Study Notes: Core Component 4 – Raw Material to Final Product

Hello future designers! Welcome to Component 4, perhaps one of the most fundamental and fascinating parts of Design Technology. This chapter is all about the incredible journey materials take—from being dug out of the ground or grown in a forest, right up until they become the products we use every day, like your phone casing or the frame of your bicycle.


Understanding materials—how they behave, why they are chosen, and where they come from—is the heart of design. If you choose the wrong material, even the most brilliant design will fail!

Don't worry if the vocabulary seems heavy at first; we will break down the complex concepts into simple, manageable pieces. Let's get started on the essential core knowledge!

Section 1: Classifying the World of Materials

Before a designer can start creating, they need to know their basic palette. Materials are grouped based on their origins and general characteristics. Memorizing these groups is essential.

1.1 The Six Main Material Families

The technological world is built using these six categories:

  • Metals
  • Polymers (Plastics)
  • Ceramics
  • Composites (Mixtures)
  • Timber (Woods)
  • Textiles/Fibres (Often combined with Polymers in design context)

1.2 Metals: Strong, Conductive, and Refined

Metals are typically strong, durable, good conductors of heat and electricity, and are usually shiny when polished. We categorize them primarily based on the presence of iron (Fe).

  • Ferrous Metals: These contain iron.
    Characteristics: Usually magnetic and are prone to rust (oxidation) unless protected.
    Examples: Mild Steel (used for construction), Stainless Steel (used for cutlery/kitchens).
  • Non-Ferrous Metals: These do NOT contain iron.
    Characteristics: Generally lighter, more expensive, and offer excellent corrosion resistance.
    Examples: Aluminium (aircraft, drink cans), Copper (wiring), Gold (jewelry, electronics).
  • Alloys: A mixture of two or more elements, where at least one is a metal. Alloying is done to enhance properties (e.g., strength, hardness, or corrosion resistance).
    Examples: Brass (Copper + Zinc), Bronze (Copper + Tin).

Quick Tip: Think of a magnet! If it sticks, it’s generally ferrous.

1.3 Polymers: The Versatile Plastics

Polymers are long chains of molecules (monomers). Their versatility makes them the most rapidly changing material group.

  • Thermoplastics: These can be softened by heating, shaped, and re-solidified repeatedly.
    Why they matter: They are easily recycled and processed using techniques like injection moulding.
    Examples: PET (water bottles), HDPE (milk cartons), PVC (pipes).
  • Thermosetting Polymers (Thermosets): These undergo a chemical change when heated (called curing) that is irreversible. They cannot be melted and reshaped.
    Why they matter: They are durable and suitable for high-heat environments or permanent structures.
    Examples: Epoxy resin (adhesives), Bakelite (old electrical fittings).

Memory Aid: Thermo-Plastics are Pliable (can be remelted). Thermo-Sets are Stuck (permanently cured).

1.4 Ceramics, Composites, and Timbers

  • Ceramics: Non-metallic materials fired at high temperatures.
    Characteristics: Hard, brittle, excellent insulators, and resistant to chemical degradation.
    Examples: Porcelain (mugs), Glass (windows), technical ceramics (spark plugs).
  • Composites: Materials made from two or more constituent materials with significantly different properties, which remain distinct but combine to give superior overall properties. They consist of a Matrix (the binder) and a Reinforcement (the strength).
    Example Analogy: Concrete (Gravel/rebar is the reinforcement, Cement is the matrix).
    Real-World Examples: Carbon Fibre Reinforced Plastic (CFRP for race cars), Glass Reinforced Plastic (GRP/Fiberglass for boats).
  • Timbers (Wood): Natural materials harvested from trees.
    Softwoods: Come from evergreen trees (conifers), grow quickly, generally softer, cheaper. (e.g., Pine, Cedar).
    Hardwoods: Come from deciduous trees, grow slowly, denser, stronger, more expensive. (e.g., Oak, Mahogany).

