Not a new idea

Part I

Composite Materials

Read and translate the text.

If translated these word-combinations thoroughly it will help you greatly to understand the text below.

an advanced society, binding power, a tension force, compressive strength, is boundtogether by cement, reinforced concrete, by sharing any stress among smth., is shaped with tools, resist wear and attack by chemicals, fine threads, fracture toughness, is exposed to high temperatures, are exposed to frictionand wear, to be exposed to extreme environments, long shelf life, are to meet specific requirements, resists both squeezing and tearing, immensely strong,add toughness to the material, exactly fit the requirements for, sandwich composites, sandwiched between, can be moulded into complex shapes, totally replace, to share the stress around.

Putting it Together – the Science and Technology of

In an advanced society like ours we all depend on composite materials in some aspects of our lives. Fiberglass developed in the late 1940s was the first modern composite and is still the most common. It makes up about 65 per cent of all the composites produced today and is used for boat hulls, surfboards, sporting goods, swimming pool linings, building panels and car bodies. You may well be using something made of fiberglass without knowing it.

What makes a material a composite?

Composite materials are formed by combining two or more materials that have quite different properties. 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 dissolve or blend into each other.

Composites exist in nature. A piece of wood is a composite with long fibres 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 (холст), but it is the binding power of the lignin that makes a piece of timber (лесоматериал) much stronger than a bundle(связка) of cotton fibres.

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 almost none when you crumple it up. But if you embed pieces of straw in a block of mud and let it dry hard, the resulting mud brick resists both squeezingand tearing and makes an excellent building material. Put more technically, it has both good compressive strength and good tensile strength.

Another well-known composite is concrete. Here aggregate (small stones or gravel) is bound together by cement. Concrete has good strength under compression, and it can be made stronger under tension by adding metal rods, wires, mesh(петля) or cables to the composite (so creating reinforced concrete).

So why use composites?

The greatest advantage of composite materials is strength and stiffness combined with lightness. By choosing an appropriate combination of reinforcement and matrix material, manufacturers can produce properties that exactly fit the requirements for a particular structure for a particular purpose.

Modern aviation, both military and civil, is a prime example. It would be much less efficient without composites. In fact, the demands made by that industry for materials that are both light and strong has been the main force driving the development of composites. It is common now to find wing and tail sections, propellers and rotor blades made from advanced composites, along with much of the internal structure and fittings. The airframes of some smaller aircraft are made entirely from composites as are the wings, body panels and tail of large commercial aircraft.

In thinking about planes, it is worth remembering that composites are less likely than metals (such as aluminium) to break up completely under stress. A small crack in a piece of metal can spread very rapidly with very serious consequences (especially in the case of aircraft). The fibres in a composite act to block the widening of any small crack and to share the stress around.

The right composites also stand up well to heat and corrosion. This makes them ideal for use in products that are exposed to extreme environments such as boats, chemical-handling equipment and spacecraft. In general composite materials are very durable.

Another advantage of composite materials is that they provide design flexibility. Composites can be moulded into complex shapes – a great asset when producing something like a surfboard or a boat hull.

The downside of composites is usually the cost. Although manufacturing processes are often more efficientwhen composites are used, the raw materials are expensive.

13. Look through the first part text again, find and write out the phrases describing a) natural composites; b) man-made composites; c) the specific features of composites.

14. Which of the following is not true? Correct the false statements.

1. Fibreglass is one of the latest composites.

2. Composite materials are formed by combining two materials that have the similar properties.

3. Composite materials can combine more than two materials.

4. Composite materials is absolutely new class of materials.

5. Modern aviation wouldn’t be much more efficient without composites.

6. The fibres in a composite can’t block the widening of a small crack but only share the stress around.

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