BMW i3 and BMW i8 – The Carbon Fiber Journey


“It all starts with one carbon fibre that’s just about one seventh the width of a human hair. The result is an extremely lightweight and robust passenger cell of the BMW i3 and BMW i8. Watch the clip to see how BMW is doing this.”

Carbon Fiber Gets Molded

Carbon Fiber Gets Molded

Says BMW of the manufacturing process for the carbon fiber material found in the i3 and i8.

BMW is the first automaker to make extensive use of carbon fiber in a mass market automobile (BMW i3).

The use of carbon fiber will soon spread across most of BMW’s vehicle lineup, starting with the 7 Series.

With carbon fiber, BMW is revolutionizing the way automobiles are made.

Watch the video to see the carbon fiber journey from a single strand to a finished component.

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12 Comments on "BMW i3 and BMW i8 – The Carbon Fiber Journey"

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how expensive is a carbon fiber body vs. steel? is it a factor of 2? what is the expected life? can a carbon body electric car give buyers access to a usable vehicle that will last for 50 years?

Right now I think the factor is much bigger than 2 over steel. Probably more expensive than aluminium. But with economies of scale this will only get cheaper. At least for BMW since they are the only car manufacturer that also makes their own carbon fibre. And expected life should be much higher than steel, but I’m not aware of any “official” numbers.

It’s speculative of course but although traditional carbon fabrication is associated with high cost that might not be the case with this carbon reinforced plastic technology.

After all, the efficiency gain of i3 compared to some of its competitors is not that impressive, so why throw massive extra cost at an efficiency gain of just 7% over an ICE conversion job like the Honda Fit EV for example?

Materials cost is probably closer to 10x steel, though, in volume, vehicle assembly costs may end up being cheaper, but CFRP still has a long, long way to go to be economical for anything but niche vehicles. Crash performance (vis-a-vis repairability) will be interesting. When I bought my CFRP bike, I was told that, if I ever crashed it, I should throw it away, whether it looked damaged or not. Damage to CFRP can be difficult to detect, and it tends to fail catastrophically. This “cut and paste” repair method that BMW is talking about is interesting, since the real value of CFRP is in using long fibers oriented to maximize the tensile strength. I wonder how they will do this with repair patches. You don’t want a vehicle that lasts 50 years. You want to match as nearly as you can the obsolescence of your vehicle to the technology development curve to yield the most overall efficiency. It would not be good for the environment if everyone was still driving cars from the 60’s. And, not to be pedantic :), it is Carbon Fibre Reinforced Polymer, not Plastic. The matrix that holds the fibers is a thermoset, not a… Read more »

Good short summary. It took a while for me to figure out that they only make the FIBER at Mose lake. They then ship it to Germany to finish the product.

The carbon fabric is impregnated with resin much like fiberglass.

GM should make the Corvette out of this.

The way to think of this is as CF being a reinforced plastic, much as steel rods and concrete make reinforced concrete. The result is simlar. Carbon fibre is very strong in tension, which plastic is not, and the resulting composite material has good overall properties.

We didn’t invent fibre reinforcement. Trees have been doing it for a while. Wood is actually a fairly amazingly strong material.

I’m very curious how this stuff will hold up over time. How will it handle crashes. How easily can a crashed car be repaired? How will the car be recycled at the end of its life?

I love the fact it is free of corrosion and lightweight.

As far as I know, it brakes like hard plastic in case of an accident. The broken part gets cut out and another part gets glued in. They do it in an overlapping way, so this part should actually be stronger (and heavier) than before.

I wonder how the material will react after 10 years of time spent in sunshine, changing temperatures and moistures…

How will it handle crashes…the car has a four star crash rating so I guess that is a valid question now that 5 stars are pretty much the norm.

This has been covered on InsideEVs in the past.

The i3 lost a star due to lack of standard safety equipment (ie seat belt warnings, and rear view cameras), not due to passive crashworthiness.


Does anyone know the percentage of carbon fiber and plastic?

Like any composite, it will last as long as the bounding resin. The resin is the weakest point.

There seems to be a mistake in the movie when they say that carbon fiber composite is half the weight of steel and one third the weight of Aluminum, it seems the other way arround.