The "Fuxing" EMU has realized the use of 350 kilometers per hour in the Beijing-Shanghai high-speed rail, and the speed of high-speed trains has undoubtedly entered a new stage. As the speed of subsequent trains further increases, the weight reduction of vehicles becomes particularly necessary. According to the current weight reduction scheme of rail trains, lighter and stronger carbon fiber composite materials are used in local structural parts of the car body.
The application of domestic carbon fiber composite materials in the field of rail transportation started relatively late, but has developed rapidly. CRRC has carried out a lot of research and experimental research. Currently, it is used in the driver's cab, head cover, console, interior panel, equipment compartment, and diversion Hoods and other aspects have been applied.
"This is a trend. High-performance composite materials will slowly extend from interior decoration to train car bodies, load-bearing structures and other components. Carbon fiber composite materials have great potential for development in the field of rail transportation. However, this pair of carbon fiber composite materials The mass application in the field of transportation equipment has put forward requirements for low cost, high efficiency, and high quality. "At the recently concluded China Rail Transit Industry Conference, Chen Chaozhong, senior engineer of the Technical Research Department of CRRC Research Institute, was interviewed by New Materials Online When said.
Chen Chaozhong, Senior Engineer, Technical Research Department, CRRC Research Institute
From a comprehensive consideration of carbon fiber composite materials' batch manufacturing capabilities, cost control, and life cycle assessment, Chen Chaozhong believes that the application prospects of carbon fiber composites in rail transit are relatively optimistic.
Application prospect is optimistic
At the International Rail Transit Technology Exhibition in Berlin, Germany, in September 2018, CRRC Quartet officially released a new generation of carbon fiber subway vehicles "CETROVO". CETROVO uses carbon fiber technology, and the vehicle "slims down" by 13%. It is worth mentioning that the birth of CETROVO marks the domestic successful breakthrough in key technologies such as structural design and manufacturing of large and complex carbon fiber components, and has realized the comprehensive use of carbon fiber composite materials in the main load-bearing structures of vehicles such as car bodies, bogie frames, and driver's cabs application.
Compared with infectious metal materials, CETROVO's body, driver's cab, and equipment compartments have reduced weight by more than 30%, bogies have reduced weight by 40%, and vehicle weight has decreased by 13%.
Although CETROVO has presented a dazzling lightweight transcript, at present, how to create more "CETROVO", that is, the mass application of carbon fiber composite materials on rail transit trains is still an issue that the industry urgently needs to crack. "Carbon fiber composites are currently receiving a lot of attention from the rail transit industry, but they are still in their infancy." Chen Chaozhong said.
Cost is one of the important factors affecting mass production. From the perspective of the development stage, materials selection, innovative design, simulation optimization, and low-cost manufacturing processes all require research on low-cost technologies. Cost control.
Taking design as an example, because carbon fiber composites are anisotropic materials, their biggest advantage is designability. Taking the design of large parts as an example, the loading conditions of each part of the large parts are inconsistent, and the thickness of the carbon fiber layer is different. At this time, design and simulation optimization techniques are needed to obtain the most functional and lightest materials. Best plan.
In addition, the design must be combined with manufacturing. The lay-up design of the amount of carbon fiber will affect the back-end manufacturing. So the two must be combined. "Chen Chaozhong said.
However, compared with the cost of the initial investment, after the mass supply of carbon fiber composites for rail transit breaks through, the later operating costs will be reduced.
From the characteristics of weather resistance of carbon fiber composite materials, carbon fiber composite materials have advantages in the long-term service of rail vehicles. The design life of high-speed trains is 30 years. According to related research, the price of metal car bodies plus maintenance price costs during service life account for more than 60% of the life cycle price costs.
After the introduction of the application of carbon fiber composite materials, compared with the cost of metal materials, referring to the case of aerospace, the life cycle of carbon fiber composite materials and metal material structures is almost the same, and even the cost is slightly lower.
"The reduction in the cost of rail vehicle operation and maintenance caused by the lightweighting of composite materials after its introduction and application is very positive." Chen Chaozhong told New Materials Online®.
Construction of applied standards has begun
The application of carbon fiber composite materials in rail transit faces more than the cost of materials. Similar to other industries, the industrialization of carbon fiber composite materials also cannot avoid the problem of standards.
From a global perspective, the structure of rail transit equipment is still dominated by metal materials. Whether it is international or domestic, the application of metal materials in rail transit equipment has formed a relatively complete standard system. For carbon fiber composite materials, the standard system is in Blank stage.
The lack of a standard system means that the carbon fiber composites industry lacks benchmarking guidelines to follow when manufacturing and designing. Chen Chaozhong exemplified that when the car body is impacted by small and hard objects, the damage to metal and carbon fiber composite materials is completely different. The impact on the composite material will lead to the occurrence of internal defects. In the long-term service of carbon fiber composite materials, the impact of such damage on the long-term service performance of composite materials needs to be studied, and relevant standards should be established for guidance.
In addition, taking process selection as an example, internal manufacturing defects caused by different processes are different. For example, in aerospace, the defect standards for primary and secondary load-bearing components are different. The porosity of the main load-bearing component must be controlled below 0.5%. As the load-carrying capacity is reduced, the standard of porosity needs to be relaxed.
"The lack of standards makes it difficult to convince downstream customers. Therefore, the establishment of standards as a systematic project requires the industry's continuous efforts to gradually establish it, which will also help promote the application of carbon fiber composites in rail transit."
Chen Chaozhong said that CRRC Research Institute, as the leading unit in the construction of the carbon fiber composite material standard system for rail transit, is currently carrying out related work. "I believe that with the continuous deepening of standard analysis and research, some very good results will emerge."
Good opportunity for localization
From China's "Advanced Rail Transit Equipment Technology Roadmap", energy-saving and environmentally friendly green intelligence is the focus of China's rail transit equipment industry. The lightweight of carbon fiber composite materials has attracted increasing attention from the industry. This may be an opportunity for localization.
The application of carbon fiber composites is not only lightweight. Judging from the information publicly disclosed by CRRC Sifang, CETROVO has a comprehensive energy saving of more than 15% compared with traditional metal subways.
Chen Chaozhong also mentioned in his speech at the Rail Transit Industry Conference that the necessity of the application of composite materials in the field of rail transit equipment lies in: energy saving, enhanced designability, reduced wheel and rail wear, reduced maintenance, improved comfort, reduced component size, increased capacity.
Chen Chaozhong said that after the weight of the body is reduced, the size of the components can be reduced accordingly. For example, after the weight of the vehicle body is reduced, the vehicle inertia is reduced, and the braking distance is also shortened. In this way, the traditional large braking system can be miniaturized, and after the components are miniaturized, the vehicle's weight reduction space becomes larger. "This is a virtuous cycle the process of."
As early as 2000, France has applied carbon fiber composite materials to the body and achieved a 40% weight reduction. Japan and Germany have also successfully applied carbon fiber composite materials to couplers, bogies and other components.
Chen Chaozhong believes that the development of carbon fiber composite materials for rail transit is a problem of the entire industrial chain, especially for upstream, the problems of domestic carbon fiber performance stability and high-performance resins matching it need to be solved. "With the development of upstream, domestic carbon fiber composite materials will become better and better, and it will bring more unobstructed environment to downstream applications such as rail transit."