Modern materials

1
Modern materials

• John Summerscales
• School of Engineering
• University of Plymouth

2
Introduction

• composite materials
• smart materials and intelligent structures
• biomimetics
• nano technology and MEMS
• opportunities

3
Composite materials

• 19xxs reinforced rubber tyres
• 1930s fibreglass
• 1960s carbon fibre
• 1970s aramid fibre
• 2000s smart materials and intelligent
  structures

4
Recent composite failures

• Team Philips
• sandwich debond
• Flight 587 ?
• shear failure ?

5
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

6
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

7
photochromic glass
8
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

9
Sensors

• piezoelectric crystals
• shape memory alloys
• electro-rheological fluids
• optical fibres
• see animated image files athttp//www.spa-inc.net
  /smtdsmart.htm

10
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

11
Electro-/magneto-rheological fluids
12
shape memory alloy
13
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

14
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

15
Biomimetics

• Notable innovations from understanding nature
• Velcro
• Lotus effect self-cleaning surfaces
• drag reduction by shark skin

16
Biomimetics

• Velcro
• small hooks enable seed-bearing burrto cling to
  tiny loops in fabric

17
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.htm
  l

18
Biomimetics

• Lotus effect self-cleaning surfaces
• surface of leaf water droplet on leaf
• Image from http//library.thinkquest.org/27468/e/l
  otus.htm

19
Biomimetics

• drag reduction by shark skin
• special alignment and grooved structure of
  tooth-like scales embedded in shark skin decrease
  drag and thusgreatly increase swimming
  proficiency
• Airbus fuel consumption down 1½when shark
  skin coating applied to aircraft
• Image from http//www.pelagic.org/biology/scales.
  html

20
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

21
Goretex
22
Controlled crystal growth

• Brigid Heywood
• Crystal Science Group at Keele
• controlling the nucleation and growthof
  inorganic materials to make crystalline
  materials

23
Mohs hardness scale

• felspar
• quartz
• topaz
• carborundum
• diamond

• talc
• gypsum
• calcite
• fluorite
• apatite

Hardness of steel about 6.5 ... but what will
scratch diamond?
24
Hardness

• Diamond begins to burn at 850C
• Boron nitride (BN) subjected to pressures of 6
  GPa and temperatures of 1650C produces crystals
  that are harder than diamond and can withstand
  temperatures up to about 1900C.

25
Auxetic materials/structures
Normal Transverse contraction
Auxetic Transverse expansion
26
Auxetic materials/structures
negative Poissons ratio
27
auxetic honeycomb
28
Nanostructures

• surface structures with feature sizesfrom
  nanometres to micrometres
• white light optics limited to 1µm
• use electron-beam or x-ray lithographyand
  chemical etching/deposition
• image calcium fluorideanalog of a photoresist
  fromhttp//mrsec.wisc.edu/seedproj1/see1high.html

29
Nanotubes

• Carbon 60 buckyballs (1985)
• graphitic sheets seamlessly wrappedto 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.ht
  m

30
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.htm
  l

31
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

32
Conclusion

• more energy efficient thro light weight
• more compact thro miniaturisation
• more environment friendly
• reduced failures, pollution

33
Acknowledgements

• Various websites from whichimages have been
  borrowed

34
To contact me

• Dr John Summerscales
• ACMC/DMME, Smeaton Room 101
• University of Plymouth
• Devon PL4 8AA
• 01752.23.2650
• 01752.23.2650
• jsummerscales_at_plymouth.ac.uk
• http//www.tech.plym.ac.uk/sme/jsinfo.htm