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T. Ford. June 2007. GENERIC
Design Technology.
International Baccalaureate Organization (IBO)
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Topic 4 – Materials.
Name: TG:
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Contents:
Introduction and internal assessment. Page 3.
□ 1. Introducing and classifying materials. Page 4.
□ 2. More knowledge and understanding. Page 4
□ 3. Re-thinking how we classify materials. Page 5
□ 4. Properties of materials. Physical properties, mechanical properties and aesthetic properties. Page 5.
□ 5. Aesthetic properties. Page 6.
□ 6. Timber. Page 7.
□ 7. Comparing particle board, plywood, pine and mahogany. Page 8
□ 8. Which timber for which product? Page 9
□ 9. Metals. Page 9.
□ 10. Solidification of a substance. Page 9.
□ 11. Modification of grain size. Page 10.
□ 12. Heat treatment of metal. Page 11
□ 13. Plastic Deformation and Alloys. Page 11.
□ 14. The ‘superalloys’. Page 12.
□ 15. Plastics. Page 12.
□ 16. Ceramics. Page 15
□ 17. Composites. Page 16
□ 18. Smart Materials. Page 17
□ Checklist. Page 18.
Students please note:
Tick each section as you go. Use the checklist at the end to make sure you have learned the unit. Your
teacher may not necessarily cover each stage in this order and some stages take longer than others to
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learn. You are expected to keep your own folder of notes and portfolio of work related to this unit which you
must bring to every lesson. This booklet is designed as a guide only – studying is where the learning takes
place! Bring this booklet with you to every lesson.
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Introduction.
In this unit, you will be learning about a broad range of materials, focusing especially on their properties
and uses. You will also be carrying out an internal assessment (project) which will assess your Research
skills.
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Your internal assessment must be handed in by the end of term 1; your teacher will give a deadline. Write
it here:
…………………………………………………………………………………………………………………………………………………………
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□ 1. Introducing and classifying materials.
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Resources needed:
Product samples, category cards (technician).
You will be given a range of products made from a range of materials. Don’t worry if you are unsure of what
the product is or what it is made from. Carry out the following tasks:
Try to group or classify the products using a system of your choice. Be prepared to defend your grouping
and record your ideas.
Your teacher will then ask you to re-group the objects using new sets of criteria. Again, be prepared to
defend your grouping and record your ideas.
Discussion points:
•What have you learned about the ways in which products and materials can be classified?
•In what circumstances is this useful?
•When might it be problematic?
□ 2. More knowledge and understanding.
Resources needed:
Powerpoint: Resources\Material bonding Powerpoint.ppt
Web:
An atom is the smallest part into which an element can be chemically divided. All atoms have the same
basic structure but they vary in size and mass. Each atom has a positively charged nucleus at its centre
containing positively charged protons and neutrons which together make up 99% of the atom. Electrons
orbit around the nucleus. The number of electrons defines what element the atom is. For example,
hydrogen has one electron and oxygen has eight.
When two or more atoms join together, they form a molecule. Hydrogen and oxygen combine to make
water. Water is a compound because it is made up from two elements which are joined.
When two or more materials are combined, one of which is a
metal, an alloy is formed. The properties of each element are still present in the alloy. For
example, solder is an alloy of lead and tin. Lead has a relatively low melting point making it easy to use
with electronic circuits. However, lead is very soft so the tin is added to make it harder and more durable.
Task 1:
Use Focus on Design & Technology Resistant Materials 2. Find 3 other metal alloys. Summarize their
properties and uses.
Composites are made by bonding two or more materials. It is possible to make many composites with
enhanced properties. For example, a milk carton is a composite of card and polyethylene. The card
makes the carton rigid and the polyethylene makes it waterproof.
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Task 2: Divide your group into 4 teams. Log on to:
Each team needs to find out about one of the following composite products: Mud bricks, car tyres,
concreteand fiberglass. Spend around 5 minutes on this. Present your information to the rest of the
group explaining how the properties of the composite are suited to its use.
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Atoms become joined or bonded when they are attracted to each other. There are three types of bonding to
be aware of: Ionic, Covalentand Metallic.Watch the following PowerPoint presentation.
Material bonding Powerpoint.ppt
In your notes, summarize ionic, covalent and metallic bonding.
□ 3. Re-thinking how we classify materials.
Resources needed:
Product samples, category cards (technician).
Go back to your products. Now classify them according to the following material groups: Timber, metal,
plastic, ceramic, composite, food, textiles.See if you can sub-divide each group as follows:
•Natural timber & man-made timber
•Ferrous metals & non-ferrous metals
•Thermo plastics & thermosetting plastics
•Earthenware, porcelain, stoneware, glass
•Natural fibre, synthetic fibre.
□4. Properties of materials: Physical properties, mechanical properties and aesthetic
properties.
Resources needed:
Resistant Materials Technology pages 20 and 21.
Video: Tacoma Narrows bridge collapse (video tape – see technician)
Web:
***Teacher’s note*** see Guide notes page 58 to help guide students with task. Save students’ work for reference next year.
