Research and innovation in the auto industry continue to produce inventions and discoveries leading to cleaner, more fuel efficient, and safer cars. These days, most discussions about the car of the future focus on the powertrain, but there are dramatic developments in other components as well.
Japan’s Toray Industries, Mitsubishi Rayon, Toyobo Takagi Seiko Corp. and researchers from the University of Tokyo recently announced their involvement in a program to develop new material for car bodies that will lighten them for fuel efficiency without sacrificing strength. The goal is to mass produce the material by the mid-2010s and to make such vehicles 40% lighter than steel-bodied cars.
Body weight is an important target for improvement. Reducing the weight of a vehicle’s body means that a smaller engine and a lighter drive train and assembly can be used. This ‘benign spiral’ leads to further mass reductions, so much so that various studies have indicated a potential for savings of up to 65% by using this material instead of steel wherever possible.
The material is a new type of carbon fiber material. Carbon fiber consists of extremely thin fibers—about 0.0002–0.0004 inches or 0.005–0.010 mm in diameter—composed mostly of carbon atoms. The carbon atoms are bonded together in microscopic crystals aligned parallel to the long axis of the fiber. This alignment of the crystals renders the fiber incredibly strong for its size. Twisting together several thousand carbon fibers forms a yarn, which can be used by itself or woven into a fabric. Carbon fiber can also be combined with plastic resin and wound or molded to form composite materials such as carbon fiber reinforced plastic, a high strength-to-weight ratio material. These properties of carbon fiber—high tensile strength, low weight, and low thermal expansion—account for its popularity in aerospace, military, and motorsports applications.
But the use of carbon fiber materials for passenger cars as distinct from racing cars presents different design challenges. The structural skin or monocoque design approach using carbon fiber for racing cars rendering them light, stiff, and stable at high speeds and in tight corners has not been directly transferable to passenger cars because they have large ‘cut-out’ (no door) areas for access. The challenges are similar to those associated with the use of fiberglass for car bodies. For example, traditionally the fiberglass Chevrolet Corvette did not have a trunk lid.
Another material that we may expect to soon see in cars is “thallium-doped lead telluride”. This will be used in the exhaust system to convert heat into electricity. Some experts argue that only 25% of the energy produced by a typical gasoline engine is used to move the car or power its accessories, while nearly 60% is lost through waste heat, much of which escapes in engine exhaust. Previously, the most efficient material used commercially in thermoelectric power generators was an alloy called sodium-doped lead telluride, which had a rating of 0.71. The new thallium material has a rating of 1.5, more than twice that of the previous leader, making it genuinely useful for this sensible purpose.
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