Development and prospect of carbon fiber bicycles
Carbon fiber has been widely used in military and civil fields because of its excellent properties, and carbon fiber bicycle is one of its typical representatives. In this article, the characteristics of carbon fiber bicycle and manufacturing process of the key parts are introduced. Moreover, the growth, present situation and development trend are reviewed.
Since the introduction of bicycles, their manufacturing materials have ranged from the initial wooden materials, to ordinary carbon steel, chromium-phase steel and chromium-manganese steel, to light alloy materials such as titanium alloy, aluminum alloy, magnesium alloy, scandium alloy, and new non-metallic materials such as carbon fiber and glass fiber composites. The innovation of bicycle manufacturing materials, its mechanical structure, process modeling, mechanical structure and other iterations, moreover, promote the improvement of bicycle performance and increased functionality. Today, bicycles have expanded from being a means of transportation to being fitness and competition equipment and recreational items. In particular, the widespread use of carbon fiber in bicycle wheel manufacturing has brought a new revolution to the bicycle industry.
The full name of carbon fiber bicycle is carbon fiber reinforced resin composite bicycle, whose manufacturing material is a combination of carbon fiber and resin. The role of carbon fiber and resin in the composite material is indistinguishable from each other. If the composite material is compared to a reinforced concrete structure, the carbon fiber is equivalent to the load-bearing steel, while the resin is equivalent to concrete, playing a role in structural molding, fixing carbon fiber and force transmission, which plays a decisive role in the ride quality and performance of the carbon fiber bicycle.
1 Characteristics of carbon fiber bicycles
The physical (Table 1) and chemical properties of the manufacturing material determine the performance of the bicycle. The density of the material is an important factor in determining the quality of the bicycle itself; the tensile strength, modulus of elasticity, and elongation of the material affect the rigidity, strength, ride feel, and appearance of the bicycle. Compared to metal materials such as titanium, steel and aluminum, carbon fiber bicycles have many advantages.
1.1 Light weight and good maneuverability
The density of carbon fiber composite material is only 20% of steel and 50% of aluminum. Theoretically, carbon fiber bicycle is 30% lighter than steel or aluminum metal material bicycle, and the effective riding force is increased by more than 45%. The lightest carbon fiber frame can be achieved within 0.7 kg, and the mass of competitive carbon fiber bicycle is only 7-8 kg, but the mass of aluminum alloy frame is hardly less than 1 kg, therefore, carbon fiber bicycle has better maneuverability and acceleration performance.
1.2 High safety
The tensile strength of carbon fiber is generally above 3,500 MPa, which is more than 4 times that of steel, and can withstand great mechanical impact; compared with metal materials, it has good fracture toughness and good fatigue resistance, and even if it fractures, it starts from the substrate and has visibility. All these greatly improve the safety of bicycle riding.
1.3 Good comfort
Carbon fiber elastic modulus is close to 3 times of aluminum alloy elastic modulus, small elastic deformation after force, high self-oscillation frequency, not easy to resonate, good resonance damping, improve the bicycle's shock absorption ability. Carbon fiber composite components are not easily deformed, and high rigidity and good force conduction make the carbon fiber frame more "hard", so that the rider can ride with better "force", more energy-saving and road feeling.
1.4 Strong resistance
Carbon fiber composite materials have good corrosion resistance to organic solvents, acids and alkalis, and there is no problem of rusting.
Of course, the strength of carbon fiber radial is very small, and the carbon fiber composite frame or parts are less resistant to the impact of sharp objects. In addition, the resin as the matrix of the composite material is easily aged by direct sunlight. With the progress of science and technology, it is believed that these shortcomings of carbon fiber bicycle will be continuously optimized and improved.
2 Manufacturing process of carbon fiber bicycle parts
Carbon fiber, as a fibrous carbon material with a carbon content of over 90%, has two characteristics: strong tensile strength of carbon material and softness and workability of fiber.
2.1 Large degree of freedom in modeling and structural design
In terms of mechanical properties, the strength of carbon fiber is different in the axial and radial directions, and the stress orientation is very high along the fiber axis, while the radial direction is very small. Therefore, when making bicycle components, according to this mechanical characteristic of carbon fiber, the optimal arrangement and placement of carbon fiber can be made by using the laminated technology to achieve the best stress or load requirements of bicycle components, especially with the development of new carbon cloth, the structural design can be optimized almost without restriction. For bicycle components made of metal, the formulation of the alloy is basically fixed, and its mechanical properties will not change greatly. Moreover, it is limited by the welding technology as well as the molding process of the tubing, and there are many restrictions on the design of the shape and structure. Of course, there are still many technical problems in the manufacture of carbon fiber composite wheels, and there are still many technical problems that need to be overcome.
2.2 Complex production process, many processes
Unlike metal bicycles, which can be welded and produced automatically, carbon fiber bicycles, especially frames, have complicated processes, and most of them still require manual operation and are difficult to use automated equipment. Among them, the curing and molding process of carbon fiber skeleton and resin matrix designed according to technical requirements and indexes under certain pressure and temperature largely determines the quality and performance of bicycle components. The more common carbon fiber composite molding technology mainly includes lay-up molding, resin transfer molding, resin injection molding, winding molding, weaving molding, roll forming, injection molding and other processes.
At present, the development of carbon fiber bicycle manufacturing technology is very fast, frame preforming began to introduce mechanical automatic weaving, which can realize three-dimensional weaving to control the strength, direction and angle, and the flatness of the woven preformed frame is very good, and the quality of the product is realized on the assembly line intelligent detection.
3 The rise and development of carbon fiber bicycle
The development and use of carbon fiber can be traced back to the 1880s, when inventors Joseph Swan and Thomas Alva Edison carbonized bamboo filaments to be used as filaments for incandescent light bulbs, and then carbon fiber was mostly used as high-temperature insulation materials, but the mechanical properties of carbon fiber were poor at that time. Until the 1950s, the U.S. military developed carbon fiber with good mechanical properties, and industrial production in the 1960s. Since then, Japan, Britain, France, Germany and other countries have had the technology to manufacture high-quality carbon fiber, especially Japan Toray has maintained the world's leading level in carbon fiber research and development and production technology. The application of carbon fiber in bicycle was tried in 1970s, and the real productization started in 1980s.