Carbon fiber spoke manufacturing method and carbon fiber spoke

Abstract

The application discloses a carbon fiber spoke manufacturing method and relates to the technical field of spoke manufacturing, which comprises the following steps: S1, resin impregnation, pulling carbon fiber raw filaments through an epoxy resin tank, and controlling the immersion time to be greater than or equal to 10s; S2, pre-extrusion resin removal, making the impregnated carbon fiber raw filaments pass through an extrusion forming die, extruding excess resin, and forming a fiber belt with a preliminary preset shape; S3, high-temperature setting and curing, introducing the fiber belt into a setting and curing die, heating at 180+ / -5 DEG C for 120-180s, hardening the fiber belt, obtaining a linear carbon rod, and performing cutting on the linear carbon rod; S4, centrifugal tumbling polishing, placing the carbon rod in a centrifugal tumbler to remove surface residual resin and improve the smoothness; and S5, installing spoke caps, installing the spoke caps at two ends of the carbon rod. The continuous long fibers can increase the crack propagation resistance, significantly improve the fatigue life of the carbon rod, and improve the axial tensile performance.

Description

Technical Field

[0001] This invention relates to the field of spoke manufacturing technology, and in particular to a method for manufacturing carbon fiber spokes and carbon fiber spokes. Background Technology

[0002] A wheel spoke typically consists of a spoke shank, a first spoke cap at one end of the spoke shank, and a second spoke cap at the other end of the spoke shank. The first spoke cap is used to connect with the rim, and the second spoke cap is used to connect with the hub. The spoke cap is a standard metal part, while the spoke shank is mainly made of carbon fiber, also known as a carbon rod. Carbon fiber composite materials are an ideal alternative to metal spokes due to their high strength, low density, and corrosion resistance, but the manufacturing process of carbon rods is relatively complex.

[0003] The manufacturing process of carbon spokes is relatively complex. For example, a Chinese invention patent published on December 18, 2020, entitled "A Method for Manufacturing Carbon Fiber Spokes and a Carbon Fiber Spoke," (publication number CN112092532A), describes a method that involves rolling carbon sand sheets into rods and inserting foaming agents at both ends. The rods are then engaged with a toothed cap and a cap-shaped head on the inner wall surface. However, carbon rods made from carbon sand sheets are prone to interlayer delamination, significantly shortening their fatigue life. Furthermore, due to the short fibers and interlayer weaknesses of carbon sand sheets, their axial tensile strength is relatively low.

[0004] Therefore, a method for manufacturing carbon fiber spokes with high axial tensile strength is needed. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for manufacturing carbon fiber spokes to solve the problem of low axial tensile strength of current spokes.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for manufacturing carbon fiber spokes, comprising:

[0007] A method for manufacturing carbon fiber spokes, comprising:

[0008] S1, resin impregnation, the carbon fiber precursor is pulled through the epoxy resin tank, and the immersion time is controlled to be ≥10s;

[0009] S2, pre-extrusion to remove resin, allows the impregnated carbon fiber filaments to pass through an extrusion molding die, extruding excess resin to form a fiber strip with a preliminary pre-set shape;

[0010] S3, High-temperature shaping and curing: The fiber tape is introduced into the shaping and curing mold and heated at 180±5℃ for 120-180s to harden and shape the fiber tape into a straight carbon rod.

[0011] S4, centrifugal tumbling polishing: After cutting the straight carbon rod, the carbon rod is placed in a centrifugal tumbling machine to remove residual resin on the surface and improve the smoothness.

[0012] S5, Install spoke caps, attach the spoke caps to both ends of the carbon rod.

[0013] Preferably, in step S5, the spoke cap installation step specifically includes:

[0014] S51, slide the spoke cap onto the carbon rod, and make sure the distance between the spoke cap and the end of the carbon rod is greater than a preset distance;

[0015] S52, the carbon rod end is struck to cause the carbon fiber to locally break and form a roughened interface, and the carbon rod end is coated with one of epoxy resin and carbon powder or graphene.

[0016] S53, place the end of the carbon rod in the end heating and curing mold, and heat and cure the end of the carbon rod to form a stepped mechanical locking layer;

[0017] S54 uses tensile testing equipment to fasten the stepped mechanical locking layer of the spoke cap and carbon rod end to form a complete spoke.

[0018] Preferably, the end heating and curing mold includes multiple end mold cavities adapted to the stepped mechanical locking layers, and an end heating unit that maintains the heating temperature inside the end mold cavity at 130±5℃.

[0019] Preferably, step S53 further includes:

[0020] S531, remove end burrs from the carbon rod after heat curing.

