IB Design Technology Topic B3.1.1: Material Selection Notes

Selecting a Material: No Winner on Every Axis

Four Filters, Applied in Order

1. A3.1 told you what materials are. This topic is about choosing one, which is a different and harder job.
2. Four filters narrow the field: properties, aesthetics, cost, availability and sustainability, and finally evidence.
3. No material passes all four cleanly. Selection is the management of that compromise, and a justification that pretends otherwise loses marks.

1. Selecting for Performance: The Properties

1. A material must first do the job. If it fails here, nothing else about it matters.
2. The three property families were defined in A3.1. Here you use them as a filter, asking what each one rules in or out:
   1. Physical properties: e.g. density, conductivity, thermal expansion
   2. Mechanical properties: e.g. strength, hardness, ductility
   3. Chemical properties: e.g. corrosion resistance, flammability, reactivity

2. Selecting for Look and Feel: The Aesthetics

1. A product that performs perfectly but nobody wants to own has still failed, which is why aesthetics is a selection criterion and not decoration.
2. The aesthetic characteristics themselves were covered in A3.1.3. At selection you are judging a material against them:
   1. Colour, texture, and form
   2. Light reflectivity (matte vs gloss)
   3. Finishing techniques (e.g. anodising, painting, polishing)
3. These choices impact brand identity and user experience, especially in consumer goods.

3. Selecting in the Real World: Cost, Availability, Sustainability

1. Even the best-performing, most beautiful material may not be practical.
2. Designers must weigh:
   1. Cost-effectiveness at the required scale
   2. Availability (local supply chains reduce carbon footprint)
   3. Sustainability (renewable or recyclable materials, ethical sourcing)

Cost

1. Initial Cost: The price of raw materials and processing.
2. Lifecycle Cost: Includes maintenance, repair, and disposal costs.

Example

Material: Mild Steel for a Bridge

• Initial Cost: cheap and easy to fabricate
• Lifecycle Cost: prone to rust and must be:
  • Regularly inspected
  • Frequently repainted (often every 15–20 years, or even more frequently in harsh environments)
  • Maintained with specialised coatings, which are labor-intensive and costly

Availability

1. Local Availability: Reduces transportation costs and environmental impact.
2. Global Availability: May offer a wider range of materials but can be affected by geopolitical factors and supply chain disruptions.