MATERIALSLeaving Cert Technology

Classification of materials

Materials used in the design and manufacture of products

Metals

Wood

Plastics

Composite

Ceramics

Fabrics

Introduction to metals

Metals for industrial use are generally be divided into three main

categories

1. Ferrous metals

2. Non-ferrous metals

3. Alloys

Introduction to metals

Ferrous metals – Ferrous metals contain iron, they usually contain

carbon as well. The amount of carbon is the main factor which

determines the properties of the steel. Ferrous metals are

magnetic.

Non-Ferrous metals – Non-ferrous metals contain little or no iron, do

not rust and are generally non-magnetic. Non-ferrous metals

include aluminium, copper, lead and tin.

Alloys – An alloy is obtained when two or more metals are

mixed. Pure metals often have substances often have

substances added to them to give them more useful properties,

to make them harder for example. Brass is an alloy of copper

and zinc, and solder is an alloy of lead and tin.

Metals

Name Properties Uses

AluminiumNon-ferrous, light, soft, ductile,

conducts heat & electricity, resistant to

corrosion, machines easily, difficult to

solder.

Foil wrapping, cooking

utensils, aircraft, window

frames, engine casting,

over-head cables.

Copper

Non-ferrous, malleable, ductile,

conducts heat & electricity, resistant to

corrosion, solders easily.

Electrical wiring, tubing,

rivets, soldering bits,

resistant to corrosion, hot

water cylinders.

Brass

Non-ferrous, an alloy of copper & zinc,

resistant to corrosion, casts well, good

conductor, can be work-hardened,

soldered easily.

Water fittings, screw,

brazing spelter, household

articles, electrical fittings,

ornamental work.

Metals

Name Properties Uses

Mild steel Ferrous, an alloy of iron &

carbon, high strength, ductile,

tough, low cost, rusts.

Bridges, girders, wires,

tubes, bolts, nuts, general

workshop use.

High carbon steel Ferrous, very hard but less

ductile, can be hardened and

tempered.

Springs and most tools,

drills, chisels, hammer

heads, files, punches.

TinNon-ferrous, strong & ductile,

resists corrosion, solders easily.

Protective coating on steel

plate, used with other

metals to form alloys.

Soft solder Non-ferrous, an alloy of lead &

tin, soft, low melting point, joins

easily to other metals

Joining of metals by soft

soldering.

Introduction to wood

Trees provide us with a broad range of woods, which vary widely in their

properties and appearance. When a tree is felled for conversion to

timber, it has to be seasoned to reduce its moisture content.

Although there are many thousands of different kinds of trees, they are

usually divided into three main groups. Deciduous, Conifers and

manufactured boards.

Types of trees

Deciduous trees (they shed there leaves in winter) –

The timber of deciduous trees is known as hardwood.

Hardwoods are usually stronger and more durable timbers.

Common hardwoods include; Oak, Ash, Walnut, Beech,

Mahogany and Teak.

Conifers – These have narrow needle-like leaves and are

usually evergreen. Examples of conifers include; Pine,

Spruce and Fir. The timber of conifers is known as softwood.

Softwoods are usually softer and less durable than

hardwoods, Common softwoods include; Scots-pine, Douglas

fir, Norway-spruce and Cedar.

Types of wood

Wood can be further categorised as;

• Hardwood

• Softwood

• Manufactured board

Hardwood SoftwoodManufactured

Board

Oak Pine Plywood

Ash Cedar Blockboard

Beech Fir MDF

Sycamore Spruce Melamine

Types of wood

Name Properties Uses

Red deal

Softwood, yellowish in

colour, easily worked,

straight grained and

finishes well.

Inside joinery, low cost

construction

White deal

Softwood, lighter in

colour, straight grained,

less durable than red

deal and relatively

cheap.

General joinery, low

cost construction

Mahogany

Hardwood has a rich red

colour, hard and strong

and takes a good finish

Furniture, high class

joinery, veneers for

chipboard and plywood

Types of wood

Names Properties Uses

Teak

Hardwood, golden brown

in colour, hard strong

and durable, takes a

good finish

External doors and

windows, furniture and

veneers

Balsa wood

Hardwood, very light,

easily cut and glued,

takes paint poorly

Light structures,

modelling, prototype

building

Manufactured boards

Manufactured boards have certain advantages over solid wood; they are

generally available in large sheets of various thicknesses and are not

prone to warping or twisting.

Manufactured boards

Plywood – this is made by gluing an odd

number of veneers together. The direction of

the grain of each layer runs at right angles to

the layers on each side of it. This prevents

shrinkage in any direction. Common plywoods

available are birch plywood and marine ply.

Chipboard – consists of ground-up chips of

wood compressed and glued together in flat

sheets. It is difficult to join and does not

take screws well. It is suitable for interior

use only.

Manufactured boards

MDF – (medium density fibreboard) is

manufactured from wood fibre and

synthetic resins, it machines well and

shapes easily

Veneers – a veneer is a very thin sheet of

wood which is cut or sliced from a log. The

vast majority of veneers are cut from

hardwoods.

Introduction to plastics

Plastics are a wide range of materials a with widely varying properties.

Some are soft and flexible, while others are hard and rigid. There use is

widespread, plastic products include; supermarket bags, toys,

toothbrushes, car parts and plastic bottles. Plastics are synthetic (man-

made) materials. They are made mostly from by-products of crude oil and

coals.

