Knowt
Materials (EdExcel)
I. Introduction to Materials in Design and Technology
Definition: Materials are substances used to make things.
Importance of Material Selection:
Functionality: The material must be suitable for the product's intended purpose and performance requirements (e.g., strength, flexibility, durability).
Aesthetics: The material's appearance (color, texture, finish) contributes to the product's design and appeal.
Manufacturing: The material must be compatible with the chosen manufacturing processes (e.g., cutting, shaping, joining, finishing).
Cost: Material costs significantly impact the overall product cost and profitability.
Sustainability: Environmental impact and ethical sourcing of materials are increasingly important considerations.
II. Material Categories
Materials are broadly classified into categories based on their origin and properties.
A. Metals
Characteristics of Metals:
Strong and Durable: Resistant to wear and tear.
Good Conductors: Excellent conductors of heat and electricity.
Malleable and Ductile: Can be shaped (malleable) and drawn into wires (ductile).
Opaque: Not transparent.
Lustrous: Shiny when polished.
Magnetic (Ferrous Metals): Some metals are magnetic.
Types of Metals:
Ferrous Metals: Contain iron and are usually magnetic and prone to rust.
Mild Steel:
Properties: Tough, ductile, malleable, good tensile strength, prone to rust.
Uses: Car bodies, construction girders, machine parts, nails, screws.
Medium Carbon Steel:
Properties: Stronger and harder than mild steel, less ductile and malleable, can be hardened by heat treatment.
Uses: Springs, gears, garden tools.
High Carbon Steel (Tool Steel):
Properties: Very hard, brittle, loses hardness if overheated when worked.
Uses: Cutting tools (drills, saws, chisels), blades.
Cast Iron:
Properties: Hard, brittle, good in compression, good castability, rusts.
Uses: Engine blocks, machine bases, cookware (cast iron pans), manhole covers.
Non-Ferrous Metals: Do not contain iron, are not magnetic, and generally more resistant to corrosion than ferrous metals.
Aluminum:
Properties: Lightweight, corrosion-resistant, ductile, malleable, good conductor of heat and electricity.
Uses: Aircraft parts, drink cans, window frames, cooking foil, bike frames.
Copper:
Properties: Ductile, malleable, excellent conductor of heat and electricity, corrosion-resistant.
Uses: Electrical wiring, plumbing pipes, cookware bases, printed circuit boards.
Brass (Alloy of Copper and Zinc):
Properties: Corrosion-resistant, harder than copper, casts well, good conductor of heat and electricity.
Uses: Musical instruments, decorative items, plumbing fittings, door handles.
Tin:
Properties: Soft, malleable, ductile, corrosion-resistant, low melting point.
Uses: Coating steel cans (tin plating), solder, alloys (e.g., pewter).
Zinc:
Properties: Corrosion-resistant, relatively weak, low melting point.
Uses: Galvanizing steel (protective coating), die casting, batteries.
Alloys: Mixtures of two or more metals (or a metal and another element) to enhance properties.
Stainless Steel (Alloy of Steel, Chromium, Nickel):
Properties: Corrosion-resistant, strong, hard, hygienic.
Uses: Cutlery, kitchen sinks, medical instruments, chemical processing equipment.
Duralumin (Alloy of Aluminum, Copper, Magnesium, Manganese):
Properties: Lightweight, strong, machines well, work hardens.
Uses: Aircraft structures, high-performance automotive parts.
B. Polymers (Plastics)
Characteristics of Polymers:
Lightweight: Generally less dense than metals and ceramics.
Insulators: Poor conductors of heat and electricity.
Versatile: Can be molded into complex shapes.
Corrosion-Resistant: Generally resistant to chemicals and weathering.
Variety of Properties: Properties vary widely depending on the type of polymer.
Types of Polymers:
Thermoplastics: Can be repeatedly softened by heating and hardened by cooling. Recyclable.
Acrylic (PMMA - Polymethylmethacrylate):
Properties: Hard, stiff, brittle, good optical clarity, weather-resistant.
Uses: Signs, lenses, safety screens, baths, aircraft canopies (Plexiglass/Perspex).
