MATERIAL PROPERTIES
Choosing Materials
When a product is being designed, one problem is
choosing the most suitable materials for the job.
A material should not be chosen just because it
looks nice. Using royal blue candle wax for
making a door handle is not a good choice! Doors
handle needs to be able to resist the heat from a
hand and also the twisting and pulling forces
required to operate it. It is therefore important
to understand the various properties of
materials, so that you can make a sensible choice
of which materials to use when you are designing
a product.
PHYSICAL PROPERTIES
Physical properties are the basic properties of
each material.
Density is the
amount of matter
(mass) in a material.
A cube made from a
high density
material will be
heavier than the
same size cube made
from a low density
material.
Fusibility
is a measure of how easy it is to melt the
material. The temperature at which the material
normally melts is known as the melting point.
Note: A highly fusible material has a low melting
point.
Thermal Conductivity is a measure of how fast
heat can travel
through a
material. A
material is known
as an insulating
material if heat
travels through it
very slowly.
Electrical Conductivity is a measure of how fast
electricity travels
through a material.
Generally a good
conductor of heat is
also a good
conductor of
electricity. A poor
conductor is an
Insulator.
Thermal Expansion is the amount of expansion
that occurs when the material is heated. A high
expansion material
will become
noticeably larger
when heated.
Optical Properties
Most materials do
not let any light pass
through them; these
are known as Opaque materials. Others like glass
can let light pass easily through them, these are
known as transparent (see-through) materials.
There are also materials like some plastics or
frosted glass that let
some light through,
but detail of what is
on the other side of
the material cannot
be seen, these are
known as Translucent
materials.
MECHANICAL
PROPERTIES
Mechanical properties are connected with how a
material reacts to forces applied to it.
A force will deform a material. If the
deformation is temporary and the material
returns to its original state then it is said to be
elastic, if it is permanent and the material stays
in its new state, it is said to be plastic.
Strength
A measure of how well a material can withstand
force without permanently bending or breaking.
There are different types of strength
measurements.
Tensile strength - resists being
crushed e.g. cast-iron
Compressive strength - resists being
crushed e.g. cast iron
Shear strength - resists sliding forces
such as those made by scissors e.g.
stainless steel
Torsion strength - resists twisting e.g.
tool steel
Bending strength - resists bending - is rigid
e.g. woods
Malleability
A measure of how easily a material can be
permanently deformed by compressive forces
e.g. hammering, without cracking.
MELTING
POINT
MATERIAL
High Tungsten
Chromium
Medium Copper
Steel
Low Zinc
Lead
THERMAL
CONDUCTIVITY
MATERIAL
High Copper
Aluminium
Medium Mild steel
Tin
Low Woods
Polystyrene
MELTING
POINT
MATERIAL
High Gold
Copper
Medium Steel
Zinc
Low Woods
Nylon
THERMAL
EXPANSION
MATERIAL
High Polythene
Nylon
Medium Aluminimum
Tin
Low Woods
Titanium
THERMAL
EXPANSION
MATERIAL
High Copper
Aluminimum
Medium Mild steel
Bronze
Low
Woods
Thermoset
plastics
W
orksheet 5a © Cable Educational Ltd
