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After years of rapid growth, China's automobile industry is entering a new period of industrial transformation and technological upgrading. Driven by the "double integral" regulation and the new energy vehicle industry policy, automotive materials have also ushered in new development opportunities. The traditional steel-based automotive material structure is developing towards the mixed application of multiple materials such as steel-aluminum hybrid, all-aluminum body, plastic composite materials and magnesium alloy.
Overall, under the general trend of global energy conservation and environmental protection, the application and development of automotive materials has always been around the general direction of "green, low carbon and lightweight". Next, we briefly introduce lightweight materials such as modified plastics for automobiles, carbon fiber composites, carbon ceramic composites, and green and low-carbon materials such as low-carbon rubber materials, and elaborate on the development and application of process technology for automotive materials.
Modified plastics for automobiles
From the perspective of the new demand for automotive plastic materials development, the main technologies include lightweight, composite, aesthetic technology, innovative function, innovative elastomer, innovative special materials, etc.
One of the directions of lightweighting is thin-walled engineering, such as the slow transition of bumpers to thinner ones, which can achieve both weight reduction and production efficiency. There is also a lightweight solution is micro-foaming, including molding methods, there is a one-time underfill, as well as full injection molding, and then through loosening, to achieve the foaming of the middle layer, similar to the structure of a sandwich.
For micro-well foaming, there are mainly injection molding micro-foaming, blow molding micro-foaming and extrusion micro-foaming, etc., injection molding micro-foaming is suitable for all kinds of automotive interior and exterior trims, such as body door panels, tail doors, air ducts, etc.; extrusion micro-foaming is suitable for sealing strips, roofs, etc.; blow molding micro-foaming is suitable for automotive air ducts, etc. The use of micro-foaming technology can reduce the quality of PP products by about 10% to 20%, and can achieve up to 50% weight reduction on components compared with traditional materials.
The use of high-performance glass fibers in reinforcing materials can make the material have a 10%-20% performance improvement. Its long-term fatigue resistance performance is also very good, even beyond the material of long glass fiber.
In terms of the application of all-plastic body structure, taking the tailgate as an example, the polypropylene modified material for the inner and outer plates is welded to achieve overall weight reduction. Among them, the inner plate should also consider more, such as stiffness, strength, fatigue resistance, and even require good emission characteristics.
Source: China Automotive Materials Network
Nano injection molding, is developed by Japan's Taisei Plas Co., Ltd. (Taisei Plas), in 2004 to achieve commercial applications, similar to the form of secondary injection molding, metal inserts, gradually replace the metal, to achieve the purpose of weight reduction, most of the engineering materials, including PPS, PBT and so on.
In addition, in terms of function, there are electromagnetic shielding materials, which can realize both electromagnetic shielding and thermal conductivity, which has a broad application prospect. For the surface marking of parts, there are also many materials that can achieve laser marking. There are also transmission-type radar components that are used in bumper-related radar components to reduce the impact on radar signals.
Carbon fiber composites
Last year, China's "double carbon" goal was proposed, forcing the application of CFRP (carbon fiber composite materials) in mass production models to accelerate.
At present, China's carbon emissions reach 11 billion tons, of which electricity accounts for 40%, automobile carbon emissions account for 7%, oil (70% for automobile fuel) accounts for 15%, automobile energy saving, consumption reduction and emission reduction are imminent, and the task is long. Lightweight is the only way to save energy and reduce emissions, CFRP will become one of the important ways of automobile lightweighting because of its high performance and low density advantages.
Image source: Nikkei Technology Online
At present, automotive OEMs, parts companies, material suppliers, carbon fiber manufacturing enterprises, research and development institutions, etc., all recognize the important role and development prospects of carbon fiber in automobile lightweighting. Many of these OEMs have gone from developing prototypes and prototypes to seeking overall solutions for the application of carbon fiber in mass production models, such as structural design, automated mass production, and batch application demonstration.
Judging from the progress of research and development, a mass production model began to use carbon fiber components, and a car CFRP manufacturer appeared. In the automobile OEMs, SAIC, BAIC, Changan, Geely, Weilai, Tesla and other mass production models have begun to apply CFRP parts; at the same time, a number of CFRP parts production and supply enterprises have emerged, such as Aosheng Technology, Hengrui, Kalai, Huayu Transmission Technology, etc., have established mass production parts demonstration production lines.
Experts suggest that the state should increase support to establish China's automotive lightweight CFRP technology system and supply chain system to form a demonstration effect for the application of mass-produced models, including: carbon fiber low-cost, high-modulus low-cost carbon fiber for automobiles; CFRP modular design, reducing the number of parts, reducing the difficulty of automated production; overcoming the problem of carbon fiber and metal hybrid structure; research and development of CFRP low-cost automated mass production technology and equipment, and improving the molding beat (fast-curing resin, thermoplastic composite materials). Reduce CFRP molding costs.
Carbon ceramic composites
Carbon/ceramic composite materials are a general term for a class of composite materials with carbon fiber, ceramic fiber and its fabric as the reinforcing phase, and ceramics such as quartz, feldspar, and silicon carbide as the matrix phase.
