Selecting materials
Choosing the right material is half of the design. Each material has a set of mechanical, thermal and electrical properties that make it ideal for one part and unsuitable for another: what holds a hammer together cannot insulate a cable, and vice versa.
The properties of materials
Each property justifies a technical decision: why the handle is made of one material and the blade of another.
Define in your own words and give an example of each of these material properties: hardness, electrical conductivity, and density.
Define in your own words and give an example of each of these material properties: hardness, electrical conductivity, and density.
Explain the difference between a mechanical property (such as hardness or elasticity) and a thermal or electrical property (such as conductivity), with an example of…
Explain the difference between a mechanical property (such as hardness or elasticity) and a thermal or electrical property (such as conductivity), with an example of each type.
State whether these statements are true or false and correct the false ones: (a) all metals are attracted to a magnet, (b) glass is an electrical insulator, (c) dry wood…
State whether these statements are true or false and correct the false ones: (a) all metals are attracted to a magnet, (b) glass is an electrical insulator, (c) dry wood conducts electricity well.
Choosing a material by comparing properties
Each object requires a different combination of properties, and the material is selected by comparing the alternatives quantitatively.
To build a garden bench that will always be outdoors, compare wood and steel across at least three relevant properties and decide which you would choose, justifying your…
To build a garden bench that will always be outdoors, compare wood and steel across at least three relevant properties and decide which you would choose, justifying your decision.
The graph compares the density of three workshop materials. For a school drone frame, it needs to be as lightweight as possible while remaining rigid. Using the data in…
The graph compares the density of three workshop materials. For a school drone frame, it needs to be as lightweight as possible while remaining rigid. Using the data in the graph, explain which material you would choose and what other property you would check before deciding.
The handles of pots and frying pans are made of plastic or wood, never the same metal as the body. Explain this design decision using at least two material properties.
The handles of pots and frying pans are made of plastic or wood, never the same metal as the body. Explain this design decision using at least two material properties.
Composite materials
When no single material meets all the requirements, the technical solution is to combine two to add together their strengths.
The handle of a screwdriver combines hard plastic with rubberised areas. Explain what properties each material provides and why the handle is not made entirely of steel…
The handle of a screwdriver combines hard plastic with rubberised areas. Explain what properties each material provides and why the handle is not made entirely of steel like the shaft.
A team chooses aluminium for an outdoor structure 'because it does not rust'. Qualify this statement: what actually happens to aluminium when exposed to air and why that…
A team chooses aluminium for an outdoor structure 'because it does not rust'. Qualify this statement: what actually happens to aluminium when exposed to air and why that ultimately protects it.
Investigate what Corten steel is and why it is used in unpainted outdoor sculptures. Relate it to the idea of a "protective layer" and compare it with the solution of…
Investigate what Corten steel is and why it is used in unpainted outdoor sculptures. Relate it to the idea of a "protective layer" and compare it with the solution of painting steel every few years.
Deciding with technical criteria and multimaterial design
Choosing a material from among several valid options requires comparing quantifiable properties and explicitly recognising which disadvantage is being accepted.
A material must be chosen for a reusable bottle for a school bag. Evaluate stainless steel, plastic, and glass based on weight, impact resistance, hygiene, and cost;…
A material must be chosen for a reusable bottle for a school bag. Evaluate stainless steel, plastic, and glass based on weight, impact resistance, hygiene, and cost; choose one and justify your decision, acknowledging which disadvantages you accept.
A yoghurt pot combines several materials (plastic pot, aluminium lid, label). Analyse why the use of multiple materials complicates its recycling and propose a redesign…
A yoghurt pot combines several materials (plastic pot, aluminium lid, label). Analyse why the use of multiple materials complicates its recycling and propose a redesign that avoids it.
Evaluate the "bioplastic versus recycled plastic" dilemma for manufacturing a bottle: raw material origin, degradation and recyclability. Defend one option while…
Evaluate the "bioplastic versus recycled plastic" dilemma for manufacturing a bottle: raw material origin, degradation and recyclability. Defend one option while acknowledging its weaknesses.
Back to the beginning: A hammer requires surface hardness and toughness to strike without breaking, whereas insulating a cable requires polymers with zero electrical conductivity and great flexibility; no single property can satisfy both functions at the same time.