed ±5°, and the deviation of the unidirectional prepreg should not exceed ±3°. Compact the layup in the R-corner area. Step 6, Bag making: Vacuum bag sealing components; Step 7, Curing: At least two thermocouples are evenly distributed on the mold to monitor the curing temperature. The temperature is slowly increased according to the curing regime requirements, and the curing pressure is 0.3MPa-0.6MPa. Step 8, Demolding and Post-processing: After curing, demold and check the surface of the parts for wrinkles, dents and other defects. Use sandpaper or pneumatic sanding tools to sand the surface of the parts, but do not damage the carbon fiber. Step 9: Apply a layer of adhesive film to the surface of the part. If there is obvious deformation on the surface of the part, a local reinforcement layer can be applied as appropriate until the surface of the part is flat. Step 10: Remove the metal liner (1) and lay the corresponding insert for the 3mm prepreg composite carbon tube, and replace the metal liner (1) and lay the corresponding insert for the 6mm prepreg composite carbon tube. Step 11: Repeat steps 5 to 9 to complete the laying, curing, demolding and post-treatment of the 6mm prepreg composite carbon tube for the metal lining (1); Step 12: Remove the metal liner (1) and lay the corresponding insert for the 6mm prepreg composite carbon tube, and replace the metal liner (1) and lay the corresponding insert for the 9mm prepreg composite carbon tube. Step 13: Repeat steps 5 to 9 to complete the laying, curing, demolding and post-treatment of the 9mm prepreg composite carbon tube for the metal lining (1); Step 14: Machin the parts according to the drawings; Step 15: Conduct quality inspection on composite pipe fittings in accordance with manufacturing and acceptance technical requirements.

2. A variable cross-section large thickness torsion composite pipe forming process according to claim 1, characterized in that: The mold treatment in step 3 includes sealing agent treatment and mold release agent treatment.

3. The forming process for a variable cross-section, large thickness torsional composite material tube according to claim 1, characterized in that: After step 14, the composite material pipe is composed of a metal liner (1) and a carbon fiber composite pipe (2). The pipe is 1000 mm long and 10 mm thick. The metal liner (1) is made of aerospace aluminum alloy or titanium alloy and has a wall thickness of 1 mm. The carbon fiber composite pipe (2) is 9 mm thick and is formed by laying and curing epoxy resin carbon fiber fabric prepreg or unidirectional tape prepreg according to the design.

4. The forming process for a variable cross-section, large thickness torsion composite material tube according to claim 1, characterized in that: In step 3, the forming mold body includes a first bolt hole (31), a first positioning pin hole (32), a weight reduction hole, and a bag-making area necessary for the forming process.

5. The forming process for a variable cross-section, large thickness torsional composite material pipe according to claim 1, characterized in that: In step 3, the three inserts are provided with a second bolt hole (41) and a second positioning pin hole (42).

6. The forming process for a variable cross-section, large thickness torsional composite material tube according to claim 1, characterized in that: In step 5, if the material size is insufficient, overlap or butt joint shall be made according to the design requirements, and the overlap distance between adjacent plies shall not be less than 25mm.

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