Forming equipment and method for carbon fiber cylinder

Abstract

The invention belongs to the technical field of carbon fiber forming, and discloses carbon fiber cylinder forming equipment and method.The carbon fiber cylinder forming equipment comprises a core mold, a pressurizing device and a heating device, the carbon fiber cylinder is manufactured in the mode that the pressurizing device and the core mold are matched, complex forming equipment is not needed, the production cost is reduced, and the production efficiency is improved. And automatic separation and demolding after curing are realized by adopting the difference of thermal expansion coefficients between the core mold and the carbon fiber cylinder, and the inner surface of the carbon fiber cylinder cannot be damaged, so that the smoothness of the inner surface of the carbon fiber cylinder can be ensured. In the forming process, a pressurizing device is used for continuously applying uniform radial flexible pressure to a preformed body, each layer of prepreg can be tightly compacted, sufficient infiltration of fibers and resin is ensured, a high-density composite material structure is formed, and the flexible pressure serves as the forming pressure of the carbon fiber cylinder, so that the carbon fiber cylinder is formed. And the outer surface of the carbon fiber cylinder cannot be damaged, so that the smoothness of the outer surface is ensured.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber molding technology, and in particular to a molding device and method for carbon fiber cylinders. Background Technology

[0002] Carbon fiber cylinders are cylindrical structures with open ends and smooth inner walls, and are widely used in medical, industrial, and sports and leisure fields. Currently, their main manufacturing processes include winding, pultrusion, and coiling.

[0003] The winding process mainly uses carbon fiber dry yarn and resin as raw materials. The equipment includes a winding machine and a fiber yarn conveying system. After the continuous fibers are impregnated with resin, they are wound onto a cylindrical mandrel according to a set program. After curing and demolding, carbon fiber cylinders are obtained.

[0004] The pultrusion process also uses carbon fiber dry yarn and resin as raw materials. The equipment includes a fiber yarn conveying system, a pultrusion heating device, a traction device, and a cutting device. After continuous fibers are impregnated with resin, they are heated and cured under traction through a cylindrical mold, and then cut to obtain carbon fiber cylinders with uniform cross-section.

[0005] The tube winding process uses prepreg as raw material, and the main equipment includes CNC tube winding machines and tape winding machines. First, the carbon fiber prepreg is wrapped around a mold, then placed in a rolling press to compact it. After trimming off the excess material, a film is wrapped around it using a tape winding machine, and finally it is sent to a curing oven to cure and shape.

[0006] However, the above-mentioned processes still face several problems in practical applications: the initial equipment investment is high, such as winding machines, yarn conveying systems, pultrusion equipment, tube winding machines, and tape winding machines, and the overall process is relatively complicated. Specifically, the cost of mandrels in the winding process is high, and the products are prone to deformation; the pultrusion process produces products with lower strength in the direction perpendicular to the fiber, exhibiting obvious anisotropy; the tube winding process is complex to operate, requiring multiple lay-up operations and demanding high skill levels from personnel.

[0007] In addition, since the molds used in winding, pultrusion and tube winding processes usually need to have a certain draft angle, otherwise it is difficult to demold, resulting in the final product not being a perfectly 90° cylindrical tube, that is, it is impossible to achieve a completely vertical tube wall.

[0008] Therefore, the above problems urgently need to be solved. Summary of the Invention

[0009] The purpose of this invention is to provide a molding equipment and method for carbon fiber cylinders, which reduces the production cost of carbon fiber cylinders, facilitates demolding, and achieves a completely vertical cylinder wall.

[0010] To achieve this objective, the present invention adopts the following technical solution: The method for forming carbon fiber cylinders includes the following steps: Provide a solid cylindrical mandrel with a coefficient of thermal expansion greater than that of the carbon fiber cylinder to be formed; A prepreg of a predetermined number of layers is wrapped around the outer surface of the core mold to form a preform. The preform and the core mold are placed together inside the pressurizing device, and the pressurizing device applies a flexible radial pressure to the preform. The preform is heated and cured under the action of the flexible pressure. After curing and cooling, the difference in thermal expansion coefficients between the core mold and the formed carbon fiber cylinder is used to separate them. The carbon fiber cylinder is removed from the pressurizing device, and the core mold is extracted from the carbon fiber cylinder to complete the demolding.

