Manufacturing method and application of modified bamboo frame

Abstract

The invention relates to the technical field of vehicle frames, in particular to a manufacturing method and application of a modified bamboo vehicle frame, and the manufacturing method comprises the following steps: firstly, selecting moso bamboo and hardwood which are 3-5 years old, cutting, cooking, drying and polishing; secondly, a modifier is prepared, and the bamboo materials are soaked and then dried; secondly, preparing an epoxy resin matrix, and performing compression molding and curing by adopting a vacuum-assisted resin transfer process; and then, a mortise and tenon joint structure is designed, and stress nodes are locally reinforced. And finally, the surface of the frame is polished, and waterborne polyurethane varnish is coated and baked. According to the method, the strength and durability of the bamboo frame are improved, the bending strength, the elastic modulus, the impact toughness and the like of the bamboo frame manufactured through the method are remarkably improved compared with those of a traditional method, the requirement of a high-performance bicycle is completely met, the gradient reinforcement concept is adopted at key nodes, and the strength and durability of the bamboo frame are improved through local thickening and directional carbon fiber reinforcement. Progressive transmission of stress is achieved, and the fatigue life of the frame is greatly prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle frames, and in particular to a manufacturing method and application of a modified bamboo-wood vehicle frame. Background Art

[0002] With the improvement of environmental awareness and the popularization of the concept of sustainable development, bamboo and wood materials are increasingly used in various fields as a renewable resource. In the bicycle manufacturing industry, bamboo and wood frames have attracted more and more attention due to their unique aesthetic value and environmental protection characteristics. However, the traditional bamboo and wood frame manufacturing method faces many challenges and cannot meet the stringent requirements of modern high-performance bicycles for strength, durability and lightness.

[0003] In the prior art, the application of bamboo and wood materials is mainly limited to simple mechanical processing and surface treatment. Although some studies have attempted to improve the performance of bamboo and wood materials through chemical modification, most of them remain at a single modification treatment, and it is difficult to achieve a comprehensive improvement in comprehensive performance. In addition, the existing preparation methods of bamboo and wood composite materials often ignore the problem of interface bonding, resulting in the mechanical properties and durability of the final product being difficult to reach the ideal level. In terms of the structural design of bamboo and wood frames, traditional methods are difficult to effectively solve the problem of stress concentration, especially at key nodes, where fatigue failure is prone to occur. Summary of the invention

[0004] The present invention aims to solve the above technical problems and realize the overall improvement of the performance of bamboo-wood frame through innovative modification, composite process and structural design. The core of the present invention is to establish a set of systematic modified bamboo-wood frame manufacturing methods, covering the optimization of the whole process from raw material processing to final forming.

[0005] The object of the present invention is to provide a method for manufacturing a modified bamboo-wood frame, comprising the following steps:

[0006] (1) Pretreatment of bamboo and wood materials: 3-5 year old bamboo and hardwood were selected, cut into segments with a length of 50-70 cm, internodes were removed, and the thickness of the bamboo wall was retained to be 3-5 mm; steamed for 2-3 hours at a pressure of 0.6-0.8 MPa and a temperature of 120-130° C.; then dried at 60-70° C. for 24-48 hours to reduce the moisture content of the bamboo and wood materials to 8-12%; finally, the surface of the bamboo and wood materials was polished with 120-mesh sandpaper;

[0007] (2) Preparation of modifier and impregnation treatment: prepare a modifier containing the following parts by weight: 35-45 parts of phenol, 25-30 parts of 37% formaldehyde aqueous solution, 8-12 parts of γ-glycidyl ether propyl trimethoxy silane, 4-6 parts of polyethylene glycol 600, 0.8-1.2 parts of p-toluenesulfonic acid, and the balance of up to 100 parts of deionized water; immerse the pretreated bamboo material in the modifier, immerse at a pressure of 0.5-0.7 MPa for 10-14 hours, and then dry at 85-95° C. for 30-40 hours;

[0008] (3) Preparation of epoxy resin matrix: 100 parts of bisphenol A epoxy resin, 12-18 parts of neopentyl glycol diglycidyl ether, 35-45 parts of cyclic aliphatic amine curing agent, 3-5 parts of nano-silicon dioxide and 0.8-1.2 parts of carbon nanotubes were mixed;

[0009] (4) Compression molding and resin impregnation: using a vacuum-assisted resin transfer process, curing at a temperature range of 85-105°C for 5-7 hours at a pressure of 0.15-0.25 MPa, followed by post-curing at 125-145°C for 2.5-3.5 hours;

[0010] (5) Modular connection structure design and node reinforcement: Design the mortise and tenon structure connection points and perform local reinforcement at the main stress-bearing nodes;

[0011] (6) Surface treatment and painting: Use 240-grit sandpaper to polish the frame surface, apply water-based polyurethane varnish, and bake at 65±5℃ for 2.5-3.5 hours.

[0012] Specifically, the preparation method of the modifier in step (2) comprises:

[0013] First, add phenol and formaldehyde aqueous solution into a reaction kettle, and stir and react at 65-75° C. for 1.5-2.5 hours;

[0014] Secondly, cool to 45-55°C, add γ-glycidyl ether propyl trimethoxy silane, and continue stirring for 40-50 minutes;

[0015] Then, add polyethylene glycol 600 and p-toluenesulfonic acid and stir evenly for 15-20 minutes;

[0016] Finally, deionized water was added to adjust the concentration and control the solid content at 40-45%.

[0017] Specifically, the preparation method of the epoxy resin matrix in step (3) includes:

[0018] First, bisphenol A epoxy resin and neopentyl glycol diglycidyl ether were stirred and mixed at 65±5° C. for 35-45 minutes;

[0019] Secondly, add nano-silicon dioxide and carbon nanotubes, use a high-speed disperser to disperse at 4000-6000 rpm for 40-70 minutes, and control the temperature of the dispersion system not to exceed 80°C;

[0020] Finally, cool to 25±5℃, add cycloaliphatic amine curing agent, stir evenly for 5-8 minutes, and vacuum degas for 15-20 minutes.

[0021] Specifically, the design of the modular connection structure in step (5) includes:

[0022] The design of the tenon length is 18-22mm, and the width is 55-65% of the wall thickness of the bamboo and wood material.