[0021] Preferably, in step S4, the centrifugal tumbling mill contains ceramic abrasive and a neutral cleaning agent, and the carbon rod is rotated at 200-300 rpm for 3-4 hours.

[0022] Preferably, step S4 further includes:

[0023] S41, laser cleaning of carbon rods;

[0024] S42, performs a second precise cut on the cleaned carbon rod.

[0025] Preferably, in step S2, the fiber tape is formed by bundling multiple carbon fiber filaments;

[0026] In step S3, the fiber tape is periodically high-temperature shaped and cured into a straight carbon rod.

[0027] Preferably, the extrusion molding die includes a fiber belt mold cavity for assembling multiple carbon fiber filaments into a fiber belt, and a fiber belt heating unit for maintaining the heating temperature inside the fiber belt mold cavity at 110±5℃.

[0028] Preferably, step S6 is also included;

[0029] S61, a tensile test is performed on the complete spokes to screen out qualified products;

[0030] S62: Qualified complete spokes are measured in length and graded before being put into storage.

[0031] This application also provides a carbon fiber spoke, which is produced by the carbon fiber spoke manufacturing method described above, and the carbon rod end of the carbon fiber spoke has a carbon powder layer or graphene embedded in the fractured pores, and an epoxy resin curing layer covering the carbon powder or graphene, wherein the carbon powder or graphene is mixed with the epoxy resin curing layer to form a stepped mechanical locking layer.

[0032] Compared with the prior art, the beneficial effects that this invention can achieve are:

[0033] Compared to existing manufacturing processes that involve rolling carbon sand sheets into rods, this invention employs a method of bundling carbon fiber precursors with epoxy resin and then heating and molding them. This results in highly axially oriented carbon rods with high axial tensile strength. The continuous long fibers also increase crack propagation resistance, significantly improving the fatigue life of the carbon rods.

[0034] Furthermore, by striking and breaking the carbon rod end, and coating the carbon rod end with epoxy resin and graphene carbon powder and then heating and curing it into a stepped mechanical locking layer, the structure becomes more stable and greatly increases the end connection strength. Compared with traditional carbon fiber spokes, which are mostly fixed by adhesive or metal sleeve pressing, but are prone to delamination or metal fatigue leading to connection failure after long-term use, the connection between the end and the spoke cap is more stable and has better tensile strength. Attached Figure Description

[0035] Figure 1 This is a schematic flowchart of the carbon fiber spoke manufacturing method according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the carbon rod in step S53.

[0037] Figure 3 This is a schematic diagram of the spoke structure in step S54.

[0038] The components include: 1. carbon rod; 2. spoke cap; 3. stepped mechanical locking layer. Detailed Implementation

[0039] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention is further described below in conjunction with specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of this invention.

[0040] like Figures 1-3 As shown, the present invention provides a method for manufacturing carbon fiber spokes, comprising:

[0041] S1: Continuously pull carbon fiber precursor fibers into an epoxy resin bath containing graphene, and control the immersion time to ≥10s to ensure that the resin penetrates the fiber gaps.

[0042] S2: The extrusion die applies pressure to the impregnated fiber, extruding excess resin and initially shaping the carbon fiber precursor into a fiber ribbon shape.

[0043] S3: The high temperature inside the tubular mold causes the epoxy resin and fiber tape to cross-link and cure, forming a rigid carbon rod 1. Each carbon rod 1 is heated at 180±5℃ for 120-180s.

[0044] S4: After the straight carbon rod 1 made of fiber belt is cut, the resin residue is removed and the surface of the carbon rod 1 is micro-polished by the collision of abrasive in centrifugal tumbling.

[0045] S5: Connect the spoke caps 2 at both ends of the carbon rod 1.

[0046] Taking the production of φ2.0mm spokes as an example: the traction carbon wire is passed through an epoxy resin bath and immersed for 30 seconds; it passes through an extrusion roller with a gap of 0.2mm to output a flat round fiber belt with a resin content of RC38%; it is introduced into an alloy mold with an inner diameter of 2.0mm and heated at 185℃ for 150 seconds to cure; it is cut into 300mm lengths and put into a centrifugal tumbling mill (zirconia abrasive Φ3mm + pH7 cleaning agent) at 250rpm×3.5min; and 7075 aluminum alloy spoke cap 2 (inner diameter 2.1mm) is installed.

[0047] Compared to existing manufacturing processes that involve rolling carbon fiber sheets into rods, this new method uses epoxy resin to bundle and heat-form carbon fiber precursors, resulting in highly axially oriented carbon rods with superior axial tensile strength. The continuous long fibers also increase crack propagation resistance, significantly improving the fatigue life of the carbon rods. Furthermore, compared to traditional processes, this method achieves higher resin penetration, a larger fiber volume content, and better removal of residual resin from the surface.

