Smart materialsIntelligent StructuresBiomimetics John Summerscales School of Marine Science and Engineering University of Plymouth
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
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
Waterproof clothing(material or structure ?) • Goretex® • micro-porous expanded PTFE discovered in 1969 by Bob Gore • ~ 14 x 1012 micropores per m². • each pore is about 700x larger thana water vapour molecule • water drop is 20,000x larger than a pore
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
Intelligent structures (IS) • embed three elements of the system: • sensors • signal processing and control • actuators
Sensors • strain gauges • microdieletric interdigitated sensors • optical fibres • piezoelectric crystals • shape memory alloys • sensitive semiconductor chip • giant magnetoimpedance (GMI) wires
Optical Fibre Bragg Grating (OFBG) image from http://en.wikipedia.org/wiki/Image:Fbg.GIF
Signal processing • issues with data fusionfor large sensor arrays
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 ...
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
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
shape memory alloy http://www.mtm.kuleuven.ac.be/Research/ADAPT/Video/05-11_11-05_1.avi
Intelligent Structures: applications • artificial hand • SMA fingers controlled bynerve (myoelectric) signals • vibration damping • apply electric field to ER fluid • skyscraper windows • acoustic emission warning system
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 theever increasing need for sympathetic technology
Biomimetics • “inspiration rather than imitation” Janine Benyus. • “design inspired by nature” BioNIS thematic network
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™ • Chobham armour vs nacre
Biomimetics • Velcro • small hooks enable seed-bearing burrto cling to tiny loops in fabric
Gecko tapeimage fromhttp://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-fibresusing very high friction to support loads on smooth surfaces.
Biomimetics: Lotus effect • most efficient self-cleaning plant= great sacred lotus (Nelumbo nucifera) • mimicked in paints andother 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
Biomimetics • Lotus effect self-cleaning surfaces • surface of leaf water droplet on leaf • Image from http://library.thinkquest.org/27468/e/lotus.htm
Biomimetics • drag reduction by shark skin • special alignment and grooved structureof tooth-like scales embedded in shark skindecrease drag and thusgreatly increase swimming proficiency • Airbus fuel consumption down 1½%when “shark skin” coating applied to aircraft • Image from http://www.pelagic.org/biology/scales.html
Biomimeticshttp://www.rarebirdphotography.co.uk Common Tern Ivory Gull Squacco Stone Curlew
Aeroelastic tailoring • Grumman X-29FSW aircraft 1984 to 1992 http://www.globalsecurity.org/military/systems/aircraft/x-29.htm
Platelet TechnologyTM • Brinker Technology Platelet TechnologyTM • discrete particles released into pipe flow • when particles encounter modified flowat a leak, fluid forces entrain them intothe leak and hold them against the pipe wall • seals and marks the positionof the leak for subsequent detection. • YouTube videos: • animationthe technologyYorkshire WaterScottish Water
Smart-fabric • pine-cone model • adapts to changing temperaturesby opening when warm or shutting tight if cold
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
Nacre (abalone/mother-of-pearl) • CaCO3 aragonite crystalshexagonal platelets: 10-20 µm x 0.5 µm thick arranged in a continuous parallel lamina. • layers separated by sheets of organic matrixcomposed of elastic biopolymers (such as chitin, lustrin and silk-like proteins). • brittle platelets and thin elastic biopolymers makes the material strong and resilientdue to adhesion by the "brickwork“ arrangement of the platelets which inhibits transverse crack propagation.
Nacre • Micrograph from Tomsia et al http://www.physorg.com/news10408.html • Schematic from http://en.wikipedia.org/wiki/Mother_of_pearl
Chobham armour • an arrangement of metal plates, ceramic blocks, aramid fabricsand open space ? • rounds get through the outer layer • ceramic material absorbsheat and impact energy • aramid fabric catches debris • hot gases or metal piecesspread around empty air pockets.
Acknowledgements • Various websites from whichimages have been extracted