Key Takeaway: Classifying materials helps a designer immediately understand the material’s source, primary structure, and basic processing limitations (e.g., whether it can be melted down or if it needs to be glued/cut).

Section 2: Material Properties and Selection Criteria

Choosing a material is not guesswork; it’s a systematic process driven by required properties. Properties dictate performance.

2.1 Understanding Material Properties

Properties can be grouped into several key categories. Designers must specify requirements for each category.

A. Mechanical Properties (How it responds to force)

These are critical for structural integrity:

  • Strength (Tensile, Compressive): The ability to withstand forces without breaking or permanently deforming. Tensile strength resists pulling apart (like a rope); Compressive strength resists squashing (like a brick).
  • Stiffness (Elasticity): The material's resistance to temporary deformation (bending or stretching) when a force is applied. Stiff materials snap rather than bend.
  • Hardness: The ability to resist surface indentation, scratching, or abrasion.
  • Toughness: The ability to absorb energy and plastically deform without fracturing (breaking). Tough materials handle sudden impact well. Example: Rubber is tough; glass is brittle.
  • Ductility: The ability to be drawn or pulled into a thin wire. (Common in metals like copper).
  • Malleability: The ability to be hammered or rolled into thin sheets without cracking. (Common in metals like gold or aluminium).
B. Physical Properties
  • Density: Mass per unit volume. Important for weight considerations (e.g., aerospace design needs low density).
  • Thermal Conductivity: How easily heat travels through the material. (Metals are high conductors; polymers are low conductors/insulators).
  • Electrical Resistivity: How much the material resists the flow of electricity. (High resistivity = insulator; Low resistivity = conductor).
C. Aesthetic Properties

These relate to how the product is perceived by the user:

  • Colour, Texture, Finish, Smell, Feel.
D. Chemical Properties
  • Corrosion/Degradation Resistance: The ability to resist chemical attack (like rusting of steel or UV degradation of some polymers).

2.2 The Selection Criteria (A Systematic Approach)

Designers use the acronym "AFP" or "FACES" to remember the essential criteria for selection.

  1. Function/Purpose: Does the material possess the necessary mechanical properties (strength, toughness) to perform the task? (e.g., A car safety cage must be tough, not brittle).
  2. Aesthetics: Does the material look, feel, or sound appropriate for the user and context?
  3. Cost: Can the cost of the raw material, and the cost of processing it, be justified by the final selling price? (Includes material cost and tooling/manufacturing cost).
  4. Environmental Impact: Is the material sustainable? Can it be recycled? What is its embodied energy?
  5. Processing/Manufacturability: Can the material be easily processed using available tools and techniques? (Some high-performance alloys are extremely difficult to machine).
  6. Availability: Is the material readily available in the required stock form and quantity?

Common Mistake to Avoid: Students often confuse Stiffness and Strength. A material can be stiff (resists bending) but weak (it will shatter). Conversely, it can be strong (can hold high loads) but flexible (not stiff).

Key Takeaway: Material selection is a balancing act. It requires meeting essential functional properties while optimizing cost, aesthetics, and environmental factors.

Section 3: The Production Journey – From Resource to Material

Before materials arrive at the factory floor, they undergo significant transformation through extraction and refining processes. This is where the raw material becomes an engineered material.

3.1 Processing Metals (Metallurgy)

Most metals exist in the earth as ores (chemical compounds mixed with rock).

Step 1: Mining and Extraction
Ores are dug up and crushed.

Step 2: Refining (Smelting)
The ore is heated in a furnace (often with coke/carbon) to extremely high temperatures. This chemical process separates the pure metal from the oxide. This is energy-intensive.

Step 3: Alloying
Once refined, the pure metal is often mixed with other metals or elements (e.g., adding carbon to iron to make steel) while molten, improving its properties for specific uses.