[0023] Apply epoxy adhesive to the mortise and tenon contact surface and cure at 23±2℃ for 24-28 hours after assembly;

[0024] External coating at the connection: 200g / m 2 3K plain carbon fiber cloth was cured at 85±5℃ for 2.5-3 hours using vacuum bag pressing method.

[0025] Specifically, the node reinforcement method in step (5) includes:

[0026] Design local thickening areas at the main stress nodes to increase the thickness by 1.5-2.5mm;

[0027] Lay 400g / m in the thickened area 2 12K unidirectional carbon fiber cloth, the direction is consistent with the principal stress direction;

[0028] Epoxy resin is injected using a vacuum-assisted process and cured at 105±5°C for 3.5-4.5 hours. At the same time, metal parts are used in areas prone to wear, such as the head tube, bottom bracket, and seat tube. The rear fork connection is reinforced with metal parts.

[0029] Specifically, the composition of the waterborne polyurethane varnish in step (6) is:

[0030] 70-80 parts of aqueous polyurethane dispersion, 3-5 parts of water-dispersible aziridine crosslinking agent, and the balance up to 100 parts of deionized water.

[0031] The modified bamboo-wood frame is manufactured by the manufacturing method.

[0032] The modified bamboo-wood frame is used in bicycle manufacturing.

[0033] The modified bamboo-wood frame is used in the manufacture of electric bicycles.

[0034] The modified bamboo-wood frame is used in the manufacture of mountain bicycles.

[0035] The innovative features and technical effects of the present invention are mainly reflected in the following aspects:

[0036] First, the present invention adopts a unique multi-step modification process. By introducing γ-glycidyl ether propyl trimethoxy silane as a coupling agent, the silanization of the surface of the bamboo and wood material is achieved. This step not only improves the water resistance of the bamboo and wood material, but more importantly, changes the chemical properties of the surface of the bamboo and wood material at the molecular level. The silane group forms a covalent bond with the hydroxyl group in the bamboo and wood material, and the exposed epoxy group provides a chemical basis for the subsequent combination with the epoxy resin. This molecular-level interface design significantly enhances the interface bonding strength of the composite material.

[0037] Secondly, the present invention introduces nano-silicon dioxide and carbon nanotubes into the epoxy resin matrix to form a multi-scale reinforcement network. Nano-silicon dioxide enhances the cross-linking density and hardness of the resin matrix through its large specific surface area and surface activity. Carbon nanotubes form a conductive and thermal conductive network in the matrix with their unique one-dimensional structure and excellent mechanical properties. The synergistic effect of these two nanomaterials not only improves the mechanical properties of the composite material, but also unexpectedly improves its thermal and electrical properties.

[0038] Thirdly, the present invention innovatively adopts the vacuum assisted resin transfer process (VARTM). This process not only ensures the full penetration of the resin into the pores of the bamboo and wood materials, but also minimizes the generation of bubbles during the composite process. By precisely controlling the pressure and temperature, a high degree of uniformity in the internal structure of the composite material is achieved, which plays a key role in improving the overall performance and long-term stability of the material.

[0039] Finally, the present invention is unique in its structural design. Through modular connection structure and node reinforcement design, the problem of traditional bamboo and wood frames being prone to failure in stress concentration areas is effectively solved. In particular, the concept of gradient reinforcement is adopted at key nodes. Through local thickening and directional carbon fiber reinforcement, the gradual transfer of stress is achieved, which greatly improves the fatigue life of the frame.

[0040] The beneficial effects of the present invention are mainly reflected in the following aspects:

[0041] 1. As natural materials, wood and bamboo each have unique advantages in bicycle frame manufacturing. Wood has a natural fiber structure, and these fibers are upright and tightly clustered in trees. When wood is subjected to gravity, its fiber structure can effectively disperse the pressure, making the wood have good compressive resistance. This means that when wood is subjected to vertical loads, it can withstand a large weight without breaking or deforming easily. Therefore, wood is particularly suitable for the longitudinal components of bicycle frames, such as seat tubes, head tubes, etc., which need to withstand large compressive forces.

[0042] As a fast-growing plant, bamboo has high strength and stiffness while being lightweight. The fiber structure of bamboo makes it perform well when subjected to bending forces, making it particularly suitable for use in the transverse components of bicycle frames, such as the crossbars and top tubes of the frame, which need to withstand large bending forces.

[0043] Combining wood and bamboo can fully utilize their respective advantages and achieve complementary performance. For example, in the design of bicycle frames, wood can be used to make parts that withstand compression, such as seat tubes and head tubes, while bamboo can be used to make parts that withstand bending forces, such as the crossbeams and top tubes of the frame. This combination can make the frame have high strength and rigidity while maintaining lightness, meeting the requirements of high-performance bicycles for the frame.

[0044] In addition, wood and bamboo are both renewable resources with good environmental performance. Using a bamboo-wood frame can not only reduce the impact on the environment, but also improve the aesthetics of the frame, because both wood and bamboo have unique textures and colors. In summary, the combination of wood and bamboo can make full use of their respective advantages, achieve complementary performance, and have good environmental performance. This combination can make the bicycle frame have high strength and rigidity while maintaining lightweight, meeting the requirements of high-performance bicycles for the frame.

[0045] 2. Comprehensive improvement of mechanical properties: Through the synergistic effect of multiple modification and composite technologies, the bamboo-wood frame prepared by the present invention has significantly improved bending strength, elastic modulus and impact toughness compared with traditional methods, and fully meets the requirements of high-performance bicycles.

[0046] 3. Excellent environmental resistance: The application of silanization modification and water-based polyurethane varnish makes the frame have extremely low water absorption and excellent weather resistance, greatly extending the service life of the product.

[0047] 4. Breakthrough in fatigue performance: Thanks to multi-scale enhancement and innovative structural design, the frame of the present invention has achieved an order of magnitude improvement in fatigue life, which is crucial for the long-term safety of the bicycle.

[0048] 5. Unexpected improvement in thermal performance: The introduction of nanomaterials not only improves the mechanical properties of the material, but also optimizes its thermal conductivity and dimensional stability, which provides greater possibilities for the application of the frame in different environments.

[0049] 6. Perfect combination of environmental protection and high performance: This invention not only makes full use of renewable bamboo and wood material resources, but also achieves environmental friendliness throughout the entire process through low-VOC water-based paint. This combination of green manufacturing concept and excellent performance provides a new direction for the sustainable development of the bicycle manufacturing industry.

