DP D&T Topic 4.1 - Properties of Materials with smart materials

Properties of Materials with smart materials

Physical properties

Characteristics that refer to the actual matter that forms the material. Can be measured using non-destructive testing.

Mechanical properties

Characteristics that determine how a material reacts to external forces.

Aesthetic characteristics

Characteristics related to beauty and pleasure derived from a material. It is related to our senses

Smart materials

Materials which change in response to changing conditions in their environment (a stimulus), for example temperature, light or electric charges.

Electro-rheostatic (ER)

Fluids that can undergo dramatic changes in their viscosity. They can change from a thick fluid to a solid in a fraction of a second when exposed to an electric field, and the effect is reversed when the field is removed.

Electro-rheostatic (ER) Applications

Used to create very small valves.

Magneto-rheostatic (MR) Applications

- Shock absorbers in cars
- Body armour can be flexible to allow for movement, but harden when an object hits it.

Magneto-rheostatic (MR)

Fluids that can undergo dramatic changes in their viscosity. They can change from a thick fluid to a solid in a fraction of a second when exposed to a magnetic field, and the effect is reversed when the field is removed.

Thermoelectricity

It involves the joining of two dissimilar conductors that, when heated, produce a direct current.

Thermoelectricity applications

- Space probes to power radio transmitters.
- Some electric and hybrid cars use it to recapture the heat energy to use to recharge the battery.

Photochromicity Applications

Sports glasses lenses

Photochromicity

Reacts to changes in light levels or ultraviolet (UV) radiation is applied.

Shape memory alloys (SMA)

Are metals that have a pseudo-elastic property that allows them body to return to its original shape after deforming. Their shape changes can be stimulated by either a change in temperature or the application of an electrical current. When the load is released, the body returns to its original shape.

Shape memory alloys (SMA) applications

- The frames of some eyeglasses use SMAs to create a flexible frame
- Medical devices to repair damaged blood vessels. to allow a thin device to be inserted into a vein. As the device heats up because of the body heat, it changes shape and keeps the blood vessel open.

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.

Piezoelectricity applications

Sensors are used to measure the force of impact in airbag sensors. When the force exceeds a pre-determined value, the sensor sends a signal to activate the airbag.

Mass

The amount of matter contained in a space. It is a constant regardless of where it is measured.
The unit measurement in kg.

Mass in a design context

Bicycle frames, for instance, must balance \----- with other factors such as stiffness in order to optimise ride performance.

Weight

Is technically a force and is measured in Newtons (N). It will change depending on the gravity.

Volume

The amount of 3-dimensional space a solid, gas, or liquid occupies.

Density

Is the mass per unit volume of a material

Electrical resistivity

Is a materials ability to conduct or resist electricity.

Electrical resistivity in a design context

Fiberglass, because it is a poor conductor of \------ , is often used for ladders intended to be used for electrical work. Metal ladders are considered too dangerous to use in this context.

Thermal conductivity in a design. context

Wood handled cooking utensils are poor conductor of \----- , and so are comfortable to use while cooking--metal handled cooking utensils conduct \----- quickly and can be a safety hazard.

Thermal conductivity

Measures how fast heat moves through a material.

Thermal expansion (expansivity)

Is the degree to which a material increases its dimensions when heated. Different materials may expand at different rates.

Thermal expansion in a design context

Pyrex glassware is made from borosilicate or soda-lime glass which have low \_____ rates. These objects can be used in ovens and on open flames for cooking.

Hardness

Is the resistance of a material to scratching or penetration.

Hardness in a design context

Ceramic tiles are very tough surfaces that are resistant to scratching, and as such are used in high-traffic public spaces like subway stations.

Tensile strength

The ability of a material to resist pulling forces

Tensile strength in a design context

Elevator cables, for instance, need to have a high \____ in order to function safely and reliably.
Cables in suspension bridges need to support the deck of the bridge.

Compressive strength

The ability of a material to resist pushing forces.

Compressive strength in a design context

In construction, concrete foundations are used to support the structure of the building.
Glass has a very high \----- and is used in modern buildings.

Stiffness

The ability to resist deflection (bending) by a force. the object can maintain its shape when a force is applied to it.

Stiffness in a design context

Airplane wings need to maintain their shape in order to efficiently provide lift and control.

Toughness

The ability to deform (change shape) but resist cracking and not fracture under impact. If a material breaks into numerous small pieces when impacted, it has a low degree of toughness.

Toughness in a design context

Car bumpers need to be able to absorb energy from an impact but not crack or break.

Ductility in a design context

Extruded aluminium has a high level of ductility, which allows it to be manufactured into the shapes below:

Ductility

The ability to be drawn or extruded into a wire-like form.

Elasticity in a design context

A pole-vaulting poles need to flex when a force is applied to it in order to propel the athlete over the bar.

Elasticity (Elastic region)

The ability to a material to bend and then return to its original shape.

Plasticity in a design context

Metal casting
Plastic blow moulding

Plasticity (Plastic region)

The ability of a material to be formed into a new shape. When the material is bent or deformed beyond its yield it does not return to its original shape.

Stress

Is the tensile force applied to a given area.

Strain

Is the percentage of change in length when a force is applied to the initial length

Young's modulus

Is a measure of the stiffness of an elastic material. It is the ratio of stress to strain of a material as force is applied along its length. Each material has its own unique modulus.

Yield Point

The point at which the material will no longer return to its original shape. It has now entered the plastic region.

Appearance

This refers to the colour or pattern of the material.

Smell

Has very powerful connections with memory. The \------ of a material is largely a concern for food, however product designers should consider it.

Sound

The \------ a material makes when it is touched or manipulated can also be part of the user experience.

Texture

Is how something feels or looks.

Form and Shape

The \------ of the material can influence how users interact and engage with it. We have different reactions to organic and geometric shapes.