OVERVIEW

Composites are materials made of a combination of two or more substances on a microscopic scale. A good example of a composite material comes from the aerospace industry. Bearings for jet engines have to be strong and tough at temperatures greater than 1000 C. At these temperatures most metals weaken or melt. Ceramics maintain strength at high temperatures but are brittle. However, a composite material can combine the strength of ceramics at high temperatures with the fracture resistance of metals. The properties of a composite are determined both by the properties of the individual components and by the way that they are combined, i.e. the microstructure. A bearing made from a single piece of metal joined to a single piece of ceramic would suffer from the shortcomings of both and have the strengths of neither. However, when the materials are mixed at a microscopic scale the desired properties are obtained.

Ice cream is also a composite material. The main ingredients provide the required sensory properties: ice gives cooling, fat provides creaminess, air gives lightness and softness, sugar provides sweetness, and flavours enhance its taste. However, if you simply put ice cubes, whipped cream, sugar and vanilla essence in a bowl and stir you end up with a mess that bears no resemblance to ice cream. Even though you have used the correct ingredients, you do not produce the combination of cooling, creaminess, softness, sweetness and flavour in a single substance. This is because you have not created a...