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Properties of Materials

• Materials selection for manufacturing products relies primarily on their properties.
• Scientific discovery and new technologies have introduced more materials for product design, allowing for smart new products and enhanced classic designs.
• Choosing the right material is complex, considering physical, aesthetic, and mechanical properties.
• Environmental, moral, and ethical issues surrounding material choices for any product or service need to be considered.
• Smart materials are likely developed in specific regions or countries, but their benefits may be limited globally in the short term.
• Materials are often developed by material engineers to possess specific properties, facilitating designers in creating innovative products to solve existing problems.
• The explosion of plastic materials post-World War II enabled products to be made without using valuable metals.

Physical Properties

Mass

• The amount of matter in an object, with the SI unit being kilogram.

Weight

• The force of gravity on an object, calculated as mass times the acceleration of gravity, measured in Newtons (N).

Volume

• The amount of 3-dimensional space an object occupies.

Density

• The mass per unit volume of a material, calculated as density = mass / volume, measured in kg/m³.
• Density is an important factor for product weight and size.
• Food packaging is an important example of how density related to product weight and size is important.
• Pre-packaged food is sold by weight or volume, and a particular consistency is required.

Electrical Resistivity

• A material's ability to conduct electricity.
• Materials with low resistivity conduct electricity well.
• Electrical resistivity is a key factor when selecting materials as conductors or insulators.
• Copper is used in electrical wires because of low electrical resistivity.

Thermal Conductivity

• Measures how fast heat is conducted through a slab of material based on a given temperature difference.
• It is an important factor for objects that will be heated, needing to conduct or insulate against heat.
• Cooking pots are an example of an important application.

Thermal Expansion (Expansivity)

• Measures the fractional increase in dimensions when an object is heated.
• It is an important factor when joining two dissimilar materials, especially with temperature fluctuations.
• Oven doors are an example of an important application.

Hardness

• The resistance of a material to penetration, cutting, denting, or scratching.
• Hardness is a key factor when resistance to cutting or scratching is required.
• Ceramic floor tiles are hard and resist scratching.

Mechanical Properties

Strength

• Represents a material's ability to resist an applied force, categorized as either tensile or compressive strength.

Tensile Strength

• The ability of a material to withstand pulling forces.
• Materials with high tensile strength resist stretching when pulled.
• Insufficient tensile strength leads to stretching and eventual breakage, e.g., ropes and cables.

Compressive Strength

• The ability of a material to withstand pushing forces.
• High compressive strength allows a material to withstand forces that try to crush or shorten it, e.g., columns.

Stiffness

• The ability of a material to resist bending deformation.
• Stiffness is important for maintaining shape, key in objects like airplane wings.

Toughness

• The ability of a material to resist the propagation of cracks.
• Toughness is important where impact may occur, e.g., hammer heads.

Ductility

• The ability of a material to be drawn or extruded into an extended shape like a wire.
• Ductility is important when materials are extruded, e.g., manufacturing copper wires.

Elasticity

• The ability of a material to deform and return to its original size and shape.
• Natural and synthetic rubbers, and metals used for springs exemplify this property.

Plasticity

• The ability of a material to undergo permanent deformation.

Young's Modulus

• Represents the stiffness of a material.
• Young's Modulus = stress/strain. Stress = Force/Area. Strain = Change of Length / Original Length.
• A stress-strain graph shows the elastic region of a material, its yield stress, Ultimate Tensile Strength (UTS) and fracture points.

Aesthetic Characteristics

• Aesthetic characteristics include smell, appearance, taste, and texture.
• These properties activate senses, but responses vary individually and are hard to quantify scientifically.
• Some properties relate specifically to food, while others apply broadly across material groups.

Properties of Smart Materials

• Smart materials react to changes in their environment altering properties in response to external conditions like temperature or light, with reversible and repeatable changes.

Piezoelectricity

• Piezoelectric materials possess two interrelated properties, generating a small electrical discharge on deformation.
• In an everyday example, an airbag sensor employs a piezoelectric material to detect impact force and trigger the airbag.
• Piezoelectric materials are used widely as sensors in different environments.
• These materials significantly increase in size when an electrical current is passed through them (up to 4% change in volume).

Shape Memory Alloys (SMAs)

• Shape memory alloys exhibit pseudo-elasticity and shape memory effect due to molecular arrangement.
• Pseudo-elasticity occurs without a change in temperature and allows molecules to rearrange themselves in a material. Applications: eye-glass frames and medical tools.
• The shape memory effect allows severe deformation of a material, which can then be returned to its original shape by heating it. Application: robotic limbs.
• SMAs help to replicate movements of the human body, like the gripping force required to handle different objects.

