smart materials and new technologies：types and characteristics of smart materials

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1、4Typesandcharacteristicsofsmartmaterials4.1FundamentalcharacteristicsThischapterfirstidentifiescharacteristicsthatdistinguishsmartmaterialsfromothermaterials,andthensystematicallyreviewsmanyofthemorewidelyusedones.Webeginbynotingthatthefivefundamentalcharacteris

2、ticsthatweredefinedasdistinguishingasmartmaterialfromthemoretraditionalmaterialsusedinarchitectureweretransiency,selectivity,immediacy,self-actuationanddirectness.Ifweapplythesecharacteristicstotheorganizationofthesematerialsthenwecangrouptheminto:1Propertychang

3、ecapability2Energyexchangecapability3Discretesize/location4ReversibilityThesefeaturescanpotentiallybeexploitedtoeitheroptimizeamaterialpropertytobettermatchtransientinputconditionsortooptimizecertainbehaviorstomaintainsteadystateconditionsintheenvironment.Aswebe

4、gintoexplorethesedistinguishingcharacteristics,wewillseethatthereasonswhysmartmaterialsexhibittheseandothertraitsisnoteasytoexplainwithoutrecoursetothinkingaboutboththematerialsciencepreceptsnotedinthelastchapterandthespecificconditionssurroundingtheplacementand

5、useofthematerial.OfparticularimportanceistheconceptofthesurroundingenergyorstimulusfieldthatwasdiscussedinChapter3.Werecallthatenergyfieldscanbeconstructedofmanytypesofenergy–potential,electrical,thermal,mechanical,chemical,nuclear,kinetic–allofwhichcanbeexchang

6、edorconvertedaccordingtotheFirstLawofThermodynamics(thelawoftheconservationofenergy).Thephysicalcharacteristicsofsmartmaterialsaredeter-minedbytheseenergyfieldsandthemechanismthroughwhichthisenergyinputtoamaterialisconverted.Ifthemechanismaffectstheinternalenerg

7、yofthematerialbyalteringeitherthematerial’smolecularstructureormicro-structurethentheinputresultsinapropertychangeofthematerial.IfthemechanismchangestheenergystateoftheTypesandcharacteristicsofsmartmaterials79SmartMaterialsandNewTechnologiesmaterialcomposition,b

8、utdoesnotalterthematerial,thentheinputresultsinanexchangeofenergyfromoneformtoanother.Asimplewayofdifferentiatingbetweenthetwomechan-ismsisthatforpropertychangetype,t