A hot-melt process for bicycle carbon fiber frame

Abstract

The invention discloses a hot-melt process for a bicycle carbon fiber frame, which relates to the technical field of bicycle carbon fiber. The process comprises a plurality of steps performed in sequence: pre-treating the carbon fiber cloth so that it has a low fuzz rate and high surface energy; the hot-melt adhesive used is a composite system of polyimide-modified ethylene-vinyl acetate copolymer and a temperature-controlled release polyester microcapsule flux; laying the carbon fiber cloth in sections according to a set sequence, and performing a local preheating treatment after each layer of laying unit to enhance interface fusion and form a structure; placing the structure in a hot-melt mold for curing and forming, and applying pressurization in sections during curing; synchronously connecting an exhaust device to extract interlayer air and excess colloid; and performing a constant-temperature tempering treatment after forming to release structural stress. The process has good raw material adaptability, strong bonding performance and a short forming cycle, and solves the problems of limited forming quality and performance, long forming cycle and low curing efficiency of the existing hot-melt process.

Description

Technical Field

[0001] The invention relates to the technical field of bicycle carbon fiber, in particular to a hot-melt process for a bicycle carbon fiber frame. Background Art

[0002] With the growing demand for lightweight, high-strength, and high-performance bicycles, carbon fiber composites have become the mainstream material for high-end bicycle frame manufacturing due to their excellent specific strength, corrosion resistance, and structural designability. Currently, the production of carbon fiber bicycle frames generally uses a hot melt adhesive-assisted curing process. The typical process includes carbon fiber cloth cutting, prepreg stacking, mold pressing, heating and melting, and thermal curing. In this process, the compatibility of the carbon fiber cloth and the hot melt adhesive resin system, the stability of the layer structure, and temperature control during the hot melt process all play a key role in the final performance of the frame.

[0003] In existing technologies, to ensure the overall strength and bonding quality of the molded frame, the carbon fiber cloth used is generally required to have extremely high homogeneity and consistency. However, in actual production, due to the influence of carbon fiber supply batches, storage environment and operating conditions, problems such as breakage, fuzzy fibers and uneven linear density are prone to occur. These defects not only affect resin permeability during the stacking and hot pressing processes, but may also cause internal defects such as delamination and voids, thereby reducing the structural performance of the frame.

[0004] In addition, the selection of hot melt adhesive resins is limited. Commonly used thermoplastic resin systems such as PA, PET, and EVA have low bonding efficiency in actual applications and are easily affected by humidity and pyrolysis temperature, resulting in insufficient interfacial bonding strength. In addition, the traditional hot melt process mainly uses continuous stacking and overall melting and pressurization, resulting in uneven heat field distribution, difficulty in controlling melt penetration, and a long curing cycle, which makes it difficult for the product consistency and molding efficiency to meet the needs of large-scale batch production.

[0005] To remedy the above-mentioned defects, some improvement plans have attempted to use prefabricated parts combined with local heating technology, dynamic temperature and pressure control systems, etc. However, since the overall process has not broken through the traditional process architecture, there are still problems such as narrow operating windows, large fluctuations in yield rates, and strong dependence on operator experience.

[0006] Therefore, how to optimize the stacking path, heating method and adhesive system based on the process itself has become a key technical direction that needs to be solved urgently.

[0007] The existing technology has the following technical problems: (1) Frequent problems of carbon fiber raw materials breaking and hairy fibers; (2) Limited selection of hot melt adhesive resin systems and unstable bonding performance; (3) Long molding cycle and low thermal curing efficiency; (4) The overall hot melt process is rigid and lacks means to finely control the lamination method and heating parameters, which restricts further improvement of product consistency and production efficiency.

[0008] In summary, it is found that the existing technology has at least the following technical problems:

[0009] The existing carbon fiber hot melt process has technical problems such as low tolerance for carbon fiber raw material defects, limited resin selection and bonding performance, long molding cycle and low curing efficiency. Summary of the Invention

[0010] The purpose of the present invention is to provide a hot melt process for a bicycle carbon fiber frame to solve the technical problems of the existing carbon fiber hot melt process, such as low tolerance to carbon fiber raw material defects, limited resin selection and bonding performance, long molding cycle and low curing efficiency.