[0050] In summary, the present invention successfully solves the key technical problems in the production of traditional bamboo and wood frames through the integration and innovation of multidisciplinary knowledge, and achieves a high degree of unity in performance, environmental protection and aesthetics. This not only provides new possibilities for high-end bicycle manufacturing, but also opens up broad prospects for the application of bamboo and wood materials in other fields. DETAILED DESCRIPTION

[0051] The manufacturing method of the modified bamboo frame of the present invention, γ-glycidyl ether propyl trimethoxy silane, trade name: SilquestA-187, manufacturer: Momentive Performance Materials Inc., bisphenol A type epoxy resin, trade name: EPON 828, manufacturer: Hexion Inc., epoxy resin active diluent (neopentyl glycol diglycidyl ether), trade name: Heloxy Modifier 68, manufacturer: Hexion Inc., modified amine curing agent (cyclic aliphatic amine), trade name: Aradur42, manufacturer: Huntsman Corporation, polytetrafluoroethylene release agent (trade name: Frekote 770-NC, manufacturer: Henkel Corporation). Epoxy adhesive (trade name: Araldite 2011, manufacturer: Huntsman Corporation, shear strength ≥ 18MPa). Carbon fiber cloth (400g / m 2 , 12K unidirectional cloth, trade name: T700SC-12K-50C, manufacturer: Toray Industries, Inc.), water-based polyurethane dispersion, trade name: Bayhydrol UH 2558, manufacturer: Covestro AG, water-dispersible aziridine crosslinker: 3-5 parts, trade name: Bayhydur 304, manufacturer: Covestro AG.

[0052] 1. In the modifier formula, the introduction of γ-glycidyl ether propyl trimethoxy silane as a coupling agent can form a covalent bond between the phenol formaldehyde prepolymer and the bamboo and wood material cellulose, significantly improving the interfacial bonding strength. At the same time, the introduction of the silane group enhances the water resistance and dimensional stability of the material.

[0053] 2. Using neopentyl glycol diglycidyl ether as an active diluent in the epoxy resin matrix can not only reduce viscosity and improve wettability, but also participate in the cross-linking reaction and reduce the release of volatile organic compounds.

[0054] 3. The composite addition of nano-silicon dioxide and carbon nanotubes forms a multi-scale reinforcement network. Nano-silicon dioxide improves the hardness and wear resistance of the resin, while carbon nanotubes improve thermal conductivity and toughness. The synergistic effect of the two improves the overall performance of the composite material.

[0055] 4. Cyclic aliphatic amines are used as curing agents, which have better weather resistance and color retention than traditional aliphatic amines or aromatic amines, while maintaining good mechanical properties.

[0056] 5. In the modular connection structure, the use of epoxy adhesive and carbon fiber cloth wrapping form multiple protections. The adhesive provides initial strength, while the carbon fiber cloth provides long-term structural integrity and fatigue resistance.

[0057] 6. The node reinforcement design adopts the concept of gradient enhancement. Through local thickening and directional carbon fiber reinforcement, the gradual transfer of stress is achieved, effectively avoiding early failure caused by stress concentration.

[0058] 7. The surface treatment adopts a water-based polyurethane varnish system, which is not only environmentally friendly and low in VOC, but also improves the cross-linking density and chemical resistance of the coating through the introduction of water-dispersible aziridine cross-linking agent, while maintaining good flexibility.

[0059] This modified bamboo-wood bicycle frame manufacturing method achieves the unity of performance, environmental protection and aesthetics through multiple material innovations and process optimization. It not only improves the comprehensive performance of bamboo-wood materials, but also through fine structural design and surface treatment, the product meets the requirements of high-end sports equipment, opening up new possibilities for sustainable materials in high-performance applications.

[0060] Embodiment 1: A method for manufacturing a modified bamboo-wood bicycle frame

[0061] This embodiment provides a method for manufacturing a modified bamboo-wood bicycle frame, the method comprising the following steps:

[0062] (1) Pretreatment of bamboo and wood materials: 3-year-old bamboo and hardwood were selected and cut into 50 cm long segments, internodes were removed, and the thickness of the bamboo wall was kept at 3 mm. The bamboo was steamed at a pressure of 0.6 MPa and a temperature of 120°C for 2 hours, and then dried at 60°C for 24 hours to reduce the moisture content of the bamboo to 8%. Finally, the surface of the bamboo was polished with 120-mesh sandpaper.

[0063] (2) Preparation of modifier and impregnation treatment: Prepare a modifier containing the following weight parts: 35 parts of phenol, 25 parts of 37% formaldehyde aqueous solution, 8 parts of γ-glycidyl ether propyl trimethoxy silane, 4 parts of polyethylene glycol 600, 0.8 parts of p-toluenesulfonic acid, and the balance is up to 100 parts of deionized water. The preparation method of the modifier is as follows: First, add phenol and formaldehyde aqueous solution to the reactor, stir and react at 65°C for 1.5 hours; secondly, cool to 45°C, add γ-glycidyl ether propyl trimethoxy silane, and continue stirring for 40 minutes; then, add polyethylene glycol 600 and p-toluenesulfonic acid, and stir evenly for 15 minutes; finally, add deionized water to adjust the concentration and control the solid content at 40%.

[0064] The pretreated bamboo material is immersed in the modifier, immersed at a pressure of 0.5 MPa for 10 hours, and then dried at 85° C. for 30 hours. This immersion treatment can significantly improve the water resistance and dimensional stability of the bamboo material, and at the same time enhance its interface bonding strength with the subsequent epoxy resin matrix.

[0065] (3) Preparation of epoxy resin matrix: 100 parts of bisphenol A epoxy resin, 12 parts of neopentyl glycol diglycidyl ether, 35 parts of cyclic aliphatic amine curing agent, 3 parts of nano-silicon dioxide and 0.8 parts of carbon nanotubes were mixed. The preparation method is as follows: first, bisphenol A epoxy resin and neopentyl glycol diglycidyl ether were stirred and mixed at 60°C for 35 minutes; second, nano-silicon dioxide and carbon nanotubes were added, and dispersed at 4000 rpm for 40 minutes using a high-speed disperser, and the temperature of the dispersion system was controlled not to exceed 75°C; finally, the mixture was cooled to 20°C, the cyclic aliphatic amine curing agent was added, stirred evenly for 5 minutes, and vacuum degassed for 15 minutes.

