DT paper 1

• Materials and their applications

  Different materials work in different ways, and designers and manufacturers must know about material properties to make sure the product is a success
• Selecting the best material


  • Compromise of factors such as aesthetics, cost and manufacturing method as well as disposal and reuse
  • Product function and the materials properties are the most influential factors
• Mechanical properties of materials

  • Compressive strength
  • Tensile strength
  • Bending strength
  • Shear strength
  • Torsional strength
  • Hardness
  • Toughness
  • Plasticity
  • Ductility
  • Malleability
  • Elasticity
• Compressive strength


  The ability to withstand being crushed or shortened by pushing forces
• Tensile strength


  The ability to resist stretching or pulling forces
• Bending strength


  The ability to resist forces that may bend the material
• Shear strength


  The ability to resist sliding forces on a parallel plane
• Torsional strength


  The ability to withstand twisting forces from applied torque or torsion
• Hardness


  The ability to resist abrasive wear such as scratching, surface indentation or cutting
• Toughness


  The ability to absorb impact force without fracture
• Plasticity


  The ability to be permanently deformed (shaped) and retain the deformed shape
• Ductility


  The ability to be drawn out under tension, reducing the cross-sectional area without cracking
• Malleability


  The ability to withstand deformation by compression without cracking, which increases with a rise in temperature
• Elasticity


  The ability to be deformed and then return to the original shape when the force is removed
• Physical properties of materials

  • Density
  • Fusibility
  • Magnetism
  • Corrosion/degradation resistance
• Density


  The mass of the material in a standard volume of space
• Fusibility


  The ability of the material to be fused or converted from a solid to a liquid or molten state, usually by heat
• Magnetism


  The natural force between objects that causes the material to attract iron or steel
• Corrosion/degradation resistance


  The ability of the material to withstand environmental attack and decay
• Electrical properties


  • Electrical conductor
  • Electrical insulator
• Electrical conductor


  Allows the flow of electrical current through the material, giving very little resistance to the flow of charge
• Electrical insulator


  Does not allow the flow of electricity through the material
• Thermal properties


  • Thermal conductor
  • Thermal insulator
  • Thermal expansion
• Thermal conductor


  Allows the transfer of heat energy through the material, enabling quick transfer of heat
• Thermal insulator


  Prevents the transfer of heat through the material
• Thermal expansion


  The increase in material volume in response to a heat input
• Optical properties


  • Opaque
  • Translucent
  • Transparent
• Opaque


  Prevents light from traveling through
• Translucent


  Allows light through but diffuses the light so that objects appear blurred
• Transparent


  Allows light to pass through easily, which means you can see clearly through the material
• Don't make unjustified statements using generic terms such as 'strong'
• Classification of materials


  • Metals
  • Woods
  • Polymers
  • Papers and boards
  • Composites
  • Smart materials
  • Modern materials
• Metals


  Ferrous metals: Magnetic, contain iron and carbon (e.g. low carbon steel, medium carbon steel, cast iron)

  Non-ferrous metals: Not magnetic, do not contain iron (e.g. aluminium, copper, zinc, gold, silver)
• Alloy


  A metal made of two or more metals, or combining two or more elements, one of which may be a metal
• Hardwood


  Wood from broad-leafed (deciduous) trees, generally slow growing and lose leaves in autumn (e.g. oak, ash, mahogany, teak, birch, beech)
• Softwood


  Wood from coniferous (cone bearing) trees, generally fast growing and tend to be evergreen (e.g. pine, spruce, Douglas fir, redwood, cedar, larch)
• Manufactured board


  Man-made wood-based composite material, available in much larger sizes than solid wood (e.g. plywood, marine plywood, aeroply, flexible plywood, chipboard, MDF)
• Thermoplastic


  Material which can be repeatedly reheated and reshaped, allowing it to be recycled after initial use (e.g. LDPE, HDPE, PP, HIPS, ABS, PMMA, PET, nylon, rigid and flexible PVC)
• Thermosetting polymer


  Material which when heated undergoes a chemical change whereby the molecules form rigid cross links, cannot be reheated and reshaped (e.g. urea formaldehyde, melamine formaldehyde, polyester resin, epoxy resin)
• Elastomer


  Material which at room temperature can be deformed under pressure and then upon release of the pressure, will return to its original shape (e.g. natural rubber, polybutadiene, neoprene, silicone)