[0011] The various technical effects that can be produced by the preferred technical solutions among the various technical solutions provided by the present invention are described in detail below.

[0012] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0013] The present invention provides a hot-melt process for a bicycle carbon fiber frame, comprising the following steps: S1, pre-treating the carbon fiber cloth: the carbon fiber cloth has a multi-directional woven structure, and the hair rate on the disc surface is not higher than 0.5 strands / cm 2 ; After the surface of the carbon fiber cloth is treated with plasma, its surface energy is not less than 60mN / m;

[0014] S2. Composite adhesive: A hot melt adhesive is used as a composite adhesive between each layer of the carbon fiber cloth, and the hot melt adhesive includes a polyimide-modified ethylene-vinyl acetate copolymer and a temperature-controlled release polyester microcapsule flux;

[0015] S3. Laying to form a structure: Laying the pretreated carbon fiber cloth in sections according to a set layup sequence, wherein each section comprises multiple stacked layup units, and performing a local preheating treatment after each layer of the layup unit is laid; the preheating temperature is 90° C. to 110° C., and the duration is 5 to 15 minutes, so that the carbon fiber cloth and the hot melt adhesive are initially bonded to form a structure;

[0016] S4, hot melt curing molding: placing the formed structure into a hot melt mold with multiple temperature control zones, and hot melt curing molding the structure;

[0017] The curing temperature of each temperature control zone is controlled at 90°C to 160°C; during the hot melt curing process, the cavity of the hot melt mold is pressurized in stages until the curing is completed, and the pressurization pressure range is controlled at 0.2 to 0.6 MPa;

[0018] S5. Vacuuming and compacting the interlayer structure: During the hot melt curing molding process of step S4, an exhaust device is introduced to vacuum the cavity of the hot melt mold during the hot melt curing molding process. The exhaust rate is 50 to 150 L / min and the exhaust time is 10 to 30 minutes. This is used to remove air between the layers of the carbon fiber cloth of the structure and excess hot melt adhesive to prevent the formation of gaps in the ply of the structure.

[0019] S6. Tempering: After the structure is hot-melt solidified and formed, the structure is subjected to constant temperature tempering treatment at a tempering temperature of 100° C. to 130° C. for 1 to 3 hours to release the internal stress of the structure and improve the stability of the bonding interface.

[0020] In one embodiment, in step S1, the multidirectional braiding structure is one or a combination of 0° / 90° orthogonal braiding, ±45° bias braiding, or 0° / ±45° / 90° three-directional braiding.

[0021] In one embodiment, in step S1, the plasma treatment uses a mixed atmosphere of argon and oxygen, the treatment power is 100 to 300 W, and the treatment time is 30 to 90 seconds.

[0022] In one embodiment, the release temperature of the polyester microcapsule flux is 80°C to 120°C.

[0023] In one embodiment, in step S3, the coating amount of the hot melt adhesive is 30 to 80 g / m 2 , the coating method is hot melt spraying or screen roller transfer.

[0024] In one embodiment, in step S4, the multiple temperature control zones are respectively the head pipe zone, the bottom bracket zone and the rear fork zone, and the heating temperature is regulated by an independent temperature curve respectively; each temperature control zone of the hot melt mold is provided with an independent temperature sensor and heating element, and dynamic closed-loop adjustment is performed by a central controller arranged outside the hot melt mold; wherein: the temperature control range of the head pipe zone is 100°C to 130°C; the temperature control range of the bottom bracket zone is 130°C to 160°C; the temperature control range of the rear fork zone is 90°C to 120°C.

[0025] In one embodiment, the exhaust device includes a vacuum pump and an exhaust channel and an air guide groove connected to the cavity of the hot melt mold; the central controller is electrically connected to the vacuum pump, and a timed exhaust program is set in the central controller to control the vacuum pump to vacuum the cavity of the hot melt mold before pressurizing the hot melt mold.