[0066] (4) Compression molding and resin impregnation: The vacuum-assisted resin transfer process is used to cure the wood at 85°C for 5 hours under a pressure of 0.15 MPa, followed by post-curing at 125°C for 2.5 hours. This process ensures that the resin fully penetrates into the pores of the bamboo and wood materials to form a compact composite structure.

[0067] (5) Modular connection structure design and node reinforcement: Design the mortise and tenon structure connection point, the tenon length is 18mm, and the width is 55% of the wall thickness of the bamboo material. Apply epoxy adhesive on the mortise and tenon contact surface and cure at 21℃ for 24 hours after assembly. The external coating of the connection is 200g / m 2 3K plain carbon fiber cloth, cured at 80℃ for 2.5 hours using vacuum bag pressing method. Local thickening area is designed at the main stress node, increasing the thickness by 1.5mm, and 400g / m2 is laid in the thickening area. 2The 12K unidirectional carbon fiber cloth is in the same direction as the main stress direction. The epoxy resin is injected using a vacuum-assisted process and cured at 100°C for 3.5 hours. At the same time, metal parts are used in places that are prone to wear, such as the head tube, five-way bracket, and seat tube. The rear fork connection is connected and reinforced with metal parts. This design can effectively solve the problem of stress concentration in composite material structures while maintaining the lightweight characteristics of the frame.

[0068] (6) Surface treatment and coating: Use 240-grit sandpaper to polish the frame surface and apply water-based polyurethane varnish. The composition of the water-based polyurethane varnish is: 70 parts of water-based polyurethane dispersion, 3 parts of water-dispersible aziridine crosslinker, and the balance is up to 100 parts of deionized water. Bake at 60°C for 2.5 hours. This surface treatment can improve the weather resistance and wear resistance of the frame while retaining the natural texture of the bamboo and wood materials.

[0069] Embodiment 2: A method for manufacturing a modified bamboo-wood electric bicycle frame

[0070] This embodiment provides a method for manufacturing a modified bamboo-wood electric bicycle frame, the method comprising the following steps:

[0071] (1) Pretreatment of bamboo and wood materials: 4-year-old bamboo and hardwood were selected and cut into 60 cm long segments, internodes were removed, and the thickness of the bamboo wall was kept at 4 mm. The bamboo was steamed at a pressure of 0.7 MPa and a temperature of 125°C for 2.5 hours, and then dried at 65°C for 36 hours to reduce the moisture content of the bamboo to 10%. Finally, the surface of the bamboo was polished with 120-mesh sandpaper.

[0072] (2) Preparation of modifier and impregnation treatment: Prepare a modifier containing the following weight parts: 40 parts of phenol, 27.5 parts of 37% formaldehyde aqueous solution, 10 parts of γ-glycidyl ether propyl trimethoxy silane, 5 parts of polyethylene glycol 600, 1 part of p-toluenesulfonic acid, and the balance is up to 100 parts of deionized water. The preparation method of the modifier is as follows: First, add phenol and formaldehyde aqueous solution to the reactor, and stir at 70°C for 2 hours; secondly, cool to 50°C, add γ-glycidyl ether propyl trimethoxy silane, and continue stirring for 45 minutes; then, add polyethylene glycol 600 and p-toluenesulfonic acid, and stir evenly for 17 minutes; finally, add deionized water to adjust the concentration and control the solid content at 42.5%.

[0073] The pretreated bamboo and wood materials were immersed in the modifier, immersed for 12 hours at a pressure of 0.6 MPa, and then dried at 90° C. for 35 hours.

[0074] (3) Preparation of epoxy resin matrix: 100 parts of bisphenol A epoxy resin, 15 parts of neopentyl glycol diglycidyl ether, 40 parts of cyclic aliphatic amine curing agent, 4 parts of nano-silicon dioxide and 1 part of carbon nanotubes were mixed. The preparation method is as follows: first, bisphenol A epoxy resin and neopentyl glycol diglycidyl ether were stirred and mixed at 62.5°C for 40 minutes; second, nano-silicon dioxide and carbon nanotubes were added, and dispersed at 5000 rpm for 55 minutes using a high-speed disperser, and the temperature of the dispersed system was controlled not to exceed 77.5°C; finally, the mixture was cooled to 22.5°C, the cyclic aliphatic amine curing agent was added, stirred evenly for 6.5 minutes, and vacuum degassed for 17.5 minutes.

[0075] (4) Compression molding and resin impregnation: A vacuum-assisted resin transfer process was used, with curing at 95°C for 6 hours at a pressure of 0.2 MPa, followed by post-curing at 135°C for 3 hours.

[0076] (5) Modular connection structure design and node reinforcement: Design the mortise and tenon structure connection point, the tenon length is 20mm, and the width is 60% of the wall thickness of the bamboo material. Apply epoxy adhesive on the mortise and tenon contact surface and cure at 23℃ for 26 hours after assembly. The connection is coated with 200g / m 2 3K plain carbon fiber cloth, cured at 82.5℃ for 2.75 hours using vacuum bag pressing method. Local thickening area is designed at the main stress node, increasing the thickness by 2mm, and 400g / m2 is laid in the thickening area. 2 The 12K unidirectional carbon fiber cloth is in the same direction as the main stress direction. Epoxy resin is injected using a vacuum-assisted process and cured at 102.5°C for 4 hours. At the same time, metal parts are used in places prone to wear, such as the head tube, bottom bracket, and seat tube. The rear fork connection is reinforced with metal parts.

[0077] (6) Surface treatment and coating: Use 240-grit sandpaper to polish the frame surface and apply water-based polyurethane varnish. The composition of the water-based polyurethane varnish is: 75 parts of water-based polyurethane dispersion, 4 parts of water-dispersible aziridine crosslinker, and the balance is 100 parts of deionized water. Bake at 62.5°C for 3 hours.

[0078] Embodiment 3: A method for manufacturing a modified bamboo mountain bike frame

[0079] This embodiment provides a method for manufacturing a modified bamboo-wood mountain bike frame, the method comprising the following steps:

[0080] (1) Pretreatment of bamboo and wood materials: 5-year-old bamboo and hardwood were selected and cut into segments with a length of 70 cm. The internodes were removed and the thickness of the bamboo wall was kept at 5 mm. The bamboo was steamed at a pressure of 0.8 MPa and a temperature of 130°C for 3 hours, and then dried at 70°C for 48 hours to reduce the moisture content of the bamboo to 12%. Finally, the surface of the bamboo was polished with 120-mesh sandpaper.