PVC (Polyvinyl Chloride):
Properties: Rigid or flexible (depending on plasticizers), tough, chemical-resistant, waterproof, good insulator.
Uses: Pipes, window frames, flooring (rigid PVC), raincoats, inflatable products (flexible PVC).
Polyethylene (Polythene - LDPE and HDPE):
LDPE (Low-Density Polyethylene): Flexible, tough, good insulator, chemical-resistant.
Uses: Plastic bags, cling film, squeeze bottles.
HDPE (High-Density Polyethylene): Stiffer, stronger, tougher than LDPE, chemical-resistant.
Uses: Milk crates, bottles, pipes, buckets, жесткая plastic toys.
Polypropylene (PP):
Properties: Tough, flexible, chemical-resistant, fatigue-resistant, can be colored easily.
Uses: Containers, packaging, hinges (living hinges), ropes, carpets, car bumpers.
ABS (Acrylonitrile Butadiene Styrene):
Properties: Tough, hard, rigid, good impact resistance, scratch-resistant.
Uses: Mobile phone cases, Lego bricks, car interior parts, vacuum cleaner bodies.
Polystyrene (PS):
Properties: Rigid, brittle, lightweight, good insulator, can be expanded (EPS - Expanded Polystyrene).
Uses: Packaging (EPS foam), model kits, disposable cups, food containers.
PET (Polyethylene Terephthalate):
Properties: Strong, tough, transparent, good barrier properties (for food and drinks), recyclable.
Uses: Drinks bottles, food packaging, synthetic fibers (fleece).
Thermosetting Polymers: Undergo a chemical change when heated, becoming permanently hard and rigid. Cannot be softened or reshaped once set. Not recyclable in the same way as thermoplastics.
Epoxy Resin:
Properties: Hard, rigid, strong adhesive, chemical-resistant, good insulator.
Uses: Adhesives, coatings, encapsulation of electronics, composites (e.g., fiberglass).
Urea Formaldehyde (UF):
Properties: Hard, rigid, brittle, good insulator, heat-resistant, scratch-resistant.
Uses: Electrical fittings (sockets, switches), worktop surfaces, adhesives in MDF and chipboard.
Melamine Formaldehyde (MF):
Properties: Hard, rigid, brittle, heat-resistant, stain-resistant, food-safe.
Uses: Laminates for worktops, tableware (plates, bowls), electrical insulation.
Polyester Resin:
Properties: Hard, rigid, brittle, good chemical resistance (when cured), can be reinforced with glass fibers (GRP - Glass Reinforced Plastic).
Uses: Boat hulls, car body parts, furniture, casting.
Elastomers (Rubbers): Can be stretched and return to their original shape.
Natural Rubber (Latex):
Properties: Elastic, flexible, tough, waterproof, good insulator, degrades in UV light and chemicals.
Uses: Tyres, seals, hoses, erasers, gloves.
Synthetic Rubber (e.g., Neoprene, Silicone Rubber):
Properties: Vary depending on type, often better resistance to heat, chemicals, and weathering than natural rubber.
Uses: Seals, hoses, gaskets, wetsuits, belts, flexible moldings.
C. Woods
Characteristics of Wood:
Natural Material: Renewable resource (if sustainably managed).
Aesthetic Appeal: Natural grain and warmth.
Strength and Durability: Varies depending on species.
Workable: Can be easily cut, shaped, and joined.
Biodegradable: Environmentally friendly at end-of-life.
Susceptible to Moisture and Pests: Can rot or be attacked by insects if not treated.
Types of Wood:
Hardwoods: Deciduous trees (lose leaves in winter), generally denser, slower-growing, and more expensive than softwoods.
Oak:
Properties: Strong, hard, tough, durable, attractive grain, can be resistant to rot (especially European Oak).
Uses: Furniture (high-quality), flooring, construction (beams), barrels, veneers.
Beech:
Properties: Hard, tough, strong, close-grained, smooth finish, prone to warping if not dried properly.
Uses: Furniture (chairs, tables), toys, tool handles, workbenches.
Mahogany:
Properties: Durable, medium density, reddish-brown color, polishes well, resistant to rot and insects.
Uses: High-quality furniture, veneers, boat building, musical instruments.