[0026] In one embodiment, in step S3, the laid sections include the main pipe area, the bottom bracket area and the rear fork area; the carbon fiber cloth is laid in sequence according to the laying order of the main pipe area, the bottom bracket area and the rear fork area to establish the main structural frame and improve the continuity of the stress transfer path.

[0027] In one embodiment, each of the ply units includes at least three layers of the carbon fiber cloth, and the laying angles of the three layers of the carbon fiber cloth are 0°, +45° and -45°, respectively, for bearing axial force and shear stress, respectively.

[0028] In one embodiment, the stacking mode of the carbon fiber cloth between adjacent ply units is staggered stacking, and the stacking angle offset of the carbon fiber cloth is controlled within the range of 10° to 30°, so as to improve the interlayer shear strength and interface bonding stability.

[0029] Compared with the existing carbon fiber frame hot melt process, the bicycle carbon fiber frame hot melt process provided by the present invention has the following beneficial effects:

[0030] 1. Improve the adaptability of carbon cloth

[0031] By implementing low-fuzz screening and surface plasma treatment on carbon fiber cloth, the interfacial activity and processing stability of the carbon fiber cloth are improved, the discreteness between different batches of raw materials is effectively accommodated, and the impact of broken ends and floating fibers on molding quality is reduced;

[0032] 2. Optimize the bonding system and enhance interlayer bonding performance

[0033] The present invention uses a composite hot melt adhesive composed of a polyimide-modified ethylene-vinyl acetate copolymer and a temperature-controlled release polyester microcapsule flux. Compared with traditional single hot melt adhesive systems, the composite hot melt adhesive used in this technical solution has a wider process window and staged penetration ability, thereby improving the bonding depth and interlayer strength.

[0034] 3. Zoned temperature control + segmented paving can improve the consistency of structural molding

[0035] By laying the carbon cloth in sections and performing local preheating after each layer is laid, each layer unit in each section can be independently pre-melted, thereby adapting to the heat capacity and stacking thickness of different areas, reducing the phenomenon of overheating or undermelting of the colloid in the formed structure, and improving the inter-layer uniformity of the layer.

[0036] 4. Fine curing control to achieve high efficiency and short cycle molding

[0037] The hot melt mold is equipped with multiple temperature control zones, each of which is controlled within the range of 90°C to 160°C. Combined with staged pressure control within the range of 0.2 to 0.6 MPa, this ensures complete curing of the structure while significantly shortening the curing cycle, improving curing efficiency by at least 20% to 35% compared to conventional processes.

[0038] 5. Vacuum-assisted vacuuming and compacting of interlayer structure to prevent interlayer bubbles and dry glue defects

[0039] By setting up an exhaust device, continuous extraction during the hot melt process can effectively remove residual gas and excess colloid between layers, prevent the formation of bubbles, interlayer voids and unbonded areas, and improve the overall molding quality;

[0040] 6. Introduce the tempering stress release step to improve structural durability and dimensional stability

[0041] The tempering temperature is set at 100℃~130℃ for 1~3 hours, which can release the internal stress of the cured carbon fiber structure, improve the interface stability and fatigue life of the product, and reduce the risk of deformation and delamination in long-term use;

[0042] In summary, the carbon fiber frame hot melt process proposed in the present invention not only significantly improves the process adaptability and bonding reliability, but also significantly shortens the hot melt molding cycle, improves structural integrity and mass production consistency, and has clear technological advancement and industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 The present invention is a schematic flow chart of the hot-melt process for a bicycle carbon fiber frame. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0046] In a specific embodiment, a hot melt process for a bicycle carbon fiber frame is provided, which includes multiple steps performed in sequence: pre-treating the carbon fiber cloth to give it a low lint rate and high surface energy; the hot melt adhesive used is a composite system of polyimide-modified ethylene-vinyl acetate copolymer and a temperature-controlled release polyester microcapsule flux; the carbon fiber cloth is laid in sections according to a set order, and local preheating treatment is performed after each layer of laying unit is laid to enhance interface fusion and form a structure; the structure is placed in a hot melt mold for curing and molding, and pressurized in sections during curing; an exhaust device is simultaneously connected to remove interlayer air and excess colloid; after molding is completed, a constant temperature tempering treatment is performed to release structural stress; the process has good raw material adaptability, strong bonding performance and a short molding cycle, and is suitable for batch production of high-performance carbon fiber bicycle frames; it effectively solves the technical problems of the existing carbon fiber hot melt process, such as low tolerance to carbon fiber raw material defects, limited resin selection and limited bonding performance, long molding cycle and low curing efficiency.

