Types of materials

You need to be familiar with the different properties of ferrous and non-ferrous metals; softwood and hardwood timbers; and thermoplastics and thermoset plastics.

When working with resistant materials you need to be able to choose the best material for a job. Wood, metal and plastics are the most common materials used, followed by composites [composites: a complex material made of two or more distinct substances ] and ceramics.

The main classification of materials is given in the chart below. You need to know these terms and their definitions.

Material classification diagram

Plastics

Plasics are divided into thermoset plastics and thermoplastics. The main difference between the two is that thermoplastics can be heated and shaped many times, while thermoset plastics can only be heated and shaped once.

Composite materials

Composite materials are formed by combining and bonding two or more materials - a reinforcing material and a bonding agent such as glue. MDF [MDF: Medium-density fibreboard - a type of engineered wood made of compressed wood and fibre particles held together with glue ] and GRP [GRP: Glass-reinforced plastic - a strong and versatile material made by combining a plastic (usually polyester resin) with fibres made of glass ] are examples of composite materials. NB alloys [alloys: mixtures of two or more metals, or of a metal with a non-metal such as carbon. ] are not composite materials.

Metals

Metals can be either ferrous or non-ferrous. Ferrous metals contain iron while non-ferrous metals do not.

Both ferrous and non-ferrous metals are divided into pure metals and alloys. A pure metal is an element - eg iron, copper, gold - unalloyed (not mixed) with another substance. An alloy is a mixture of two or more elements (eg, iron and carbon) to make another metal with particular properties (eg steel).

Ceramics

Ceramics are made from clay, sand and feldspar [feldspar: a very common group of hard, crystalline minerals containing silicon ]. These materials are ground to a fine powder, mixed together and fired at high temperatures (700 - 2000°C) in the production process.

Timbers

Timbers are divided into hardwood timbers and softwood timbers. Hardwood timbers get their name because of their cellular structure when seen under a microscope - not because they are hard to cut.Softwoods do not have this same hard cellular structure.