Introduction to plastics

Advantages of plastics

o They are easy to cut using ordinary workshop tools

o They have good chemical and weather resistance

o They can be supplied in sheet form, and in a wide

range of textures and colours

o Plastics do not conduct heat or electricity well

Disadvantages of plastics

o waste plastic products are difficult to dispose of

o Some plastics area fire risk

Types of plastics

Plastics can be further classified as;

•Thermoplastic

•Thermo-setting

•Elastomers

Thermoplastics Thermosets Elastomers

Acrylics Epoxy resins Rubbers

Nylons Phenolic Silicones

PVC Polyesters Polyurethanes

Polyethylene

Types of plastics

Thermoplastics – these plastics become soft when heated.

In there softened state they can be formed into

different shapes. These new shapes will be retained

when the plastic cools. Thermoplastics can be reheated

and reshaped again. The strip-wire heater and vacuum

former are generally used to shape thermoplastics.

Thermosetting plastics – thermosetting plastics undergo a

chemical reaction when setting which allows then to

withstand heat without softening. These plastics are

generally strong, inflexible and resistant to heat.

Thermoplastics

Name Properties Uses

Acrylic

(Perspex)

A commonly used plastic in school

workshops. In sheet form it can be

cut, drilled, machined, bonded and

formed into simple shapes when

heated.

Glass substitute, shop sign,

shop fittings, baths, lids for

electrical goods, photo

frames.

Polyethylene

(Polythene)

High density is a strong stiff plastic.

Low density is flexible.

High density is used for

making washing bowls and

buckets. Low density is used

for making plastic bags and

flexible containers such

washing up liquid bottles.

NylonNylon has a good resistance to wear,

low frictional properties, good

temperature resistance and it is a

strong, tough and rigid plastic.

It is used for gearwheels,

hinges, bearings, cams,

fishing lines and textile

fibre.

Thermoplastics

Names Properties Uses

Polystyrene (rigid)

Stiff hard material

Food containers, cosmetic

bottles. In thin sheets it is used

for vacuum forming items like

disposable cups.

Polystyrene

(expanded)This is an aerated version

which is very lightweight,

normally white in colour

It is common in use as an

insulating and packaging

material. Very useful for model

making. Also used in bicycle

helmets.

P.V.C.

PolyvinylchlorideThe rigid form is tough, hard

and stiff.

Can be welded or joined

with adhesives

Used for making sewerage and

water pipes, gutters, rain-

water downpipes. Flexible PVC

is a softer variety used for

hosepipes, shoes & inflatable

dingies.

Composites

A composite is a combination of two or more chemically distinct materials

whose physical characteristics are superior to its constituents acting

independently.

Because of their high strength/stiffness to weight ratio they are widely

used in the;

• Aerospace industry

• Offshore structures

• Boats

• Sporting goods

Composites

Examples of composites

include;

• Reinforced Plastics

• Ceramic-matrix

• Metal-Matrix

• Laminates

Glass reinforced plastic hull

Kevlar, taffeta polyester sails

Outer skin panels & fuselage A380

Ceramics

Ceramics are compounds of metallic and non-metallic elements, examples

include;

• Oxides (alumina – insulation and abrasives, zirconia – dies for metal

extrusion and abrasives)

• Carbides (tungsten-carbide tools)

• Nitrides (cubic boron nitride, 2nd in hardness to diamond)

Fabrics

Fabrics can be further classified as natural

and syntheticNatural Synthetic

Cotton Nylon

Canvas Polyester

Canvas deck chair Polyester marine rope

Smart materials

A smart material can be described as a material that has a useful response to external influences or stimuli.

•Shape memory polymers and alloys

Heat shrink tubing and packaging

Automatic actuators – open/close greenhouse window

Thermostats for heating control

•Smart Wire

Actuators, linear, angular and rotary

Anthromorphic actuation – human like robotic motion

Smart materials

• Smart Fluids

Motion control gel – CD tray opening/closing, camera lenses

Ferro fluids – earthquake dampers in buildings, hard disks

•Piezoelectric Materials

Sensors, musical cards, motors, actuators, clocks

•Chameleon Colours

Car paints, printing inks, packaging

Smart materials

Other more modern examples of smart

materials include;

•Polymorph

This is a unique polymer that

fuses in hot water and can then

be moulded to any form. When

solid it has similar properties to

nylon

Used to make the moulds

for the vacuum formed

seat and fuel tank of this

motorcycle project

Smart materials

Other more modern examples of smart

materials include;

•Thermocolour Sheet

This is a self adhesive

sheet whose colour

changes according to the

temperature. Used for

thermometers, heat

warning patches and

novelty advertising of

productsSheet changes colour according to temp

Smart materials

Other more modern examples of smart

materials include;

•Phosphorescent Sheet

This is a sheet that absorbs

light energy and re-emits it

as white light for up to

eight hours. Used

extensively for emergency

lighting in the event of a

power cut

Smart materials

Other more modern examples of smart

materials include;

•Magnetic Sheet

This is a flat polymer

magnetic sheet as used in

fridge magnets. Also available

in thin A4 sheets that can be

printed on

Smart materials

Other more modern examples of smart

materials include;

•Lenticular Sheet

This sheet is about 1mm

thick but gives the illusion

that it is nearer to 6mm

thick. An object placed on

the sheet appears to sink

below the surface