affordable 100 mpg carbon composite car (OT?)

[JamesWyatt]

Hmm, not even sure it was carbon fiber... it's been a while and my memory is rusty. I do remember it was a composite of some sort. My guess would be that the race car designers will sacrifice durability over weight to the extreme. I remember having a carbon fiber tennis racket in the late 1980s that was very tough. It would scratch but never shatter. And trust me, my tennis playing was bad enough that I slammed that thing down on the concrete in frustration quite often! My friends with metal rackets always bent theirs.

[RonH]

There was a spectacular crash in the tour de france the other day in which a rider smacked straight into a median road sign. All you saw from behind was him catapulting above the crowd and then the two halves of his carbon fiber bike following him. The sign was tipped back about 10 degrees! May not be relevant to a car body, but it was a dramatic example of what happens when you exceed the yield strength of carbon fiber.

[Rybold]

Originally Posted by effwitt

It's great to see that carbon fiber can be made more durable. Earlier this year the Red Bull Formula 1 cars had a couple of minor "offs" hitting a few bumps on the grass and the cars literally broke into hundreds of pieces. A few years ago the FIA and Ferrari did some work using Kevlar with the carbon fiber to reduce the number of shards produced from even small accidents, but I don't recall anything coming from it. Granted, a Formula 1 car and a passenger car do have a few small differences with its design goals, but I was worried about the tendency of carbon fiber to shatter when hit.

The street legal Porsche Carrera GT uses a carbon fiber chassis, as do the street legal Ferrari F50 and Ferrari Enzo cars. If the NHTSA approved these cars public roads, then I'm sure Toyota could design something similar if they really wanted to. I'm guessing it's probably more expensive than metal frames though.

[Wiyosaya]

My guess is that they were not using the type of sandwich technology that I am talking about. One method of construction is simply to layer carbon fiber, and I am willing to bet that the shattered formula 1 race cars were using this type of construction. Some might call that sandwich technology, however, what I am speaking of is using say 8 layers of carbon fiber on either side of a light-weight core material such as aluminum honeycomb, or balsa wood. It is common to see this type of construction in things like snowboards. Believe it or not, this gives the overall structure more of an ability to resist bending and shear. Though I cannot say for sure, the formula 1 car sounds like it broke apart at least partly because it had little shear resistance. They may also have been using one of the stiffer carbon fibers, and it sounds like their design goal may just have been to have an aerodynamic skin.

Also, I think it is common practice to use a carbon body on formula 1 cars with all the parts attached to the body; the cars are designed to break apart in crashes. This allows more energy to dissipate in the parts falling off the car and, believe it or not, is a safety measure. If they did not make the parts so that they broke off the car, they might penetrate the body of the vehicle and, perhaps, seriously injure or kill the driver.

[alanh]

I'm dubious of such an increase in mileage just from reducing the weight. Lightweight cars like the Geo Metro or Smart Fortwo don't get anywhere near 100mpg. Drive train losses, braking, and wind resistance are big factors too.