Materials behave in different ways under different conditions. These types of behaviour are called material
properties. We need to be very careful to describe material properties accurately. Discuss the following
question:
Is glass a strong material?
(Think about the different functions that glass has, its various applications and different types).
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Have a look at the following link to help:
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Hopefully, you realize that the word strong does not adequately describe glass; glass can be very brittle (it
shatters easily) but it is also very hard (difficult to scratch). Some types of glass like Pyrex® are good
thermal conductors (absorb heat well) which makes them good for cooking food in. Other types of glass
are poor thermal conductors and will shatter easily if they are heated because they cannot absorb the heat
rapidly.
We also need to remember that materials have properties that we can’t always observe. For example,
concrete and steel have elastic properties just like rubber – it can bend and return to its original shape
provided it is not forced beyond its elastic limit. We don’t notice this most of the time but….
Video: Tacoma Narrows Bridge Collapse
Watch the Tacoma Narrows bridge collapse. Can you work out what factor/s caused the bridge to behave in
this way?
In groups, define the following physical properties and identify a design context or situation in which one of
the above properties is an important consideration. Present your group’s work as a PowerPoint slide
•Density
•Electrical resistivity
•Thermal conductivity
•Thermal expansion
•Hardness
•Tensile strength
•Stiffness
•Toughness
•Ductility
□5. Aesthetic properties:
Resources needed:
Video: Design 4 life 01 Super Modern Wardrobe – Fashion Design
Video: Design 4 life 02 The Colour of Emotion - the importance of colour & light
‘Aesthetics’ is a hard word to define but put very simply, aesthetics are the properties that products have
that make them appealing or unattractive to us. Aesthetic properties depend completely on your own
personal point of view – this means they are subjective.Your tastes depend as much on your moodas
they do on your beliefsand values.
For example; you probably have a favourite food, like a particular type of music, enjoy wearing certain
styles of clothing which are unique to you. Your aesthetic tastes are personal and no-one can say if they are
right or wrong. Sometimes though, large groups of people or ‘target market’ like similar things, so a
company can design a product to meet the aesthetic demands of that group.
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However, our aesthetic demands are constantly changing so products must also adapt to meet those
changing demands.
Have a look at the following video:
Design 4 life 01 Super Modern Wardrobe – Fashion Design
(You can access this video at any time from the CLC – log in, go to ‘Technology’ and click on ‘Technology
Video Library’)
You should also watch the following video (this might be set as a homework task):
Design 4 life 02 The Colour of Emotion - the importance of colour & light
In groups, define the following aesthetic characteristics and identify a design context or situation in which
one of the above properties is an important consideration. Present your group’s work as a PowerPoint slide
•Taste
•Smell
•Appearance
•Texture
•Colour
□6. Timber.
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Resources needed:
Design and Technology (Caborn, Mould & Cave) pages 309-311
Resistant Materials Technology pages 72 - 75.
Labeled veneer and timber samples: Technician.
Video: Isokon Long Chair
Web:
***Teacher’s note***: see syllabus notes page 59 to help guide students with task. Save students’ work for reference next year.
Natural timber is timber that is used directly from the tree. It is actually a type of composite material
because it is made up of cellulose (wood fibres) held together with a natural adhesive (lignin). Read
Design and Technology (Caborn, Mould & Cave) pages 309-311.
Study the sample of veneer closely. You will see that it is stronger in one direction than the other. How can
you explain this difference? Try to use the material property definitions that you have learned.
The following video shows the manufacture of a chair using veneers layered together with glue to form a
new composite material (plywood). As you watch the video, make a note of the materials and processes
that are used in the chair’s manufacture.
Isokon Long Chair
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Answer the following questions (you may want to break into groups and take a question each then feed
back to the whole group).
1.What properties does plywood have that veneer (natural timber) does not?
2.What manufacturing methods were used that ensured quality control?
3.What parts of the manufacturing process were carried out by hand?
4.What parts of the manufacturing process were carried out by using machinery?
5.How would you describe the scale of production of this chair?
6.What design features of the chair have been made possible by using laminated veneers instead of
natural timber?
Take a look at the following link:
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In groups, answer the following questions. Use a combination of web-based and textbook material. Present
your groups work as a PowerPoint slide
•Explain the difference between temperate and tropical climates.
•Give a general description of the geographical locations of world timber sources.
•Explain the characteristics of softwood trees
•Explain the characteristics of hardwood trees
•Explain how dry rot and wet rot are identified and treated
•Explain how woodworm infestation is identified and treated
•Outline ways in which timber can be preserved
□7. Comparing particle board, plywood, pine and mahogany.
Resources needed:
Testing timber samples of particle board, plywood, pine and mahogany: Technician.
Workshop for testing materials.
You will be given a sample of each material. Use the samples to make observational comparisons between
each material. Here are the categories that you need to use:
•Composition (show the structure of the material as a hand-drawn cross-sectional view)
•Grain
•Colour
•Texture
Now carry out some comparative testing to add to your sheet. In groups, devise and carry out a test to
compare the following properties of each material:
•Hardness
•Tensile strength
•Resistance to dampness
•Longevity
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For example; hardness is the ability of a material to withstand scratching. Can you design and make a
simple test rig that will provide a comparison of each material’s hardness?
