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Lighter, stronger and safer: Can they co-exist?
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Tuesday, 15 July 2014
More and more experts in automotive design and materials research agree that the overall weight of the vehicle is the most important factor in green technology, since this is what will ultimately result in better performance and lower emissions per mile. However, one of the key debates that has not subsided is whether reduction in weight compromises safety. With this in mind, vehicle designers have taken a whole-vehicle approach to design. In this, every attempt at reducing weight – in parts from bulbs and wiring harnesses to major body units – must be scrutinized for its effect on the safety of the entire vehicle.

Safety is paramount. Vehicle accidents continue to take a heavy toll on human lives and health. Injuries are costly beyond any other accident category in most top industrialized countries. The World Health Organization expects vehicle accident injuries to move from the ninth major cause of injury in 1990 to the third major cause by 2020. (1) Consequently, every vehicle manufacturer must insure that safety is never compromised in its decisions to achieve weight reduction.

Vehicle engine systems create only one part of the overall carbon footprint affecting the world’s pollution, but they are part of a large and growing sector that can be addressed in a managed way. Power plants, for example, are much more likely to remain using the same fuels in the same proportions as they have for 30 years or more. Recently, the United States through Pres. Obama asked for severe cutbacks in emissions from coal powered plants, but acknowledged it will take many years and that coal is not soon to be dropped as a fuel. Replacement of these plants is near impossible in most countries, and upgrades are expensive and slow to be implemented, leaving motor vehicles as one of the best solutions for reducing carbon emissions.

Lighter, stronger and safer: Can they co-exist?So, the race to produce even lighter vehicles continues around the world. We will look at several kinds of material being researched as replacements for traditional materials. However, to the surprise of many people, one material getting fresh looks for more use is also the one that has taken the most hits for the last several decades: steel. According to some reports (2), high strength and ultra-high-strength steel is as durable and lightweight as the newer materials. This article cites the example of Volkswagen, which uses even more high-strength steel in its Golf model this year than in previous years. The density of the steel is reduced, therefore reducing its weight. A typical new Golf now weighs 220 pounds less than the previous model.
According to the World Steel Association, this product has improved strength and durability as well as lightness. The association also notes that the production of this steel rivals that of carbon fiber, titanium and aluminum in reduced emissions from these factories. After all, the idea of reducing carbon footprints is all interrelated: creating lighter vehicles is of no end purpose if the production of the materials to build them creates more pollution than the automobiles are going to save in the long run. The lower weight of each vehicle is significant, however. Reducing a typical model 220 pounds and including a cylinder de-activation feature in the engine allows this model to get from 49 to 62 miles per gallon.

Steel neatly fits the scope of designers’ plans in that it can be formed with new geometry to save weight through less material, but still conform to all the safety and convenience rules needed to produce and sell automobiles (3). The key is to use less, but better, steel, according to Edward Opbroek, an advisor at WorldAutoSteel. The report says that the latest high strength steels allow carmakers to boost fuel economy and reduce weight over 35 percent. “Our latest light-weighting projects show the continuing potential of steel and demonstrate how carmakers can take advantage of steel’s design flexibility and use advanced high-strength steels to meet their difficult challenges for improving fuel economy and reducing greenhouse gas emissions,” Opbroek said.

Study the function

Last year, a group put together to study the use of lighter materials for large components gathered with the idea that the overall vehicle design and function must be the first consideration. Lighter, stronger and safer: Can they co-exist?(4) The overall design of a car must allow for the use of many materials, including steel and aluminum. This can be achieved through design and miniaturization, in part, but the group specifically looked to create a new, strong, light material. Addressing the problem that “it is a question of manufacturers deciding which components can really afford to have weight shaved off and how to integrate them into the overall systems,” this group led by the Fraunhofer Institute for Chemical Technology designed a polyurethane-based sandwich material with resilient strength properties.

