Lightweight car

The more important a car is, the heavier and safer it is, but its weight is an inescapable topic for car lightweighting.

Plastic cars are no longer just toys.

A few days ago, a 3D printed plastic car named Urbee2 was introduced. In addition to chassis and engine, most of the rest of the materials were plastic. Its designer Jim Kor said in an interview with the media that his plastic car is as hard as steel, but it is half the weight of a steel car.

Although the car is currently limited to the experimental stage and is far from the level of mass production, there is no doubt that this means at least that the auto parts and even the whole vehicle are moving toward the direction of lightweighting.

According to studies, a 10% reduction in the weight of a car reduces fuel consumption by 6% to 8% and reduces emissions by 5% to 6%, which is of great significance for achieving energy conservation and emission reduction in automobiles.

Wang Zhiwen, deputy secretary-general of the National Automotive Lightweight Technology Innovation Strategic Alliance, said in an interview with a reporter from China Economics and Information Technology that “high-strength steel and plastic (non-metallic materials) can achieve both lightweight and low cost control of automobiles. Good material."

Plastic steel

Under the pressure of energy-saving and emission-reduction, the concept of "plastic-based steel" has been widely circulated in the automotive industry. According to the data from the American Chemical Industry Association, the total weight of automotive plastic parts is still less than one-tenth of the total weight of automobiles. Therefore, the space for expanding applications is still very wide.

In recent years, in order to enhance the competitive advantage of the market, various car companies have developed and launched lightweight models. The world’s leading car companies are at the forefront of this field. BMW will mass-produce BMWi3 pure electric vehicles this fall. The most important feature of this car is that the outer shell is made of plastic and the chassis material is made of aluminum alloy. Compared with the conventional models, the weight loss is 250 to 350 kg. This reality will not only lead the new trend of automotive design, but will also disrupt the automotive manufacturing process and the overall market structure.

As the inventor of the car, Mercedes-Benz is shouldering a heavier responsibility and mission in the field of lightweight vehicles. At the Guangzhou Motor Show in November 2012, Mercedes-Benz released a hydrogen-powered sports car called the F125. The car is mainly made of carbon fiber, aluminum alloy and plastic. It ensures the rigidity of the car body while minimizing the weight of the car body.

In addition, Cadillac and Ford are also outstanding representatives of lightweight vehicles. Cadillac already uses fiber reinforced plastic on the hood, and Ford is studying how to reduce the cost of producing carbon fiber components. According to Zhang Zhiyong, a veteran automotive industry analyst, carbon fiber materials are too costly and complicated to be industrialized and are only suitable for racing cars and a few luxury sports cars.

The body weight loss wind has certainly been blown into the country. Among the local car companies, Great Wall Motor Co., Ltd. (hereafter referred to as Great Wall) and Chery Automobile Co., Ltd. (hereinafter referred to as Chery) are the two car companies that have gone farthest in this research field.

In November 2011, Chery Automobile and Bayer MaterialScience (China) Co., Ltd., one of the world's largest polymer production companies, jointly created the "Chery-Bayer Automotive Lightweight Joint Laboratory" on both polyurethane composite materials and poly. Carbonate plastic window materials, new energy lithium battery materials, sound absorption and noise reduction materials and other materials in the automotive application of common research, and joint application projects and promotion. Before that, Chery’s A3CC Coupé was exhibited at the Sabic booth of the K show in Germany. Its front fenders were made of Noryl GTX resin.

Great Wall Motor (601633, shares) also cooperated with Bayer. At the 2012 Beijing Auto Show, the seven window components of the Haval E concept car displayed at the Great Wall were made of Bayer miquelon polycarbonate and equipped with a large panoramic sunroof. This is the first time that Chinese domestic automakers have applied polycarbonate windows so widely.

In November 2012, plastic electric vehicles jointly invested by Yangzhou Kells & Meyer Co., Ltd., Tsinghua University and Zhejiang University have attracted the attention of the domestic industry and are known as “armored vehicles” in cars. The body of the car is composed of two layers of plastic profiles, each about half a centimeter thick. The middle of the two layers is in a hollow state. It is made of composite plastic and glass fiber and other components by one-time stamping. At present, it has successfully passed the authority of the 9 member states of the European Union. Testing agency certification.

However, this kind of plastic electric car also stays in the experimental stage. Professor Xue Xuexun, a doctoral supervisor at the Wuhan University of Technology’s School of Automotive Engineering, believes that because of the technical considerations, plastics require specialized tooling to form stamps once and cannot be quickly formed like metal, like the new automobile body developed by Kells & Meyer. Relatively large, it is difficult to build a mold production line, which is currently difficult to achieve.

In addition, in addition to the family-car market, the weight of trucks has long been on the agenda. Beiqi Foton has changed the bumpers of its medium- and heavy-duty trucks from steel to plastic materials, and has activated glass-reinforced plastic in some auto parts. It also replaced some steel engine parts with plastic parts.

At present, foreign vehicle companies have become increasingly sophisticated in light weight, and Chinese domestic car companies are still learning or catching up. Especially in the development of lightweight materials, although some achievements, it is still in its infancy.

Plastic puzzle

In recent years, China's auto plastic products manufacturing enterprises have used the technology of imported vehicles to expand the level of application of plastic materials in automobiles, and formed a number of large-scale and specialized automotive plastic product suppliers. Some of the production technologies have reached domestic leading level. International synchronization. Such as Shanghai Yanfeng Visteon, Changchun Fuao - Johnson Company, Wuhu Shunrong Company. The latter six-layer plastic fuel tank has been widely used in Chery, JAC, Dongfeng, Geely, Great Wall, Maple, Haima, Changfeng and other domestic brands.

