简介:TwogradesofDyneema~?compositelaminateswiththecommercialdesignationsofHB26andHB50werecutintoblockswithorwithoutanedgecrackandcompressedinthelongitudinalfiberdirection.Thecrackedanduncrackedspecimensshowsimilarcompressiveresponsesincludingfailurepatternandfailureload.ThetwogradesofDyneema~?compositesexhibitsdifferentfailuremodes:adiffuse,sinusoidalbucklingpatternforDyneema~?HB50duetoitsweakmatrixconstituentandakinkbandforDyneema~?HB26duetoitsrelativelystrongermatrixconstituent.AneffectivefiniteelementmodelisusedtosimulatethecollapseofDyneema~?composites,andthesensitivityoflaminatecompressiveresponsestotheoveralleffectiveshearmodulus,interlaminarshearstrength,thicknessandimperfectionangleareinvestigated.Thechangeoffailuremodefromkinkbandtosinusoidalbucklingpatternbydecreasingtheinterlaminarshearstrengthisvalidatedbythefiniteelementanalyses.
简介:Inordertoimprovethemechanicalpropertiesofpolypyrrole,compositesweremadebyelectropolymerizingpolypyrroleinapolyurethanematrix.Polypyrrole/polyurethane(PPY/PU)compositefilmscontainingCLO4-,BF4-orCH3-C6H4-SO3-counterionsweremadeinavarietyofsolventsystemsandcharacterizedbySEM,electronicconductivity,FTIR,andmechanicalproperties.Compositefilmsshowingmuchgreaterfiexibilitythanpurepolypyrrolewereobtained,buttheirelectronicconductivitiesweresubstantiallylower.Measuredeonductivitiesrangedfrom0.001to8S/cm,tensilestrengthsfrom44to592psi,andelongationtofailurefrom3to70%.
简介:Thioglycolicacid(TGA)-stabilizedCdTenanocrystals(NCs)werepreparedwithsodiumtelluriteastelluriumsource,whichavoidsthecumbersomeprocessesassociatedwithH2TeorNaHTesources.FluorescentCdTe/SiO2compositesweresynthesizedbyasol-gelmethodwithouttheexchangeofsurfaceligands.ThephasestructureofCdTeNCswasinvestigatedbyX-raydiffractometry.Forcomparison,somecharacterizationsweredoneforboththeCdTeNCsandthecomposites.CdTeNCsandCdTe/SiO2compositeswerecharacterizedwithTEM,digitalcameraandfluorescencespectrophotometer.ThestabilityofCdTeNCsandthecompositeswereinvestigatedinphosphate-bufferedsaline(PBS)bufferandthefluorescentpropertiesofthecompositeswerediscussedindetail.
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简介:PP/claycompositeswithdifferentdispersions,namely,exfoliateddispersion,intercalateddispersionandagglomeratesandpanicle-likedispersion,werepreparedbydirectmeltintercalationorcompounding.TheeffectofclaydispersiononthecrystallizationandmorphologyofPPwasinvestigatedviaPLM,SAXSandDSC.Experimentalresultsshowthatexfoliatedclaylayersaremuchmoreefficientthanintercalatedclayandagglomeratesofclayinservingasnucleationagentduetothenano-scaledispersionofclay,resultinginadramaticdecreaseincrystalsize(lamellarthicknessandspherulites)andanincreaseofcrystallizationtemperatureandcrystallizationrate.Ontheotherhand,adecreaseofmeltingtemperatureandcrystallinitywasalsoobservedinPP/claycompositeswithexfoliateddispersion,duetothestronginteractionbetweenPPandclay.Comparedwithexfoliatedclaylayers,theintercalatedclaylayershavealessimportanteffectonthecrystallizationandcrystalmorphology.Noeffectisseenforsampleswithagglomeratesandpanicle-likedispersion,inregardtomeltingtemperature,crystallizationtemperature,crystalthicknessandcrystallinity.
简介:这份报纸学习多相的thermoelasticcomposites的有效性质。把免费精力和吉布斯基于Helmholtz多相的composites的单个阶段,有效有弹性的张肌,热扩大的张肌,和特定的热的免费精力借助于体积一般水准被导出这些阶段免费精力。特别强调以经常紧张、经常压力的状况,修改Eshelby的micromechanics理论在被开发被放在有效的特定的热的新分析表情的推导上,在包括之间的相互作用被考虑。作为一个解说性的例子,为三阶段的thermoelastic的有效的特定的热的分析表示合成被介绍。
简介:Despitethewideusageofisotropicfibrouscompositeswithaviscoelasticpolymermatrix,noanalyticmodelfortheirmechanicalbehaviourisknown.Thispaperdevelopssuchamodelfortime-dependentYoung'smodulus,showingthatfortypicalconstituentsthetimeconstantsofcompositesareuptoabout6%greaterthanthematrixsheartimeconstant.Viscoelasticityisstronglysuppressedforstifffibresevenatmodestfibrevolumefractions.Comparisonwithknownresultsforparticleandorientedfibrecompos...
