Aluminium body structures: solution to increase vehicles’ sustainability?

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In the last few years laws such as the EU Cars Regulation setting at 130 grams of carbon dioxide per kilometre the maximum average emission per fleet by 2015, have pushed the automotive industry towards the route of enhanced safety and environmental sustainability. All the vehicles recently launched are equipped with several driver assistance technologies and with engines significantly greener than those of previous generations. The development of environmentally friendly cars, however, is just at the beginning, with many new hybrid and electric vehicles just about to be launched and with new technologies and materials such as carbon fibre being employed in order to reduce the weight of vehicles, and as a consequence the power needed to achieve a given performance.

An interesting case in this sense is that of the recently launched Range Rover Sport, 40 per cent lighter than its predecessor (420kg less) thanks to its all-aluminium body structure. Simon Black, senior manager of Jaguar Land Rover Group (JLR) explains: “The key technical challenge for body structures is to balance weight, cost and function…all of our attribute groups such as vehicle dynamics, noise-vibration-harshness and safety want the best for their attribute, so that will force you to make the car perform as good as it can; we are trying to make it as low mass as possible from an environmental point of view and from a material cost point of view and then all of this stuff costs and we are trying to maintain the cost base low”. Among these conflicting aspects, the interesting one in terms of improving the environmental impact of the vehicle while keeping it fast and safe is undoubtedly the reduction of its mass. The latter, indeed, according to Mr. Black, initiates a virtuous circle. “If you reduce the mass of the body shell and of other components such as the seats, you then can look at the size of the brakes because you have a much lighter car, so you can have smaller brakes, and you can have a smaller engine to get the same speed and when you have a smaller engine you are using less fuel and so you have lower CO2 emissions”. In the case of the Range Rover Sport, the mass and weight reduction was mostly achieved with the all-aluminium body structure replacing the steel one of its predecessor. Aluminium, in fact, is four times lighter than steel, allowing to reach the same functional performance with a lower vehicle’s total weight, it is more versatile and absorbs more energy per kilogram, meaning enhanced safety for the driver in case of an impact.

But if the advantages of an aluminium body structure are so clear, why does steel remain so preponderant in the automotive market?

“There is a cost for everything in this world” explains Simon Black, “The aluminium is more expensive than steel and some of the products at the smaller scale can’t afford a 100 per cent aluminium structure just on a cost basis”. Furthermore, being aluminium less formable than steel, it makes it more difficult to produce certain body parts out of it than out of steel sheets. If JLR could make it economically and technically feasible for the Range Rove Sport to have an all-aluminium body it is because it could count on two generations of experience on aluminium usage in body structures with the Jaguar XJ and XK and on several years of research. It will take thus a while before volume cars producers such as Fiat-Chrysler, Renault or Opel will catch up with the employment of such material. The bet of Mr. Black is that in the near future it will be more likely to see hybrid body structures made of both aluminium and steel rather than all-aluminium ones.

Aluminium, however, is not the only way to make cars greener. According to Mr. Black, indeed, also at the production level there are many elements that can be designed and engineered to reduce energy consumption and the need for water cooling. For example, using secondary metals retrieved from engineering scrap) instead of virgin ones (produced only by smelting) to produce panels for body parts, ensures significant energy savings as there is no need to get the metal out of the ground and to process it.

Therefore, on the bright side, car manufacturers have many tools in their hands (e.g. usage of aluminium and secondary metals, employment of hybrid or electric engines, design of production facilities, etc.) to increase the environmental sustainability of their vehicles. On the downside, all these innovations have a cost and not everyone can afford. Given that more regulations aimed at environmental protection are expected and that environmental concerns of the public opinion are on a constant rise, it seems that automotive engineers might just have found their new big challenge: discovering new technologies and materials that can allow cars to get greener at the lowest possible cost.

Photo/JohnBootyman