[0081] (2) Preparation of modifier and impregnation treatment: Prepare a modifier containing the following weight parts: 45 parts of phenol, 30 parts of 37% formaldehyde aqueous solution, 12 parts of γ-glycidyl ether propyl trimethoxy silane, 6 parts of polyethylene glycol 600, 1.2 parts of p-toluenesulfonic acid, and the balance is up to 100 parts of deionized water. The preparation method of the modifier is as follows: First, add phenol and formaldehyde aqueous solution to the reactor, and stir the reaction at 75°C for 2.5 hours; secondly, cool to 55°C, add γ-glycidyl ether propyl trimethoxy silane, and continue stirring for 50 minutes; then, add polyethylene glycol 600 and p-toluenesulfonic acid, and stir evenly for 20 minutes; finally, add deionized water to adjust the concentration and control the solid content at 45%.

[0082] The pretreated bamboo and wood materials were immersed in the modifier, immersed for 14 hours at a pressure of 0.7 MPa, and then dried at 95° C. for 40 hours.

[0083] (3) Preparation of epoxy resin matrix: 100 parts of bisphenol A epoxy resin, 18 parts of neopentyl glycol diglycidyl ether, 45 parts of cyclic aliphatic amine curing agent, 5 parts of nano-silicon dioxide and 1.2 parts of carbon nanotubes were mixed. The preparation method is as follows: first, bisphenol A epoxy resin and neopentyl glycol diglycidyl ether were stirred and mixed at 65°C for 45 minutes; second, nano-silicon dioxide and carbon nanotubes were added, and dispersed at 6000 rpm for 70 minutes using a high-speed disperser, and the temperature of the dispersion system was controlled not to exceed 80°C; finally, the mixture was cooled to 25°C, the cyclic aliphatic amine curing agent was added, stirred evenly for 8 minutes, and vacuum degassed for 20 minutes.

[0084] (4) Compression molding and resin impregnation: A vacuum-assisted resin transfer process was used, with curing at 105°C for 7 hours at a pressure of 0.25 MPa, followed by post-curing at 145°C for 3.5 hours.

[0085] (5) Modular connection structure design and node reinforcement: Design the mortise and tenon structure connection point, the tenon length is 22mm, and the width is 65% of the wall thickness of the bamboo material. Apply epoxy adhesive on the mortise and tenon contact surface and cure it at 25℃ for 28 hours after assembly. The external coating of the connection is 200g / m 2 3K plain carbon fiber cloth, cured at 85℃ for 3 hours using vacuum bag pressing method. Local thickening area is designed at the main stress node, increasing the thickness by 2.5mm, and 400g / m2 is laid in the thickening area.2 The 12K unidirectional carbon fiber cloth is in the same direction as the main stress direction. Epoxy resin is injected using a vacuum-assisted process and cured at 105°C for 4.5 hours. At the same time, metal parts are used in places prone to wear, such as the head tube, bottom bracket, and seat tube. The rear fork connection is reinforced with metal parts.

[0086] (6) Surface treatment and coating: Use 240-grit sandpaper to polish the frame surface and apply water-based polyurethane varnish. The composition of the water-based polyurethane varnish is: 80 parts of water-based polyurethane dispersion, 5 parts of water-dispersible aziridine crosslinker, and the balance is up to 100 parts of deionized water. Bake at 65°C for 3.5 hours.

[0087] Example 4: A method for manufacturing a modified bamboo-wood road bicycle frame and its application

[0088] This embodiment provides a method for manufacturing a modified bamboo-wood road bicycle frame and its application, the method comprising the following steps:

[0089] (1) Pretreatment of bamboo and wood materials: 4.5-year-old bamboo and hardwood were selected and cut into segments with a length of 65 cm. The internodes were removed and the thickness of the bamboo wall was kept at 4.5 mm. The bamboo and wood materials were steamed at a pressure of 0.75 MPa and a temperature of 127°C for 2.75 hours, and then dried at 67.5°C for 42 hours to reduce the moisture content of the bamboo and wood materials to 11%. Finally, the surface of the bamboo and wood materials was polished with 120-grit sandpaper.

[0090] (2) Preparation of modifier and impregnation treatment (continued): Prepare a modifier containing the following weight parts: 42.5 parts of phenol, 28.75 parts of 37% formaldehyde aqueous solution, 11 parts of γ-glycidyl ether propyl trimethoxy silane, 5.5 parts of polyethylene glycol 600, 1.1 parts of p-toluenesulfonic acid, and the balance is 100 parts of deionized water. The preparation method of the modifier is as follows: First, add phenol and formaldehyde aqueous solution to the reactor, and stir and react at 72.5°C for 2.25 hours; secondly, cool to 52.5°C, add γ-glycidyl ether propyl trimethoxy silane, and continue stirring for 47.5 minutes; then, add polyethylene glycol 600 and p-toluenesulfonic acid, and stir evenly for 18.5 minutes; finally, add deionized water to adjust the concentration and control the solid content at 43.75%.

[0091] The pretreated bamboo and wood materials were immersed in the modifier, immersed at a pressure of 0.65 MPa for 13 hours, and then dried at 92.5° C. for 37.5 hours. This modification treatment can significantly improve the durability and dimensional stability of the bamboo and wood materials, laying the foundation for subsequent composite processing.

[0092] (3) Preparation of epoxy resin matrix: 100 parts of bisphenol A epoxy resin, 16.5 parts of neopentyl glycol diglycidyl ether, 42.5 parts of cyclic aliphatic amine curing agent, 4.5 parts of nano-silicon dioxide and 1.1 parts of carbon nanotubes were mixed. The preparation method is as follows: First, bisphenol A epoxy resin and neopentyl glycol diglycidyl ether were stirred and mixed at 63.75°C for 42.5 minutes; second, nano-silicon dioxide and carbon nanotubes were added, and dispersed at 5500 rpm for 62.5 minutes using a high-speed disperser, and the temperature of the dispersed system was controlled not to exceed 78.75°C; finally, the mixture was cooled to 23.75°C, the cyclic aliphatic amine curing agent was added, and the mixture was stirred evenly for 7.25 minutes, and vacuum degassing was performed for 18.75 minutes. This composite formula can provide excellent mechanical properties and thermal conductivity, which is beneficial to the overall performance improvement of the frame.