[0011] Preferably, after forming the preform, the molding method further includes: A perforated isolation membrane and a breathable felt are wrapped sequentially on the outer surface of the preform, and then placed inside an exhaust bag. The interior of the exhaust bag is pre-vacuumed to remove interlayer gas; After venting is complete, remove the isolation membrane and breathable felt.

[0012] Preferably, placing the preform and the core mold together inside the pressurizing device includes: A release film and a silicone sheet are sequentially wrapped around the outer surface of the preform, and then placed together in a vacuum bag. During the heating and curing process, the vacuum bag is evacuated, and the silicone sheet applies radial flexible pressure to the preform under vacuum pressure.

[0013] Preferably, wrapping the outer surface of the core mold with a predetermined number of prepreg layers includes: The seams of adjacent layers of prepreg are staggered.

[0014] Preferably, the step of heating and curing the pressurizing device under the action of the flexible pressure includes: The preform is heated in stages according to a preset curing temperature curve.

[0015] Preferably, the outer diameter of the mandrel at room temperature is smaller than the designed inner diameter of the carbon fiber cylinder to be formed, and the difference between the two is configured such that, at the heating and curing temperature, the outer diameter of the mandrel can reach the designed inner diameter due to thermal expansion.

[0016] Preferably, the core mold is made of metal.

[0017] Preferably, the molding method further includes: The cured carbon fiber cylinder is divided into multiple sub-carbon fiber cylinders, with a cutting allowance reserved between adjacent sub-carbon fiber cylinders.

[0018] A carbon fiber cylinder forming device, used to heat and cure prepreg into carbon fiber cylinders, comprising: A core mold is formed by wrapping the prepreg of a predetermined thickness onto the core mold to form a preform. A pressurizing device for continuously applying a flexible pressure toward the mandrel to the prepreg; A heating device is used to heat and cure the preform. The thermal expansion coefficient of the core mold is greater than that of the carbon fiber cylinder, so that during the cooling process, the difference in thermal expansion coefficients between the core mold and the carbon fiber cylinder can be used to create a demolding gap for demolding.

[0019] Preferably, the pressurizing device includes: Release film and silicone sheet are sequentially wrapped around the outer surface of the preform; A vacuum bag is used to contain the core mold, the preform, the release film, and the silicone sheet; A first vacuum pump, connected to the vacuum bag, is configured to evacuate the vacuum bag to apply radial flexible pressure to the preform via the silicone sheet.

[0020] The beneficial effects of this invention are: This invention proposes a molding device and method for carbon fiber cylinders. By employing a solid cylindrical mandrel and utilizing the difference in thermal expansion coefficients between the mandrel and the carbon fiber cylinder, automatic separation and demolding after curing are achieved. This avoids damage to the inner surface of the carbon fiber cylinder, ensuring its smoothness. Compared to existing technologies using winding, pultrusion, and tube winding processes, this method eliminates the need for a draft angle on the mandrel, enabling the molded carbon fiber cylinder to achieve a perfectly vertical wall, meeting the stringent requirements for absolute verticality in specific high-end applications. During the molding process, a pressure device continuously applies uniform radial flexible pressure to the preform, tightly compacting each layer of prepreg and ensuring sufficient impregnation of the fiber and resin, forming a high-density composite material structure. Furthermore, using this flexible pressure as the molding pressure for the carbon fiber cylinder prevents damage to its outer surface, ensuring its smoothness. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the carbon fiber cylinder forming equipment in this invention; Figure 2This is a schematic diagram of the interlayer venting structure of the preform in this invention; Figure 3 This is a schematic diagram of the carbon fiber cylinder in this invention.