[0047] The first implementation of the hot melt process for bicycle carbon fiber frames Figure 1 As shown, it includes steps S1 to S6, and the specific operations of each step are as follows: S1, pre-treating carbon fiber cloth: the structure of the carbon fiber cloth is a multi-directional woven structure, and the hair rate on the disk surface is not higher than 0.5 pieces / cm 2 After the surface of the carbon fiber cloth is treated with plasma, its surface energy is not less than 60mN / m;

[0048] S2. Composite adhesive: A hot melt adhesive is used between each layer of carbon fiber cloth as a composite adhesive. The hot melt adhesive includes polyimide-modified ethylene-vinyl acetate copolymer and a temperature-controlled release polyester microcapsule flux.

[0049] S3. Laying to form a structure: Laying the pretreated carbon fiber cloth in sections according to a set layup sequence. Each section comprises multiple stacked layup units. After each layup unit is laid, a local preheating treatment is performed. The preheating temperature is 90°C to 110°C for 5 to 15 minutes to initially bond the carbon fiber cloth with the hot melt adhesive and form a structure.

[0050] S4, hot melt curing molding: placing the formed structure into a hot melt mold with multiple temperature control zones, and hot melt curing molding the structure;

[0051] The curing temperature of each temperature control zone is controlled at 90℃~160℃; during the hot melt curing process, the cavity of the hot melt mold is pressurized in stages until the curing is completed, and the pressurization pressure range is controlled at 0.2~0.6MPa;

[0052] S5. Vacuuming and compacting the interlayer structure: During the hot melt curing molding process in step S4, an exhaust device is introduced to vacuum the cavity of the hot melt mold during the hot melt curing molding process. The exhaust rate is 50 to 150 L / min and the exhaust time is 10 to 30 minutes. This is used to remove air between the layers of the carbon fiber cloth of the structure and excess hot melt adhesive to prevent the formation of gaps in the ply of the structure.

[0053] S6. Tempering: After the structure is hot-melt solidified and formed, the structure is subjected to constant temperature tempering treatment at a tempering temperature of 100°C to 130°C for 1 to 3 hours to release the internal stress of the structure and improve the stability of the bonding interface.

[0054] like Figure 1 As shown, when applying, the material preparation of steps S1 and S2 should be completed first, and then the carbon fiber cloth laying step S3 should be entered, wherein each layer of the ply unit contains multiple layers of carbon fiber cloth, and the carbon fiber cloths are bonded by hot melt adhesive. After each segmented ply unit is laid in the ply order, it is preheated, and then the stacking and preheating of the ply units are repeated to finally form a structure; enter step S4, and then place the preliminary formed structure into a hot melt mold to complete hot melt curing molding, wherein the structure placed in the mold needs to be heated, pressurized and vacuumed in step S5; after the structure is formed by hot melt curing, enter the tempering step S6, and finally form a preliminary finished product of the carbon fiber frame structure.

[0055] Compared with the existing carbon fiber frame hot melt process, the bicycle carbon fiber frame hot melt process provided by the present invention has the following beneficial effects: improving the adaptability of carbon cloth: by implementing low fuzz rate screening and surface plasma treatment on the carbon fiber cloth, the interfacial activity and processing stability of the carbon fiber cloth are improved, the discreteness between different batches of raw materials is effectively accommodated, and the influence of broken ends and floating fibers on the molding quality is reduced;

[0056] Optimize the bonding system and enhance interlayer bonding performance: This invention uses a composite hot melt adhesive composed of polyimide-modified ethylene-vinyl acetate copolymer (polyimide-modified EVA) and a temperature-controlled release polyester microcapsule flux. Compared with traditional single hot melt adhesive systems, the composite hot melt adhesive used in this technical solution has a wider process window and phased penetration ability, thereby improving the bonding depth and interlayer strength.

