BMW has started production of its revolutionary i3 city car, which is the first mass-produced automobile using a composite frame. The company invested $533 MM (€ 400 MM) in its composite and assembly facilities in Germany and expects first deliveries to European customers in November. Production facilities have been sized to support a rate of 40,000 vehicles per year.
The heart of the structure is the 330 pound (150 kg) passenger compartment, called the Life Module. It is made from dry, carbon non-crimp fabric (NCF) preforms that are resin transfer molded (RTM). This permits substantial parts integration of the Life Module comprising 150 parts total, with two thirds fewer parts and 50% less production floor space than with a steel design, according to BMW. Parts consolidation of this magnitude cannot be achieved using steel or aluminum according to BMW’s Project Director Dr. Carsten Breitfeld. The Gr/Ep Life Module weighs half of a steel design, and contributes to total vehicle weight savings of 770 pounds (350 kg).
Production cost and rate of the i3 composite structure are critically important. Compared with existing production of composite parts for the BMW M3 and M6, 50% cost savings are realized with the i3 process and cycle time is reduced by 30%. “We have optimized the process, achieved a shorter manufacturing time, and succeeded in taking a lot of the cost out” says Breitfeld. He attributes these achievements to “a fresh approach to manufacturing and materials use and a very clear business plan…… The production process is a very significant time saver and means that industrialization of large CFRP components is now realistic.”
BMW’s experience has been so favorable that its larger i8 electric sports car to be offered next year will be built the same way.