When the plasticization was in full swing and became the banner of the automotive industry, Prof. Xuexue put forward his own calm thinking: “Plastics is not the only way to reduce the weight of automobiles. Plastics have a shorter fatigue period than metals, and are particularly exposed. In the high temperature environment and contact with gasoline, the aging phenomenon is particularly serious, and when applied to gears or other parts of the transmission force, the strength of the metal cannot be achieved.Moreover, the carbon fiber composite materials currently used more often lose their mechanical properties after use. Can not be recycled, only as a waste or degraded. I think that high-strength steel and aluminum-containing metal are more suitable for vehicle lightweighting materials."

This is indeed an unavoidable problem in the automotive plastics process. In countries such as Japan and the United States that have issued mandatory requirements for vehicle recyclability, both Toyota and Ford have clearly stated that they will seek to expand the use of renewable materials and natural materials. range.

On the other hand, Ruan Zhihong, general manager of the Raw Materials Industry Research Center in China, pointed out that the state has not promulgated highly specific laws and standards, and only some general laws and regulations, such as the “Regulations for Regenerating Resource Recycling,” have been adopted in the planning of new materials, petrochemical and chemical industries.” "Twelve Five" development plan also has some involved. The prospects for environmental protection and recycling of plastic cars are worrying.

In view of this, domestic auto parts and automotive plastics companies must take a place in the market, must improve their international competitiveness, raise the level of enterprise development capabilities and product levels to a higher level, and participate in the development and competition of the auto industry, from design and development. At the same time, research on the recycling and recycling of automotive plastic materials is required to meet the needs of environmental protection.

One of the most immediate problems associated with lightweight development is car self-respect. How to control the degree of lightweight? After all, energy saving and emission reduction cannot be exchanged for personal safety. This may be the first question anyone would consider when he heard the concept of a plastic car.

Wang Zhiwen has his own view on this: “The car is not as heavy and safe as the car. Even if the car uses light materials, if you take high-strength processing technology, you can achieve very light but very good elasticity effect. The safer it is."

At present, the National Strategic Alliance for Automotive Lightweight Technology Innovation is working with Changan Automobile (000625, Share Bar) Group to jointly develop and promote the “Al-Aluminum Steel” hood. Wang Zhiwen introduced that this study is based on the consideration of pedestrian safety protection in the event of an accident. Because the application of aluminum alloy in the hood and other parts can reduce the secondary impact of the impact on the human body.

Although the weight of the aluminum plate is about 1/3 of the steel plate, its absorbable collision energy is twice that of the steel plate. Aluminum alloys have a higher safety factor in the event of an impact because their material has a very good energy absorption.

Development bottlenecks

Although automobile lightweighting is a general trend, the domestic automobile lightweighting technology is still immature, and related industries have not formed a scale, which largely affects the enthusiasm of domestic automobile enterprises for developing vehicle lightweighting.

In addition, there is still a big gap between the domestic automobile industry and foreign advanced level in lightweight technology, especially in the application and development of high-end materials, and it is even more restricted by others. "The same car, can be achieved abroad, 1.3 tons, and we must be more than 1.5 tons, not deliberately doing so heavy, but we do not light." Wang Zhiwen said.

The average weight of passenger cars in China is 5% to 10% more than that of European cars, and the figure for commercial vehicles is 17%. For example, the domestic tractor with a 40-ton load has a weight of 9 tons, while the foreign equivalent model has only 7 tons, while the domestic dump truck weighs 3 to 4 tons more than the foreign.

Wang Zhiwen stressed that there is not much difference between the proportion of traditional automotive plastics applications and foreign car companies. However, when it comes to high-end development, both material technology and design level face various difficulties. “Making materials into parts is a very complicated process. Although domestic channels, joints, interior parts, bumpers and even dashboards are all made of plastic, it is difficult to develop functional parts and structural parts. It's big."

The domestic raw materials themselves are very backward. In particular, the high-end materials are completely monopolized by some foreign chemical manufacturers, such as DuPont, BASF, and Bayer. They have mastered the design techniques and analytical techniques of materials, as well as the design techniques of components.

As high-end materials are subject to foreign technology monopoly for a long time, resulting in high product costs, forcing some companies to abandon the use of high-end materials in automobiles.

Wang Zhiwen also pointed out that the high cost of lightweight materials does not meet the current market positioning of domestic models. “Foreign car companies mostly apply lightweight materials to sports cars and concept cars, favoring small-volume and multi-category products, and pursuing personalized service. In China, car companies have low brand value in high-end products, so the market demand is small.”

At present, the key factor hindering the research and development of China's auto lightweight technology is that R&D institutions often focus on the research and development of a single technology, and rarely carry out the intersection and integration of technologies. Just like chickens or eggs first, material companies often only make materials, while car companies are responsible for manufacturing and assembly. The lack of communication and collaboration between the two sides has also led to the difficulty of lighter materials in the industry.

The development of lightweight technologies involves many disciplines and requires the use of a comprehensive and systematic knowledge system formed through the integration of multiple disciplines. Therefore, the lightweighting of the automobile industry in the future requires the joint efforts and exploration of upstream and downstream enterprises in the industrial chain.

With the continuous increase of vehicle ownership in China and the increase of automobile exhaust emissions on urban air pollution, the demand for lighter vehicle body development becomes more urgent. In this regard, relevant research institutions or government agencies should make strategic advance deployments.