Softwoods: Coniferous trees (evergreen, needles), generally less dense, faster-growing, and cheaper than hardwoods.
Pine (e.g., Scots Pine, Yellow Pine):
Properties: Relatively soft, lightweight, easy to work, knotty, resinous.
Uses: Construction (framing, roofing), furniture (cheaper), paper pulp, packaging.
Fir (e.g., Douglas Fir):
Properties: Lightweight, straight-grained, good strength-to-weight ratio, less knotty than pine.
Uses: Construction (framing, plywood), furniture, musical instruments.
Cedar (e.g., Western Red Cedar):
Properties: Lightweight, aromatic, naturally resistant to rot and insects, low shrinkage.
Uses: Cladding, shingles, outdoor furniture, wardrobes, pencils.
Manufactured Boards: Engineered wood products made by bonding wood strands, particles, or fibers together with adhesives.
Plywood:
Construction: Layers of wood veneer glued together with grains at right angles for strength.
Properties: Strong, stable, good dimensional stability, available in large sheets.
Uses: Construction (flooring, walls, roofing), furniture, boat building, packaging.
MDF (Medium Density Fiberboard):
Construction: Fine wood fibers bonded with resin under heat and pressure.
Properties: Smooth surface, easy to machine, dense, uniform, less strong than plywood, absorbs moisture.
Uses: Furniture (flat-pack), cabinets, interior moldings, speaker boxes.
Chipboard (Particle Board):
Construction: Wood chips bonded with resin under heat and pressure.
Properties: Cheapest manufactured board, less strong and moisture-resistant than MDF, can be veneered or laminated.
Uses: Low-cost furniture, flooring underlayment, shelving (often laminated).
D. Textiles
Characteristics of Textiles:
Flexible: Can be bent and draped.
Porous: Allow air and moisture to pass through (breathable).
Variety of Textures and Finishes: Can be woven, knitted, non-woven, dyed, printed, etc.
Absorbent: Can absorb liquids (varies depending on fiber).
Insulating: Can provide thermal insulation.
Types of Textiles:
Natural Fibers: Derived from plants or animals.
Cotton:
Properties: Soft, absorbent, breathable, comfortable, relatively inexpensive, creases easily, shrinks.
Uses: Clothing (t-shirts, jeans), bed linen, towels, upholstery.
Linen (Flax):
Properties: Stronger than cotton, absorbent, breathable, cool to wear, creases easily, more expensive than cotton.
Uses: Clothing (suits, shirts), bed linen, tablecloths, tea towels.
Wool:
Properties: Warm, absorbent, elastic, naturally flame-resistant, can shrink when washed, can be itchy for some people.
Uses: Clothing (sweaters, coats), carpets, blankets, upholstery, felt.
Silk:
Properties: Luxurious, smooth, lustrous, strong, absorbent, drapes well, expensive, delicate.
Uses: Clothing (dresses, scarves, ties), bed linen, upholstery, parachutes.
Synthetic Fibers: Man-made fibers produced from chemical processes, often derived from petrochemicals.
Polyester:
Properties: Strong, durable, crease-resistant, hydrophobic (water-repellent), inexpensive, can be blended with other fibers.
Uses: Clothing (shirts, trousers), sportswear, bedding, curtains, upholstery, fleece.
Nylon (Polyamide):
Properties: Strong, elastic, tough, abrasion-resistant, quick-drying, can melt when heated.
Uses: Stockings, sportswear, ropes, tents, carpets, parachutes.
Acrylic:
Properties: Soft, warm, bulky, good drape, crease-resistant, less absorbent than natural fibers, can pill.
Uses: Sweaters, blankets, fake fur, carpets, upholstery.
Lycra (Elastane/Spandex):
Properties: Highly elastic, can stretch many times its original length and return to shape, lightweight, breathable.
Uses: Sportswear, swimwear, underwear, figure-hugging clothing.
Blended Fabrics: Made by combining two or more different types of fibers to get the benefits of each.
Polycotton (Polyester and Cotton): Combines the crease resistance and durability of polyester with the comfort and absorbency of cotton.
Wool and Acrylic Blends: Combines the warmth of wool with the crease resistance and lower cost of acrylic.
