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No peace for passive safety design yet

Despite considerable change facing the automotive industry, the steel versus aluminium debate looks set to rumble on, writes Xavier Boucherat

Active safety features are the heart of autonomous driving. Automatic emergency braking (AEB) and other advanced driver assistance systems (ADAS) could soon become standard on vehicles, and possibly even legislated. With these technologies in place, and the risk of collision lowered, will tomorrow’s car manufacturers have to pay as much attention to passive safety? Could features be removed, materials weakened, and costs reduced?

David Ward, Global NCAP’s Secretary General, suggests the temptation is there. “We’ll see more and more autonomous technology coming,” he says, “and this is very, very good. But what would be a hugely naive move would be to assume that cars won’t crash any more.” This, he continues, could be used to justify building cars from cheaper, less stiff materials. Already, he claims, there are some voices in the automotive industry wondering if vehicle front-end crash requirements could be relaxed on vehicles equipped with AEB.

However, Ward admits that any serious move in this direction is unlikely. It could endanger overall public trust in the autonomous vehicle, and if nothing else, the scenario assumes that all OEMs are keen to embrace autonomous technology. This is not true. Consider Mazda: the OEM is among a number of manufacturers who are less than enthusiastic about the advent of autonomous technology, adamant instead that the experience of driving will remain central to their brand. Speaking at a seminar in September 2015, Russell Wager, VP Marketing, Mazda North America, said cars that drove themselves held no interest to the OEM and its engineers.

“From a marketing perspective, I think it will be disastrous for the industry,” he added. “If you just got in and sat there, why would you need different brands?” Chief Executive Masamichi Kogai expressed similar sentiments in February 2016, saying that driving involved more than simply getting from point A to point B.

Aston Martin thinks along similar lines. As Chief Executive Andrew Palmer points out, it’s a strange driver who shells out a fortune on a luxury car, only to sit in the cabin with their hands off the wheel. “These are technologies we’ll lag in,” he said, “and perhaps never even offer, unless legislative requirements are brought in.”

The OEM will remain reliant on passive safety design, and building a vehicle stiff enough that it can withstand a crash whilst meeting lightweighting targets will remain crucial. This is an area that pits advanced high strength steel (AHSS) against aluminium, but the trend seems clear – premium is going aluminium.

Stiff competition

Palmer says the company is lucky to be in a position where it can build its cars with aluminium and bond them using structural adhesives, borrowing heavily from aerospace engineering. “This means we can build a stiff vehicle that can manage a crash.” The US-based Aluminum Association, an advocacy and standards group, argues that pound for pound, the material can absorb double the amount of crash-induced energy that steel can absorb, enabling designers to build bigger crush zones without corresponding weight penalties. The OEM stands with Jaguar Land Rover (JLR) and Ford in proclaiming aluminium’s superiority over AHSS. Several JLR models, most notably the Range Rover series, are aluminium intensive, as is the Ford F-150. Ford reportedly spent US$1.5bn converting plants for aluminium-intensive production.

OEMs know that customers are taking material choices into account when purchasing a vehicle, particularly when considering safety and crashability. An advert for the Chevrolet Silverado that appeared online in July 2015 dragged the battle between steel and aluminium into the public domain. In the advert, supposed members of a focus group were taken to a room where they were presented with steel and aluminium cages. When a grizzly bear is released into the room, most group members run to the steel cage for cover. Despite aluminium being used to make the Silverado’s hood, the message from GM seemed clear – it’s for cans, not cars.

Growth expected

But Pierre Labat, Vice President, Sales and Marketing, Global Automotive at aluminium supplier Novelis, is convinced this plays on completely out-dated notions, and that the public’s perception of the material has long moved on. “The consumer response to automakers promoting aluminium as a selling feature for their iconic vehicles, such as the Ford F-150 and Jaguar Land Rover’s (JLR) entire fleet, has been positive,” he says. Both Ford and JLR have been very public in their embrace of aluminium, and JLR is reporting record sales volumes, whilst the F-150 remains the best-selling vehicle in North America, even since the switch to an aluminium-intensive body. More widely, Novelis supplies aluminium for use in over 180 vehicles.

