2. Materials, their Properties & Uses Introduction to Materials Properties of Materials Metals Plastics Woods Composites Heat Treatment

3. Introduction to Materials Materials are used to make or build objects. During the past 200 years there has been an enormous increase in the range of materials available to us. It is therefore important that the correct materials be used for a particular use. In Selecting the best material you need to look at 4 things: Physical properties, Cost and Time, Shaping and Forming and Availability.

4. Selecting the best material – A checklist 2 WHAT COST? The materials The extras (fittings etc) 3 SHAPING & FORMING Cutting out Moulding Casting Joining 4 AVAILABILITY Are they easy to obtain including fittings. 1 PHYSICAL PROPERTIES Hardness Tensile Strength Compressive Strength Shear Strength Stiffness Toughness Malleable Corrosive Appearance Weight Conductivity SELECTIONSELECTION

5. Properties of Materials Each material has many properties. It is incorrect, for example to describe a material as just ‘strong’ or ‘weak’ as for example concrete is strong in compression but weak in tension. HardnessToughness HardnessToughness StrengthStrength BrittlenessMalleabilityDuctility ElasticityPlasticityConductivity DensityFatigueStiffness

6. Hardness The ability of a material to resist wear indentation and scratching. An example of a hardness test that can be carried out in the lab. Different materials are used and the depth of indentation measured

7. Toughness The ability of a material to withstand blows or sudden impact. Different materials are used, the hammer is swung from the same height each time about a fixed fulcrum. The distance travelled after impact or fracture is used to find toughness

8. Strength The ability of a material to withstand forces of tension, compression and torsion Tensile Strength – the ability to withstand pulling forces or Tension forces Compressive Strength – the ability to withstand ‘squeezing’ forces or Compression forces Torsional Strength – the ability to withstand ‘twisting’ forces or Torsion forces

9. Brittleness The same as the toughness test however those materials that fracture easily are said to be brittle. A material that is easily fractured by impact is said to be brittle e.g. Glass

10. Malleability A material that can be rolled or hammered into shape without rupture. As ring rises the side of Coke can is thinned out

11. Ductility A material that can be pulled or stretched into a thin wire or thread.

12. Elasticity The ability of a material to return to its original shape after deformation.

13. Plasticity The ability of a material to be permanently deformed without fracture..

14. Conductivity The ability of a material to allow Heat or electricity to flow through it. Ball Bearing drops from most conductive 1 st.

15. Density Is the mass of 1 cubic centimetre (cm 3 ) of a substance. (Mass per unit Volume) Q.Which is heavier a tonne of feathers or a tonne of lead? Q. Which has the greatest density? Density = Mass Volume

16. Fatigue Occurs when materials have become overworked and fracture or fail.

17. Stiffness The ability of a material to resist bending deformation.