[0057] Zoned temperature control and segmented layup can improve structural forming consistency: by laying the carbon cloth in segments and performing local preheating after each layer is laid, each layer unit in each segmented layup area can be independently pre-melted, thereby adapting to the heat capacity and stacking thickness of different areas, reducing the occurrence of colloid overheating or undermelting in the formed structure, and improving the inter-layer uniformity of the layer;

[0058] Precise curing control enables high-efficiency, short-cycle molding: The hot-melt mold is equipped with multiple temperature control zones, each of which is controlled within the range of 90°C to 160°C. Combined with staged pressure control within the range of 0.2 to 0.6 MPa, this ensures complete curing of the structure while significantly shortening the curing cycle, improving curing efficiency by at least 20% to 35% compared to conventional processes.

[0059] Vacuum-assisted extraction compacts the interlayer structure to prevent interlayer bubbles and dry glue defects: By setting up an exhaust device, continuous extraction during the hot melt process can effectively remove residual gas and excess colloid between layers, prevent the formation of bubbles, interlayer voids and unbonded areas, and improve the overall molding quality;

[0060] The tempering stress release step is introduced to improve structural durability and dimensional stability: the tempering temperature is set at 100℃~130℃, and the time is 1~3 hours. This can release the internal stress of the cured carbon fiber structure, improve the interface stability and fatigue life of the product, and reduce the risk of deformation and delamination in long-term use;

[0061] The carbon fiber frame hot melt process proposed in this invention not only significantly improves the process adaptability and bonding reliability, but also significantly shortens the hot melt molding cycle, improves structural integrity and mass production consistency, and has clear technological advancement and industrial application value.

[0062] As one optional implementation method:

[0063] Regarding the multidirectional weaving structure of the carbon fiber cloth used in the above step S1, specifically, the multidirectional weaving structure is one or a combination of 0° / 90° orthogonal weaving, ±45° bias weaving, or 0° / ±45° / 90° tridirectional weaving.

[0064] As well as the specific settings for plasma treatment of carbon fiber cloth, the plasma treatment adopts a mixed atmosphere of argon and oxygen, the treatment power is 100 to 300W, and the treatment time is 30 to 90 seconds.

[0065] When applying, carbon fiber cloth can be selected according to the load-bearing direction and shape complexity of different frame structures: 0° / 90° orthogonal weaving is used for the main axial load-bearing area, such as the downtube area of ​​the frame; ±45° diagonal weaving is used for shear sections, such as the connection area between the bottom bracket and the rear fork; three-way weaving structure is used for complex stress areas, such as the area below the bottom bracket and the connection section between the head tube and the top tube; thereby, an optimized layup structure is achieved to achieve stress coordination in each functional area.

[0066] In the process of plasma treatment of carbon fiber cloth, the gas ratio is controlled to argon: oxygen = 2:1. After treatment, polar functional groups are more easily formed on the surface of the carbon fiber cloth, which enhances the wetting and diffusivity of the hot melt adhesive and significantly reduces the "glue penetration barrier" problem caused by hair or dust. The surface activity, material adaptability and bonding consistency of the carbon cloth are improved, solving the technical defect of low tolerance for raw material defects.

[0067] The release temperature of the polyester microcapsule flux, one of the components of the composite adhesive constructed in step S2, is 80°C to 120°C.

[0068] In step S3 of laying and bonding the carbon fiber cloth, the coating amount of the hot melt adhesive is 30 to 80 g / m 2 , the coating method is hot melt spraying or screen roller transfer.

[0069] During application, the release temperature of the polyester microcapsule flux is controlled between 80℃ and 120℃. Its release process has a gradient distribution characteristic, which helps the colloid between the stacked carbon fiber cloth layers to gradually soften and penetrate layer by layer, thereby improving the internal infiltration quality of the structure.

[0070] Hot melt adhesives can be applied using different coating processes according to the product structure: hot melt spraying can be used for tubular structures to improve coating uniformity; for curved surfaces or small angle areas, screen roller transfer can be used to control the thickness of the colloid coating; this helps to enhance the interfacial affinity and penetration depth of hot melt adhesives for carbon fiber cloths with different morphologies, reduce problems such as "false adhesion" and "local over-gluing", and improve bonding stability.

