Best of K2013: Number 4
The BMW i3
The BMW all-electric i3 car, which officially went on the market last Saturday, is a tour-de-force of plastics applications, including all-plastic body panels and a carbon composite structural passenger compartment. It represents the most extensive use of carbon fiber in a mass-produced car. An aluminum frame incorporates the powertrain, chassis, battery, and provides primary crash protection.
The payoff is weight savings: the i3 tips the scales at just 2,646 pounds, about one-third less than the Nissan Leaf, another important new electric car. The i3 has some pop: it can accelerate to 60 mph in about seven seconds. It has a sporty look, but it is marketed as an urban, get-around-town-kind of car, not a pedal-to-the-metal autobahn-kind-of-car. Starting price is $41,350.
Several applications were prize winners at the Society of Plastics Engineers Central European Awards program held in the Düsseldorf environs in conjunction with K2013. Several K exhibitors participated in the applications (KraussMaffei, Engel, LyondellBasell, Kraiburg, Bayer MaterialScience, and BASF), and work on the car was a major talking point at the K.
In one example, recycled carbon-fiber composites from SGL Carbon are used in the polyurethane rear seat shells. F. S. Fehrer Automotive GmbH’s composite components division integrated a weather strip channel, a clamp, fastenings, cup-holder and storage receptacle functions in a 1.4mm part.
Right now carbon composites cost 12 to 20 times more than steel, depending on grades and volumes. BMW is building a vertical supply chain, including a fiber production plant in Washington that uses hydroelectric power. The carbon fiber is shipped to Germany, where the fibers are woven into mats and composite parts are produced with the resin transfer molding (RTM) process. Carbon composite parts are bonded in a new BMW body ship in Leipzig. The assembled parts are 525 inches long. BMW said it has greatly shortened the hardening period through proprietary technical advances.
The outer panels are made of injection molded thermoplastic, while the roof is made of composite using recycled carbon fiber from the Washington manufacturing plant.
Three thermoplastic processes are used to make the body panels. One is a standard approach. The second is a twin injection molding process in which the outer skin and substructure are molded then bonded in separate, successive stages. In the third process, the outer skin and substructure are injection molded in parallel and joined at the same time.
BMW says it has invested $538 million in the Leipzig plant to produce the i3.