[0022] In the picture: 100. Carbon fiber cylinder; 10. Preform; 1. Core mold; 2. Pressurizing device; 21. Release film; 22. Silicone sheet; 23. Vacuum bag; 24. First vacuum pump; 31. Separating membrane; 32. Breathable felt; 33. Exhaust bag; 34. Second vacuum pump; 4. Heating device. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0024] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0026] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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 the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0027] Please see Figures 1 to 3 This embodiment proposes a method for forming a carbon fiber cylinder, which includes the following steps: S1: Provide a solid cylindrical mandrel 1 with a coefficient of thermal expansion greater than that of the carbon fiber cylinder 100 to be formed; S2: Wrap the prepreg material with a preset number of layers around the outer surface of the core mold 1 to form a preform 10; S3: Place the preform 10 and the core mold 1 together inside the pressurizing device 2, and apply radial flexible pressure to the preform 10 using the pressurizing device 2; S4: The preform 10 is heated and cured under flexible pressure; S5: After curing and cooling, the difference in thermal expansion coefficients between the core mold 1 and the formed carbon fiber cylinder 100 is used to separate the two. S6: Remove the carbon fiber cylinder 100 from the pressurizing device 2 and extract the core mold 1 from the carbon fiber cylinder 100 to complete the demolding.

[0028] Understandably, by employing a solid cylindrical mandrel 1 and utilizing the difference in thermal expansion coefficients between it and the carbon fiber cylinder 100 to achieve automatic separation and demolding after curing, compared to the existing technologies using winding, pultrusion, and tube winding processes, there is no need to set a demolding draft angle on the mandrel 1. This allows the formed carbon fiber cylinder 100 to achieve a completely vertical cylinder wall, meeting the stringent requirements for absolute verticality of the cylinder in specific high-end applications. Furthermore, by using prepreg as raw material and continuously applying uniform radial flexible pressure to the preform 10 using the pressurizing device 2 during the molding process, each layer of prepreg can be tightly compacted, ensuring sufficient impregnation of fibers and resin to form a high-density composite material structure. Moreover, using flexible pressure as the molding pressure for the carbon fiber cylinder will not damage the outer surface of the carbon fiber cylinder, thus ensuring the smoothness of the outer surface.

[0029] The molding method further includes, after forming the preform 10, the molding process as follows: A perforated isolation membrane 31 and a breathable felt 32 are wrapped sequentially on the outer surface of the preform 10, and then placed inside the exhaust bag 33. The interior of the exhaust bag 33 is pre-vacuumed to remove interlayer gas; After the venting is completed, remove the isolation membrane 31 and the breathable felt 32.

[0030] Understandably, the exhaust bag 33 provides a sealed environment and is connected to the second vacuum pump 34. Under the action of the second vacuum pump 34, gas inside the exhaust bag 33 can be extracted. During vacuuming, interlayer air can pass through the through-holes of the isolation membrane 31 and the breathable felt 32 before being discharged. Furthermore, the isolation membrane 31 prevents uncured, viscous resin from being directly sucked in and clogging the upper breathable felt 32 and the vacuum lines of the second vacuum pump 34. The breathable felt 32 forms a continuous, low-resistance gas flow path across the entire workpiece surface, ensuring that gas passing through the isolation membrane 31 is quickly and evenly extracted, avoiding localized vacuum dead zones.

[0031] Furthermore, placing the preform 10 and the core mold 1 together inside the pressurizing device 2 includes: A release film 21 and a silicone sheet 22 are sequentially wrapped around the outer surface of the preform 10, and then placed together in a vacuum bag 23. During the heating and curing process, the vacuum bag 23 is evacuated, and the silicone sheet 22 applies radial flexible pressure to the preform 10 under the vacuum pressure.

[0032] Understandably, after removing the release film 31 and the breathable felt 32, a release film 21 and a silicone sheet 22 are wrapped again on the outer surface of the preform 10. The release film 21 can prevent the silicone sheet 22 from sticking to the uncured resin. The silicone sheet 22 undergoes uniform elastic deformation under vacuum negative pressure, which can closely fit the outer contour of the preform 10 and convert the vacuum pressure into uniform and flexible radial flexible pressure. This can effectively ensure that the resin flows fully and wets the fiber during the curing process, thereby greatly improving the interlayer bonding strength, density and uniformity of the overall mechanical properties of the carbon fiber cylinder 100, reducing internal defects, and ensuring the smoothness of the outer surface of the carbon fiber cylinder 100.