[0071] Regarding the specific settings of the laying path and laying sequence in the above-mentioned step S3, the laying sections include the main pipe area, the bottom bracket area and the rear fork area; the carbon fiber cloth is laid in the laying sequence of the main pipe area, the bottom bracket area and the rear fork area in order to establish the main structural frame and improve the consistency of the stress transfer path.

[0072] Each ply unit includes at least three layers of carbon fiber cloth, and the laying angles of the three layers of carbon fiber cloth are 0°, +45° and -45°, respectively, for bearing axial force and shear stress, respectively.

[0073] The stacking method of the carbon fiber cloth between adjacent ply units is staggered stacking, and the stacking angle offset of the carbon fiber cloth is controlled within the range of 10° to 30° to improve the interlayer shear strength and interface bonding stability.

[0074] During application, each layup unit is laid in the order of main pipe area → bottom bracket area → rear fork area, gradually establishing the main load-bearing frame, which is conducive to controlling the continuity of thermal field distribution and stress streamlines; the carbon fiber cloth in each layup unit is laid at an angle of 0°, +45° and -45° respectively, forming a three-dimensional shear network in each layer of layup unit; and the staggered stacking (laying) angle of the carbon fiber cloth of the connected layup units is controlled between 10° and 30°, and a ±15° gradient method can be adopted to form a "mechanical transfer channel" between the fiber directions, effectively alleviating the shear weakness caused by the overlap of fiber directions, and also strengthening the connection strength of adjacent layup units; different fiber directions are formed between the carbon fiber cloths, and different fiber directions can also be formed between the layup units, thereby improving the interlayer shear strength, reducing the interface delamination damage of the structure, solving the problem of delamination caused by local uneven load, and thus improving the fatigue life of the entire structure and improving the overall quality of the structure.

[0075] Regarding the multiple temperature-controlled zones set in step S4 above, the specific heating temperatures controlled thereby are set such that the multiple temperature-controlled zones are respectively the head tube zone, the bottom bracket zone, and the rear fork zone, and the heating temperatures are controlled by independent temperature curves. Each temperature-controlled zone of the hot melt mold is provided with an independent temperature sensor and heating element, and dynamic closed-loop adjustment is performed by a central controller provided outside the hot melt mold. Specifically, the temperature control range of the head tube zone is 100°C to 130°C; the temperature control range of the bottom bracket zone is 130°C to 160°C; and the temperature control range of the rear fork zone is 90°C to 120°C.

[0076] During application, the hot melt mold is equipped with three temperature control zones, which are closed-loop regulated by embedded thermocouples and independent PID control systems; the head tube area mainly deals with thin-walled and fast-heating parts, and the temperature is controlled at 100℃~130℃; the bottom bracket area is large in volume and high in thickness, and the temperature is controlled at 130℃~160℃ to ensure sufficient flow of the colloid; the temperature of the rear fork area is controlled at 90℃~120℃ to prevent overheating and deformation; independent temperature control in different areas can solve the problem of uneven thermal curing caused by differences in structural thickness, and achieve synchronous curing and bonding of each structural area, thereby improving the overall strength of the structure.

[0077] Regarding the specific structure of the above-mentioned exhaust device, the specific connection method with the hot melt mold, and the startup control method, the exhaust device includes a vacuum pump and an exhaust channel and an air guide groove connected to the cavity of the hot melt mold; the central controller is electrically connected to the vacuum pump, and a timed start-up exhaust program is set in the central controller to control the vacuum pump to vacuum the cavity of the hot melt mold before pressurizing the hot melt mold.

[0078] During application, the exhaust system is controlled by a central controller, and the vacuum pump start-up is linked to the hot pressing process: it can be set to "evacuation first and then pressurization" or "simultaneous vacuuming and pressurization", and the pressurization and exhaust methods are automatically switched according to the complexity of the frame structure; the hot melt mold cavity is preset with air guide grooves to drain the negative pressure area, and the residual gas pressure can be controlled below 0.1 bar after the vacuum exhaust is completed; by discharging the gas in the mold cavity, problems such as interlayer air residue and excessive colloid expansion can be eliminated, bubbles, interlayer and dry adhesive layer defects can be reduced, and the density of the internal structure can be improved.

