Do they make cars out of aluminum ? A lot of bumpers are plastic now.
A lot of bumpers are plastic now - and they're designed as "break-away" parts. I.e. in an impact, regardless of how small, they're designed to crack apart and fall off. Compare that to the metal bumpers of 20 years ago which only get dented up in an impact.
From wikipedia:
"While bumpers were originally constructed of heavy steel and held clear from the bodywork, they have evolved into light-weight structures of thermo-plastic or painted light metal —
leaving them susceptible to damage from even light contact."
But bumpers are not made of polycarbonate, and therefore it's an invalid comparison.
Actually, I think more cars have plastic parts than aluminum, especially those that take wear and tear, like bumper covers, trim, etc. The last aluminum car I remember seeing was a 1982 DeLorean!
Yes, far more plastic than aluminum is used in cars - because it is cheaper to manufacture, not because it's a superior material. And all this plastic parts are designed to be disposable and replaceable. See my comment above about disposable bumpers.
No, the DeLorean was not aluminum, nor was any of its body panels. It was
stainless steel. The AC Cobra had some aluminum body panels, as do a variety of other sports cars from Porsche, Jaguar, and others. The Audi A8 is the only car made entirely from an
Aluminum frame/chassis.
That's not to say that polycarbonate is bad - it's quite good in fact. It's used as one of the layers in making "bullet-proof" glass. It's also used for the cockpit canopy of the
F-22 Raptor fighter jet. The big downside to polycarbonate as a computer casing is not in it's strength (it's plenty strong, how many cracked Macbooks have you seen?) - the downside is that it's very susceptible to scratching.
Also noteworthy in this comparison is that Aluminum is a great heatsink material and will help keep the laptop cooler whereas polycarbonate is an insulator and therefore traps heat inside. This is why the Powerbook/MBP can be used in "clamshell" mode with the lid closed whereas the iBook/Macbook cannot.