Copyright © 2007 Dorling Kindersley A composite is a combination
of two or more different materials. The new material combines
the best properties, such as strength and lightness, of each of
the individual materials. There are examples of composites all
around us. Boats, bikes, tennis rackets, even dental fillings
are all made of composites. Most composites are synthetic
materials, but they also occur in nature. Bone is a composite of
hydroxyapatite and a protein called collagen. The hydroxyapatite
is a brittle but hard and rigid material that gives bone its
structural strength. The collagen is soft and spongy, giving
bone its flexibility. Bone is 80–90 per cent hydroxyapatite and
10–20 per cent collagen protein. The Smart car is a modern two-
seater car that is very light, so it uses less fuel than heavier
cars. It has also been designed to take up less room in city
centres. Over 40 per cent of a Smart car is made from composite
materials. It has been put together in panels, so each composite
panel can be eas