Training - Plymouth University
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Transcript Training - Plymouth University
Modern materials
John Summerscales
School of Engineering
University of Plymouth
Introduction
composite materials
smart materials and intelligent structures
biomimetics
nano technology and MEMS
opportunities
Composite materials
19xxs
1930s
1960s
1970s
2000s
reinforced rubber tyres
fibreglass
carbon fibre
aramid fibre
smart materials
and intelligent structures
Recent composite failures
Team Philips
sandwich debond
Flight 587 ?
shear failure ?
Smart materials
normal materials have limited responses
smart materials have appropriate responses
... but response is the same every time
“smart responds to a stimulus with one
predictable action”
Smart materials
smart materials have appropriate responses
photochromic glass
darkens
in bright light
acoustic emission
sounds
emitted under high stress
optical fibres
broken
ends reflect light back
self-healing tyres
photochromic glass
Intelligent structures (IS)
composites made at low temp
can embed sensors-control-actuators
control can decide on novel response
“intelligent responds to a stimulus
with a calculated response and
different possible actions”
Sensors
piezoelectric crystals
shape memory alloys
electro-rheological fluids
optical fibres
see animated image files at
http://www.spa-inc.net/smtdsmart.htm
Actuators
hydraulic, pneumatic and electric
piezoelectric crystals
shape changes when voltage applied
shape memory materials
shape changes at a specific temperature
electro-rheological fluids
viscosity changes with electric field
Electro-/magneto-rheological
fluids
shape memory alloy
Applications for
Intelligent Structures
artificial hand
SMA fingers control by nerve 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 artificial silk 3 000 years ago
Daedalus' wings - early design failures
gathering momentum due to the ever
increasing need for sympathetic
technology
Biomimetics
Notable innovations
from understanding nature
Velcro
Lotus effect self-cleaning surfaces
drag reduction by shark skin
Biomimetics
Velcro
small hooks enable seed-bearing burr
to cling to tiny loops in fabric
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
Biomimetics
Lotus effect self-cleaning surfaces
surface of leaf
Image from http://library.thinkquest.org/27468/e/lotus.htm
water droplet on leaf
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
Image from http://www.pelagic.org/biology/scales.html
Waterproof clothing
Goretex®
micro-porous expanded PTFE
discovered in 1969 by Bob Gore
~ 1.4 billion micropores per cm².
each pore is about 700x larger than a
water vapour molecule
water drop is 20,000x larger than a pore
Goretex
Controlled crystal growth
Brigid Heywood
Crystal Science Group at Keele
controlling the nucleation and growth
of inorganic materials to make
crystalline materials
Mohs hardness scale
talc
felspar
gypsum
quartz
calcite
topaz
fluorite
carborundum
apatite
diamond
Hardness of steel about 6.5
... but what will scratch diamond?
Hardness
Diamond begins to burn at 850°C
Boron nitride (BN) subjected to
pressures of 6 GPa and temperatures of
1650°C produces crystals that are
harder than diamond and can withstand
temperatures up to about 1900°C.
Auxetic materials/structures
Normal
Auxetic
Transverse contraction
Transverse expansion
Auxetic materials/structures
negative Poisson’s ratio
auxetic honeycomb
Nanostructures
surface structures with feature sizes
from nanometres to micrometres
white light optics limited to ~1μm
use electron-beam or x-ray lithography
and chemical etching/deposition
image = calcium fluoride
analog of a photoresist from
http://mrsec.wisc.edu/seedproj1/see1high.html
Nanotubes
Carbon 60 buckyballs (1985)
graphitic sheets seamlessly wrapped
to form cylinders (Sumio Iijima, 1991)
few nano-meters in diameter, yet
(presently) up to a milli-meter long
Image
from
http://www.rdg.ac.uk/~scsharip/tubes.htm
MEMS: micro electro
mechanical systems
Microelectronics
and micromachining on a silicon
substrate
MEMS has enabled electrically-driven
motors smaller than the diameter of a
human hair to be realized
Image from http://www.memsnet.org/mems/what-is.html
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
Conclusion
more energy efficient thro’ light weight
more compact thro’ miniaturisation
more environment friendly
reduced failures, pollution
Acknowledgements
Various websites from which
images have been borrowed
To contact me:
Dr John Summerscales
ACMC/DMME, Smeaton Room 101
University of Plymouth
Devon
PL4 8AA
01752.23.2650
01752.23.2650
[email protected]
http://www.tech.plym.ac.uk/sme/jsinfo.htm