INSIGHT

【Technology】Efforts to reduce weight

As the importance of protecting the global environment increases around the world, automakers are working to reduce vehicle weight in order to reduce CO2 emissions (and improve fuel efficiency). In recent years, fuel economy regulations have been tightened around the world, and the trend toward weight reduction is not waiting to happen. In particular, hybrid vehicles, electric vehicles, fuel cell vehicles, and other so-called "eco-cars," which are equipped with heavy batteries, are required to have lighter bodies. On the other hand, crashworthiness, i.e. the rigidity of the body, cannot be sacrificed. The following is a guide to the main trends in weight reduction in such an environment.

Reducing the weight of exterior car parts by 35% with resin

The JP-F series of polymer alloys (PC/PET alloys) developed by Kaneka are polycarbonate (PC) and polyethylene terephthalate (PET), which are suitable for the exterior parts of cars.

The new PC/PET alloy contains 21 mass percent of inorganic filler and additional compounding agents for enhanced performance. It has high rigidity, with a flexural modulus of 6300 MPa, up from the conventional 6,000 MPa, achieving strength and rigidity that can be used for automotive exterior parts. In addition, the coefficient of linear expansion is smaller than before, and it is close to that of steel (iron). It has excellent appearance design properties due to minimal warping and shrinkage due to temperature changes. In addition, its high fluidity at the time of melting enables it to be used for large and thin molded products.

This is a difficult part to form by pressing steel plate because of its complex shape, which is used for sliding door rail covers and is curved at the back of the sides and bent at the top, but the wall thickness is 3.0 mm, which is thicker than the conventional steel plate with a thickness of 0.8 mm, maintaining strength and rigidity and reducing weight by 35%. has been achieved.

Weight reduction of 50% by joining dissimilar materials

A frame-shaped part with a hollow cross section is made of polyphenylene sulfide (PPS), and it is sandwiched from both sides by aluminum alloy plate press-formed products, which makes it possible to reduce the weight by 50%. Dissimilar material joining techniques are used to join PPS and aluminum alloys. The current product is made by welding solid steel parts, but we insert a conversion-treated aluminum alloy sheet into a mold and inject PPS into the mold. It is difficult to maintain machining accuracy when trying to create a hollow shape for weight reduction by welding, and the weight can be reduced by 50%, but the number of parts becomes larger and the price increases, but it seems that a Japanese automaker has already decided to adopt it.

We have presented some published examples of other companies' examples of weight reduction, but there are various other methods.

Tokyo Byokane has a lot of experience in reducing weight, so please contact us for more information.

In the past, steel was the main material used for bodies and parts, but recently there has been a shift to "multi-materials," in which the most appropriate material is used for each part. The U.S. research firm CAR (Michigan) estimates that the share of steel, which accounted for more than 90% of the world's car body materials in 2010, will decline to around 70% by 2040.

Instead, non-ferrous materials such as aluminum, carbon fiber and resin materials are emerging. Material manufacturers are entering the automotive field one by one, seeing weight reduction as a commercial opportunity, but steel currently has the advantage in terms of cost. The conflicting issues of cost, lightness and strength are not easy to solve.

 

Nippon Steel Corporation has unveiled a model for developing the next generation of vehicles that can be 30% lighter using steel alone in 2019. The combination of super high-tensile material, which is even stronger and lighter than high-tensile material, appeals to the superiority of steel in terms of cost competitiveness. JFE Steel is also working to unify its automotive steel sheets and related technologies under a single brand, which will lead to joint development and increased orders for high-tensile materials.

 

To date, European automakers have been at the forefront of efforts to increase the use of materials other than steel to reduce weight. Japanese automakers have been reluctant to replace steel with EVs, but with the global shift to EVs, there is a widespread movement to increase adoption.

Chemical manufacturers and others are selling carbon fiber reinforced plastic (CFRP). Toray has acquired CFRP processing companies in Japan and Italy.

Tokyo Byokane has a lot of experience with CFRP, so please contact us.

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