E. Paper and Boards
Characteristics of Paper and Boards:
Made from Cellulose Fibers: Usually derived from wood pulp, but can also be from recycled paper or other plant sources.
Versatile: Can be used for drawing, printing, packaging, construction.
Biodegradable and Recyclable: Environmentally friendly if responsibly sourced and managed.
Relatively Inexpensive: Generally cheaper than other materials.
Wide Range of Types and Thicknesses (GSM - Grams per Square Meter): Different types are suited for different purposes.
Types of Paper and Boards:
Layout Paper:
Properties: Thin, translucent, smooth surface, lightweight, inexpensive.
Uses: Sketching, quick ideas, tracing, overlays.
Tracing Paper:
Properties: Very thin, transparent, smooth surface, allows for detailed tracing.
Uses: Tracing detailed drawings, technical drawings, overlays.
Cartridge Paper:
Properties: Medium thickness, slightly textured surface, good for general drawing and sketching, takes color well.
Uses: Drawing, sketching, painting, general purpose paper.
Card (Cardstock):
Properties: Thicker and stiffer than paper, available in various thicknesses and finishes, can be scored and folded.
Uses: Greeting cards, packaging, model making, business cards, presentation folders.
Corrugated Cardboard:
Construction: Fluted (wavy) inner layer sandwiched between two outer layers of card.
Properties: Strong for its weight, provides cushioning, good insulator, recyclable.
Uses: Packaging (shipping boxes), protective packaging, model making.
Bleed-Proof Paper:
Properties: Coated paper that prevents marker ink from bleeding through, smooth surface.
Uses: Marker pen drawings, illustrations, graphic design.
Foam Board (Foamcore):
Construction: Polystyrene foam core sandwiched between two layers of paper or card.
Properties: Lightweight, rigid, smooth surface, easy to cut, good for mounting.
Uses: Model making, architectural models, presentations, mounting posters.
Solid White Board/Grey Board:
Properties: Thick, rigid, strong board, good for structural models and packaging prototypes.
Uses: Model making (structural parts), packaging prototypes, bookbinding.
III. Material Properties
Understanding material properties is essential for selecting the right material for a specific application.
A. Physical Properties
Density: Mass per unit volume (how heavy a material is for its size).
Example: Aluminum is less dense than steel (lighter).
Strength: Ability to withstand forces without breaking or deforming.
Tensile Strength: Resistance to pulling forces (tension).
Example: Steel has high tensile strength, good for cables.
Compressive Strength: Resistance to squashing forces (compression).
Example: Concrete has high compressive strength, good for foundations.
Shear Strength: Resistance to forces acting across the material, causing layers to slide past each other.
Example: Rivets and bolts need good shear strength.
Hardness: Resistance to scratching, indentation, or wear.
Example: Diamond is very hard, used for cutting tools.
Toughness: Ability to absorb energy and withstand sudden impacts without fracturing.
Example: Nylon is tough, used for gears and bearings.
Elasticity: Ability to return to its original shape after being deformed and the force is removed.
Example: Rubber bands are very elastic.
Plasticity: Ability to be permanently deformed without fracturing.
Example: Clay is very plastic, easily molded.
Durability: Ability to withstand wear, weathering, and degradation over time. Example: Stainless steel is durable and corrosion-resistant.
Melting Point: Temperature at which a solid material changes to a liquid.
Example: Solder has a low melting point for easy joining.
Thermal Conductivity: Ability to conduct heat.
Example: Copper has high thermal conductivity, used in heat exchangers.
Electrical Conductivity: Ability to conduct electricity.
Example: Copper and aluminum are good electrical conductors.
Magnetism: Property of being attracted to magnets (primarily for ferrous metals).
Example: Steel is magnetic, aluminum is not.
Corrosion Resistance: Ability to resist chemical attack and degradation (rusting, oxidation).
Example: Stainless steel and plastics are corrosion-resistant.
Water Resistance/Waterproof: Ability to repel or prevent water penetration.
Example: PVC is waterproof.
Biodegradability: Ability to decompose naturally by microorganisms.
Example: Paper and wood are biodegradable.
