One of the unique features of the BMW i3 is the carbon fiber monocoque chassis – a single unibody type construction that encloses the passengers and protects them from the elements, or in the case of an accident, from injury.
Since the i3 doesn’t have a pillar in between the front and the rear doors, strength needs to come from the body of the vehicle, and that’s where the carbon fiber comes in. Being super strong for it’s weight, BMW can use carbon fiber to give the vehicle incredible strength while maintaining a manageable weight for the i3 to be energy friendly and maximize the range one can expect on a charge of the batteries.
The manufacturing time for the carbon fiber shells was a concern, but BMW says the time required to make an i3 is now less than it is for an equivalent conventional vehicle. BMW started molding pre-production carbon fiber panels for the i3 in February and has been able to modify and perfect the process to the point where a carbon fiber sub-assembly is the same price as the equivalent piece in aluminum. The alignment of the carbon fibers are critical to the strength of the shell and BMW has devised methods to ensure precise construction at sensible costs.