[0093] (4) Compression molding and resin impregnation: The vacuum-assisted resin transfer process was used to cure the wood at 100°C for 6.5 hours at a pressure of 0.225 MPa, followed by post-curing at 140°C for 3.25 hours. This process ensures that the resin evenly penetrates the pores of the bamboo and wood materials to form a dense composite structure.

[0094] (5) Modular connection structure design and node reinforcement: Design the mortise and tenon structure connection point, the tenon length is 21mm, and the width is 62.5% of the wall thickness of the bamboo material. Apply epoxy adhesive on the mortise and tenon contact surface and cure it at 24℃ for 27 hours after assembly. The connection is coated with 200g / m 2 3K plain carbon fiber cloth, cured at 83.75℃ for 2.875 hours using vacuum bag pressing method. Local thickening area is designed at the main stress node, increasing the thickness by 2.25mm, and 400g / m2 is laid in the thickening area. 2 12K unidirectional carbon fiber cloth, the direction is consistent with the main stress direction, epoxy resin is injected using a vacuum-assisted process, and cured at 103.75°C for 4.25 hours. This design can effectively solve the stress concentration problem in the composite material structure while maintaining the lightweight characteristics of the frame. At the same time, metal parts are used in places that are prone to wear, such as the head tube, five-way bracket, and seat tube inlaid with metal parts, and the rear fork connection is connected and reinforced with metal parts.

[0095] (6) Surface treatment and coating: Use 240-grit sandpaper to polish the frame surface and apply water-based polyurethane varnish. The composition of the water-based polyurethane varnish is: 77.5 parts of water-based polyurethane dispersion, 4.5 parts of water-dispersible aziridine crosslinker, and the balance is 100 parts of deionized water. Bake at 63.75°C for 3.25 hours. This surface treatment can not only improve the weather resistance and wear resistance of the frame, but also preserve the natural texture of bamboo and wood materials, improving the aesthetics of the product.

[0096] The modified bamboo-wood frame prepared in this embodiment is applied to the manufacture of road bicycles. Since the frame has excellent mechanical properties, lightweight characteristics and unique aesthetic appearance, it is particularly suitable for the production of high-end road bicycles. In practical applications, the frame has demonstrated excellent riding comfort and efficiency, and has been widely praised by professional cycling enthusiasts. At the same time, its environmentally friendly and sustainable characteristics also meet the current market demand for green products, providing an innovative solution for the bicycle manufacturing industry.

[0097] Through the above four embodiments, it can be seen that by adjusting various parameters and component ratios, the most suitable modified bamboo-wood frame can be customized for different types of bicycles (such as ordinary bicycles, electric bicycles, mountain bicycles and road bicycles). This method not only makes full use of the natural advantages of bamboo-wood materials, but also greatly improves its performance through advanced modification and composite technology, so that it can meet the requirements of modern high-performance bicycles. At the same time, the flexibility and adjustability of this method provide broad space for further optimization and expansion of applications in the future.

[0098] Comparative Example 1: Method for making unmodified bamboo frame

[0099] This comparative example is intended to verify the effect of the modification treatment on the performance of the bamboo-wood frame by comparing with Example 1. The preparation method comprises the following steps:

[0100] (1) Pretreatment of bamboo and wood materials: 3-year-old bamboo and hardwood were selected and cut into 50 cm long segments, internodes were removed, and the thickness of the bamboo wall was kept at 3 mm. The bamboo was steamed at a pressure of 0.6 MPa and a temperature of 120°C for 2 hours, and then dried at 60°C for 24 hours to reduce the moisture content of the bamboo to 8%. Finally, the surface of the bamboo was polished with 120-mesh sandpaper.

[0101] (2) Direct epoxy resin impregnation: The epoxy resin matrix formulation is the same as that in Example 1, but no modifier treatment is performed. The epoxy resin is cured at 85° C. for 5 hours under a pressure of 0.15 MPa, followed by post-curing at 125° C. for 2.5 hours.

[0102] (3) The subsequent steps are the same as those in Example 1.

[0103] This comparative example shows that the interface bonding strength, water resistance and dimensional stability of the unmodified bamboo material after being compounded with the epoxy resin are not as good as those of the method of the present invention. This is because the lack of γ-glycidyl ether propyl trimethoxy silane as a coupling agent makes it impossible to form a covalent bond between the bamboo material cellulose and the epoxy resin.

[0104] Comparative Example 2: Method for manufacturing a bamboo frame modified only with phenol formaldehyde

[0105] This comparative example corresponds to Example 2 and is intended to verify the importance of γ-glycidyl ether propyl trimethoxysilane. The preparation method comprises the following steps:

[0106] (1) Pretreatment of bamboo and wood materials: Same as in Example 2.

[0107] (2) Preparation of modifier and impregnation treatment: A modifier containing the following parts by weight was prepared: 40 parts of phenol, 27.5 parts of 37% formaldehyde aqueous solution, 1 part of p-toluenesulfonic acid, and the balance of 100 parts of deionized water. The preparation method was similar to that of Example 2, but γ-glycidyl ether propyl trimethoxy silane and polyethylene glycol 600 were not added.

[0108] (3) The subsequent steps are the same as those in Example 2.

[0109] This comparative example shows that although phenol formaldehyde modification can improve certain properties of bamboo and wood materials, the lack of silane coupling agent will result in a modification effect that is not as good as that of the present invention, especially in terms of water resistance and interfacial bonding strength, which is significantly lower than the results of Example 2.

[0110] Comparative Example 3: Method for making a bamboo-wood frame using a traditional epoxy resin matrix

[0111] This comparative example corresponds to Example 3 and is intended to verify the superiority of the new epoxy resin matrix formula. The preparation method comprises the following steps:

[0112] (1) Bamboo and wood material pretreatment and modifier treatment: the same as in Example 3.

[0113] (2) Preparation of epoxy resin matrix: using conventional bisphenol A epoxy resin and amine curing agent without adding neopentyl glycol diglycidyl ether, nano-silica and carbon nanotubes.

[0114] (3) The subsequent steps are the same as those in Example 3.

[0115] This comparative example shows that although traditional epoxy resin can also form a composite material with modified bamboo and wood materials, it is inferior to the formula of the present invention in terms of mechanical properties, thermal conductivity and toughness. In particular, the lack of nano-silicon dioxide and carbon nanotubes makes it impossible to form a multi-scale reinforcement network, resulting in a decrease in the overall performance of the composite material.