B. Aesthetic Properties
Texture: Surface feel and appearance (rough, smooth, glossy, matte).
Color: Visual hue of the material.
Finish: Surface treatment or coating applied to the material (polished, painted, varnished).
Formability: How easily a material can be shaped into different forms.
Transparency/Opacity: How much light passes through the material (transparent, translucent, opaque).
C. Working Properties
Machinability: How easily a material can be cut, shaped, or machined using tools.
Example: MDF machines well.
Formability: How easily a material can be shaped into different forms (bending, molding, casting).
Example: Thermoplastics are easily formable when heated.
Joinability: How easily a material can be joined to itself or other materials (welding, soldering, gluing, screwing).
Example: Wood is easily joined with adhesives and screws.
Workability: Overall ease with which a material can be processed and manufactured.
Finishability: How easily a material can be finished (painted, polished, varnished, etc.).
Example: Wood and metals can be finished in many ways.
IV. Material Selection Criteria
Choosing the right material is a critical design decision. Consider these factors:
Functionality/Performance Requirements:
Strength and Load Bearing: Will it support weight or stress?
Durability and Lifespan: How long must it last?
Environmental Conditions: Will it be exposed to weather, chemicals, heat, etc.?
Movement and Flexibility: Does it need to bend, flex, or move?
Insulation (Thermal/Electrical): Does it need to insulate or conduct?
Water Resistance/Waterproof: Must it repel or block water?
Safety: Is it safe for its intended use (non-toxic, flame-retardant)?
Aesthetic Considerations:
Appearance: Color, texture, finish, form, style.
Visual Appeal: Does it match the desired aesthetic and target market?
Tactile Qualities: How does it feel to the touch?
Cost:
Material Cost: Price per unit of material.
Manufacturing Cost: Cost of processing and shaping the material.
Overall Product Cost: Material cost as a percentage of the total product cost.
Budget Constraints: Does it fit within the project budget?
Availability:
Supply Chain: Is the material readily available and reliably sourced?
Lead Times: How long does it take to obtain the material?
Local vs. Global Sourcing: Impact on cost and environmental footprint.
Manufacturing Processes:
Forming and Shaping: Is the material suitable for the intended manufacturing techniques (molding, machining, etc.)?
Joining Methods: Can it be easily joined using available methods?
Finishing Processes: Can it be finished to the desired standard?
Production Volume: Is the material suitable for the intended production scale (mass production, batch production, etc.)?
Environmental Impact and Sustainability:
Life Cycle Assessment (LCA): Evaluate environmental impact from raw material extraction to disposal.
Renewable vs. Non-Renewable Resources: Is it from a renewable source?
Recyclability: Can it be recycled at the end of its life?
Biodegradability: Will it decompose naturally?
Energy Consumption in Production: How energy-intensive is its production?
Carbon Footprint: Greenhouse gas emissions associated with the material.
Toxicity: Are there any harmful chemicals involved in its production or disposal?
Ethical Considerations:
Fair Trade: Is it sourced ethically, ensuring fair wages and working conditions?
Child Labor: Is child labor involved in its extraction or production?
Conflict Minerals: Is it sourced from conflict zones?
Social Impact: Does its production have negative social impacts on communities?
V. Sustainability of Materials
Sustainability is increasingly important in material selection.
Life Cycle Assessment (LCA): A method to evaluate the environmental impacts of a product or material throughout its entire life cycle ("cradle-to-grave"):
Raw Material Extraction: Mining, logging, etc. - energy use, pollution, habitat destruction.
Material Processing and Manufacturing: Energy use, waste generation, emissions.
Product Use: Energy consumption during product use, emissions.
End-of-Life: Disposal (landfill, incineration) or recycling, reuse, composting.
Renewable vs. Non-Renewable Resources:
Renewable Resources: Replenish naturally over a relatively short time (e.g., wood from sustainably managed forests, natural fibers).
Non-Renewable Resources: Finite resources that take millions of years to form (e.g., metals, fossil fuels for plastics). Using non-renewable resources depletes them and can have greater environmental impacts.
Recycling and Upcycling:
Recycling: Processing waste materials to create new products of similar quality. Reduces landfill waste and conserves resources.
