This article is from the Formula One Motor Racing FAQ, by firstname.lastname@example.org (Mitchell McCann) with numerous contributions by others.
The tub, the part that the driver sits in, is made of a
composite material consisting of an aluminum honeycomb
sandwiched between two sheets of carbon. The result is an
extremely strong, lightweight material. Smaller sections, such
as the nose-cone and engine cover, use a nomex honeycomb instead
of aluminum to allow greater flexibility.