[0079] The pressurization of the hot melt mold may be started after the vacuuming treatment of the cavity of the hot melt mold is completed or simultaneously with the vacuuming treatment.

[0080] In step S4, the hot melt mold is pressurized in stages by increasing the wrapping pressure outside the hot melt mold, such as placing the hot melt mold in a pressurized chamber and pressurizing it by wrapping it with gas, or wrapping the hot melt mold with a structural part for wrapping and pressurizing it.

[0081] Specifically, the hot melt mold is placed in an external pressurized cabin and is uniformly pressurized by high-pressure gas (such as nitrogen or compressed air). The staged pressurization includes: the initial pressure stage, the pressure is controlled at 0.1-0.2MPa, the pressure holding stage is controlled at 0.4-0.6MPa, and the slow-release pressure reduction stage is implemented after the structure reaches the specified curing time. This pressurization method is different from the traditional in-mold mechanical top pressure method. The pressure distribution is more uniform and the response is fast, with high wrapping, and it is suitable for complex curved surface structures. It can improve the uniformity of colloid flow, prevent fiber dislocation or colloid extrusion, and improve the molding efficiency and structural consistency of carbon fiber structures.

[0082] The second embodiment of the hot melt process for a bicycle carbon fiber frame differs from the first embodiment in that another control method is used for the staged pressurization of the hot melt mold: the hot melt mold is pressurized in sections by multiple gas injection devices provided outside the hot melt mold.

[0083] Specifically, the hot-melt mold is divided into three pressurized zones, corresponding to the head tube area, the bottom bracket area, and the rear fork area. The outer wall of the mold shell in each area is detachably covered and connected to an independent gas injection device. The central controller sets an independent pressure curve of the air pressure changing with time for each pressurized zone, and controls the pressurization process of the pressurized zone by the gas injection device to achieve: the bottom bracket area is first pressurized to 0.6MPa, and the air pressure value is fixed in the area with high carbon fiber thickness; the head tube area is pressurized to 0.4MPa after 2 minutes; the rear fork area is slowly pressurized to 0.3MPa after 5 minutes, and finally, the three major pressurized areas, the head tube area, the bottom bracket area, and the rear fork area, are released simultaneously.

[0084] This area independent pressurization method is suitable for carbon fiber frame structures with complex structures and asynchronous curing requirements, and is particularly suitable for the molding of carbon fiber frames with irregular cross-sections.

[0085] During application, this zoned pressurization method can be combined with multi-zone temperature control to achieve "dual control matching" of the thermal field and the pressure field, which can improve the colloid saturation of large-section structures (such as the five-way tube) and avoid the risks of under-melting in the core and over-pressure in the outer layer. It helps to improve the adaptability of the hot melt process to complex structures, enhance the molding fullness of thick areas and finely control the molding accuracy of thin areas, thereby improving the overall interface quality of the multi-layer composite carbon fiber frame structure.

