One of our readers, Noble713, commenting on a news items about the BMW i3, asked if TTAC could provide more coverage on BMW’s carbon fiber productions methods. The i3 EV, and upcoming i8, are built upon CFRP structures. Weight is the enemy of electric vehicles. The more weight you can take out of the actual structure of the car, the more battery cells you can carry for more power and better range, hence BMW turning to carbon fiber. It turns out that BMW has released a series of videos (bilingual, wait for the English) on that very topic. Their CFRP production uses materials made by SGL Automotive Carbon Fibers, a joint venture between the BMW and SGL groups and the effort spans the globe. SGL has expertise in carbon fiber and in 2011 BMW took a 15% stake in the company. Pure polyacrylonitrile fibers are made by Mitsubishi Rayon Co. in Japan and shipped to a state of the art SGL ACF factory in Moses Lake, Washington, where the PAN fibers are first oxidized and then baked into carbon. Wound on spools, the raw carbon fiber is shipped to a SGL ACF facility in Wackersdorf, Germany, were the carbon fibers are woven (actually sewn) into fabrics. The fabrics in turn go to BMW’s Landshut facility were they are laminated in the proper orientations, resins are added, patterns are cut and the finished parts are molded.
BMW has been publicizing how environmentally sensitive their CFRP manufacturing is, stressing how the Washington state facility is powered by renewable hydro power.
While carbon fiber is regarded as almost magical stuff because of its superior strength to weight ratio and the ability to orient the fabric so the resulting parts are stiff in some directions and flexible in other directions, it is still relatively costly to work with, compared to aluminum and steel. Like the CFRP shop at Toyota’s LFA works, BMW is using carbon fiber for the i3 and i8 not just because of those inherent characteristics but also so they can develop processes for the inexpensive mass production of CFRP parts.
Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can get a parallax view at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading – RJS