They then chose a very large component with which to demonstrate the strength of this material: a diesel engine housing for a locomotive. What better way to magnify the stress and shock delivered to the material than using it as the protective barrier between the track and the diesel engine? According to this report, the housing was the barrier for flying debris such as stones and also kept any oil from escaping the compartment. Additionally the sandwich material was fire retardant and easily met safety standards for railway vehicles. Should the material be translated into automotive parts, the manufacturer noted that the process of layering this material has been refined to extremely tight tolerances, which in the past was difficult to do. New computerized layer inspection and manufacturing now determine exact thicknesses of the layers.

Sitting in the middle

Positioned in the middle of this research and development debate is aluminum. It was the great new material for automotive components decades ago when it was first successfully used as an engine body. Easily machined and lightweight, aluminum has one particular drawback: its linear strength per unit of thickness is far less than steel and many other materials. Many designers believe aluminum has peaked as a material for reducing weight in vehicles; there are few if any ways to use it in new parts and parts that are being miniaturized.
Lighter, stronger and safer: Can they co-exist?
Aluminum will most certainly continue to be used throughout the automotive chassis, electric and body systems. It is still ideal for many applications, but can its properties be used for dynamic new designs including bodies and other major parts? A report on the uses of aluminum in new automotive designs (5) argues that it can and will fill those requirements. Along with other aluminum makers and users, the report touts the safety of aluminum as a structural material, and includes the fact that aluminum components in military vehicles wear as well as other materials and “aluminum-intensive military vehicles survive battlefield conditions.”

The authors conclude that while the use of aluminum has steadily risen in the last two decades, it still is not used as a major body material. Both reports are optimistic that wrought aluminum is the next big material for frames and panels. Hopefully, they conclude, aluminum will become the perfect blend of lightness and safety.

Carbon – the most important element
: The most difficult problem for the use of carbon-fiber reinforced plastics has been the cost. Every automaker wants to include some of this remarkable material in its products, but many find the price prohibitive in a fiercely competitive business. Fiber companies have been working to get mass production techniques perfected. Fiber technology has increasingly improved. Companies are trying to improve two processes: producing the fiber material more efficiently and molding auto parts from material more quickly. They are also trying to combine the light weight of the material with enhanced safety (or at least no reduction in safety rating).Lighter, stronger and safer: Can they co-exist?
One ideal example comes from Volkswagen’s research and development chief Dr. Ulrich Hackenburg, who is quoted (6) as saying that a carbon fiber roof will reduce the vehicle’s weight and lower its center of gravity, which provides a safer overall ride. The process is rapidly becoming more affordable, he said. “The lower parts of the safety cabin, up to the bottom of the A pillars, are done in one shot. We have a tool that closes, the CFRP material is brought into this form, the form is closed, and then you inject the resin. Takes half an hour.” Several companies are now mass producing larger CFRP parts. For about two years, plants have started to find faster methods of molding CFRP into parts as large as a frame.

Finally, nanotechnology is playing a role in the use of resinous plastics, carbon and other fibers, and other moldable materials. Changing or adapting the molecular structure of non-metallic materials could be the future of automotive building. With the goal of reducing emissions in mind, weight reduction and aerodynamic designs could come from chemical breakthroughs at the molecular level. The technology has been applied to steel products like NanoSteel®, which is a thinner, higher strength steel product like those mentioned earlier. Now, microscopic research in other materials can create nano-production techniques for combinations of other materials.
Miniaturization is a key to all of these technologies: reducing size while including more sophisticated designs and materials. Technology that began in electronic design is now used to aid design down to the molecular level. All these materials are connected by the whole-vehicle production/control mindset.

About the Author:

Al Tuttle is news and features editor whose experience includes Media News Group, Reed Elsevier and New York Times New England. He specializes in industrial and commercial writing. He was in sales for industrial companies and manufacturers for 15 years. He is a regular technical writer for Automotive IQ,Germany.

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