Transcript Smart materials - intelligent structures

Smart materials
Intelligent Structures
Biomimetics
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
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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.
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each pore is about 700x larger than
a water vapour molecule
 water drop is 20,000x larger than a pore
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Goretex:
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
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Optical Fibre Bragg Grating (OFBG)
image from http://en.wikipedia.org/wiki/Image:Fbg.GIF
Non-Destructive Testing of Fibre-Reinforced Plastics Composites
Signal processing

issues with data fusion
for large sensor arrays
Control
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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
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advanced systems ...
Advanced control
proportional integral derivative (PID)
 fuzzy logic control (FLC)
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 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
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shape memory materials
 shape changes at a specific temperature
 alloys = SMA .... polymers = SMP
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magneto-rheological (MR) fluids
 viscosity changes with magnetic field
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electro-rheological (ER) fluids
 viscosity changes with electric field
shape memory alloy
http://sirius.mtm.kuleuven.be/Research/ADAPT/Video/05-11_11-05_1.avi
Magneto-rheological (MR) fluids
Electro-rheological (ER) fluids
Intelligent Structures: applications
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artificial hand
 SMA fingers controlled by
nerve (myoelectric) signals
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vibration damping
 apply electric field to ER fluid

skyscraper windows
 acoustic emission warning system
Biomimetics
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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
Biomimetics
“inspiration rather than imitation”
Janine Benyus.
 “design inspired by nature”
BioNIS thematic network
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Biomimetics
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Notable innovations
from understanding nature
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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
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Velcro
 small hooks enable seed-bearing burr
to cling to tiny loops in fabric
Gecko tape
image from
http://www.netcomposites.com/news.asp?3922
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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.
Biomimetics: Lotus effect
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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
Biomimetics
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Lotus effect self-cleaning surfaces
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surface of leaf
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Image from http://library.thinkquest.org/27468/e/lotus.htm
water droplet on leaf
Biomimetics
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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
Biomimetics
http://www.rarebirdphotography.co.uk
Common Tern
Ivory Gull
Squacco
Stone Curlew
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Aeroelastic tailoring
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Grumman X-29
FSW aircraft 1984 to 1992
http://www.globalsecurity.org/military/systems/aircraft/x-29.htm
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Hydroelastic
tailoring
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marine sterngear
 propellers
 composite
twisted rudders
for USN DDG51
class destroyers
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marine renewable
energy (MRE)
devices
image from http://d2n4wb9orp1vta.cloudfront.net/resources/images/cdn/cms/1408-a.jpg
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.
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YouTube videos:
 animation the technology Yorkshire Water Scottish Water
Smart-fabric
pine-cone model
 adapts to changing
temperatures
by opening when warm
or shutting tight if cold
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ElekTex™
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looks and feels like a fabric
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capable of electronic x-y-z sensing
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fold it, scrunch it or wrap it
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lightweight, durable, flexible
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cost competitive
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cloth keyboards and keypads
 details: http://www.electrotextiles.com
Nacre (abalone/mother-of-pearl)
•
CaCO3 aragonite crystals
hexagonal platelets: 10-20 µm x 0.5 µm thick
arranged in a continuous parallel lamina.
•
layers separated by sheets of organic matrix
composed of elastic biopolymers
(such as chitin, lustrin and silk-like proteins).
•
brittle platelets and thin elastic biopolymers
makes the material strong and resilient
due to adhesion by the "brickwork“
arrangement of the platelets
which inhibits transverse crack propagation.
Nacre
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Micrograph from Tomsia et al http://www.physorg.com/news10408.html
Schematic from http://en.wikipedia.org/wiki/Mother_of_pearl
Chobham armour
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an arrangement of metal plates,
ceramic blocks, aramid fabrics
and open space ?
 rounds get through the outer layer
 ceramic material absorbs
heat and impact energy
 aramid fabric catches debris
 hot gases or metal pieces
spread around empty air pockets.
Acknowledgements
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Various websites from which
images have been extracted