[0048] Furthermore, step S5 also includes an end-strengthening process, specifically...

[0049] S51, slide the spoke cap 2 into the carbon rod, with a distance greater than the preset distance from the end of the carbon rod; the preferred reserved space of 2-5CM is the subsequent fracture zone.

[0050] S52 involves striking the end of a carbon rod to cause localized fragmentation of the carbon fiber, forming a textured interface. The end of the carbon rod is then coated with either epoxy resin or carbon powder or graphene. The impact energy is converted into carbon fiber fracture energy (brittle fracture principle). The textured interface increases the specific surface area. The effective addition amount of carbon powder or graphene is 0.3~0.7WT. Graphene can significantly enhance the mechanical properties of composite materials. Polymer composite materials with a small amount of graphene added can have their strength and hardness significantly improved.

[0051] S53, the carbon rod end is placed in the end heating and curing mold, and the carbon rod end is heated and cured to form a stepped mechanical locking layer 3; the carbon powder is embedded in the cracks, and the epoxy resin fills the pores, so that the stepped mechanical locking layer 3 formed is integrated with the original end of the carbon rod; heating causes the resin and carbon powder to cure and shrink, and the end of the end heating and curing mold tightly holds the carbon powder and fiber.

[0052] S54, using a tensile testing device, the spoke cap 2 and the stepped mechanical locking layer 3 at the end of the carbon rod are fastened together to form a complete spoke. Under the drive of tension, the spoke cap 2 slides to the stepped mechanical locking layer 3 at the end of the carbon rod, forming a stepped locking fit, thereby forming a structure with extremely strong end tensile strength.

[0053] In a preferred embodiment, after the spoke cap is fitted onto the carbon rod, it is 4 cm behind the end face. A pneumatic hammer (impact energy 8J) is used to strike the end to form a 0.8 mm deep fracture layer. A mixed slurry of 40 g of 100 mesh carbon powder and 60 g of epoxy resin is then applied. The mixture is placed in a mold at 130°C and cured for 45 min. A hydraulic tensioner applies an assembly force of 380 N.

[0054] Furthermore, the end heating and curing mold includes multiple end mold cavities adapted to the stepped mechanical locking layer. The end mold cavities are stepped in shape to shape the end covered with toner and resin.

[0055] It also includes an end heating unit for maintaining the heating temperature inside the end mold cavity at 130±5℃, which achieves precise local curing through a PID temperature-controlled heating rod.

[0056] By maintaining the consistency of the stepped mechanical locking layer through the end mold cavity with a tolerance of ±0.05mm, the overall heat-affected zone can be prevented from expanding, thus saving energy.

[0057] Furthermore, after the heat curing in step S53 forms a stepped mechanical locking layer, the process further includes: S531, removing end burrs from the heat-cured carbon rod.

[0058] Because burrs form at the edges of the cured resin, these burrs need to be removed. This can be done using a cutting tool or precision belt grinding. Removing burrs prevents scratches on the wheel rim during assembly, eliminates stress concentration points, and improves fatigue strength.

[0059] Furthermore, in step S4, the centrifugal tumbling mill contains ceramic abrasive and a neutral cleaning agent, and rotates the carbon rod at 200-300 rpm for 3-4 hours. In a preferred embodiment, the surface roughness Ra of the carbon rod is reduced from 1.2 μm to 0.6 μm through the tumbling process, and the fiber is damaged to zero.

[0060] Furthermore, after centrifugal tumbling and polishing in step S4, the process also includes: S41, laser cleaning of the carbon rod; and S42, a second precise cut of the cleaned carbon rod. This controls the end face perpendicularity to ≤0.5° and the length tolerance to ±0.15mm. Specifically, high-speed cutting can be performed using a diamond grinding wheel to control dimensional accuracy.

[0061] Furthermore, in step S2, the fiber tape is formed by bundling multiple carbon fiber filaments; the multiple bundles of fibers are stranded together to enhance the axial strength, and epoxy resin is used to enhance the degree of fixed connection between the fiber filaments.

[0062] In step S3, the fiber strips are periodically high-temperature shaped and cured into straight carbon rods. The periodic curing leaves flexible intermediate sections, which facilitates initial cutting; and the relatively flexible intermediate carbon fiber sections between adjacent straight carbon rods facilitate certain turns in the adaptive production line.

[0063] Furthermore, the extrusion molding die includes a fiber strip cavity for assembling multiple carbon fiber filaments into a single fiber strip, and a fiber strip heating unit for maintaining the heating temperature within the fiber strip cavity at 110±5℃. Preheating to 110℃ reduces resin viscosity, promotes tight fiber arrangement, and decreases the fiber gap ratio from 5% to 1.2%; it also prevents the fiber strip from directly curing, thus avoiding impact on the subsequent high-temperature setting and curing effect.

