The six material families

A-level Product Design groups materials into families you must be able to select and justify. Each family has a typical make-up, working properties and forms of supply.

• Papers & boards — cellulose-based sheet, sold by grammage (gsm).
• Timbers — natural hardwoods & softwoods, plus manufactured boards.
• Metals — ferrous, non-ferrous and alloys.
• Polymers — thermoplastics and thermosetting plastics.
• Textiles — natural, synthetic and blended fibres and fabrics.
• Composites & smart/modern materials — engineered for enhanced or responsive properties.

Selection thinking: examiners reward choices justified against function, aesthetics, cost, availability and environmental impact — never just naming a material.

Papers and boards

Paper and board are graded by grammage, the mass of one square metre in grams (gsm or g/m²). As a rough industry convention, sheet above about 200 gsm is described as board or card.

• Layout paper (~50 gsm) — thin, translucent, for quick design sketches.
• Cartridge paper (~120-150 gsm) — good quality drawing paper that takes paint and ink.
• Corrugated board — fluted core between two liners; strong, light packaging.
• Foam board — polystyrene foam faced with card; stiff and light for models.
• Solid white board / mount board — smooth, rigid, for high-quality printing and models.

Standard form matters: board is bought in standard sheet sizes, so nesting parts efficiently on a sheet reduces waste and cost.

Reading a manufactured board

Timbers: hardwoods, softwoods and boards

Natural timber is classified by the tree it comes from, not by how hard it feels.

• Hardwoods — from broadleaved (deciduous) trees, usually slow-growing and dearer: oak (strong, durable, its tannic acid corrodes steel fixings), ash (tough and flexible — tool handles, sports goods), beech (hard, close-grained — furniture, toys), mahogany (stable, attractive), balsa (very low density — modelling).
• Softwoods — from coniferous trees, faster-growing and cheaper: Scots pine (construction, joinery), spruce, cedar (naturally durable, aromatic).
• Manufactured boards — plywood (cross-banded veneers), MDF (fine fibres and resin; smooth, no grain, machines cleanly but heavy and produces hazardous dust), chipboard (resin-bonded chips; cheap, veneered for flat-pack furniture).

Enhancement: before use, timber is seasoned (air- or kiln-dried) to lower its moisture content, reducing later shrinkage, warping and fungal attack.

Hardwood or softwood?

Metals: ferrous, non-ferrous and alloys

Metals split into three groups you must know with examples:

• Ferrous (contain iron, magnetic, rust if unprotected): mild (low-carbon) steel (~0.15-0.30% carbon — tough, ductile, easily welded, cannot be hardened much by heat treatment); high-carbon steel (~0.6-1.4% carbon — hard, used for cutting tools); cast iron (brittle but strong in compression, self-lubricating).
• Non-ferrous (no iron): aluminium (low density, corrosion-resistant, good conductor), copper (excellent electrical/thermal conductor, ductile), zinc (galvanising), tin.
• Alloys (a metal mixed with other elements to improve properties): stainless steel (steel + at least ~10.5% chromium — resists corrosion), brass (copper + zinc), bronze (copper + tin), duralumin (aluminium alloy — strong yet light).

Why alloy? Pure metals are often too soft or corrode; alloying tailors hardness, strength and corrosion resistance for the job.

Sort the materials

Tap a material, then tap the family it belongs to.

Polymers: thermoplastic vs thermosetting

Polymers are long-chain molecules, usually from crude oil. The two classes behave very differently when heated.

• Thermoplastics soften every time they are heated, so they can be moulded and re-moulded (and recycled): HDPE, LDPE, PP (polypropylene), PVC, PS/HIPS, PMMA/acrylic, ABS, PET.
• Thermosetting polymers cure once — heat and/or a catalyst form permanent cross-links between chains, after which they cannot be melted again: epoxy resin, polyester resin, urea-formaldehyde (electrical fittings), melamine-formaldehyde (worktop laminates), phenol-formaldehyde (Bakelite).

Rule of thumb: if it can be re-melted it is a thermoplastic; if heating only chars it, it is a thermoset.

The thermoset difference

Composites

A composite combines two or more materials so the mixture out-performs each part alone — usually a strong reinforcement held in a matrix.

• GRP (glass-reinforced polyester) — glass fibres in cured resin; strong, light, waterproof (boat hulls, ponds).
• CFRP (carbon-fibre reinforced polymer) — very high strength-to-weight (bike frames, aircraft parts).
• Concrete — aggregate bound by cement; strong in compression, often steel-reinforced to add tensile strength.
• Kevlar (aramid) — high tensile strength for body armour.

Plywood and MDF are also composites — timber fibres/veneers bonded with adhesive.

Smart and modern materials

Smart materials change a property reversibly in response to their environment:

• Shape memory alloy (SMA, e.g. Nitinol, nickel-titanium) — returns to a pre-set shape when heated (glasses frames, stents).
• Thermochromic pigment — changes colour with temperature (kettles, mood spoons).
• Photochromic pigment — darkens in bright light (reactive lenses).
• Piezoelectric — generates a voltage when squeezed, and vice versa (sensors, igniters).

Modern materials are developed through new processes: graphene, metal foams, nanomaterials, Kevlar, breathable membranes (Gore-Tex) and biopolymers such as PLA (corn-starch based).

Which smart material?

Match the material to its stand-out property

Tap an item on the left, then its match on the right.

Your turn — grammage (gsm)

The big ideas to know

You have covered the full Materials topic — families, properties and justified selection.