What Is the Design Rationale for the 2014 i3 Roof (Composition, Appearance, etc.)?

  1. i3 is, unusually for a modern car, basically a "Body on Frame". Propulsion and much of the torsional rigidity come from the skateboard or "drive module" in BMW parlance. The result is that the "Life module", or body, need only be a roll cage type of thing. Now where I'm going with this is that unlike in a more common unibody design, the roof of the i3 is not really load bearing. Unless you roll the car obviously. When BMW went fully in on CFRP for the i project one of their overarching goals was to reduce waste and landfill. The roof of the i3 is composed of the fiber cuttings removed when trimming and forming the body panels. They chop them up then embed the into a thin resin sheet. Since it's not structural there was no reason to use fully layered CFRP and the resulting sheet is unique in appearance and lightweight.

  2. The roof is actually considered a critical part of the life module. The random layup of the scraps actually makes for a very strong panel. It didn't have to be structural, but it ended up being an important aspect.

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