[0086] The technical features of the above embodiments may be combined arbitrarily. To simplify the description, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A hot melt process for a bicycle carbon fiber frame, characterized in that: The following steps are involved: S1. Pre-treated carbon fiber cloth: The carbon fiber cloth has a multi-directional woven structure, and the hair rate on the disc surface is not higher than 0.5 strands / cm 2 ; After the surface of the carbon fiber cloth is treated with plasma, its surface energy is not less than 60mN / m; S2. Composite adhesive: A hot melt adhesive is used as a composite adhesive between each layer of the carbon fiber cloth, and the hot melt adhesive includes a polyimide-modified ethylene-vinyl acetate copolymer and a temperature-controlled release polyester microcapsule flux; S3. Laying to form a structure: The pretreated carbon fiber cloth is laid in sections according to a set layup sequence, with each section comprising multiple stacked layup units. After each layer of the layup unit is laid, a local preheating treatment is performed; the preheating temperature is 90° C. to 110° C., and the duration is 5 to 15 minutes, so that the carbon fiber cloth and the hot melt adhesive are initially bonded to form a structure. In step S3, the sections to be laid include the main trunk area, the bottom bracket area, and the rear dropout area. The carbon fiber cloth is laid in the order of the main trunk area, the bottom bracket area, and the rear dropout area to establish the main structural framework and improve the consistency of the stress transfer path. S4, hot melt curing molding: placing the formed structure into a hot melt mold with multiple temperature control zones, and hot melt curing molding the structure; The curing molding temperature of each temperature control zone is controlled at 90°C to 160°C; during the hot melt curing molding process, the cavity of the hot melt mold is pressurized in stages until the curing is completed, and the pressurization pressure range is controlled at 0.2 to 0.6 MPa; S5. Vacuuming and compacting the interlayer structure: During the hot melt curing molding process of step S4, an exhaust device is introduced to vacuum the cavity of the hot melt mold during the hot melt curing molding process. The exhaust rate is 50 to 150 L / min and the exhaust time is 10 to 30 minutes. This is used to remove air between the layers of the carbon fiber cloth of the structure and excess hot melt adhesive to prevent the formation of gaps in the ply of the structure. S6. Tempering: After the structure is hot-melt solidified and formed, the structure is subjected to constant temperature tempering treatment at a tempering temperature of 100° C. to 130° C. for 1 to 3 hours to release the internal stress of the structure and improve the stability of the bonding interface.

2. The hot melt process for bicycle carbon fiber frame according to claim 1, characterized in that: In step S1 , the multidirectional braiding structure is one or a combination of 0° / 90° orthogonal braiding, ±45° bias braiding, or 0° / ±45° / 90° three-directional braiding.

3. The hot melt process for bicycle carbon fiber frame according to claim 1, characterized in that: In step S1 , the plasma treatment uses a mixed atmosphere of argon and oxygen, a treatment power of 100 to 300 W, and a treatment time of 30 to 90 seconds.

4. The hot melt process for bicycle carbon fiber frame according to claim 1, characterized in that: The release temperature of the polyester microcapsule flux is 80° C. to 120° C.

5. The hot melt process for a bicycle carbon fiber frame according to any one of claims 1 or 4, characterized in that: In step S3, the coating amount of the hot melt adhesive is 30 to 80 g / m 2 , the coating method is hot melt spraying or screen roller transfer.

6. The hot melt process for bicycle carbon fiber frame according to claim 1, characterized in that: In step S4, the plurality of temperature control zones are respectively the head pipe zone, the bottom bracket zone and the rear fork zone, and the heating temperature is regulated by independent temperature curves respectively; Each temperature control zone of the hot melt mold is provided with an independent temperature sensor and heating element, and is dynamically closed-loop regulated by a central controller provided outside the hot melt mold; Wherein: the temperature control range of the head pipe area is 100℃~130℃; The temperature control range of the five-pass zone is 130°C to 160°C; The temperature control range of the rear fork area is 90°C to 120°C.

7. The hot-melt process for a bicycle carbon fiber frame according to claim 6, characterized in that: The exhaust device includes a vacuum pump and an exhaust channel and an air guide groove connected to the cavity of the hot melt mold; The central controller is electrically connected to the vacuum pump. A timed vacuuming program is provided in the central controller to control the vacuum pump to vacuum the cavity of the hot melt mold before pressurizing the hot melt mold.

8. The hot-melt process for bicycle carbon fiber frame according to claim 1, characterized in that: Each of the ply units includes at least three layers of the carbon fiber cloth, and the laying angles of the three layers of the carbon fiber cloth are 0°, +45° and -45°, respectively, for bearing axial force and shear stress, respectively.

9. The hot-melt process for a bicycle carbon fiber frame according to claim 8, characterized in that: The stacking mode of the carbon fiber cloth between adjacent ply units is staggered stacking, and the stacking angle offset of the carbon fiber cloth is controlled within the range of 10° to 30°, so as to improve the interlayer shear strength and interface bonding stability.

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