[0064] In a further preferred embodiment, the length of the mold preheating zone can be set to 20CM~80CM, and a temperature gradient can be adopted: 110℃ at the inlet to 130℃ at the outlet.

[0065] Furthermore, it also includes quality inspection and grading steps S6 and S61, which involve conducting tensile tests on complete spokes to screen for qualified products; and S62, which involves measuring the length of qualified complete spokes and grading them before storing them in the warehouse.

[0066] This application also provides a carbon fiber spoke, which is manufactured by the carbon fiber spoke manufacturing method described above. The carbon rod end of the carbon fiber spoke has a carbon powder layer or graphene embedded in fragmented pores, and an epoxy resin cured layer coating the carbon powder. The carbon powder and the epoxy resin cured layer are mixed to form a stepped mechanical locking layer. This fills the cracks to form mechanical anchor points, and the curing shrinkage provides clamping force, enhancing tensile strength.

[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 method for manufacturing carbon fiber spokes, characterized in that: include: S1, resin impregnation, the carbon fiber precursor is pulled through the epoxy resin tank, and the immersion time is controlled to be ≥10s; S2, pre-extrusion to remove resin, allows the impregnated carbon fiber filaments to pass through an extrusion molding die, extruding excess resin to form a fiber strip with a preliminary pre-set shape; S3, High-temperature shaping and curing: The fiber tape is introduced into the shaping and curing mold and heated at 180±5℃ for 120-180s to harden and shape the fiber tape into a straight carbon rod. S4, centrifugal tumbling polishing: After cutting the straight carbon rod, the carbon rod is placed in a centrifugal tumbling machine to remove residual resin on the surface and improve the smoothness. S5, Install spoke caps, attaching the spoke caps to both ends of the carbon rod; step S5, specifically the step of installing spoke caps, includes: S51, slide the spoke cap onto the carbon rod, and make sure the distance between the spoke cap and the end of the carbon rod is greater than a preset distance; S52, the carbon rod end is struck to cause the carbon fiber to locally break and form a roughened interface, and the carbon rod end is coated with one of epoxy resin and carbon powder or graphene. S53, place the end of the carbon rod in the end heating and curing mold, and heat and cure the end of the carbon rod to form a stepped mechanical locking layer; S54 uses tensile testing equipment to fasten the stepped mechanical locking layer of the spoke cap and carbon rod end to form a complete spoke.

2. The method for manufacturing carbon fiber spokes according to claim 1, characterized in that: The end heating and curing mold includes multiple end mold cavities adapted to the stepped mechanical locking layers, and an end heating unit that maintains the heating temperature inside the end mold cavity at 130±5℃.

3. The method for manufacturing carbon fiber spokes according to claim 1, characterized in that: Step S53 also includes: S531, remove end burrs from the carbon rod after heat curing.

4. The method for manufacturing carbon fiber spokes according to claim 1, characterized in that: In step S4, the centrifugal roller mill contains ceramic abrasive and neutral cleaning agent, and the carbon rod is rotated at 200-300 rpm for 3-4 hours.

5. The method for manufacturing carbon fiber spokes according to claim 4, characterized in that: Step S4 also includes: S41, laser cleaning of carbon rods; S42, performs a second precise cut on the cleaned carbon rod.

6. The method for manufacturing carbon fiber spokes according to claim 1, characterized in that: In step S2, the fiber tape is formed by bundling multiple carbon fiber filaments; In step S3, the fiber tape is intermittently high-temperature shaped and cured into straight carbon rods; the intermittent high-temperature shaped and cured process leaves a flexible intermediate section between adjacent straight carbon rods.

7. The method for manufacturing carbon fiber spokes according to claim 6, characterized in that: The extrusion molding die includes a fiber belt mold cavity for assembling multiple carbon fiber filaments into a fiber belt, and a fiber belt heating unit for maintaining the heating temperature inside the fiber belt mold cavity at 110±5℃.

8. The method for manufacturing carbon fiber spokes according to claim 1, characterized in that: It also includes step S6; S61, a tensile test is performed on the complete spokes to screen out qualified products; S62: Qualified complete spokes are measured in length and graded before being put into storage.

9. A carbon fiber spoke, characterized in that, The carbon fiber spokes are manufactured by the carbon fiber spoke manufacturing method according to any one of claims 1 to 8, and the carbon rod end of the carbon fiber spokes has a carbon powder layer or graphene embedded in the fractured pores, and an epoxy resin curing layer covering the carbon powder or graphene, wherein the carbon powder or graphene is mixed with the epoxy resin curing layer to form a stepped mechanical locking layer.

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