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