Forming method of carbon fiber elliptical tube

Abstract

The invention provides a forming method of a carbon fiber elliptical tube, which enables the internal surface quality of a tube body to be good, the strength of the tube body to be high, the production cost to be low and the production efficiency to be high. A silica gel hose and a high-temperature-resistant air pipe serve as a lining assembly, prepreg is laid on the outer surface of the silica gel hose in advance, then the lining assembly with the prepreg laid is placed in a forming mold, the forming mold is heated and pressurized, compressed air is injected into the air pipe at the same time, after curing, a carbon fiber oval pipe wraps the outer surface of the lining assembly, and the lining assembly is formed. And then the carbon fiber oval tube is taken out, the lining assembly and the carbon fiber oval tube are separated, and the lining assembly is continuously used for machining and manufacturing the carbon fiber oval tube.

Description

Technical Field

[0001] This invention relates to the technical field of processing irregularly shaped carbon fiber tubes, specifically a method for forming carbon fiber elliptical tubes. Background Technology

[0002] The processing methods for carbon fiber elliptical tubes with an elliptical cross-section include internal and external steel mold molding, prepreg duct air blowing molding with a mold, EPS duct air blowing molding, and EPS latex air blowing molding; all four of these carbon fiber elliptical tube molding methods have their own defects. Compression molding with internal and external steel molds can achieve better internal and external product surfaces and higher product dimensional accuracy, but it has disadvantages such as high mold precision requirements, high mold manufacturing cost, difficulty in removing the core from the product, severe sand inclusion, and low production efficiency. Prepreg duct air blowing molding can achieve better external surface and shape, but it has disadvantages such as low joint strength of mold laying and mold closing, poor internal surface quality and low production efficiency. EPS air duct blowing molding can achieve a better outer surface and shape, and the product strength is also good, but there will be obvious wrinkles on the inner surface. EPS latex blow molding can achieve better internal and external surface quality and higher production efficiency, but EPS latex bags are disposable consumables and require special molds for production, resulting in higher production costs. Therefore, there is an urgent need to find a molding method for carbon fiber elliptical tubes that can integrate good internal surface quality, high strength, low production cost, and high production efficiency. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for forming carbon fiber elliptical tubes, which results in good internal surface quality, high tube strength, low production cost, and high production efficiency.

[0004] A method for molding a carbon fiber elliptical tube is characterized by: using a silicone hose and a high-temperature resistant air duct as inner lining components, pre-impregnating material is pre-applied to the outer surface of the silicone hose, then placing the inner lining component with the pre-impregnated material in a molding mold, heating and pressurizing the molding mold, and simultaneously injecting compressed air into the air duct. After curing, the carbon fiber elliptical tube covers the outer surface of the inner lining component, then the carbon fiber elliptical tube is removed, and the inner lining component and the carbon fiber elliptical tube are separated.

[0005] Its further features are: It includes the following steps: S1 Selects a high-temperature resistant silicone tube with an outer contour perimeter that is close to or the same as that of the product as the inner liner; S2 completes the prepreg application on the outer surface of the silicone tubing; The inner cavity of the S3 silicone hose is permeated by a high-temperature resistant air duct. One end of the high-temperature resistant air duct is sealed, and the other end is connected to an air inflator. The high-temperature resistant air duct and the silicone hose are combined to form an inner lining component. S4 Place the prepreg-laid liner assembly into the molding mold. The high-temperature resistant air duct should be filled to the mold cavity to prevent the bag from bursting. The air inflator should be properly aligned with the guide slot of the mold to prevent the high-temperature resistant air duct from leaking. S5 places the molding die on a hot press for heating and pressurization, and uses compressed air to pressurize the high-temperature resistant air duct, so that the inner and outer walls of the prepreg are subjected to corresponding pressure. After S6 curing is complete, open the upper mold of the molding mold, remove the product, and take out the high-temperature resistant air duct, silicone hose, and air nozzle from the unsealed end of the product.

