Structure and mechanical properties of crab exoskeletons

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1、Availableonlineatwww.sciencedirect.comActaBiomaterialia4(2008)587–596www.elsevier.com/locate/actabiomatStructureandmechanicalpropertiesofcrabexoskeletonsPo-YuChen*,AlbertYu-MinLin,JoannaMcKittrick,MarcAndre´MeyersDepartmentofMechanicalandAerospaceEngineeringandMaterialsScienceandEngineeringPro

2、gram,UniversityofCalifornia,SanDiego,LaJolla,CA92093-0411,USAReceived15June2007;receivedinrevisedform27November2007;accepted18December2007Availableonline17January2008AbstractThestructureandmechanicalpropertiesoftheexoskeleton(cuticle)ofthesheepcrab(Loxorhynchusgrandis)wereinvestigated.Thecrabe

3、xoskeletonisanaturalcompositeconsistingofhighlymineralizedchitin–proteinfibersarrangedinatwistedplywoodorBouligandpattern.Thereisahighdensityofporecanaltubulesinthedirectionnormaltothesurface.Thesetubuleshaveadualfunction:totrans-portionsandnutritionandtostitchthestructuretogether.Tensiletestsi

4、nthelongitudinalandnormaltothesurfacedirectionswerecarriedoutonwetanddryspecimens.Samplestestedinthelongitudinaldirectionshowedaconvexshapeandnoevidenceofpermanentdeformationpriortofailure,whereassamplestestedinthenormalorientationexhibitedaconcaveshape.Theresultsshowthatthecom-positeisanisotr

5、opicinmechanicalproperties.Microindentationwasperformedtomeasurethehardnessthroughthethickness.Itwasfoundthattheexocuticle(outerlayer)istwotimesharderthantheendocuticle(innerlayer).Fracturesurfacesaftertestingwereobservedusingscanningelectronmicroscopy;thefracturemechanismisdiscussed.Ó2008Acta

6、MaterialiaInc.PublishedbyElsevierLtd.Allrightsreserved.Keywords:Arthropodexoskeletons;Biomineralization;Bouligandstructure;Biologicalcomposite;Chitin1.Introductionisfurtherdividedintotwoparts,theexocuticle(outer)andtheendocuticle(inner),whichhavesimilarcomposi-Arthropodsarethelargestanimalphyl

7、um.Theyincludetionandstructure.Theendocuticlemakesuparound90thetrilobites,chelicerates,myriapods,hexapods,andcrus-vol.%oftheexoskeleton.Theexocuticleisstackedmoretaceans.Allarthropodsarecoveredbyanexoskeleton,denselythantheendocuticle.T