Carbon / ceramic materials not only have the advantages of high-performance ceramics such as high strength, high modulus, high hardness, impact resistance, oxidation resistance, high temperature resistance, acid and alkali resistance and all chemicals, small coefficient of thermal expansion, light specific gravity, etc., but also completely overcome the shortcomings of general ceramic materials such as large brittleness and single function, and are recognized as the world's ideal high-temperature structural materials, friction materials and cryogenic materials, carbon ceramic composite materials can be applied on passenger car brake discs.
The current problem of carbon ceramic brake discs for passenger cars is high cost, which limits the promotion and application of carbon ceramic discs for passenger cars, and the current application of domestic carbon ceramic discs is mainly concentrated in modified vehicles. To achieve low-cost preparation of carbon ceramic plates, it is possible to start from five dimensions.
Source: Shenzhen Lema Brake Technology
1
First of all, in terms of raw materials, most of the raw material costs of carbon ceramic disks come from carbon fiber, which can reduce the cost of raw materials by optimizing the grade and content of carbon fiber.
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Secondly, in terms of preparation process, the long preparation cycle of the long fiber disc is mainly limited by the thermal process, and the production cycle can be greatly reduced by developing the multi-column limit CVI process and the rapid melting process.
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The third is the intelligence aspect, the existence of ceramic components makes the processing of carbon ceramic plates difficult and the processing efficiency low. Through intelligent online testing and production, production efficiency can be greatly improved and further reduced costs.
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Fourth, in terms of new processes and new methods, there is also a lot of work to be done. The current long-fiber disc precast is cut from the top of the square plate, which will form a middle and four corners of five pieces of residual material, resulting in a very low utilization rate of the entire raw material.
5
The fifth area is energy prices. Because the temperature required for the preparation of the carbon ceramic plate heat process is high and the time is long, the electricity consumption is very large, so if you can win a preferential energy special price, it is very helpful for the cost reduction of the carbon ceramic disk.
Tires are made of green low carbon rubber material
Because tires also have a more serious carbon emission problem. Therefore, as a new generation of tires, it is also necessary to achieve greening.
The research team of Beijing University of Chemical Technology has been committed to the development of the second generation of natural rubber in recent years, and found some wild rubber grass in the border areas of Xinjiang and Kazakhstan in China, called dandelion rubber grass, and its latex is the same as the latex of natural rubber trees. At present, the rubber extracted from dandelion has successfully manufactured tires and has received relatively high attention.
Dandelion rubber sketch Source: Linglong tires
Zhang Liqun, vice president and professor of Beijing University of Chemical Technology, proposed the concept of "bio-based engineering elastomer" for the first time. Original bio-based coat-based ester elastomers and bio-based polyester elastomers are designed and synthesized. Among them, the production of bio-based coat carnate rubber is relatively large, the cost is low, and a lot of structure and performance regulation are realized through esterification. Tires made of this rubber have been tested on sports cars, and wet grip, anti-wet slip, and concrete tests have all obtained double B grades.
Source: Tire Notes
Another bio-based polyester rubber material is degradable, using bio-based degradable polyester rubber as a tire, which is the world's first batch of degradable tires independently developed by Beijing University of Chemical Technology.
Of course, in addition to raw materials, the development of green additives, the recycling of waste rubber, and more fuel-efficient tires can help reduce the carbon emissions of tires.
Development trend of new automotive materials
Under the background of "double carbon", electrification, intelligence and lightweight have become an inevitable trend. In order to improve the mileage of new energy vehicles, some carbon fiber materials have put forward relatively high requirements. Around the "three electricity" system, the development of various new materials has also been put on the agenda.
Source: Automotive powertrain
Among these three technologies, the battery is the most important, which affects the driving range of the car on a single charge and the production cost of the car. Motor, electronic control technology is relatively mature. The types of materials and performance requirements involved in the battery system are quite different from those of traditional cars. For example, diaphragms, positive and negative electrode materials, module materials, cabinet materials, adhesive materials, thermal insulation materials, electrical system materials and so on.
Battery cell composition figure Source: automotive powertrain
For intelligence, especially intelligent driving, intelligent cockpit, etc., higher requirements are also put forward for intelligent materials from the three aspects of integration, functionality and decoration. In the future, we must create personalized needs, so the demand for material technologies in terms of intelligence, such as dielectric materials, electromagnetic shielding materials, surface interaction materials, and high shock absorption materials, has increased significantly.
From the current distribution ratio of vehicle materials, there are more than 40 types of vehicle composition materials, of which metal materials account for 72%, and non-metallic materials include paint, tires and other related materials account for 28%. From the perspective of the development trend of vehicle materials, the future focus of the development direction is lightweight, and relatively high requirements are also put forward in this regard. At present, the lightweight aspect is mainly around the development of tops and bottoms, as well as the lightweight of battery packs, such as hybrid body, aluminum chassis, SMC materials and so on.
In addition, in the interior part of the car, because it is necessary to improve some comfort, it is like transparent leather, which has also become a trend in the development of future interiors. At present, the central control armrest of the transparent epidermis has been realized, which can meet the requirements of consumers for the soft covering of the entire area.
The realization path of automotive material process technology at this stage mainly includes structural optimization design, as well as high-strength steel, light metal, engineering plastics, composite materials and related forming process technologies, while the future development direction should focus on optimizing design and multi-material mixing applications.
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