Read the text and answer the questions.

Metals and non-metals

Engineering materials can be divided into:

• metals- examples of metallic materials are iron (Fe) and copper (Cu)

• non-metals- examples of non-metallic materials are carbon (C) and silicon (Si).

As iron is such a widely used material, metals can be divided into:

• ferrous metals- those that contain iron

• non-ferrous metals- those that do not contain iron.

- Elements, compounds and mixtures

With regard to the chemical composition of materials -the chemicals they contain, and how those chemicals are combined- three main categories can be used:

• Elements are pure materials in their most basic form. They cannot be broken down into different constituents ('ingredients'). Examples of elements widely used in engineering materials are iron, carbon and aluminium (AI).

• Compounds consist of two or more elements that are chemically bound - that is,

combined by a chemical reaction. An everyday example is water, which is a compound of hydrogen (H) and oxygen (0).

• Mixtures consist of two or more elements or compounds which are mixed together, but which are not chemically bound. In engineering, common examples are alloys -that is, metals which have other metals and/or non-metals mixed with them. A common example is steel, which is an iron-carbon alloy, and can include other alloying metals- metals which are added to alloys, in small quantities relative to the main metal. Examples of widely used alloying metals are chromium (Cr), manganese (Mn) and tungsten (W).

· BrE: aluminium ; ArnE: aluminum

Materials under the microscope: composites

Professional English in Use Engineering

When you think of examples of hi-tech materials, composite materials come to mind- such as carbon-fibre, used in aerospace and Formula 1 cars. But although we think of composites as hi-tech and highly expensive, that's not always true. The earliest examples of composite materials were bricks made from mud and straw. Or, to use the correct composite terms, from straw reinforcement- the structural

network that reinforces the material inside, and a mud matrix- the material surrounding the reinforcement. These terms explain what a composite material is: a matrix with a reinforcing material inside it. A modern, everyday example is fibreglass- correctly called glassreinforced plastic (GRP) -which has a plastic matrix reinforced with glass fibres.

Exercises

1.Complete the sentences using the words in the box.

1 Carbon (C) is a ................................ .

2 Copper (Cu) is a ................................ metal.

3 Aluminium (AI) is a common ................................ .

4 Steel (Fe + C) is a widely used ................................ metal.

5 Although it is used in steel, carbon is ................................ .

6 Aluminium is relatively lightweight for a ................................ material.

2.Decide whether the sentences below are true or false, and correct the false sentences.

1 The elements that make up a compound are chemically bound.

2 Alloys are chemical compounds that are frequently used in engineering.

3 Alloys can contain both metallic and non-metallic constituents.

4 In an alloy, an alloying metal is the biggest constituent, by percentage.

5 Steel is a metallic element.

3. Complete the extract about concrete and steel, using suitable forms of the word reinforce from C. Sometimes there is more than one possible answer.

(1) ................................ concrete is one of the most widely used construction materials, and one we

take for granted. However, using steel bars to (2) ................................ concrete structures located

outdoors is only possible thanks to a fortunate coincidence: concrete and steel have practically the

same coefficient of thermal expansion - in other words, as atmospheric temperature varies, the

concrete and the steel (3) ................................ expand and contract at the same rate, allowing uniform

movement. Using a (4) ................................ material with a different coefficient of expansion would not

be feasible. For example, (5) aluminium-................................ concrete would quickly disintegrate.

4Read the text below and find two elements, two compounds, an alloy and a composite.

Generally, the steel used in reinforced concrete will have previously been exposed to water and to the oxygen in the air. As a result, it will usually be partly corroded, being covered with a layer of iron oxide (rust). However, once the steel is inside the hardened concrete, it will be protected from air and water, which prevents further rusting. Additionally, the cement in concrete does not react aggressively with the iron in steel.

Fibreglass

Read the text and do exercises after the text

When you think of examples of hi-tech materials, composite materials come to mind- such as carbon-fibre, used in aerospace and Formula 1 cars. But although we think of composites as hi-tech and highly expensive, that's not always true. The earliest examples of composite materials were bricks made from mud and straw. Or, to use the correct composite terms, from straw reinforcement- the structural networkthat reinforces the material inside, and a mud matrix- the material surrounding the reinforcement. These terms explain what a composite material is: a matrix with a reinforcing material inside it. A modern, everyday example is fibreglass- correctly called glassreinforced plastic (GRP) -which has a plastic matrix reinforced with glass fibres.

Fibreglass (also called fibreglass and glass fibre) is material made from extremely fine fibers of glass. It is used asa reinforcing agent for many polymer products; the resulting composite material, properly known as fibre-reinforced polymer (FRP) or glass-reinforced plastic (GRP), is called "fibreglass" in popular usage.

Glassmakers throughout history have experimented with glass fibers, but mass manufacture of fibreglass was only made possible with the advent of finer machine-tooling. In 1893, Edward Drummond Libbey exhibited a dress at the World's Columbian Exposition incorporating glass fibers with the diameter and texture of silk fibers. What is commonly known as "fibreglass" today, however, was invented in 1938 by Russell Games Slayter of Owens-Corning as a material to be used as insulation. It is marketed under the trade name Fiberglas, which has become a genericized trademark.

Glass fibers are useful because of their high ratio of surface area to weight. However, the increased surface area makes them much more susceptible to chemical attack.

By trapping air within them, blocks of glass fibre make good thermal insulation, with a thermal conductivityof 0.05 W/m-K.

Contemporary surfers use lightweight fibreglass boards to catch waves of varying shapes and sizes as they roll in towards the beach. One of the main attractions of the sport is its simplicity – all a surfer really needs is a surfboard, a wetsuit and a way of getting to the beach.

Find the meaning of the highlighted words

Fill in the gaps

1. When you think of examples of hi-tech materials, …………come to mind- such as carbon-fibre, used in aerospace and Formula 1 cars.

2. The earliest examples of composite materials were bricks made from………..

3. Or, to use the correct composite terms, from straw reinforcement- ………that reinforces the material inside, and a mud ………. - the material surrounding the reinforcement.

4.………. (also called fibreglass and glass fibre) is material made from extremely fine fibers of glass.

5. It is marketed under the trade name Fiberglas, which has become a …………...

6. However, the increased surface area makes them much more …………. to chemical attack.

7. By trapping air within them, blocks of glass fibre make good ………….., with a thermal ………………of 0.05 W/m-K.