Today, quite often found on modern cars body, made of aluminum.
This “winged” metal is not subject to corrosion, but its strength is no worse than the strength of a metal. But it weighs almost two times less than its steel counterpart. But with such visible advantages, there are pitfalls. With all its excellent qualities, the aluminum body has a big drawback - it is a high conductivity of noise and vibration. Therefore, manufacturers have to reinforce such a body with noise insulation, which ultimately leads to a rise in price of the machine, especially since aluminum costs more than metal.
Of course, all this affects the repair of such a body. After all, non-ferrous metal is not black, special equipment will be needed here. Aluminum made the entire body, can not afford all the manufacturers, one of them is Audi. Of course, most often you have to combine steel and aluminum in the same body. For example, the BMW 5 Series, the entire front part of the body is made of aluminum and further welded to the steel frame.
Not so long ago in the automotive industry, plastic was considered a promising body material. Of course, it is lighter than aluminum, it can be brought to absolutely any shape, cheap painting (it can be done even at the production stage, by adding various chemical additives). And of course such a body will never know what corrosion is. On the shortcomings, we can also talk for quite some time.See also: Distinction between forged and light alloy wheels
But the most important thing is that in the cold plastic becomes brittle, and under the influence of high temperatures, it simply stretches. For these reasons, it is not possible to manufacture plastic parts from plastic that will be charged with high loads. Some parts of such a body can not be repaired and require its complete replacement. Having counted the pros and cons, the engineers decided to leave the plastic body alone, and continue to carry out plastic parts only attachments (bumper, awnings, wings).