[0006] Its further characteristic is: The silicone hose is a round or nearly round tube at room temperature. The silicone hose has a temperature resistance of 300°C or close to 300°C. The silicone hose does not deform when the molding mold is heated, so that the silicone hose will return to its initial shape after the product is processed and removed. In step S2, the prepreg is laid using multi-layer carbon fiber prepreg, with the joints of each layer staggered. In step S3, the expansion dimension of the high-temperature resistant air duct under high pressure is greater than the cross-sectional dimension of the silicone hose, ensuring that the high-temperature resistant air duct can reliably conform to the inner cavity shape of the molding mold for expansion without leaving any dead corners when it is inflated and deformed. In step S2, the axial length of the prepreg is recessed relative to the end of the silicone hose furthest from the air nozzle, ensuring that the high-temperature resistant air duct, silicone hose, and air nozzle can be easily removed from this end of the product after curing in step S6. Step S5 includes the following steps: S501 presses the molding die tightly with a press, and the heat insulation softens the silicone hose and carbon fiber prepreg, making the subsequent inflation and pressurization more effective. S502 connects the exposed air inlet to compressed air, and the high-temperature resistant air duct, silicone hose, carbon fiber prepreg, and molding die are tightly pressed together. S503 is kept under heat and pressure until curing is complete; It also includes step S7, which removes the burrs at both ends of the product along its length to obtain a carbon fiber elliptical tube of the required length.

[0007] The present invention uses silicone tubing and high-temperature resistant duct as inner lining components, and prepreg is applied to the outer surface of the silicone tubing. The inner lining component with prepreg is then placed in a molding mold, the molding mold is heated and pressurized, and compressed air is injected into the duct. After curing, carbon fiber elliptical tubes cover the outer surface of the inner lining component. The carbon fiber elliptical tubes are then removed, and the inner lining component and the carbon fiber elliptical tubes are separated. The silicone tubing provides the laying shape and makes the inner wall of the corresponding elliptical tube relatively flat. Moreover, the silicone tubing is inexpensive and can be reused multiple times if properly protected. This results in good internal surface quality, high tube strength, low production cost, and high production efficiency. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the molding process using the method of the present invention (the molding mold is not closed). Figure 2 for Figure 1 A sectional view of the molded state; Figure 3 for Figure 2 A magnified schematic diagram of the structure at point A; The names corresponding to the serial numbers in the diagram are as follows: Silicone hose 10, high temperature resistant air duct 20, prepreg 30, molding die 40, guide slot 401, upper mold 41, lower mold 42, air inflator 50. Detailed Implementation

[0009] A method for forming carbon fiber elliptical tubes, see Figures 1-3 The device uses a silicone hose 10 and a high-temperature resistant air duct 20 as inner lining components. Prepreg 30 is pre-applied to the outer surface of the silicone hose 10. The inner lining component with the prepreg 30 applied is then placed in a molding mold 40. The molding mold 40 is heated and pressurized, while compressed air is injected into the high-temperature resistant air duct 20. After curing, a carbon fiber elliptical tube covers the outer surface of the inner lining component. The carbon fiber elliptical tube is then removed, and the inner lining component and the carbon fiber elliptical tube are separated.

[0010] It includes the following steps: S1 selects a high-temperature resistant silicone tube 10 with an outer contour perimeter close to or the same as that of the product as the inner liner. The silicone tube 10 is a round tube or nearly round tube at room temperature. The silicone tube 10 has a temperature resistance of up to or close to 300℃. The silicone tube 10 will not deform under the heating state of the molding mold, so that the silicone tube 10 will return to its initial shape after the product is processed and removed. S2 completes the prepreg 30 of the product on the outer surface of the silicone tube 10. The prepreg 30 is laid with multiple layers of carbon fiber prepreg, and the joints of each layer are staggered. The inner cavity of the S3 silicone hose 10 is penetrated by a high-temperature resistant air duct 20. One end of the high-temperature resistant air duct 20 is sealed and the other end is connected to the inflation nozzle 50. The high-temperature resistant air duct 20 and the silicone hose 10 are combined to form an inner lining component. The expansion dimension of the high-temperature resistant air duct 20 under high pressure is greater than the cross-sectional dimension of the silicone hose 10, ensuring that the high-temperature resistant air duct 20 can reliably expand by conforming to the inner cavity shape of the molding mold 40 without leaving any dead corners when it is inflated and deformed. S4 places the lining assembly with the prepreg 30 laid in the molding mold 40. The high-temperature resistant air duct 20 should be filled to the mold cavity to prevent the bag from bursting. The air inflator 50 should be aligned with the guide slot 401 of the molding mold 40 to prevent the high-temperature resistant air duct 20 from leaking air. S5 places the molding mold 40 on a hot press for heating and pressurization, and uses compressed air to press the high-temperature resistant air duct 20, so that the inner and outer walls of the prepreg 30 are subjected to corresponding pressure. S501 presses the molding die 40 tightly, and the heat insulation softens the silicone hose 10 and carbon fiber prepreg, making the subsequent inflation and pressurization more effective. S502 connects the exposed air inlet 21 to compressed air, and the high-temperature resistant compressed air duct 20, silicone hose 10, carbon fiber prepreg, and molding die 40 are tightly pressed together. S503 is kept under heat and pressure until curing is complete; After S6 has cured, open the upper mold 41 of the molding mold 40, take out the product, and take out the high temperature resistant air duct 20, silicone hose 10, and air nozzle 50 from the unsealed end of the product. S7, remove the burrs at both ends of the product along its length to obtain a carbon fiber elliptical tube of the required length.