Did you know? Recycling aluminium requires about 95% less energy than extracting virgin aluminium from bauxite ore. This massive energy saving makes material recycling a crucial DT concept.

3.2 Processing Polymers (The Oil Route)

Polymers are derived from crude oil, a fossil fuel, making their production complex and finite.

Step 1: Fractional Distillation of Crude Oil
Crude oil is heated, and various components (fractions) are separated based on their boiling points. The fraction used for plastics is naphtha.

Step 2: Cracking
Naphtha is heated further to break down the large hydrocarbon molecules into smaller molecules called monomers (the building blocks of plastics).

Step 3: Polymerization
Monomers are linked together chemically under heat and pressure to form long chains called polymers (plastics). This is when a designer specifies which additives are needed (e.g., UV inhibitors, colourants).

Analogy: Think of polymerization like LEGOs. Monomers are the individual bricks, and polymerization is clicking them all together to make a long chain (the polymer).

3.3 Processing Timbers (Seasoning)

Wood is a natural, organic material that contains a lot of moisture when first cut (called ‘green’ wood).

Felling and Conversion: Trees are cut down and then sawn into usable planks or boards.

Seasoning (Drying): This is the most critical step. Wood must be dried to remove excess moisture and stabilize its internal structure. If wood is not seasoned, it will warp, shrink, and split as it dries naturally in the product.

  • Air Seasoning: Stacking wood outdoors, protected from rain, allowing natural slow drying. Takes months/years.
  • Kiln Seasoning: Placing wood in large, heated ovens (kilns) to dry rapidly under controlled conditions. Faster, but more expensive and energy-intensive.

Key Takeaway: The processes of extraction and refinement are crucial because they determine the material's purity, cost, and initial environmental footprint (embodied energy).

Section 4: Standard Stock Forms

Once materials are processed, they are sold to manufacturers in efficient, predictable shapes and sizes called stock forms. Using stock forms saves manufacturing time, reduces material waste, and standardizes production across the industry.

4.1 Common Stock Forms

A material can be purchased in many forms, depending on the manufacturing process required:

  • Sheets/Plates: Large, flat rectangular sections. Used for body panels, packaging, cladding. Thickness is usually the defining dimension. (e.g., steel sheet metal, plywood, acrylic sheets).
  • Rods/Bars: Solid, long cylindrical or rectangular sections. Used for axles, shafts, structural supports, or materials that will be turned on a lathe.
  • Tubes/Pipes: Hollow cylindrical sections. Used for fluid transport (pipes) or lightweight rigid structural frames (bicycle frames).
  • Sections: Extruded or rolled forms with specific cross-sections (e.g., L-shaped angle iron, T-section beams, I-beams, U-channels). These provide high strength for their weight.
  • Granules/Pellets: Small beads of polymer material, sold in large sacks for processes like injection moulding or extrusion.
  • Powders: Finely ground material (metals, polymers, ceramics) used in sintering, 3D printing, or coating processes.

4.2 Why Standard Stock Forms are Essential

Standardization benefits the designer and the manufacturer in several ways:

  • Cost Efficiency: Buying standard sizes is cheaper than ordering bespoke material sizes.
  • Time Saving: Materials are ready to use immediately, minimizing pre-preparation.
  • Interchangeability: If a designer specifies a standard I-beam size, any supplier can provide it, ensuring consistency.
  • Process Suitability: Specific stock forms (like pellets for injection moulding) are necessary for certain manufacturing techniques.

Key Takeaway: Stock forms are the standardized, pre-prepared building blocks of manufacturing, streamlining the process from raw material to final component.


Quick Review Box: Material Vocabulary Check

Metals: Ferrous (contains iron) vs. Non-ferrous (no iron).

Polymers: Thermoplastics (can be reheated) vs. Thermosets (cured, permanent).

Strength: Resists breaking/deformation.

Toughness: Resists fracture under impact.

Ductility: Pulled into a wire.

Malleability: Pressed into a sheet.