Uma Thurman with the BMW i8
Uma Thurman with the BMW i8. Click image to enlarge

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Article and photos by Mike Schlee

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BMW Carbon Fibre Plastics

BMW is serious about carbon fibre plastics. It will be the sole structure for their upcoming line of ‘I’ electric and hybrid vehicles, and they invited us to New York City for an Uma Thurman-starring presentation to tell us all about it. Now I know we have heard such claims before; some manufacturer is claiming an expensive cutting edge technology will be included in their future space age-looking vehicle. However, what is different this time around is that BMW isn’t just pulling a fast one full of marketing hyperbole. The ‘I’s will be coming to market starting in the next year or two, and they will be constructed with carbon fibre.

To support this ambitious endeavour, BMW has set up a joint venture that includes a factory in Moses Lake, USA where the actual threads of carbon fibre will be produced and then shipped to Wackersdorf, Germany. Of course, since the i3 and i8 are all about green living and sustainability, the plant in Moses Lake uses 100% renewable hydro-electric power. BMW claims that this production takes 50% less energy than their usual steel production and 70% less water.

BMW i3
BMW i3
BMW i3. Click image to enlarge

Once the strands of fibre arrive in Wackersdorf, Germany, they are moulded into components that will be used in the production of the i3 and i8 in Leipzig, Germany such as the LifeDrive body structures. These body structures are the passenger compartments which are separate from the drivetrain architecture. This allows bodies to be interchangeable within the same electric and/or hybrid chassis and makes each drivetrain more flexible; to get the general idea, think of it as a modern take on body-on-frame construction.

The reason BMW is making such a big deal about carbon fibre plastics is due to them being both incredibly strong and incredibly light. Anyone with an interest in racing or supercars will be well acquainted with this material as it has been used for decades to both increase chassis rigidity while reducing weight. Carbon fibre is 50% lighter than steel and 30% lighter than aluminum, so the weight savings are significant. As a real-world bonus, carbon fibre is also not susceptible to corrosion like metals are.

BMW i8
BMW i8. Click image to enlarge

Since carbon fibre is so incredibly strong, the monocoque design for the i3 and i8 will be completely rigid. It is so strong in fact that the structure can make do without any extra crash worthiness protection additions, thus further reducing weight. When a carbon fibre vehicle is crashed, it is more flexible than steel or aluminum. The fibre ‘net’ absorbs a lot of the crash force as it flexes, then releases it in a rebound.

The added rigidity also allows no ‘B’ pillar on the i3 concept car and thus permits a large, dual-door single passenger entrance area. With less space eaten up from the actual structure, carbon fibre–built vehicles allow more interior space so that a vehicle that borders on city car sizing, like the BMW i3, can offer interior space closer to a mid-size sedan. Finally, the carbon fibre chassis can accommodate a secondary engine (range extender) in the i3 as an option, without any need to vastly modify the structure.

BMW Carbon Fibre Plastics
BMW Carbon Fibre Plastics. Click image to enlarge

BMW expects production versions of the hybrid i8 to come in around 1,480 kg and knows it would weigh considerably more with conventional steel and aluminum architecture. For example, the 1-series based all electric ActiveE is close to 1,814 kg compared to the automatic equipped 128i that only weighs 1,490 kg. The real question then becomes how much will it cost. That has always been the stumbling block with carbon fibre. If it were cheap, every car in the world would most likely use the material. It will be interesting to see where the i3 and i8 end up on price once they hit the market. All BMW is currently saying is that the i3 will start below the price of a BMW 5-series.

However, with BMW investing heavily in carbon fibre plastic research and production, one can only hope raw material and production costs will decrease in the future. If the i car concept really takes off, other manufacturers will likely follow suit and join BMW in the carbon fibre plastic game which will only expedite the transition of carbon fibre from an exotic resource to an everyday material.

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