Magneto-Rheostatic (MR) and Electro-Rheostatic (ER)

• Can change from a thick fluid to a solid rapidly when exposed to a magnetic (MR) or electric (ER) field.
• The effect will reverse when the field is removed.
• MR fluids are in car shock absorbers, damping washing machine vibration, prosthetic limbs, exercise equipment, and surface polishing of machine parts.
• ER fluids are in clutches and valves, as well as engine mounts designed to reduce noise and vibration in vehicles.

Photochromicity

• Photochromic materials react reversibly to light by changing color. Application: color-changing lenses in sunglasses.
• A chemical on the surface of the lens or embedded within the glass reacts to ultraviolet light, which causes it to change form and therefore its light absorption spectra.

Thermoelectricity

• Electricity is produced directly from heat, involving the joining of two dissimilar conductors that, when heated, produced a direct current.
• Thermoelectric circuits occur in remote areas and in space probes to power radio transmitters and receivers.

Materials

• Materials are classified into six basic groups based on their properties.

Metals and Metallic Alloys

• Typically hard, shiny, and possess good electrical and thermal conductivity.
• Metals are resources for the manufacturing industry.
• Pure metals are often too soft, brittle, or chemically reactive for practical use.
• Manipulating these materials affects the application of the materials.
• Extraction transpires locally with added value often occurring in another country.
• Design for disassembly is an important aspect of sustainable design.
• Valuable metals, like gold and copper, are being recovered from millions of mobile phones.
• Some laptops and mobile phones can be disassembled very quickly without tools to allow materials to be recovered easily.

Metals and Alloys

• Can be divided into ferrous and non-ferrous metals:

Ferrous metals

• Contain iron, including cast iron (vices, heavy machinery), mild steel (car bodies), medium carbon steel (garden tools), and high carbon steel (hand tools).

Non-ferrous metals

• Do not contain iron, for example, copper (electrical wires), aluminum (kitchen utensils), lead (radiation insulation), and zinc (galvanized steel).
• Non-ferrous metals do not rust.

Extraction of Metals from Ores

• A quarter of the Earth's crust contains metals.
• Most of these metals, such as iron oxide and aluminum oxide, are chemically combined in the form of metallic ores.
• The choice of extraction method from its ore depends on metal reactivity.
• Reactive metals, such as aluminum and copper, are extracted by electrolysis.
• Less reactive metals, like iron, may be extracted by reduction.
• Iron is extracted from iron ore in a huge container called a blast furnace.
• Iron ores contain iron oxide (Fe2O3). The oxygen must be removed from the iron oxide to leave the iron behind.
• Aluminum, as bauxite, is purified into aluminum oxide (Al2O3).
• Aluminum is extracted by electrolysis.

Grain Size

• Metals, pure or alloyed, exist as crystals and as a regular arrangement of positive ions in a sea of electrons.
• Grain size refers to the arrangement of crystals which form a different pattern for different metals.
• Grain structure and size determine the metal's important properties.
• Grain size can be controlled/modified in a number of ways.

Rate of cooling:

• Slow cooling allows larger grains to form.
• Rapid cooling allows smaller grains to form.

Heat treatment after solidification

• Directional properties in the structure are achieved by selectively cooling one area.
• Reheating a solid metal or alloy allows material to diffuse between grain structure.

Modifying properties by altering, work hardening and tempering

• Pure metal properties can be changed by adding other elements in a process called alloying.
• An alloy is a mixture of two or more elements, among them at least one metal.
• Alloys contain atoms of different sizes, which distorts base metal arrangements and changes properties like tensile strength, hardness, and ductility.

Alloys may be grouped into:

Ferrous alloys:

• Like stainless steel (cooking utensils and kitchen sinks), which resists corrosion.

Non-ferrous alloys:

• Like brass (musical instruments) and duralumin (aircraft structure).

Work Hardening

• Plastically deforming a metal by cold working increases hardness and resistance to further plastic deformation.

Tempering

• Tempering removes some of a metal's hardness and brittleness, achieved by heating the metal to a high temperature then cooling it.

Design criteria for super alloys

• The strength of most metals and alloys decreases as temperature increases.
• Super alloys are metallic alloys that can be used at high temperatures, often in excess of 0.7 of their absolute melting temperature.
• A super alloy's base alloying element is usually nickel.

Design criteria for super alloys include:

• Creep resistance.
• oxidation and corrosion resistance.

Super alloys best applications:

• Aircraft engines
• Rocket engines
• Chemical and nuclear plants

Recovery and disposal of metals and metallic alloys

• Recovery, reuse, and recycling preserve non-renewable resources, cause less pollution, and require less energy than extracting metals from ores.
• Recycled metals include aluminum, iron, and steel.
• Collection and transport costs offset these benefits to a minor extent.

Timber

• Renewable building material, renewing via Sun's energy, but deforestation must be considered.

Natural Timber

• Is a natural composite material comprising cellulose fibers in a lignin matrix. The tensile strength that timber shows is shown to be greater along the grain rather than across the grain.
• Natural wood may be divided into softwood and hardwood.

