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.html

18. Biomimetics • Lotus effect self-cleaning surfaces • surface of leaf water droplet on leaf • Image from http://library.thinkquest.org/27468/e/lotus.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 1½%when “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. felspar quartz topaz carborundum diamond talc gypsum calcite fluorite apatite Mohs hardness scale Hardness of steel about 6.5 ... but what will scratch diamond?

24. 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.

25. Auxetic materials/structures Normal Transverse contraction Auxetic Transverse expansion

26. Auxetic materials/structures negative Poisson’s 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.htm

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.html

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@plymouth.ac.uk • http://www.tech.plym.ac.uk/sme/jsinfo.htm