Modern materialsModern materials

John SummerscalesSchool of Engineering

University of Plymouth

Introduction Introduction

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

Composite materialsComposite materials

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

and intelligent structures

Recent composite failuresRecent composite failures Team Philips

sandwich debond Flight 587 ?

shear failure ?

Smart materialsSmart 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 materialsSmart 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)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”

SensorsSensors

piezoelectric crystals shape memory alloys electro-rheological fluids optical fibres

see animated image files athttp://www.spa-inc.net/smtdsmart.htm

ActuatorsActuators

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 Electro-/magneto-rheological fluidsfluids

shape memory alloy

Applications for Applications for Intelligent StructuresIntelligent Structures artificial hand

SMA fingers control by nerve signals vibration damping

apply electric field to ER fluid skyscraper windows

acoustic emission warning system

BiomimeticsBiomimetics 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

BiomimeticsBiomimetics

Notable innovations from understanding nature

Velcro Lotus effect self-cleaning surfaces drag reduction by shark skin

BiomimeticsBiomimetics

Velcro small hooks enable seed-bearing burr

to cling to tiny loops in fabric

Biomimetics: Lotus effectBiomimetics: 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

BiomimeticsBiomimetics

Lotus effect self-cleaning surfaces

surface of leaf water droplet on leaf

Image from http://library.thinkquest.org/27468/e/lotus.htm

BiomimeticsBiomimetics

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

Waterproof clothing 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

GoretexGoretex

Controlled crystal growthControlled crystal growth

Brigid Heywood Crystal Science Group at Keele

controlling the nucleation and growthof inorganic materials to make crystalline materials

Mohs hardness scaleMohs hardness scale

felspar quartz topaz carborundum diamond

talc gypsum calcite fluorite apatite

Hardness of steel about 6.5

... but what will scratch diamond?

HardnessHardness

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/structuresAuxetic materials/structures

Normal

Transverse contraction

Auxetic

Transverse expansion

Auxetic materials/structuresAuxetic materials/structures

negative Poisson’s ratio

auxetic honeycomb

NanostructuresNanostructures 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 fromhttp://mrsec.wisc.edu/seedproj1/see1high.html

NanotubesNanotubes

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 MEMS: micro electro mechanical systemsmechanical 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™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

ConclusionConclusion

more energy efficient thro’ light weight more compact thro’ miniaturisation more environment friendly

reduced failures, pollution

AcknowledgementsAcknowledgements

Various websites from whichimages have been borrowed

To contact me:To contact me: Dr John SummerscalesACMC/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