Composite materials

Michael is choosing a new tent. This one has poles made from aluminium, and this one has poles made from fibreglass. Hmm… Michael knows that aluminium is a lightweight metal, but what is fibreglass? Fibreglass is a material made of extremely thin threads of glass — glass fibres, combined with a polymer. These two materials have very different physical and chemical properties.

Glass fibres are stiff and strong, yet very brittle, while polymers are usually weak, but flexible. When the glass fibres and the polymer are combined, the polymer binds the glass fibres together. It also adds flexibility and makes the material lightweight and easy to form into a desired shape. The glass fibres reinforce the polymer, making the material stiffer and stronger. The resulting new material — fibreglass — has desirable properties — such as strength, stiffness, elasticity, and low weight, while undesired properties, such as brittleness, are eliminated.

That is why fibreglass is commonly used to make not only tent poles, but even parts of cars, aeroplanes, and more! Fibreglass is an example of a composite material. Composite materials, or simply composites, are made of two or more different materials. At least one of these materials is in the form of thin fibres or fragments. These are embedded into another material — a matrix.

The matrix binds the fibres together, and the fibres act as reinforcement for the matrix. The materials do not dissolve in each other or combine chemically. They remain separate and retain their original properties. Apart from fibreglass, other common composite materials include concrete reinforced with steel, carbon-fibre-reinforced plastics, or plywood. Although some composites are quite technologically advanced, composite materials aren’t a modern invention.

Humans were creating them even in ancient times! Archeologists have found old bricks made of mud and clay reinforced with plant material, such as grass or straw. Thanks to the plant fibres embedded in the matrix of clay, these bricks could carry much larger loads. This made them stronger than other bricks made of just clay. Many composite materials are designed and manufactured by humans, but not all.

Your own skeleton is an example of a natural composite! Your bones are made up of long protein fibres — collagen, embedded in a matrix of hard crystals of calcium-containing minerals. The mineral crystals make your bones hard, stiff and brittle, while collagen adds elasticity and toughness. Together, they make your bones rigid enough to hold your body upright, and elastic enough not to snap too easily. Composites are combinations of two or more materials that are bound together.

Each of the materials retains its original properties. Combined, these properties mean the composite material performs a task better than its constituent materials would alone.