This section explores the properties and characteristics of various materials commonly used in design and technology, and their suitability for different applications.
Material Properties and Characteristics
Mechanical Properties
Mechanical properties describe how a material behaves under stress. Key mechanical properties include:
Strength: The ability of a material to withstand an applied force without breaking or deforming permanently. There are different types of strength:
Tensile Strength: Resistance to being pulled apart.
Bending Strength: Resistance to bending or breaking under load.
Shear Strength: Resistance to forces acting parallel to the surface.
Stiffness (Modulus of Elasticity): The ability of a material to resist elastic deformation. A stiffer material will deform less under the same load.
Hardness: Resistance to indentation or scratching.
Elasticity: The ability of a material to return to its original shape after a deforming force is removed.
Ductility: The ability of a material to be drawn into a wire.
Malleability: The ability of a material to be hammered or rolled into thin sheets.
Brittleness: The tendency of a material to fracture with little or no plastic deformation.
Thermal Properties
Thermal properties describe how a material behaves with changes in temperature. Important thermal properties are:
Thermal Conductivity: The ability of a material to conduct heat. High thermal conductivity means heat is transferred quickly.
Specific Heat Capacity: The amount of heat energy required to raise the temperature of a unit mass of a material by one degree.
Thermal Expansion: The tendency of a material to change in volume with temperature changes.
Electrical Properties
Electrical properties describe how a material conducts or resists the flow of electricity.
Electrical Conductivity: The ability of a material to conduct electricity. Metals are generally good conductors.
Electrical Resistance: The opposition to the flow of electric current.
Insulation: Materials that resist the flow of electricity.
Other Properties
Other important properties include:
Corrosion Resistance: The ability of a material to resist degradation due to chemical reactions with its environment.
Density: Mass per unit volume.
Appearance: Colour, texture, and finish.
Suitability of Materials for Use
The choice of material for a particular application depends on the required properties and characteristics. A table summarizing the suitability of common materials is provided below.
Material
Strength
Stiffness
Hardness
Corrosion Resistance
Thermal Conductivity
Typical Uses
Steel
High
High
High
Good (with coatings)
Moderate
Structural components, tools, machinery
Aluminium
Moderate
Moderate
Moderate
Excellent
High
Lightweight structures, transport, packaging
Wood
Low to Moderate
Low
Low
Poor (unless treated)
Low
Furniture, construction, carving
Plastic (e.g., Acrylic)
Low
Low
Low
Good
Low
Lamps, displays, glazing
Glass
Low
High
Moderate
Excellent
Low
Windows, containers, optical fibres
Copper
Moderate
High
Low
Good
Very High
Electrical wiring, plumbing, cookware
Note: This table provides general guidance. Specific grades and treatments of materials can significantly alter their properties and suitability.
Material Examples
Metals
Metals are generally strong, stiff, and ductile. Examples include steel, aluminium, copper, and iron.
Plastics
Plastics are lightweight, corrosion-resistant, and can be molded into complex shapes. Examples include acrylic, nylon, and polyethylene.
Wood
Wood is a natural material that is strong in tension and compression, but weak in shear. It is also relatively lightweight and easy to work with. Examples include hardwoods (oak, maple) and softwoods (pine, fir).
Ceramics
Ceramics are hard, brittle, and resistant to heat and corrosion. Examples include glass, porcelain, and bricks.
Composites
Composites are made from two or more materials combined to produce a material with improved properties. Examples include fibre-reinforced plastics (e.g., carbon fibre, glass fibre).
Suggested diagram: A visual representation of different materials (metal, plastic, wood, ceramic, composite) with labels indicating their key properties.
Material Selection Considerations
When selecting a material for a design and technology project, consider the following:
Functionality: What does the material need to do?
Strength and Durability: How strong and long-lasting does it need to be?
Weight: Is weight a critical factor?
Cost: What is the budget?
Workability: How easy is it to shape and finish the material?
Aesthetics: What does the material look like?
Environmental Impact: Consider the environmental impact of the material's production and disposal.