Quote:
Originally Posted by Captain Awesome
You assume that I believe that "composites" are 100% carbon fiber, which they are not.
The original Saturns and 4th Gen F-Bodies, as well as a few GM Minivans were made of "composite" body panels, which is a generic term that doesn't mean "carbon fiber".
As I said above, carbon fiber is a great lightweight and strong material, but it is very brittle and is prone to damage and failure from fatigue, etc. This is well documented in the field of aircraft design. It also costs a LOT more to produce than metal alloys. For the most part it doesn't pay for itself in weight savings and the manufacturing process for the material has a rather beefy "carbon footprint". Once everyone is fully committed to building cars with it, someone will figure out that it must be helping kill polar bears and we'll be back to square 1 with some even more expensive process making cars even more unobtainable.
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I spent years of research in the crashworthiness of composites for structural components. Number 3 misses the point about composites usage in automotive. Up to now, composites have been used mainly as non-structural components and you can only reduce so much weight with this stuff, body panels, interior, bumpers....ALL of the crash structural parts are still metal. Strong light weight metals are being used. A few manufacturers are experimenting with composites (CF) structural parts but they are not cheap and they are certainly not ready for cheap mass produced cars.
The major difference in the design requirements of cars versus aircrafts and others is: the structural parts must be able to dissipate energies during the crash to protect the occupants. The ductility in metal allows for this plastic work (converting kinetic energies into the crumbled metals). This ductility in metal is a huge advantage that composites do not have. In aircraft design for example, the composites can be used to up to its brittle failure limit minus the safety factor and engineers do not have to worry about post brittle failure, i.e. if the stresses in the composite parts are exceeding the brittle failure, you already have a failure. In cars, we have to continue to work with the metals post yield because plastic flow and work hardening are what we rely on for energy dissipation.
Personally, I believe we will have to come up with more active safety systems so that we can keep the occupants safe without completely relying on the plasticity of metals before we can truly have composite structural components in cars. Got up too early this morning to run some "blast on composites" simulations and couldn't stay away. I have spent way too many years doing this stuff and it's still as interesting as it was when I got started in the 80's
I love getting paid for doing stuff I enjoy doing anyway.