BMW limits carbon fibre use to make cars lighter, more profitable

28 October 2016

German auto maker BMW Group is limiting its use of costly but lightweight carbon fibre and turning to cheaper lightweight materials for its biggest selling cars to keep profit margins high.

Lighter cars consume less fuel or if they are battery-powered can drive for longer on a full charge, vital attributes for manufacturers seeking to score points with consumers and regulators.

After investing heavily in carbon fibre, which is stiffer and lighter than aluminium, BMW is now faced with tough choices on how to build its cars more profitably, as competitors close in with their own electric car offerings.

"The main equation is how much cost do I spend for a kilogram reduction in weight. It is not about one material it is about the combination of materials," Oliver Zipse, BMW's board member responsible for manufacturing, said at the opening of a new 20 million euro high-tech research facility specialising in lightweight materials.

The lighter you can make an electric car, the less you need a large battery to power it, saving costs. Batteries are the most expensive part of electric vehicles, which remain an unprofitable segment in the auto industry.

After launching two cars which made heavy use of carbon fibre including the i3 city car and the i8 hybrid in 2013, BMW's new 5-series, presented earlier this month, does not use the material for major components.

Sales of BMW's i3 electric car have failed to take off, analysts say, in part because of the extensive use of carbon fibre, which has made the vehicle expensive. It costs around 45,000 euros.

The BMW i8's passenger cell is made of carbon fibre reinforced plastic, a manufacturing technique which involves bonding carbon fibres to make components which would otherwise have been made using conventional welding and stamping methods if they had been made of metal.

Carbon fibre costs around 16 euros per kilo, compared with less than a euro for a kilo of common steel, according to consultants at Frost & Sullivan.

BMW is under pressure to raise its game now German rivals Daimler AG, parent company of Mercedes-Benz and Volkswagen AG, which owns Audi, as well as Tesla Motors Inc in the United States have outlined aggressive plans to court affluent buyers - and satisfy regulators' demands - with new electric cars.

BMW said last month it would expand its electric offerings with all-electric versions of Mini, and its BMW X3 compact sport utility vehicle, for 2019 and 2020, respectively.

Zipse declined to comment on whether future BMW and Mini vehicles will make extensive use of composite materials. BMW Chief Executive Harald Krueger was more direct, effectively ruling it out for smaller low margin cars.

"The material is still too expensive and for smaller segments and smaller vehicles it can be not competitive," Krueger said at an event in Los Angeles earlier this month.

Advances in battery technology have improved vehicle operating range by about 50 percent since 2013, taking some pressure off the need to use ultra expensive lightweight materials in manufacturing.

After investing between 1.5-2 billion euros to develop carbon-fibre based hybrid and electric cars, BMW is now working hard to develop "hybrid" methods, which combine carbon with other materials like steel and aluminium.

BMW's past investment in carbon fibre will be a great help, said Jochen Kopp, who specialises in product and process planning for carbon fibre reinforced plastics.

The Munich-based carmaker now has a two year lead on rivals in terms of carbon fibre mass production know-how, he said.

"It takes time to learn how it behaves in manufacturing, how it reacts to being bonded to other materials. This has implications for tooling, purchasing and manufacturing. We understand the complete development chain," Kopp said.


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