Experts are divided in their opinions regarding the use of carbon fiber in auto manufacture. Critics say that the material is too costly when compared to aluminum and high-strength steel. They also observe that most body shops won’t know how to repair or replace the new materials.
On the other side of the debate, proponents of carbon fiber hail it as a ‘paradigm shift’ that will change the way cars are engineered. They argue that most repairs will be very simple, and that body shops will be able to repair or replace components with relative ease. The BMW 13 even has markings showing where the carbon fiber components should be cut away when replacements are needed.
As for the safety benefits of carbon fiber combined with adhesives, engineers are impressed. The new BMW i3 has a life module consisting of 90% carbon fiber and is constructed from nine molded parts. It has performed very well in crash tests in the EU, and US results are expected to be as favorable.
The use of adhesives to bond the body to its aluminum frame raised eyebrows, but this choice was vindicated by fruitless attempts to rip the body from the frame. Munro and Associates, whose company disassembled a BMW i3 RX down to the ball bearings (and is regularly contracted to do these teardowns for the industry), was blown away by the car’s engineering and implications. Ultimately, a vibrational cutter had to be used to slice through the epoxy and the whole process took a week. Munro senior associate Mark Ellis says that he will trust epoxy over spot welds from now on. Adhesives are also used to bond overlapping carbon fiber panels to the aluminum floor pan, eliminating galvanic corrosion and reducing noise.
However, the concerns regarding the cost of carbon fiber are warranted, and may limit or delay the widespread adoption of this material in vehicle manufacturing.