What makes a material a composite?
Combining two or more materials that have quite different properties forms composite materials. The different materials work together to give the composite unique properties, but within the composite you can easily tell the different materials apart – they do not dissolved or blended into each other. Composites exist in nature. A piece of wood is a composite, with long fibers of cellulose (a very complex form of starch) held together by a much weaker substance called lignin. Cellulose is also found in cotton and linen, but it is the binding power of the lignin that makes a piece of timber much stronger than a bundle of cotton fibers. Not a new idea Humans have been using composite materials for thousands of years. Take mud bricks for example. A cake of dried mud is easy to break by bending, which puts a tension force on one edge, but makes a good strong wall, where all the forces are compressive. A piece of straw, on the other hand, has a lot of strength when you try to stretch it but
