Resistant Materials

Our ability to shape and use materials is one of the things that sets human beings apart from other animals. To begin with human beings used those natural materials which were readily available. They used wood, stone clay, animal skins and bones to make weapons, tools and clothes.

Gradually over thousands of years, humans learnt how to make new materials like iron, bronze and glass.

Each new material offered possibilities for change. This process is still going on today. Although we still use materials such as iron, glass, wood and ceramics, we now have many more materials to choose from. Each new discovery opens up opportunities which had previously been impossible.

The materials which have probably had the most impact on the 20th century are concrete and plastics, but many new metal alloys and ceramic based materials are becoming increasingly important. These materials are known as manufactured materials because they do not exist naturally.

If you are to be successful at designing and making you will need to know what materials are available to us and how they behave when worked.

These pages will help you to recognize and get to know some of main materials used in Design and Technology. You will also learn about their working properties. These should help you to decide which is the best material to use for a particular purpose.

It is easy to forget that all materials come from somewhere. Some materials are renewable they come from living things and if we are careful they should last forever.

Some are non-renewable they are obtained by digging them out of the ground. These materials will not last forever and we need to use them wisely.

This is one way of classifying materials they can be divided into two categories: organic which means 'from living things' and inorganic meaning 'not from living things'. Most organic materials are also biodegradable. This means that if they are left to decay they eventually become part of the earth from which they were grown. Many materials are non-biodegradable and will not decay. This can present problems but it is possible to recycle some of them

Remember - many of the materials we use in D&T are becoming scarce, try to avoid waste and use them sensibly !

SELECTING A MATERIAL

You will need to think carefully about the materials to use in your project work. The final choice will depend on a number of factors. The main ones are :

What is available ?

How much will it cost ?

What sizes are available in stock ?

How easy is it to work ?

What does it look like ?

What will it be used for ?

How long will it last ?

Is it the best material for the job ?

Most of the answers to these questions can be found by learning about the properties and characteristics of materials.

WOOD

Wood is produced naturally as trees grow. Wood is the only important material that we can grow more of. It is a renewable material, so we need never run out.

Unfortunately Trees are being used up faster than they are being replaced. We need to avoid waste so that we can conserve some for the future.

METALS and ALLOYS

Metals are very important materials. Whole chapters of human history (Bronze and Iron ages for instance) have been named after the metals used at the time.

We depend on them for many things in our lives. You will have seen many metals, or products made from metal at home, so you will almost certainly know what they look and feel like.

All metals are made from ores. These ores are found in rocks and have to be extracted before they can be converted into metal. Although nearly one quarter of the earths crust is made of metal, some sources of ore will run out in the not-to-distant future.

Re-cycling is very important, if we are to make these precious resources last.

PLASTICS

Compared with wood and metal, plastics are relatively modern materials.

It is only in the last forty years or so that they have developed to replace wood and metal in a wide variety of products.

There are many different kinds of plastic and they are used for many different jobs. Plastics can be made to behave in a variety of ways. They can be brittle or flexible, hard or soft, transparent or coloured etc.

Most plastics are made from oil, which like other non-renewable resources is becoming increasingly expensive as it begins to run out. We often throw out plastic containers because they are much more difficult to re-cycle.

Smart Materials

The term 'Smart Materials' is used to identify a range of materials that change their properties or characteristics in response to changes in environmental conditions.

Smart materials can respond to environmental change in three ways:

	By changing their working or aesthetic properties.
	By changing their shape or composition.
	By changing the way they work or behave.

Many kinds of smart materials are currently being developed. Only a few are commercially available and they tend to be more expensive than traditional materials.

Some smart materials you might encounter in school are:

	Thermochromic Inks
	Shape Memory Alloy (SMA)
	Polymorph (Polycapralactone)
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"The Right Tools for the Job"

There are three main reasons why we work with materials in design and technology. They are:

To change the shape or size of the material

To change the properties of the material

To change the appearance of the material

There are 3 main ways of changing the shape of materials:

Cutting and trimming

Forming

Fabrication

Cutting and trimming involves removing waste. Sawing, filing, drilling and turning are all examples which involve cutting or trimming bits from the original material to change its shape.

Forming involves changing the shape of a piece of material by bending, pressing or moulding it into a different shape. Vacuum forming, injection moulding, casting and bending are all examples of forming processes.

Fabrication involves changing the shape of a piece of material by joining or adding pieces onto it. This can be done in a variety of ways. Welding, gluing, nailing and riveting are all examples of fabrication processes.

When we are working with materials in any of these ways we need to use the correct tools and do things in the right order. These pages should help you decide how to choose the right piece of equipment for a particular task.