Modern and Smart Materials

Modern and Smart Materials

1. Modern

   • Fibre optics
     • transmit light as a digital signal (in pulses)
     • more data can be sent because each glass fibre in the cable can carry data
   • Liquid Crystal Displays (LCD)
     • allow light to pass through when aligned 'naturally''; when a small voltage is applied the path of the electron flow changes, blocking light
     • reflective or backlit
     • e.g. calculator displays, TV screens
   • Glulam
     • the laminating of large spans of timber for use in the construction industry
     • curved and arched beams are possible
     • good strength-to-weight ratio
     • manufactured by gluing timber of known quality together, end-gluing to make long lengths
     • uses offcuts - some environmental benefits
   • Kevlar
     • has 5x the strength-to-weight ratio of steel
     • fibres are woven together flat
     • used for bulletproof vests
     • Nomex (a deriavtive) protects against heat and is worn by racing drivers
   • Carbon fibre
     • made up of carbon woven into a cloth, impregnatted with resin to hold them together
     • very lightweight
     • high strength
     • often used in F1 racing and sports equipment
   • Polymorph
     • a low melt polymer (60˚c) which can be remoulded easily
   • Man made boards
     • Flexible MDF
       • thin grooves cut into the material, allowing it to bend
       • usually the grooves cannot be seen as they are inside
       • only able to bend at 90˚ to the grooves
     • Flexi ply
       • as with ordinary plywood, there is an odd number of layers - usually 3
       • two outer layers are open grained, and are much thicker than the core
       • direction of grain determines direction of curvature
       • expensive
       • used for aesthetics and on furnitiure
     • Aeroply
       • thin section of very high quality plywood
       • very lightweight, whilst retaining good strength
       • bendable, so is formed around a supporting framework
       • can be laser cut and steam bent
       • commonly used for jewellery and in the aircraft industry (not so much now)

2. Smart

   • Thermochromic pigments
     • Change colour in response to heat
   • Phosphorescent pigments
     • absorb light and then release the light energy over a period of time
     • e.g. emergency warning signs, 24hr clock faces
   • Shape memory alloys
     • e.g. nitinol wire
       • shrinks in length by 5% when an electrical current is passed through it
     • e.g. stent
       • bio-engineering - it shrinks when chilled, so when placed into a blocked/collapsed artery it returns to its original size
     • e.g. memoflex glasses
       • nickel/titanium alloy which will return to its original shape at room temperature after being deformed. A 'superelastic' alloy
   • Piezoelectric devices
     • Produce an electrical signal when compressed
     • e.g. sensors on bridges - will produce a signal when the load is above a certain amount
   • Quantum tunnelling composites
     • change from an insulator to a conductor when a deliberate force is applied
       • e.g. touch sensitive clothing