[0033] In this embodiment, wrapping the prepreg with a predetermined number of layers around the outer surface of the core mold 1 includes: The seams of adjacent prepreg layers are staggered. This arrangement allows the flexible pressure to be evenly transmitted to every area of ​​the cylinder wall during the pressure curing process, and avoids the formation of a continuous "weak line" by the axial overlap of all the seams. This results in a more uniform distribution of the circumferential and axial strength of the carbon fiber cylinder 100, further improving the integrity and load-bearing reliability of the carbon fiber cylinder 100.

[0034] For example, taking a carbon fiber cylinder 100 with a wall thickness of 2mm as an example, before molding, the thickness of a single prepreg is selected according to the expansion amount of the cylindrical core mold 1, such as 0.25mm, then 10 pieces of prepreg are needed. The 10 pieces of prepreg are divided into two groups of 5 pieces each, and they are laid alternately and symmetrically to obtain two layers of prepreg. When wrapping, the side walls on both sides of the prepreg stack can be set opposite to each other to form a seam. The seam of the two layers of prepreg stack is located on opposite sides of the core mold 1.

[0035] It should be noted that after the prepreg is laminated, its thickness will be greater than the design thickness. During the heating, pressurizing, curing and expansion of the core mold 1, the preform 10 can be tightly compacted and the preform will become thinner to meet the design thickness requirements.

[0036] Furthermore, when processing carbon fiber cylinders 100 of different thicknesses, only the prepreg of different thicknesses and number of layers needs to be replaced, without the need to change the production equipment, thereby further reducing production costs.

[0037] In this embodiment, heating and curing the pressurizing device 2 under flexible pressure includes: The preform 10 is heated in stages according to a preset curing temperature curve.

[0038] Understandably, the phased heating curve allows the mandrel 1, prepreg, and pressurizing device 2 to be heated more evenly and the temperature difference to be reduced before the prepreg reaches the curing temperature. This ensures that the mandrel 1 deforms uniformly at all locations during thermal expansion, further ensuring that the carbon fiber cylinder 100 has a completely vertical wall. It also ensures that the resin releases some internal stress through flow at a lower viscosity, effectively suppressing curing deformation and internal stress caused by uneven thermal expansion or resin shrinkage. This ensures that the final carbon fiber cylinder 100 has excellent dimensional accuracy, roundness, and low residual stress, avoiding twisting or warping.

[0039] For example, taking a prepreg curing temperature of 150°C as an example, the preset curing temperature curve is to raise the temperature from room temperature to 90°C and hold it for 0.5 hours, then raise the temperature to 150°C and hold it for 1 hour.

[0040] It should be noted that the curing temperature profile can be determined based on the actual working conditions, but at least one heat preservation stage must be ensured before reaching the curing temperature.

[0041] In this embodiment, the outer diameter of the mandrel 1 at room temperature is smaller than the designed inner diameter of the carbon fiber cylinder 100 to be formed, and the difference between the two is configured such that the outer diameter of the mandrel 1 can reach the designed inner diameter due to thermal expansion at the heating and curing temperature.

[0042] Understandably, after the prepreg is wrapped around the outer surface of the mandrel 1, the inner diameter of the preform 10 is consistent with the outer diameter of the mandrel 1. Under the action of thermal expansion, the outer diameter of the mandrel 1 can increase. During the increase, the inner diameter of the prepreg can be expanded to reach the designed inner diameter, thereby ensuring the molding accuracy of the carbon fiber cylinder 100 during the molding process. During the cooling process, the temperature of the mandrel 1 decreases, so that its outer diameter is smaller than the designed inner diameter. Since the prepreg is a thermosetting material, the inner diameter of the carbon fiber cylinder 100 will not change after curing, thus forming a demolding gap between the mandrel 1 and the carbon fiber cylinder 100.

[0043] For example, when the inner diameter is designed to be 80mm, the outer diameter of the core mold 1 at room temperature can be 79.5mm, 79.6mm, 79.7mm or 79.8mm. The difference between the outer diameter and the inner diameter can be determined according to the actual working conditions. The factors that can be referenced include the coefficient of thermal expansion of the core mold 1 and the curing temperature of the prepreg, etc., which are not specifically limited here.