Take digital photographs of your test rig and testing procedure. Present this with your sketches above on
NO MORE THAN 2 sides of A3 paper.
□ 8. Which timber for which product?
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Resources needed:
Spreadsheet: Resources\Criteria for timber selection.xls
Use the resources you have already examined to complete the above spreadsheet. You need to do the
following:
1.Write down the criteria that you would use to select an appropriate timber for each product.
2.Suggest an ideal timber and two alternatives that would meet these selection criteria.
□ 9. Metals
Resources needed:
Resistant Materials Technology pages 66 and 67.
Powerpoint: Heat treatment of Metals Powerpoint.ppt
***Teacher’s notes***: see syl abus notes page 60 to help guide students with task. Save students’ work for reference next year.
Draw and describe metallic bonding (use the PowerPoint presentation to find the answer)
Heat treatment of Metals Powerpoint.ppt
You will have noticed that metals have plenty of freeelectrons. This is why they are such good electrical
and thermalconductors; energy can easily be transferred from one atom to the next by the free
electrons.
□10. Solidification of a substance.
This is how liquid metals solidify when they cool:
•Minute nuclei (crystals) of a solid form when a pure, molten metal is cooled to just below its
freezing temperature. Impurities in the molten material provide the centre for growth for the
nuclei.
•All metals (except mercury) are solid at room temperature.
•A process of nucleation & growth achieves solidification.
•‘Dendrites’ grow out from the nuclei forming a tree-like structure in the direction of the
fastest heat loss.
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The atoms arrange themselves in a regular pattern or lattice structure. Most metals form one of
three types of lattice structure (see text book pages 66 and 67). Draw the following:
1.Close packed hexagonal (CPH)
2.Face-centred cubic (FCC)
3.Body-centred cubic (BCC)
•This crystallinestructure gives metals their properties (strength, stiffness, ductility,
conductivity & toughness).
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•Eachdendrite grows in ageometricpattern consistent with the lattice structure until each one
touches its neighbour. At this point the dendrites begin to thicken to form a totally solid grain of metal.
•The grain boundaries between are visible under a microscope, each grain having the same structure
but a different orientation. This boundary is a narrow zone (perhaps three atoms) in which the atoms are
not properly spaced according to the lattice structure.
□11. Modification of grain size
Resources needed:
Video: 01 Story of Steel.mpg
02 Making Steel.mpg
03 Shaping Steel.mpg
04 Using Steel.mpg
05 A Canny Design.mpg
The rate of cooling and the amount of impurities in the molten metal will affect grain size:
1.Gradual cooling - a fewnuclei are formed - largegrain size
2.Rapid cooling - manynuclei formed - small grain size.
3.Reheating a solid metal / alloy allows the grain structure to re-align itself.
4.Directionalcooling in a structure is achieved by selectivelycoolingone area of a solid.
5.The effect of impurities (or additives) in a molten metal can induce a largenumberof fine
grains that will give a stronger and harder metal. This addition must be carefully control ed as too
many impurities may cause an accumulation at the grain boundaries, which will weaken the material.
The following videos are each about 20 minutes long. Watch them to help put this knowledge into
context. These may be set as homework tasks:
01 Story of Steel.mpg
02 Making Steel.mpg
03 Shaping Steel.mpg
04 Using Steel.mpg
05 A Canny Design.mpg
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□12. Heat treatment of metal.
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Resources needed:
Resistant Materials Technology pages 80 and 81.
Metal samples for heat treatment, workshop (technician)
Read and summarise the information on ‘Mechanical Properties’ and ‘Heat Treatment and Work
Hardening’ on pages 80 and 81.
Workshop demonstration and task: This will teach you the following processes: Hardening,
tempering, normalising, planishing, annealingand case-hardening.
In the workshop you will be provided with the materials to conduct these experiments:
1.Harden then temper a piece of mild carbon steel to the level required for a punch.
2.Hammer a piece of mild carbon steel then try filing it. ‘Normalise’ the steel then file again and
note any difference in the resistance experienced.
3.Planish a piece of copper until it work hardens. Anneal the copper then test to see how soft it has
become.
4.File piece mild steel and note the resistance. Case harden the same sample then repeat filing
and note the difference in resistance.
5.Anneal a piece of aluminium then file it. Leave for 5 days and repeat the filing. Note any
differences.
Summary: Reheating a solid metal or alloy allows material to diffuse between neighbouring grains and the
grain structure to change. Slow cooling allows larger grains to form; rapid cooling produces smaller grains.
□13. Plastic Deformation and Alloys
Resources needed:
Resistant Materials Technology pages 66 and 68.
Plastic deformation occurs when a force permanently deforms a material even after the force is removed. If
you bend a paper clip a little, it will spring back to its original position. However, if you bend it too far (beyond