Research from BMI Research suggests that aluminium use will rise. Alcoa predicts that the average amount of aluminium used in a car will rise from its current level of 394 lbs (178 kg) per vehicle to 473 lbs per vehicle by 2020, as the material becomes suitable for further applications. Future variants of the F-150, already an aluminium-intensive model, will feature more inner structural parts, including door inners, made of aluminium.

“We see continuing interest from OEMs to create durable, high-performing vehicles with best-in-class safety features,” argues Labat. “Lightweight aluminium body styles support faster acceleration, shorter brake time, better handling and increased energy absorption in the event of a crash.” The supplier is now developing new alloys to further increase strength and durability to meet standards. “Our military grade strength aluminium provides new and innovative safety features, leading the way for manufacturers to meet new industry standards without compromising on toughness or durability.

“Consumers are demonstrating that they understand aluminium makes a great vehicle, not just in terms of fuel economy, but in overall performance, durability and safety,” he says. “Every aluminium car and truck crash tested in the US has earned a 5-star safety rating. Consumers are seeing the proof.”

Taking form

Steel advocates have argued that aluminium is less design-friendly and harder to form than steel, and that without that geometric freedom, OEMs will have a difficult time making stiff, torsional rigid shapes while retaining the weight advantage. According to Tad Machrowicz, Vice President, Automotive Engineering at NanoSteel: “Aluminium feels light, because its density is a third that of steel. If you were to make parts with equal geometries, an aluminium part would require three times as much material as the steel part to be equally stiff.”

But others take a different view. Ford claims that its aluminium-intensive F-150 has higher safety ratings than the previous-generation steel-bodied model. Mark White, Chief Technical Specialist for Advanced Body at JLR, says that whilst NanoSteel’s argument is probably true in traditional terms, the work JLR has been involved in since the late 1990s in aluminium alloy development means that the material is on par with steel for stiffness.

“For example,” he says, “we can get our skin panels to nearly the same radius, through a combination of the alloy and the way it is processed. What’s more, we can get to the same level of dent performance. In fact, the aluminium cars are slightly stronger for dent performance than our current steel cars.” The OEM will also embrace aluminium hot-pressing technology, which works much like steel hot-stamping. This will grant further ductility, allowing it to make stiffer shapes.

With steel still reigning supreme, Novelis is looking to position itself accordingly – not as an outright steel replacement solution, but as one that works in harmony with the many materials that will be used to build tomorrow’s car.

Labat says Novelis believes tomorrow’s vehicles will use a multi-material mix, combining steel, aluminium, carbon fibre and other materials to achieve the weight, cost and performance targets of the various car manufacturers. “The right material mix will be inevitably important for the future, which is why Novelis is investing in researching techniques for joining different materials.”

Some OEMs have committed to bringing models with autonomous drive technology to the market by 2020; other OEMs have suggested that 2030 might be more realistic. Thus, the ability to build a car that relies exclusively on electronics for safety, at the expense of passive safety, remains at least a decade and a half away. Even if autonomous drive technology arrives in the near future, it will arrive in low volumes, built within current vehicle designs reliant on passive safety structures.

“The vehicle fleets of the world are forecast to double in size over the next ten to 15 years,” says Global NCAP’s Ward, “from one billion to two billion units. So the proportion of fully autonomous vehicles is going to remain tiny, and largely restricted to high income country markets.”

Although the cars of tomorrow will use a mix of materials, they need to be affordable materials offering high levels of crash performance. The autonomous car may be coming – but not so soon that the industry can forget about passive safety.

This article appeared in the Q1 2016 issue of Automotive Megatrends Magazine. Follow this link to download the full issue.

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