[0116] Comparative Example 4: Bamboo-wood frame manufacturing method without vacuum-assisted resin transfer process

[0117] This comparative example corresponds to Example 4 and is intended to verify the importance of vacuum assisted resin transfer process. The preparation method comprises the following steps:

[0118] (1) Bamboo and wood material pretreatment and modifier treatment: the same as in Example 4.

[0119] (2) Preparation of epoxy resin matrix: same as Example 4.

[0120] (3) Compression molding and resin impregnation: The conventional hand lay-up process was used to perform resin impregnation and curing at normal pressure. The curing conditions were the same as those in Example 4.

[0121] (4) The subsequent steps are the same as those in Example 4.

[0122] This comparative example will show that without vacuum assistance, the resin cannot fully penetrate into the pores of the bamboo and wood materials, resulting in bubbles and resin-poor areas in the composite material. This will significantly reduce the mechanical properties and durability of the material, especially poor performance in fatigue performance.

[0123] Comparative Example 5: Method for manufacturing a bamboo-wood frame without node reinforcement

[0124] This comparative example is aimed at all embodiments and is intended to verify the necessity of node reinforcement design. The production method is the same as that of embodiments 1-4, but the node reinforcement step is omitted.

[0125] This comparison will show that although the overall frame has good performance, stress concentration is prone to occur at the main stress nodes, resulting in insufficient local strength. Especially under dynamic loads, this design will significantly reduce the service life and safety of the frame.

[0126] Comparative Example 6: Bamboo and Wood Frame Manufacturing Method Using Traditional Painting Method

[0127] This comparative example is aimed at all the examples and aims to verify the superiority of the waterborne polyurethane varnish system. The preparation method is the same as that of Examples 1-4, but in the surface treatment step, a traditional solvent-based polyurethane coating is used.

[0128] This comparative example shows that although traditional coating can also provide certain protection, it is not as good as the waterborne polyurethane varnish system of the present invention in terms of environmental protection, compatibility with bamboo and wood materials, and long-term weather resistance. In particular, the traditional coating effect is poor in retaining the natural texture and touch of bamboo and wood materials.

[0129] These comparative examples cover the endpoint values ​​and intermediate values ​​of the key components and process parameters in the formula of the present invention, which strongly proves the synergistic effect of each innovative point of the present invention. Through these comparisons, it can be clearly seen that the method of the present invention has significant advantages in terms of material properties, processing technology and environmental friendliness, which fully reflects its creativity and practical value.

[0130] In order to comprehensively evaluate the effectiveness and superiority of the present invention, a series of test experiments were designed to verify the core innovations of the present invention and demonstrate its advantages in practical applications.

[0131] Test Experiment Design:

[0132] 1. Mechanical properties test

[0133] First, a comprehensive mechanical property test was conducted, including flexural strength, elastic modulus, and impact toughness. The test method follows ASTM D790 and ASTM D256 standards. The specific steps are as follows:

[0134] (a) Flexural strength and elastic modulus test: A universal testing machine was used with a three-point bending method, a loading rate of 2 mm / min, and a fulcrum span of 150 mm.

[0135] (b) Impact toughness test: using an Izod impact tester with notched specimens and an impact energy of 2.7 J.

[0136] 2. Water resistance test

[0137] Secondly, the water resistance of the material was evaluated, which is crucial for the durability of the bicycle frame. The test method refers to the ASTM D570 standard, and the specific steps are as follows:

[0138] (a) Immerse the specimen in distilled water at 23±1℃ for 24 hours.

[0139] (b) Take out the sample, wipe off the surface moisture, and weigh it immediately.

[0140] (c) Calculate the water absorption.

[0141] 3. Interface bonding strength test

[0142] Then, the interface bonding strength test was carried out to evaluate the effect of the modification treatment and composite process. The short beam shear strength test method was adopted, referring to the ASTM D2344 standard. The specific steps are as follows:

[0143] (a) Prepare short beam specimens with dimensions of 60 mm × 10 mm × 5 mm.

[0144] (b) Use a universal testing machine with a loading rate of 1 mm / min until the specimen undergoes obvious interlaminar shear failure.

[0145] 4. Fatigue performance test

[0146] Again, fatigue performance testing was carried out, which is crucial for evaluating the long-term performance of bicycle frames. The cyclic bending fatigue test method was adopted, referring to the ASTM D7774 standard. The specific steps are as follows:

[0147] (a) Prepare a sample with a size of 250 mm × 25 mm × 3 mm.

[0148] (b) Using a fatigue testing machine, apply a cyclic bending load with a maximum stress of 60% of the static bending strength and a frequency of 10 Hz.

[0149] (c) Record the number of cycles to failure.

[0150] 5. Thermal performance test

[0151] Finally, the thermal properties of the materials were evaluated, including the coefficient of thermal expansion and thermal conductivity. The test methods refer to ASTM E831 and ASTM E1530 standards respectively.

[0152] Test results:

[0153] According to the above test method, Examples 1-4 and Comparative Examples 1-6 were fully tested. The test results are shown in the following table:

[0154]

[0155] According to the test results, Example 3 performs best and can be regarded as the best embodiment of the present invention.

[0156] In-depth analysis and unexpected technical effects:

[0157] 1. Synergistic enhancement of mechanical properties: The present invention achieves a significant improvement in mechanical properties through the innovation of modification treatment and composite process. In particular, γ-glycidyl ether propyl trimethoxy silane as a coupling agent not only enhances the interface bonding between bamboo and wood materials and epoxy resin, but also forms a multi-scale reinforcement network with nano-silica and carbon nanotubes. This synergistic effect leads to a significant improvement in flexural strength, elastic modulus and impact toughness, far exceeding the effect of single modification or traditional composite methods.

[0158] 2. Excellent water resistance: Through silanization modification and the application of water-based polyurethane varnish, the present invention achieves extremely low water absorption. This not only improves the dimensional stability of the material, but also unexpectedly enhances its ability to maintain mechanical properties in a hot and humid environment. This effect is of great significance for the use of bicycles in various climatic conditions.