[0044] In this embodiment, the molding method further includes: The cured carbon fiber cylinder 100 is divided into multiple sub-carbon fiber cylinders 100, with a cutting allowance reserved between adjacent sub-carbon fiber cylinders 100.

[0045] This configuration allows multiple sections of carbon fiber cylinder 100 to be obtained at once during the molding process, thereby improving production efficiency and enabling mass production.

[0046] For example, with a design length of 100mm for a single carbon fiber cylinder 100, one carbon fiber cylinder 100 can be divided into 5 carbon fiber cylinders 100, and a 5mm cutting allowance is reserved between two adjacent carbon fiber cylinders 100. Therefore, when selecting the mandrel 1, a mandrel with an axial length of at least 520mm needs to be selected.

[0047] It should be noted that the length of each section of carbon fiber cylinder 100 can be cut according to actual needs, so that carbon fiber cylinders 100 of different lengths can be obtained without changing the production conditions.

[0048] Based on the above, this embodiment also proposes a carbon fiber cylinder molding device for heating and curing prepreg into a carbon fiber cylinder 100. The device includes a core mold 1, a pressurizing device 2, and a heating device 4. A prepreg of a preset thickness is wrapped around the core mold 1 to form a preform 10. The pressurizing device 2 is used to continuously apply a flexible pressure toward the core mold 1 to the prepreg. The heating device 4 is used to heat and cure the preform 10. The heating device 4 is preferably an oven in the prior art. The thermal expansion coefficient of the core mold 1 is greater than that of the carbon fiber cylinder 100. During the cooling process, the difference in thermal expansion coefficients between the core mold 1 and the carbon fiber cylinder 100 is used to form a demolding gap between them for demolding.

[0049] Understandably, processing the carbon fiber cylinder 100 using a combination of pressurizing device 2 and mandrel 1 eliminates the need for complex molding equipment, reducing production costs. Furthermore, the difference in thermal expansion coefficients between the mandrel 1 and the carbon fiber cylinder 100 enables automatic separation and demolding after curing, preventing damage to the inner surface of the carbon fiber cylinder 100 and ensuring its smoothness. Compared to existing technologies using winding, pultrusion, and tube winding processes, there is no need to set a draft angle on the mandrel 1, allowing the molded carbon fiber cylinder 100 to achieve a completely vertical cylinder wall, meeting the stringent requirements for absolute verticality of cylindrical tubes in specific high-end applications.

[0050] The core mold 1 is made of metal, preferably aluminum, which not only further reduces production costs, but also the coefficient of thermal expansion of aluminum is much greater than that of the carbon fiber cylinder 100. During the cooling process, this significant difference ensures that the shrinkage of the core mold 1 is much greater than that of the carbon fiber cylinder 100, thereby forming a separation gap between the two, realizing near-automatic non-destructive demolding without mechanical force, and completely avoiding damage to the inner wall.

[0051] In this embodiment, the pressurizing device 2 includes a release film 21, a silicone sheet 22, a vacuum bag 23, and a first vacuum pump 24. The release film 21 and the silicone sheet 22 are sequentially wrapped around the outer surface of the preform 10. The vacuum bag 23 is used to contain the core mold 1, the preform 10, the release film 21, and the silicone sheet 22. The first vacuum pump 24 is connected to the vacuum bag 23 and is configured to evacuate the vacuum bag 23 to apply radial flexible pressure to the preform 10 via the silicone sheet 22.

[0052] Understandably, the silicone sheet 22, acting as a flexible pressure-transmitting medium, deforms uniformly under vacuum negative pressure, transmitting flexible pressure losslessly and non-directionally to the entire outer surface of the preform 10. Furthermore, the silicone sheet 22's chemical properties are relatively mild, maintaining its elasticity even at the curing temperature. This flexible pressurization method allows the mandrel 1 to expand freely during heating and contract freely during cooling. Compared to rigid pressurization, this method ensures the smoothness of the carbon fiber cylinder's outer surface. During the cooling phase, after the first vacuum pump 24 stops working, the silicone sheet 22 recovers its deformation. Simply separating the release film 21 from the carbon fiber cylinder allows for external demolding of the carbon fiber cylinder. Compared to the equipment used in the process, the use of the release film 21, silicone sheet 22, and vacuum bag 23 significantly reduces production costs.