简介:AnewtypeofSiO_2-MgO-CaO(SMC)whiskerwasusedtomodifyhighdensitypolyethylene(HDPE).Themeltingbehaviorandcrystallinitywereinvestigatedbydifferentialscanningcalorimetry(DSC).ThedispersionofwhiskersandinterfacialadhesioninthepreparedHDPE/SMCwhiskercompositeswereinvestigatedbyscanningelectronmicroscopy(SEM).Themechanicalpropertieswereevaluatedbymechanicaltestsanddynamicmechanicalanalysis(DMA).DSCdataindicatedthatthemeltingtemperatureandthecrystall...
简介:Themixedmatrixmembranes(MMMs)weredevelopedbyincorporatinggraphiteoxide(GO)flakesfunctionalizedwithironoxide(Fe3O4)intoPebaxmatrix.ThePebax/Fe3O4-GOMMMswereusedtoseparateCO2/CH4andCO2/N2gasmixture.TheresultsshowedthattheMMMswithmagneticalignmentpresentedthebettergasseparationperformancethanthatofrandomarrangementofPebax/Fe3O4-GOmixedmatrixmembranes.ThereasonwasthattheFe3O4-GOflakesarrangedmagneticallyinthemembraneplayedamultipleroleinimprovingtheperformanceofMMMs.Firstly,undertheactionofthemagneticfield,themagneticalignmentofFe3O4-GOflakesinPebaxmatrixconstructedtheshortertransferpathforgasmolecule,increasingtheCO2permeability.Secondly,thehydroxylgroupsinGOflakesandthepresenceofFe3O4havestrongerbindingforceforwater,improvingtheCO2solubilityselectivity.Thirdly,thebetterinteractionbetweenthemagneticalignmentofGOcompositesandpolymermatrix,reducedtheinterfacedefects.Especially,theoptimumgasseparationperformsneewasobtainedattheFe3O4-GOflakescontentof3wt%inPebaxmatrixatverticalarrangementwithselectiv让yof47and75forCO2/CH4andCO2/N2,respectively,andCO2permeabilityof538Barrerat0.2MPaandroomtemperature.
简介:Theapplicabilityandlimitationofseveralquadraticstrengththeorieswereinvestigatedwithrespectto2D-C/SiCand2.5D-C/SiCcomposites.Akindofdamage-basedfailurecriterion,referredtoasD-criterion,isproposedfornonlinearceramiccomposites.Meanwhile,thenewlydevelopedcriterionispreliminarilyvalidatedundertension-shearcombinedloadings.ThepredictionshowsthatthefailureenvelopegivenbyD-criterionislowerthanthatfromTsai–HillandHoffmancriteria.Thisrevealsthatthedamage-basedcriterionisreasonableforevaluationofdamage-dominatedfailurestrength.
简介:Thisstudyinvestigatedtheinfluenceofvariousorganicallymodifiedmontmorillonites(organoclays)onthestructureandpropertiesofrigidpolyurethanefoam(RPUF)nanocomposites.Theorganoclaysweremodifiedwithcetyltrimethylammoniumbromide(CTAB),methyltallowbis(2-hydroxyethyl)quaternaryammoniumchloride(MT2ETOH)andtris(hydroxymethyl)aminomethane(THMA)anddenotedasCMMT,Cloisite30BandOMMT,respectively.MT2ETOHandTHMAcontainhydroxylgroups,whileTHMAdoesnothavelongaliphatictailinitsmolecule.X-raydiffractionandtransmissionelectronmicroscopyshowthatOMMTandCloisite30BcanbepartiallyexfoliatedintheRPUFnanocompositesbecausetheirintercalatingagentsMT2ETOHandTHMAcanreactwithisocyanate.However,CMMTmodifiedwithnonreactiveCTABismainlyintercalatedintheRPUFmatrices.Atarelativelylowfillercontent,theRPUF/CMMTcompositefoamhasahigherspecificcompressivestrength(theratioofcompressivestrengthagainsttheapparentdensityofthefoams),whileatrelativelyhighfillercontents,RPUF/Cloisite30BandRPUF/OMMTcompositeshavehigherspecificcompressivestrengths,highermodulusandmoreuniformporesizethantheRPUF/CMMTcomposite.
简介:Withtheadventofleft-handedmagneticmaterials,itisdesirabletodevelophigh-performancewavedevicesbasedontheirnovelpropertiesofwavepropagation.Thisletterreportsthespecialpropertiesofelasticwavepropagationinmagnetoelasticmultilayeredcompositeswithnegativepermeabilityascomparecdtothoseincounterpartstructureswithpositlvepermeability.Thesenovelpropertiesofelasticwavesarediscernedfromthediversifieddispersioncurves,whichrepresentthepropagationandattenuationcharacteristicsofelasticwaves.Tocomputethesedispersioncurves,themethodofreverberation-raymatrixisextendedfortheanalysisofelasticwavesinmagnctoelasticmultilayeredcomposites.Althoughonlytheresultsofasinglepiezomagneticandabinarymagnetoelasticlayerswithmechanicallyfreeandmagneticallyshortsurfacesaswellaspelrfectinterfaceareillustratedinthenumericalexamples,theanalysisisapplicablelomagnetoelasticmultilayeredstructureswithotherkindsofboundaries/interfaces.