Modern materials John Summerscales School of Engineering University

Modern materials John Summerscales School of Engineering University of Plymouth

Introduction composite materials l smart materials and intelligent structures l biomimetics l nano technology and MEMS l opportunities l

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

Recent composite failures l Team Philips #sandwich debond l Flight 587 ? #shear failure ?

Smart materials normal materials have limited responses l smart materials have appropriate responses l. . . but response is the same every time l “smart responds to a stimulus with one predictable action”

Smart materials l 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 l can embed sensors-control-actuators l control can decide on novel response l “intelligent responds to a stimulus with a calculated response and different possible actions”

Sensors piezoelectric crystals l shape memory alloys l electro-rheological fluids l optical fibres l l see animated image files at http: //www. spa-inc. net/smtdsmart. htm

Actuators hydraulic, pneumatic and electric l piezoelectric crystals l #shape changes when voltage applied l shape memory materials #shape changes at a specific temperature l electro-rheological fluids #viscosity changes with electric field

Electro-/magneto-rheological fluids

shape memory alloy

Applications for Intelligent Structures l artificial hand #SMA fingers control by nerve signals l vibration damping #apply electric field to ER fluid l skyscraper windows #acoustic emission warning system

Biomimetics l a. k. a bionics, biognosis l the concept of taking ideas from nature to implement in another technology #Chinese artificial silk 3 000 years ago #Daedalus' wings - early design failures l gathering momentum due to the ever increasing need for sympathetic technology

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

Biomimetics l Velcro #small hooks enable seed-bearing burr to cling to tiny loops in fabric

Biomimetics: Lotus effect l l l 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/lotusv 2. gif # http: //www. nees. uni-bonn. de/lotus/en/vergleich. html

Biomimetics l Lotus effect self-cleaning surfaces l surface of leaf l 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® l micro-porous expanded PTFE discovered in 1969 by Bob Gore l #~ 1. 4 billion micropores per cm². #each pore is about 700 x larger than a water vapour molecule #water drop is 20, 000 x larger than a pore

Goretex

Controlled crystal growth l Brigid Heywood #Crystal Science Group at Keele l controlling the nucleation and growth of inorganic materials to make crystalline materials

Mohs hardness scale Ê talc Ï felspar Ë gypsum Ð quartz Ì calcite Ñ topaz Í fluorite Ò carborundum Î apatite Ó diamond Hardness of steel about 6. 5. . . but what will scratch diamond?

Hardness Diamond begins to burn at 850°C l 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. l

Auxetic materials/structures Normal Auxetic Transverse contraction Transverse expansion

Auxetic materials/structures negative Poisson’s ratio

auxetic honeycomb

Nanostructures l surface structures with feature sizes from nanometres to micrometres white light optics limited to ~1μm l use electron-beam or x-ray lithography and chemical etching/deposition l l image = calcium fluoride analog of a photoresist from http: //mrsec. wisc. edu/seedproj 1/see 1 high. html

Nanotubes Carbon 60 buckyballs (1985) l graphitic sheets seamlessly wrapped to form cylinders (Sumio Iijima, 1991) l l 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 l Microelectronics and micromachining on a silicon substrate l MEMS has enabled electrically-driven motors smaller than the diameter of a human hair to be realized l Image from http: //www. memsnet. org/mems/what-is. html

Elek. Tex™ l looks and feels like a fabric l capable of electronic x-y-z sensing l fold it, scrunch it or wrap it l lightweight, durable, flexible l cost competitive l cloth keyboards and keypads # details: http: //www. electrotextiles. com

Conclusion more energy efficient thro’ light weight l more compact thro’ miniaturisation l more environment friendly l l reduced failures, pollution

Acknowledgements l Various websites from which images have been borrowed

To contact me: J Dr John Summerscales *ACMC/DMME, Smeaton Room 101 University of Plymouth Devon PL 4 8 AA % 01752. 23. 2650 2 01752. 23. 2650 < jsummerscales@plymouth. ac. uk : http: //www. tech. plym. ac. uk/sme/jsinfo. htm