4.1 Properties of Materials

Physical Properties

Any property that is measurable that describes a state of materials and can be identified through non-destructive testing.

Mechanical Properties

Properties of a material that involve the relationship between stress and strain or a reaction to an applied force.

Smart Materials

Materials that have been designed to have one or more properties that can be modified when subject to an external stimuli in a way that the output can be controlled.

Shape Memory Alloys (SM)

Metals that when deformed, can spring back into its original shape once released.

Photochromicity (SM)

A smart property that changes colour in response to an increase in light.

Piezoelectricity (SM)

A smart property that gives off a small electrical discharge when deformed.

Electro-rheostatic (SM)

A smart property that relates to a fluid which can undergo a dramatic change in its viscosity when exposed to an electric field.

Magneto-rheostatic (SM)

A smart property that relates to a fluid which can undergo a dramatic change in its viscosity when exposed to a magnetic field.

Thermo-electricity (SM)

A smart property that when heated can produce an electric current.

Thermochromicity (SM)

A smart property that changes colour in response to an increase in heat.

Mass (P)

The amount of matter contained by a body in kg.

Elasticity (M)

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

Ductility (M)

The ability of a material to be drawn or extruded into a wire or other extended shape.

Hardness (P)

The resistance a material offers to penetration or scratching.

Brittleness (M)

A material that is unable to undergo plastic deformation, breaking into numerous shards.

Compressive Strength (M)

The ability of a material to withstand being pushed or squashed.

Density (M)

The mass per unit volume of a material (important for portability).

Plasticity (M)

The ability of a material to be changed in shape permanently.

Strain (M)

The response of a material due to stress, defined as the change in length divided by the original length.

Stress (M)

A force on a material divided by the cross-sectional area of that material.

Stiffness (M)

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

Tensile Strength (M)

The ability of a material to withstand pulling forces.

Toughness (M)

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

Volume (P)

The quantity of 3D space enclosed by a boundary.

Thermal Expansion (P)

A measure of the degree of increase in dimensions when an object is heated.

Weight (M)

Depends on mass and gravitational forces.

Thermal Conductivity (P)

A measure of the efficiency with which thermal energy will travel through a material.

Electrical Resistivity & Electrical Conductivity (P)

The measure of how easily free electrons move through a material, dependent on temperature.

Hardness Testing (P)

Scratch hardness test, static indentation hardness test, dynamic hardness test

Types of Forces

shear (two opposing forces), tension, compression, torsion (twisting), friction, electrical, gravitational

Young's Modulus Curve

Used to measure a material's stiffness through tensile test.

Limit of Proportionality

The boundary between elastic and plastic region.

Elastic Limit

Point beyond means that the sample is permanently destroyed.

Yield Stress

Point beyond means that there is significant increase in the ease of distortion.

Creep

The slow, permanent deformation of a solid material under the influence of a mechanical stress.

Aesthetic Properties

taste, smell, appearance, texture