[0011] In specific implementation, in step S2, the axial length of the prepreg 30 is recessed relative to the end of the silicone hose 10 that is away from the air nozzle 50, so as to ensure that after curing in step S6, the high-temperature resistant air duct 20, silicone hose 10 and air nozzle 50 can be easily removed from this end of the product.

[0012] In a specific embodiment, the inner contour circumference of the product corresponding to the carbon fiber elliptical tube is 183.5 mm, the diameter of the corresponding circle is calculated to be 58.4 mm, and the wall thickness of the product is 1 mm. The process includes the following steps: S1 uses a silicone hose 10 with an outer diameter of 58mm and a wall thickness of about 2mm. Since the silicone hose 10 is easy to stretch when heated and pressurized, a slightly smaller diameter silicone hose is selected. S2 lays the prepreg 30 on the outer surface of the silicone tube 10. The thickness of a single layer of carbon fiber prepreg is 0.2mm. Five layers of carbon fiber prepreg are wrapped on the silicone tube, and the joints of each layer are staggered. The inner cavity of the S3 silicone hose 10 is penetrated by a high-temperature resistant air duct 20. One end of the high-temperature resistant air duct 20 is sealed and the other end is connected to the inflation nozzle 50. The high-temperature resistant air duct 20 and the silicone hose 10 are combined to form an inner lining component. The expansion dimension of the high-temperature resistant air duct 20 under high pressure is greater than the cross-sectional dimension of the silicone hose 10, ensuring that the high-temperature resistant air duct 20 can reliably expand by conforming to the inner cavity shape of the molding mold 40 without leaving any dead corners when it is inflated and deformed. S4 places the prepreg-laid lining assembly into the molding mold 40. The high-temperature resistant air duct 20 should fill the mold cavity to prevent the bag from bursting. The air inflator 50 should be aligned with the guide slot 401 of the molding mold 40 to prevent the high-temperature resistant air duct 20 from leaking air. S5 places the molding mold 40 on a hot press for heating and pressurization, and uses compressed air to press the high-temperature resistant air duct 20, so that the inner and outer walls of the prepreg 30 are subjected to corresponding pressure. S501 presses the molding die 40 onto the press and keeps it warm for 5 minutes to soften the silicone hose 10 and carbon fiber prepreg, making the subsequent inflation and pressurization more effective. S502 connects the exposed air inlet 21 to compressed air, and sets the compressed air pressure to 0.6MPa, so that the high-temperature resistant air duct 20, silicone hose 10, carbon fiber prepreg, and the inner wall of the mold cavity of the molding die 40 are tightly pressed together. S503 is kept under heat and pressure for 60 minutes until curing is complete; After S6 has cured, open the upper mold 41 of the molding mold 40, take out the product, and take out the high temperature resistant air duct 20, silicone hose 10, and air nozzle 50 from the unsealed end of the product. S7, remove the burrs at both ends of the product along its length to obtain a carbon fiber elliptical tube of the required length.

[0013] Carbon fiber prepregs are classified into low-temperature, medium-temperature, and high-temperature types, with medium-temperature prepregs being the most commonly used, accounting for about 70% of the total usage. The curing temperature of low-temperature prepregs is 80~120℃, that of medium-temperature prepregs is 120~180℃, and that of high-temperature prepregs is 180~250℃. Silicone hoses can withstand temperatures up to or close to 300℃, so they will not deform under the heating state of the molding mold, which can meet production needs.

