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IB Design Technology
SL · Lesson 38 · Material Selection
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Lesson 38 · Unit 5

Material Selection

Justify a material choice by connecting performance, aesthetics, context and research—not by naming a favourite material.

80 minutesB3.1.1–B3.1.4
Guiding question: How can a designer defend a material choice when every option involves trade-offs?01
Today’s destination

By the end of class, you should be able to…

01

Select by properties

Match physical, chemical and mechanical behaviour to application.

02

Select by aesthetics

Consider texture, form, colour and finishing.

03

Balance context

Include cost, availability and sustainability.

04

Justify with research

Use primary and secondary evidence to defend the choice.

Success check: Explain the concept accurately, then use it to make a justified design decision.
B3.1 · material selection as evidence-based design02
ComponentWhat part are you selecting for?
FunctionWhat must it do?
EnvironmentHeat? moisture? chemicals? forces?
CriteriaWhich properties/aesthetics/context factors matter?
EvidenceWhich research shows the best fit?
Selection starts from the component’s job03

Physical

Density, conductivity, expansion, melting point, etc.

Chemical

Corrosion resistance, reactivity, hygroscopy, flammability.

Mechanical

Strength, stiffness, toughness, hardness, elasticity, ductility, etc.

Use only relevant properties. A long list is weaker than a small set tied directly to the application.
B3.1.1 · relevant properties04
Beyond performance

Texture

Tactile quality, grip, comfort, perceived warmth/precision, surface language.

Form

Can the material/finish support the intended geometry, thinness, transparency or visual mass?

Colour

Natural colour, pigmentation, coating and long-term colour stability can influence perception/usability.

B3.1.2 · texture · form · colour05

Same base material

Raw / brushed / polished / coated / textured finishes can change visual and tactile characteristics.

→

Design consequence

Aesthetic selection includes the material + finishing strategy, not only the base material name.

B3.1.2 · aesthetics can be enhanced by finishing06

Cost

Material price, waste, finishing and processing may affect feasibility.

Availability

Regional supply, standard stock forms, lead time and replacement access matter.

Sustainability

Source, embodied impacts, durability, recovery and end-of-life can alter the decision.

B3.1.3 · cost · availability · sustainability07

Outdoor seat shell

Option A is lightweight and low cost but fades outdoors. Option B is durable and colour-stable but more expensive. Option C is recycled and repairable but harder to source locally.

Design task: define which criteria are essential, then justify the compromise rather than searching for a mythical “perfect material.”

Appropriate ≠ perfect08
Primary research

Generate evidence yourself

1
Prototype/material test
2
User perception test
3
Supplier/manufacturer interview
4
Direct measurement/observation
+
Secondary research

Use credible existing evidence

1
Material datasheet
2
Standards / technical documentation
3
Academic/industry source
4
Supplier data with critical evaluation
B3.1.4 · justify through research09
CriterionWeightMaterial AMaterial BEvidence
Low mass353Density data
Wet grip525User/prototype test
Cost253Supplier quote
A matrix can support a choice, but weights and scores need justification. Do not hide subjective assumptions behind arithmetic.
Use structured comparison carefully10
Choose the stronger justification

Which sentence better supports a material choice?

Justification = requirement + behaviour + evidence11
Before naming the material
1
Define the component and application.
2
Identify only the relevant physical, chemical and mechanical properties.
3
Add aesthetic characteristics: texture, form, colour, finish.
4
Consider cost, availability and sustainability.
5
Gather primary/secondary evidence.
6
Explain the trade-off and justify the final choice.
This same reasoning transfers directly into your IA annotations and later solution development.
B3.1.1–4 · complete selection chain12
What three aesthetic characteristics are named in B3.1.2?
Texture, form and colour; they can also be enhanced through finishing techniques.
What three additional contextual factors are named in B3.1.3?
Cost, availability and sustainability.
Why should material choice be justified with both primary and secondary research when appropriate?
They can provide complementary evidence: real contextual/user/testing evidence plus technical performance information from credible sources.
B3.1 · retrieve the complete framework13
Exit ticket

Before you leave…

1. Name the most important property for one component in your IA product.
2. Identify one aesthetic requirement that could change the material choice.
3. Name one research source or test that could justify your choice.
Next lesson

IA Day 11 — Material Decisions for the Redesign

Keep the evidence chain moving: user → research → decision → test.

Curriculum alignment
B3.1.1 select materials from physical, chemical and mechanical properties. B3.1.2 aesthetic characteristics: texture, form, colour, enhanced by finishing techniques. B3.1.3 additional factors: cost, availability, sustainability. B3.1.4 justify selection through appropriate primary and secondary research.
Lesson complete14 slides
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IB Design Technology SL · Lesson 3814