FalloutJack said:
Your analogy has nothing to do with the physics of cars and crashes. Please give me something better to work with. They don't buy fiberglass cars for safety. They buy it for speed because it's lighter, which also means it's probably hitting solid objects twice as fast as everyone else. And frankly? You hit ANYTHING fast enough, it will still injure or even kill. Tell me about anyone who falls flat into water. It's water, totally fluid, but BAM that can hurt too.
Uhh... you realize that water is
incompressible right? It gives no fuck what hits it, it doesn't give or compress in the slightest, very much unlike foam. If you're lucky, the shape you hit it in is aquadynamic enough to let it flow around you without imparting undue force, but that's pretty rate. Water is one of the worst things to hit at speed, in terms of cushioning the impact and reducing the damage done. It's much closer to steel than foam, for the purposes of this comparison. That's pretty much the worst example you could have provided to make your point.
And you're right, they don't buy fiberglass cars for safety, or at least not only. It's both cheaper and lighter, meaning higher top speeds, better gas mileage, and either lower prices or higher profit margins. That doesn't change the fact that a crumple zone in a car is, effectively, a cushion. It behaves on the exact same principles as a piece of foam does when hit. It allows the force of the impact to deform the material, robbing it of some portion of its energy or force (how much depends on the material) before it continues on to whatever's behind it.
It's exactly like the analogy I gave above. Two objects collide, and when one or both of the objects have sufficient amounts of cushion (read: can deform to absorb impacts), the collision is much less jarring and severe to either.
Now, you're right in that having crumple zones and the like means that most cars aren't going to survive after a strong impact. The frame will, by its nature, have been deformed and while you can beat it back into shape, it will be expensive and never end up as good as it was originally. That doesn't mean it's any less safe, just more expensive if you frequently wreck cars.