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This lesson defines and explains the key physical and working properties of materials. Understanding these properties is essential for material selection in both the exam and NEA for AQA GCSE Design and Technology (8552), Section 3.1.6.
Designers select materials based on their properties — the characteristics that determine how a material behaves under different conditions. Choosing the wrong material leads to product failure.
The AQA specification requires you to understand two categories:
Hardness is the ability of a material to resist scratching, indentation or abrasion on its surface.
| Hard Material | Soft Material |
|---|---|
| Diamond (hardest natural material) | Balsa wood |
| High-speed steel (HSS) | Lead |
| Stainless steel | Copper |
| Acrylic | Polypropylene |
Relevance: A hard material is needed for cutting tools (HSS drill bit), worktops (melamine), and floor tiles (ceramic). Hardness is tested using the Mohs scale, Brinell test or Vickers test.
Toughness is the ability of a material to absorb energy and resist fracture when subjected to impact or shock loading. A tough material will bend or deform rather than shatter.
| Tough Material | Brittle Material (not tough) |
|---|---|
| Mild steel | Cast iron |
| ABS plastic | Acrylic |
| Copper | Glass |
| Nylon | Urea formaldehyde |
Relevance: Toughness is essential for products that may be dropped or subjected to impacts — e.g. ABS for a power tool casing, mild steel for a car body.
AQA Exam Tip: Do NOT confuse hardness and toughness. They are different properties. A material can be hard but not tough (e.g. glass is hard but shatters easily — it is brittle). A material can be tough but not hard (e.g. rubber absorbs impacts but is easily scratched). This distinction is tested frequently.
Malleability is the ability of a material to be permanently deformed (shaped) by compression (pressing, hammering, rolling) without cracking or fracturing.
| Malleable Material | Less Malleable |
|---|---|
| Gold (most malleable metal) | Cast iron |
| Copper | High-speed steel |
| Aluminium | Acrylic |
| Mild steel | MDF |
Relevance: Malleable materials are needed for products that are formed by pressing, stamping or hammering — e.g. car body panels (mild steel), jewellery (gold, silver), kitchen foil (aluminium).
Ductility is the ability of a material to be drawn (stretched) into a wire or thin shape without breaking.
| Ductile Material | Less Ductile |
|---|---|
| Copper | Cast iron |
| Gold | Concrete |
| Mild steel | Acrylic |
| Aluminium | MDF |
Relevance: Ductile materials are essential for products made by drawing — e.g. copper wire (electrical cables), gold wire (jewellery), steel wire (springs, paper clips).
Elasticity is the ability of a material to return to its original shape after a deforming force is removed. The elastic limit is the point beyond which the material deforms permanently.
| Elastic Material | Less Elastic |
|---|---|
| Rubber | Glass |
| Spring steel | Concrete |
| Elastane (Lycra) | Cast iron |
| Nitinol (SMA) | MDF |
Relevance: Elasticity is needed for springs, rubber bands, sportswear (elastane), and SMA spectacle frames.
| Type | Definition | Example |
|---|---|---|
| Tensile strength | Resistance to being pulled apart (stretched) | Steel cables, climbing ropes, Kevlar |
| Compressive strength | Resistance to being crushed (compressed) | Concrete, cast iron, brick |
| Shear strength | Resistance to forces acting in opposite parallel directions (sliding) | Rivets, bolts, adhesive joints |
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