Crash worthiness and Composites

[ecoangel]

My work is in the aerospace industry and I am intrigued by the use of CF composites in these vehicles.

Recycling:

How does BMW intend to re-cycle CF? This is a major problem with aircraft as the amount of energy requires is far more than for aluminium.

http://auto.howstuffworks.com/fuel-efficiency/fuel-economy/carbon-fiber-oil-crisis2.htm

Crash worthiness:

CFC has advantages (see: F1 developments) but it's a one off impact before the car is written off.

Fire crews worry about CF dust:

http://www.netcomposites.com/news/dangers-of-carbon-fibre-debris-from-aircraft-crashes-exposed/3306

Some more CF info here: http://www.bbc.co.uk/news/technology-12691062

 

[Stevei3]

Hi,

I am NOT working in the aerospace industry, so my knowledge of CRFP is not that extensive But I consider it a highly interesting material.

Regarding recycling of CRFP the jury is still out, I'll give you that. I don't have high hopes for real recylcing yet, all that is done today is downcycling at its best...

But about crashing I'm more optimistic. First, CRFP is used to create the safety cell. Unlike F1 cars, other parts of the i3 (mainly made of alu or thermoplastics) will take the first hit. They will deform as programmed protecting the CRFP cell. Next, the benefit of the CRFP cell is that only the point of impact should shatter, absorbing energy. The cell itself should not deform like traditional alu or steel cells. I can flex a bit, but it should spring back. This will lead to relatively localized damage, which will, in turn (I expect), lead to lower write-off rates. What kind of splintering to expect, who knows ? This will depend on the bonding material, one would guess.

Finaly, there is the carbon dust in case of a crash one could be worried about. According to your sources, this is not a real problem when CRFP is shattered. It should also be no problem if it is burned. It could be a problem, however, if it is shattered and burned at very high temperatures, mainly because of toxic chemicals deposited on the fine airborne CRFP fibers during the fire, which can reap havoc when absorbed through the skin. This is mainly a problem in the aviation industry, one would think, as there is a lot more CRFP present in an airplane (28 t in the dreamliner if I'm not mistaken), a lot more shattering involved in an airplane crash and, last but not least, much more highly combustible material in the form of jet-fuel.

Please feel free to react because it could be interesting to learn more about the way that CRFP is used in the i3.