Smart materials

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Smart materials

  1. 1. Smart materialsIntelligent StructuresBiomimeticsJohn SummerscalesSchool of Marine Science and EngineeringUniversity of Plymouth
  2. 2. Smart materials “smart responds to a stimulus with one predictable action” normal materials have limited responses smart materials have appropriate responses ... but response is the same every time
  3. 3. Smart materials smart materials have appropriate responses  photochromic glass • darkens in bright light  low melting point wax in a fire sprinkler • blocks the nozzle until it gets hot  acoustic emission • sounds emitted under high stress  embedded optical fibres • broken ends reflect light back  microporous breathable fabrics
  4. 4. Waterproof clothing Goretex® micro-porous expanded PTFE discovered in 1969 by Bob Gore ~ 14 x 1012 micropores per m². each pore is about 700x larger than a water vapour molecule water drop is 20,000x larger than a pore
  5. 5. Goretex:
  6. 6. Intelligent structures (IS) “intelligent responds to a stimulus with a calculated response and different possible actions” composites made at low temp  can embed additional components control can decide on novel response
  7. 7. Intelligent structures (IS) embed three elements of the system:  sensors  signal processing and control  actuators
  8. 8. Sensors strain gauges microdieletric interdigitated sensors optical fibres piezoelectric crystals shape memory alloys electro-rheological fluids giant magnetoimpedance (GMI) wires
  9. 9. Optical Fibre Bragg Grating (OFBG) image from http://en.wikipedia.org/wiki/Image:Fbg.GIFNon-Destructive Testing of Fibre-Reinforced Plastics Composites
  10. 10. Signal processing issues with data fusion for large sensor arrays
  11. 11. Control proportional integral derivative (PID)  proportional: output = (gain x error) + bias  integral: output = gain x (error + ∫error w.r.t. time)  derivative: output = gain x derivative x de/dt advanced systems ...
  12. 12. Advanced control proportional integral derivative (PID) fuzzy logic control (FLC)  sliding mode control artificial neural networks (ANN) genetic algorithms (GA) knowledge-based systems/ artificial intelligence/expert systems
  13. 13. Actuators hydraulic, pneumatic and electric piezoelectric crystals  shape changes when voltage applied shape memory materials  shape changes at a specific temperature  alloys = SMA .... polymers = SMP magneto-rheological (MR) fluids  viscosity changes with magnetic field electro-rheological (ER) fluids  viscosity changes with electric field
  14. 14. shape memory alloyhttp://www.mtm.kuleuven.ac.be/Research/ADAPT/Video/05-11_11-05_1.avi
  15. 15. Magneto-rheological (MR) fluidsElectro-rheological (ER) fluids
  16. 16. Intelligent Structures: applications  artificial hand  SMA fingers controlled by nerve (myoelectric) signals  vibration damping  apply electric field to ER fluid  skyscraper windows  acoustic emission warning system
  17. 17. Biomimetics a.k.a bionics, biognosis the concept of taking ideas from nature to implement in another technology  Chinese silk cultivation begins c.4000BC • Colin Thubron, Shadow of the Silk Road, Chatto & Windus, 2006.  Daedalus wings - early design failures gathering momentum due to the ever increasing need for sympathetic technology
  18. 18. Biomimetics “inspiration rather than imitation” Janine Benyus. “design inspired by nature” BioNIS thematic network
  19. 19. Biomimetics Notable innovations from understanding nature  Velcro  Gecko tape  Lotus effect self-cleaning surfaces  Drag reduction by shark skin  Platelet TechnologyTM for pipe repair  Smart-fabric  ElekTex™
  20. 20. Biomimetics Velcro  small hooks enable seed-bearing burr to cling to tiny loops in fabric
  21. 21. Gecko tape image from http://www.netcomposites.com/news.asp?3922 geckos to hang single-toed from sheer walls and walk along ceilings using fine hairs on feet University of California - Berkeley created an array of synthetic micro-fibres using very high friction to support loads on smooth surfaces.
  22. 22. Biomimetics: Lotus effect most efficient self-cleaning plant = great sacred lotus (Nelumbo nucifera) mimicked in paints and other surface coatings pipe cleaning in oil refineries (Norway) Images from  http://library.thinkquest.org/27468/e/lotus.htm  http://www.villalachouette.de/william/lotusv2.gif  http://www.nees.uni-bonn.de/lotus/en/vergleich.html
  23. 23. Biomimetics Lotus effect self-cleaning surfaces surface of leaf water droplet on leaf Image from http://library.thinkquest.org/27468/e/lotus.htm
  24. 24. Biomimetics drag reduction by shark skin  special alignment and grooved structure of tooth-like scales embedded in shark skin decrease drag and thus greatly increase swimming proficiency  Airbus fuel consumption down 1½% when “shark skin” coating applied to aircraft o Image from http://www.pelagic.org/biology/scales.html
  25. 25. Biomimeticshttp://www.rarebirdphotography.co.ukCommon Tern Ivory GullSquacco Stone Curlew 26
  26. 26. Aeroelastic tailoring Grumman X-29 FSW aircraft 1984 to 1992 http://www.globalsecurity.org/military/systems/aircraft/x-29.htm 27
  27. 27. Platelet TechnologyTM Brinker Technology Platelet TechnologyTM discrete particles released into pipe flow when particles encounter modified flow at a leak, fluid forces entrain them into the leak and hold them against the pipe wall seals and marks the position of the leak for subsequent detection. YouTube videos:  animation the technology Yorkshire Water Scottish Water
  28. 28. Smart-fabric pine-cone model adapts to changing temperatures by opening when warm or shutting tight if cold
  29. 29. ElekTex™ looks and feels like a fabric capable of electronic x-y-z sensing fold it, scrunch it or wrap it lightweight, durable, flexible cost competitive cloth keyboards and keypads  details: http://www.electrotextiles.com
  30. 30. Acknowledgements Various websites from which images have been extracted

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