[0159] 3. Breakthrough improvement in fatigue performance: The fatigue life of the present invention is 3-6 times higher than that of the traditional method, which is far beyond expectations. This is mainly due to the synergistic effect of multiple factors: the modification treatment enhances the bonding between the fiber and the matrix, the nano-reinforcement phase improves the toughness of the matrix, and the modular design and node reinforcement effectively disperse the stress. This comprehensive optimization enables the frame to perform well under long-term cyclic loads and greatly extends the service life of the product.

[0160] 4. Unexpected improvement in thermal performance: Although the initial design focused on mechanical properties, test results show that the invention has also made significant progress in thermal performance. The lower thermal expansion coefficient and higher thermal conductivity mean that the frame has better dimensional stability and thermal conductivity under different temperature environments. This effect may be due to the addition of nano-silica and carbon nanotubes, which not only enhance the strength of the material, but also optimize the heat conduction path.

[0161] 5. Perfect combination of environmental friendliness and performance: The application of water-based polyurethane varnish not only achieves low VOC emissions, but also unexpectedly improves the weather resistance and chemical resistance of the material. This coating forms a synergistic protective effect with the modified bamboo and wood material matrix, significantly extending the service life of the product while maintaining the beauty of the natural texture.

[0162] In summary, the present invention achieves a high degree of unity of performance, environmental protection and aesthetics through the synergistic effect of multiple innovative points. These unexpected technical effects not only verify the creativity of the present invention, but also open up a new direction for the design of high-performance and sustainable bicycle frames, and have broad application prospects.

Claims

1. A method for manufacturing a modified bamboo-wood frame, characterized in that: The following steps are involved: (1) Pretreatment of bamboo and wood materials: 3-5 year old bamboo and hardwood were selected, cut into segments with a length of 50-70 cm, internodes were removed, and the thickness of the bamboo wall was retained to be 3-5 mm; steamed for 2-3 hours at a pressure of 0.6-0.8 MPa and a temperature of 120-130° C.; then dried at 60-70° C. for 24-48 hours to reduce the moisture content of the bamboo and wood materials to 8-12%; finally, the surface of the bamboo and wood materials was polished with 120-mesh sandpaper; (2) Preparation of modifier and impregnation treatment: prepare a modifier containing the following parts by weight: 35-45 parts of phenol, 25-30 parts of 37% formaldehyde aqueous solution, 8-12 parts of γ-glycidyl ether propyl trimethoxy silane, 4-6 parts of polyethylene glycol 600, 0.8-1.2 parts of p-toluenesulfonic acid, and the balance of up to 100 parts of deionized water; immerse the pretreated bamboo material in the modifier, immerse at a pressure of 0.5-0.7 MPa for 10-14 hours, and then dry at 85-95° C. for 30-40 hours; (3) Preparation of epoxy resin matrix: 100 parts of bisphenol A epoxy resin, 12-18 parts of neopentyl glycol diglycidyl ether, 35-45 parts of cyclic aliphatic amine curing agent, 3-5 parts of nano-silicon dioxide and 0.8-1.2 parts of carbon nanotubes were mixed; (4) Compression molding and resin impregnation: using a vacuum-assisted resin transfer process, curing at a temperature range of 85-105°C for 5-7 hours at a pressure of 0.15-0.25 MPa, followed by post-curing at 125-145°C for 2.5-3.5 hours; (5) Modular connection structure design and node reinforcement: Design the mortise and tenon structure connection points and perform local reinforcement at the main stress-bearing nodes; (6) Surface treatment and painting: Use 240-grit sandpaper to polish the frame surface, apply water-based polyurethane varnish, and bake at 65±5℃ for 2.5-3.5 hours.

2. The method according to claim 1, characterized in that: The preparation method of the modifier in step (2) comprises: First, add phenol and formaldehyde aqueous solution into a reaction kettle, and stir and react at 65-75° C. for 1.5-2.5 hours; Secondly, cool to 45-55°C, add γ-glycidyl ether propyl trimethoxy silane, and continue stirring for 40-50 minutes; Then, add polyethylene glycol 600 and p-toluenesulfonic acid and stir evenly for 15-20 minutes; Finally, deionized water was added to adjust the concentration and control the solid content at 40-45%.

3. The method according to claim 1, characterized in that: The preparation method of the epoxy resin matrix in step (3) comprises: First, bisphenol A epoxy resin and neopentyl glycol diglycidyl ether were stirred and mixed at 65±5° C. for 35-45 minutes; Secondly, add nano-silicon dioxide and carbon nanotubes, use a high-speed disperser to disperse at 4000-6000 rpm for 40-70 minutes, and control the temperature of the dispersion system not to exceed 80°C; Finally, cool to 25±5℃, add cycloaliphatic amine curing agent, stir evenly for 5-8 minutes, and vacuum degas for 15-20 minutes.

4. The method according to claim 1, characterized in that: The design of the modular connection structure in step (5) includes: The design of the tenon length is 18-22mm, and the width is 55-65% of the wall thickness of the bamboo and wood material. Apply epoxy adhesive to the mortise and tenon contact surface and cure at 23±2℃ for 24-28 hours after assembly; External coating at the connection: 200g / m 2 3K plain carbon fiber cloth was cured at 85±5℃ for 2.5-3 hours using vacuum bag pressing method.

5. The method according to claim 1, characterized in that: The node reinforcement method in step (5) includes: Design local thickening areas at the main stress nodes to increase the thickness by 1.5-2.5mm; Lay 400g / m in the thickened area 2 12K unidirectional carbon fiber cloth, the direction is consistent with the principal stress direction; Epoxy resin is injected using a vacuum-assisted process and cured at 105±5°C for 3.5-4.5 hours. At the same time, metal parts are used in areas prone to wear, such as the head tube, bottom bracket, and seat tube. The rear fork connection is reinforced with metal parts.

6. The method according to claim 1, characterized in that: The composition of the waterborne polyurethane varnish in step (6) is: 70-80 parts of aqueous polyurethane dispersion, 3-5 parts of water-dispersible aziridine crosslinking agent, and the balance up to 100 parts of deionized water.

7. A modified bamboo-wood frame made according to the manufacturing method according to any one of claims 1 to 6.

8. Use of the modified bamboo-wood frame according to claim 7 in bicycle manufacturing.

9. Use of the modified bamboo-wood frame according to claim 7 in the manufacture of electric bicycles.

10. Use of the modified bamboo-wood frame according to claim 7 in the manufacture of mountain bicycles.

Images