Examples: Recycling aluminum cans, paper, some plastics.
Upcycling: Transforming waste materials or unwanted products into new products of higher quality or value.
Example: Making furniture from pallets.
Biodegradability and Composting:
Biodegradable Materials: Can be broken down by microorganisms into natural components.
Examples: Paper, wood, natural fibers.
Compostable Materials: Biodegradable materials that can be broken down in a compost heap, enriching soil.
Example: Some bioplastics, paper-based packaging.
Sustainable Sourcing:
FSC (Forest Stewardship Council) Certified Wood: Wood from forests managed sustainably to protect biodiversity and ecosystems.
Organic Cotton: Cotton grown without synthetic pesticides and fertilizers, reducing environmental impact.
Fair Trade Materials: Sourced ethically, ensuring fair wages and working conditions for producers.
Ethical Sourcing:
Conflict-Free Minerals: Ensuring materials are not sourced from areas where their extraction funds conflict or human rights abuses.
Responsible Mining and Extraction Practices: Minimizing environmental damage and ensuring worker safety.
VI. Material Processes and Techniques
Understanding how materials are processed is important for design and manufacturing.
Metals:
Cutting: Sawing, shearing, laser cutting, plasma cutting.
Shaping: Bending, rolling, forging, pressing, casting, machining (turning, milling, drilling).
Joining: Welding, soldering, brazing, riveting, bolting, adhesives.
Finishing: Polishing, painting, powder coating, plating, anodizing.
Polymers (Plastics):
Cutting: Sawing, laser cutting, die cutting, guillotining.
Shaping: Injection molding, blow molding, rotational molding, vacuum forming, extrusion, thermoforming.
Joining: Adhesives, welding (plastic welding), mechanical fixings.
Finishing: Painting, printing, polishing.
Woods:
Cutting: Sawing (hand saws, power saws), chiseling, turning (wood lathe).
Shaping: Carving, bending (steam bending), laminating.
Joining: Adhesives, screws, nails, dowels, joints (mortise and tenon, dovetail).
Finishing: Sanding, varnishing, painting, staining, polishing, waxing.
Textiles:
Cutting: Scissors, rotary cutters, die cutting.
Shaping: Sewing, knitting, weaving, felting, embroidery.
Joining: Sewing, adhesives, heat sealing.
Finishing: Dyeing, printing, embroidery, embellishment.
Paper and Boards:
Cutting: Scissors, craft knives, guillotines, die cutting.
Shaping: Folding, scoring, bending, creasing.
Joining: Adhesives, staples, tape.
Finishing: Printing, laminating, varnishing.
VII. Emerging and Smart Materials
Smart Materials: Materials whose properties can change in response to external stimuli (temperature, light, pressure, electricity, etc.).
Shape Memory Alloys (SMAs): Metals that can return to a predefined shape when heated.
Uses: Medical stents, eyeglass frames, actuators.
Thermochromic Materials: Change color with temperature.
Uses: Color-changing mugs, novelty items, temperature indicators.
Photochromic Materials: Change color with light intensity.
Uses: Light-sensitive sunglasses.
Piezoelectric Materials: Generate electricity when pressure is applied, or change shape when electricity is applied.
Uses: Sensors, actuators, spark lighters.
Electrochromic Materials: Change color when voltage is applied.
Uses: Smart windows, dimmable mirrors.
Composites: Materials made from two or more constituent materials with significantly different physical or chemical properties, which when combined, produce a material with characteristics different from the individual components.
Fiberglass (GRP - Glass Reinforced Plastic): Glass fibers embedded in a polyester resin matrix. Properties: Strong, lightweight, corrosion-resistant.
Uses: Boat hulls, car body parts, shower trays.
Carbon Fiber Composites (CFRP - Carbon Fiber Reinforced Plastic): Carbon fibers embedded in a resin matrix (often epoxy). Properties: Very strong, very lightweight, stiff, expensive.
Uses: Aircraft parts, high-performance sports equipment, racing car components.
Kevlar: Aramid fibers. Properties: Very high tensile strength, impact resistant, lightweight, heat resistant.
Uses: Bulletproof vests, body armor, ropes, tires.