[0014] It uses silicone hoses and high-temperature resistant air ducts as inner lining components, and pre-impregnated material is pre-applied to the outer surface of the silicone hoses. Then, the inner lining component with pre-impregnated material is placed in a molding mold, the molding mold is heated and pressurized, and compressed air is injected into the air duct. After curing, carbon fiber elliptical tubes cover the outer surface of the inner lining component. Then, the carbon fiber elliptical tubes are removed, and the inner lining component and carbon fiber elliptical tubes are separated. The silicone hoses not only provide the laying shape, but also make the inner wall of the corresponding elliptical tube relatively flat. Moreover, silicone hoses are inexpensive and can be reused many times if properly protected. This results in good internal surface quality and high tube strength, as well as low production cost and high production efficiency.

[0015] 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.

[0016] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method of forming a carbon fiber elliptical tube, the method comprising: It is through the silicone hose, high temperature resistant air pipe as the lining component, and pre-impregnated on the outer surface of the silicone hose, then the completed pre-impregnated lining component is placed in the forming mold, the forming mold is heated and pressurized, while the compressed air is injected into the air pipe, after curing, the carbon fiber elliptical pipe is wrapped on the outer surface of the lining component, then the carbon fiber elliptical pipe is taken out, and the lining component and the carbon fiber elliptical pipe are separated. ​ 2. The method of claim 1, wherein It comprises the following steps: S1 selects a high-temperature-resistant silicone hose with an outer contour circumference close to or the same as that of the product as the lining; S2 complete the pre-impregnated laying of the product on the outer surface of the silicone hose; S3 the inner cavity of the silicone hose penetrates a high-temperature-resistant air pipe, one end of the high-temperature-resistant air pipe is sealed, the other end is connected to an inflation air nozzle, and the high-temperature-resistant air pipe and the silicone hose form a lining component; S4 the completed pre-impregnated lining component is placed in the forming mold, the high-temperature-resistant air pipe is fully filled in the mold cavity to prevent bag explosion, and the inflation air nozzle is well matched with the guide clamping groove of the mold to prevent air leakage of the high-temperature-resistant air pipe; S5 the forming mold is placed on the heating press for heating and pressurizing, and the high-temperature-resistant air pipe is pressurized with compressed air, so that the inner and outer walls of the pre-impregnated material are subjected to corresponding pressure; S6 after curing, the upper mold of the forming mold is opened, the product is taken out, and the high-temperature-resistant air pipe, the silicone hose and the inflation air nozzle are taken out from the unsealed end of the product.

3. The method of claim 2, wherein: The silicone hose is a circular pipe or a nearly circular pipe at room temperature, the temperature resistance of the silicone hose reaches or approaches 300 DEG C, and the silicone hose will not denature in the heating state of the forming mold, so that the silicone hose will restore the initial shape after the product is processed and formed.

4. The method of claim 2, wherein: In step S2, the pre-impregnated laying adopts multi-layer carbon fiber pre-impregnated laying, and the interfaces of each layer are staggered.

5. The method of claim 2, wherein: the carbon fiber oval tube is formed by winding a carbon fiber sheet around a mandrel in a spiral pattern. In step S3, the expansion size of the high-temperature-resistant air pipe under high pressure is greater than the cross-sectional size of the silicone hose, ensuring that the high-temperature-resistant air pipe can reliably expand to the shape of the inner cavity of the forming mold when inflated, without dead angle.

6. The method of claim 2, wherein: In step S2, the axial length of the pre-impregnated laying is retracted relative to the end of the silicone hose away from the inflation air nozzle, ensuring that the high-temperature-resistant air pipe, the silicone hose and the inflation air nozzle can be smoothly taken out from the end of the product after curing in step S6.

7. The method of claim 2, wherein the carbon fiber oval tube is formed by winding a carbon fiber sheet around a mandrel in a spiral pattern. Step S5 comprises the following steps: S501 the forming mold is tightly pressed on the press, and the silicone hose and the carbon fiber pre-impregnated material are softened to make the subsequent inflation and pressurization more accurate; S502 the exposed inflation air nozzle is connected to compressed air, and the compressed air pressure tightly presses the high-temperature-resistant air pipe, the silicone hose, the carbon fiber pre-impregnated material and the forming mold together; S503 keep temperature and pressure until curing is completed.

8. The method of claim 2, wherein: the carbon fiber oval tube is formed by winding a carbon fiber sheet around a mandrel in a spiral pattern. It further comprises step S7, cutting off the burrs at both ends of the product in the length direction to obtain a carbon fiber elliptical pipe with the required length.

Images