4.1 Properties of Materials

Contains info on: Smart Materials, Mechanical Properties, Physical Properties.

Smart Materials

• Smart materials have one or more property that is dramatically altered by an external stimulus

• Properties such as colour, shape, viscosity, volume and conductivity are affected by a given stimulus

Piezoelectricity

• The ability to release an electric charge when deformed. When an electric current is passed through a piezoelectric material its volume will increase or it will vibrate.

Shape memory alloys (SMA)

SMA are alloys that when deformed can spring back to its original state once released.

Can be programmed to have a initial shape

SMA can be effected by temperature or electric

SMA is made out of Nitinol (Nickel and titanium)

Photochomacity

The ability to change color under light

Is made from silver and copper chloride to help in the UV changing process

Magneto-Rheostatic

The change in viscosity of a fluid when a magnetic force is applied. The change is rapid from a thick liquid to a solid.

Electro-Rheostatic

The change in viscosity of a fluid when an electric charge is applied. The change is rapid from a thick liquid to a solid.

Thermoelectricity

Refers to smart materials that when heated can generate electricity. The thermoelectric material requires two dissimilar conductors.

The process can also work the other way around (Seebeck effect). The charge is dependent on the materials of the conductor.

Tensile strength

The ability of the material to withstand pulling forces.

The tensile strength of the material is also known as the ultimate tensile strength

Compressive strength

The ability of the material to withstand pushing forces.

Stiffness

The resistance of an elastic body to deflection by an applied force.

Toughness

The ability of the material to resist the propagation of cracks.

Toughness varies with temperature. Some materials go from tough to brittle under cold temperature (steel)

Ductility

The ability of a material to be pulled and extruded into wires and extended shapes.

Elasticity

The extent of which a material can return to its original shape after being deformed.

The physical feature is used when making a product that can return to its original shape after a force is applied.

Plasticity

The ability of a material to to be changed in shape permanently (plastic deformation)

After the material is bent beyonds it s yield it wont bounce back to its original shape

Mass

The amount of matter contained in a space. Mass is a constant and is measured in kg

Weight

Weight is technically a force and is measured in Newtons

Volume

Is the amount of 3-dimensional space in an object

Density

Is the relationship between mass and volume

Electrical resistivity

The degree of how a material can conduct or resist electricity

Thermal conductivity

The degree of which heat moves in a material

Thermal expansion

The degree of which a material expands or contract under temperature

Hardness

The ability of a product to resist scratches or penetration.

Scratch testing

How well a material will resist scratching against a material with confirmed hardness

Hardness Testing - Rockwell

Rockwell tests use either a steel ball or a diamond indenter ground to form a cone