Softwood

• Produced from trees in colder temperate regions, are coniferous and evergreen.
• Coniferous trees are fast growing. Example: Pine and Spruce.

Hardwood

• Produced from deciduous trees that grow in warm temperate and tropical regions.
• Deciduous trees are slow growing and have broad leaves (shed their leaves annually).
• Hardwood is used for quality furniture and other structures that durability is important on.
• Example: Mahogany, Beech, Teak and Oak.

Man-Made Timbers (Manufactured Boards)

• MDF: Made by gluing and compressing wood fibers into a stable, solid board that machines and paints well.
• Plywood: Made from thin layers of wood bonded together with adhesive.
• Plywood is used for furniture, interior doors, drawer bottoms, laminated floors etc...

Timber Boards

• Blockboard: Made up of parallel strips of wood glued side by side, sandwiched between thin layers of wood. It is a good substitute for plywood when greater thicknesses (12-25mm) are required.
• Particle board: Made glueing and compressing tiny structures of wood
• Hardboard: Where space is required, hardboard structures is used rather than strength such as cupboards backs.

Boards produced from man-made timbers have a number of advantages over natural timber boards:

• Available in larger standard sizes.
• May be veneered.
• Produced in uniform thicknesses and consistent quality.
• More stable.
• Readily available material with little resource implications.

Treating and finishing timbers

• A growing tree may contain 50% or more of its weigh in the form of water
• The material has been referred to as water content (MC), this is expressed as what percent of its dry weight it dries to.
• Free moisture occurs within timber that is contained within the cavities and intercellular spaces
• Absorbed moisture occurs within cells walls.
• Moisture content is affected by humidity and temperature.
• Equilibrium refers to the moisture content of wood that achieves with the environment.
• Seasoning (drying) the commercial drying of national timber which reduces its moisture content to be less than 20%
• If unseasoned timber is placed in a room, twists when drying

There are two basic methods

Natural air seasoning

• Stacks of large timber are placed in large sheds and left to dry

Kiln seasoning

• Stacks of timber are placed in here where air circulation and humidity is closely controlled.

Defects in natural timber

• Defects affect the appearance of timber
• Common defects in timber include warp, splitting, and twisting.
• Finishing timber is for appearance.
• It protects against decay

Glass

• Used in aesthetics or safety.

Characterisitcs:

• Brittle
• Transparent
• Hard
• Aesthetic
• Hygenic
• Good resistance to compression

Glass Aplications

• Soda-lime glass: High volume products.
• Borosilicate glass (Pyrex): Has good thermal shock resistance.
• Toughened glass: If broken, it shatter into tiny fragments, Safer applications.
• Laminated glass: Provides more structure as breaks spread out

Plastics

• Produced by petrochemicals.
• Degrading materials, bio-plastics are being made.

Two structrures:

• Thermo: They are linear chains that makes clumps like speghetti
• Thermosetting: Has linear chains with covalent bonds between them

Material Properties

Thermoplastics

• Polythylene (Low density): Flexible, good electrical resistance
• Polythelyne (High density): Stiffer, stronger that low density
• High Impact Polystyrene: Very high durability
• PET: Very transparent, able to handle heat

Thermosetting

• Urea-formaldehyde: Good elctrical insulator
• Melamine resin: Moisture resistant
• Epoxy resin: Strong adhesive for chemicals and bonds
• Polyurethan: Good for flexible foam

Textiles

• Wide array of markets
• Smart textiles

Properties of Natural Fibres

• Wool: Has overlapping scales and is crimped. If washed in hot water is will skrink, is long
• Cotton: Is absorbent and strength in when wet. It is easy to crease
• Silk: Straight and smooth. Can be soiled by chemicals.
• The can be dyed or treated to protect it

Synthetic fibres

• Nylon is elastic and crease resistant.
• Polyester is very strong and resistant to wear
• Lycra is a material for stretch

Composites

• The are produced frequently
• Can be created with certain properties

They include:

• Concretre
• Laminated glass
• Ply wood
• Fiber glass

Advantages and Disadvantages

Good:

• Improved properties

Bad:

• Expensive and hard to recycle

Scales of Production

• The Scale of production depends on the number of products required.
• mass customization can enable global products to become individual items.

3 Main types of production.

One-Off

• An individual product in larger scale, for larger scale products.

Batch production

• Limited volume production, set number of items produced.

Mass and continuous flow reduction

• The continuous production of large products on production lines.

Mass customisation

• Sophisticated CIM that offers a wide range of produts to the customer.

Processes

Additive

• Add layers in the production process

Wasting and Subtracting.

• Removes and cut back on materials

Shaping

• Modifying shape of the materials

Joing

• Joines and more similar material.

Robots

Key Primary characteristcis

• Work envelope and load Capacity
• Single and multi stack robots

Advantages

• Increased prodcutivity
• Accuracy and Reduced waste
• Quality control

Disadvantages

• High set up cost
• Loss of Jobs