[0053] The vacuum bag 23 is made of high-temperature resistant material, preferably nylon.

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method of forming a carbon fiber cylinder, characterized by, The forming method comprises the following steps: providing a solid columnar core mold (1) with a thermal expansion coefficient greater than that of a carbon fiber cylinder (100) to be formed; wrapping a predetermined number of plies of prepreg on the outer surface of the core mold (1) to form a preform (10); placing the preform (10) and the core mold (1) in a pressurizing device (2) and applying a flexible pressure in the radial direction to the preform (10) by using the pressurizing device (2); heating and curing the preform (10) under the flexible pressure; cooling after curing and separating the carbon fiber cylinder (100) from the core mold (1) by using the difference in thermal expansion coefficients between the core mold (1) and the carbon fiber cylinder (100); taking out the carbon fiber cylinder (100) from the pressurizing device (2) and extracting the core mold (1) from the carbon fiber cylinder (100) to complete demolding.

2. The method of forming a carbon fiber cylinder according to claim 1, wherein After forming the preform (10), the forming method further comprises: sequentially wrapping a separation film (31) and a breather fabric (32) with uniformly distributed through holes on the outer surface of the preform (10) and placing them all in an exhaust bag (33); pre-vacuumizing the inside of the exhaust bag (33) to remove interlayer gas; removing the separation film (31) and the breather fabric (32) after exhausting.

3. The method of forming a carbon fiber cylinder according to claim 1, wherein The step of placing the preform (10) and the core mold (1) in the pressurizing device (2) comprises: sequentially wrapping a release film (21) and a silica gel sheet (22) on the outer surface of the preform (10) and placing them together in a vacuum bag (23); vacuumizing the vacuum bag (23) during heating and curing, and the silica gel sheet (22) applies a flexible pressure in the radial direction to the preform (10) under the action of vacuum pressure.

4. The method of forming a carbon fiber cylinder according to claim 1, wherein The step of wrapping a predetermined number of plies of prepreg on the outer surface of the core mold (1) comprises: staggering the seams of adjacent plies of prepreg.

5. The method of forming a carbon fiber cylinder according to claim 1, wherein The step of heating and curing the preform (10) under the flexible pressure comprises: staging the temperature rise of the preform (10) according to a predetermined curing temperature curve.

6. The method of forming a carbon fiber cylinder according to claim 1, wherein The outer diameter of the core mold (1) at room temperature is less than the designed inner diameter of the carbon fiber cylinder (100) to be formed, and the difference between them is configured so that at the heating and curing temperature, the core mold (1) can expand due to heat to reach the designed inner diameter.

7. The method of forming a carbon fiber cylinder according to claim 1, wherein The core mold (1) is made of metal.

8. The method of forming a carbon fiber cylinder according to claim 1, wherein, The forming method further comprises: segmenting the cured carbon fiber cylinder (100) into multiple sub-carbon fiber cylinders (100), and reserving a cutting allowance between adjacent two sub-carbon fiber cylinders (100).

9. A forming apparatus for carbon fiber cylinders for curing a prepreg into a carbon fiber cylinder (100), characterized in that, It comprises: a core mold (1) on which a predetermined thickness of prepreg is wrapped to form a preform (10); a pressurizing device (2) for continuously applying a flexible pressure to the prepreg towards the core mold (1); a heating device (4) for heating and curing the preform (10); The core mold (1) has a thermal expansion coefficient greater than that of the carbon fiber cylinder (100) to form a demolding gap between the core mold (1) and the carbon fiber cylinder (100) for demolding during cooling by virtue of the difference in thermal expansion coefficients.

10. The carbon fiber cylinder forming apparatus according to claim 9, wherein The pressurizing device (2) comprises: a release film (21) and a silica gel sheet (22) wrapped in sequence on the outer surface of the preform (10); a vacuum bag (23) for accommodating the core mold (1), the preform (10), the release film (21) and the silica gel sheet (22); a first vacuum pump (24) in communication with the vacuum bag (23) and configured to perform vacuumization on the vacuum bag (23) to apply a flexible pressure in the radial direction to the preform (10) through the silica gel sheet (22).

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