Table Of ContentQUANTITATIVEFRACTUREANALYSISOFA
BIOLOGICALCERAMICCOMPOSITE
By
THOMASJERALDHILL
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2001
ACKNOWLEDGMENTS
First,I wouldliketothankmywife, Aidines. She ismyreason. Herlove,
encoiiragement,andfriendshipthroughthetoughtimeshavealwaysbeenstrongandfor
thatIcannevertrulyrepay. Iwouldalsoliketothankmymotherforherunending
support. Shetaughtmethevalueofperseveranceandhardworkamongotherthings,and
thevaluessheinstilledhavebeeninstrumentalinwhereIamtoday.
Secondly, I would like to thank my professors and mentors, especially
Dr. KennethAnusaviceandDr. JackMecholsky,whoprovided guidanceandmuch-
neededadvicewheneveraskedfor. Icanneverrepaythecountlesshourstheyspent
assistingme,teachingme,andhelpingtomakemeabetterscientisteachday.
Next,IwouldliketothankJasonGriggsandAlvaroDeliaBona. Icouldnotask
forbetterresearchpartnersandfriends. AndIwouldalsoliketothankalltheotherswho
havecrossedmypathalongthisjourneyandhavebeenmorethanfriendsbutverymuch
likefamily:AUyson,Ben,Zhang,Nicola,Kallaya,andCliff.
TABLEOFCONTENTS
Eage
ACKNOWLEDGMENTS
ii
LISTOFTABLES v
LISTOFFIGURES vi
ABSTRACT x
CHAPTERS
1PURPOSE 1
1.1ResearchRationale 1
1.2MaterialSelection 2
1.3ResearchObjectives 2
1.3.1SpecificAim1 2
1.3.2SpecificAim2 2
1.3.3SpecificAim3 3
1.3.4SpecificAim4 3
2BACKGROUND 4
2.1BiologicalCeramics 4
2.1.1Introduction 4
2.1.2MolluscShells 5
2.1.3Strombusgigas 6
2.2FractureofBiologicalComposites 8
2.2.1CompositeAnalysis 8
2.2.2StrainRate 13
2.2.3Water 14
2.3FractalAnalysis 16
2.3.1FractalDimension 16
2.3.2MeasurementMethods 18
2.3.3FractalAnalysisofBrittleComposites 20
iii
3MATERIALSANDMETHODS 22
3.1SpecimenFabrication 22
3.1.1Forming 22
3.1.2WaterStorage 23
3.1.3ProteinRemoval 24
3.2MaterialProperties 24
3.2.1Density 24
3.2.2Hardness 27
3.2.3ElasticModulusandPoisson'sRatio 27
3.2.4CrystalPhaseIdentification 28
3.3MechanicalPropertyDetermination 29
3.3.1FlexureStrength 29
3.3.2WorkofFracture 32
3.3.3FractureToughness 33
3.4FractalAnalysis 35
3.4.1ModifiedSlitIslandMethod 35
3.4.2BoxCountingTechniqueUsingthe
AtomicForceMicroscope 38
4RESULTSANDDISCUSSION 40
4.1PhysicalPropertiesAnalysis 40
4.1.1Density 40
4.1.2Hardness 41
4.1.3ElasticModulusandPoisson'sRatio 42
4.1.4CrystalStructure 46
4.2MechanicalPropertiesAnalysis 50
4.2.1Strength 50
4.2.2FractureToughness 54
4.2.3WorkofFracture 56
4.2.4Fracture 58
4.2.5Water 64
4.3FractalAnalysis 75
4.3.1ModifiedSlitIslandAnalysis 75
4.3.2BoxCountingTechniqueUsingthe
AtomicForceMicroscope 78
5CONCLUSIONS 79
APPENDIXTABULATEDDATA 82
LISTOFREFERENCES 96
BIOGRAPHICALSKETCH 101
iv
LISTOFTABLES
Table Page
1. Four-pointflexuralstrengthdatafromStrombusgigasspecimensstoredinair 82
2. Four-pointflexuralstrengthdatafromStrombusgigasspecimensstoredinartificial
seawater 83
3. Four-pointflexuralstrengthdatafromStrombusgigasspecimensheattreatedat200°C
for24h 84
4. Four-pointflexuralstrengthdatafromStrombusgigasspecimensstoredindeionized
water 85
5. Four-pointflexuralstrengthdatafromStrombusgigasspecimensstoredinpH4buffer
solution 86
6. Four-pointflexuralstrengthdatafromStrombusgigasspecimensstoredinpHl0
buffersolution 87
7. Four-point flexural strengthdatafromStrombusgigas specimens stored innatural
seawater 88
8. Four-pointflexuralstrengthdatafromStrombusgigasstressingratespecimensin
water 89
9. Four-pointflexuralstrengthdatafromStrombusgigasstressingratespecimensinair..91
V
8
LISTOFFIGURES
Figure Page
2.1. Threeordersoflamellaofthehierarchicalstructureofthecross-lamellar
Strombusgigasconchshell 7
2.2. Mechanicalbehaviorofnon-transformationtoughenedlaminates
basedonthelaminatestructure 12
2.3. Stress-straindiagramsfordryStrombusgigasconchincompressiveloadingatquasi
static(a)anddynamic(b)stressingrates 15
2.4. Fracturetoughnessversussquarerootoffractaldimensionalincrementforthree
groupsofmaterials 1
2.5. Relationoffractaldimensionandsteplengthasafunctionofworkoffracture
(Curreyetal.) 21
3.1. Specimencutindirectionparalleltotheaxisofshell 23
3.2.Thermogravimetric/differentialthermalanalysis(TG/DTA)graphs(a)priortoheat
treatmentand(b)postheattreatment 25
3.3.Differentialscanningcalorimetry(DSC)graphs(a)priortoheattreatmentand(b)
postheattreatment 26
3.4. Four-pointloadingconfiguration 31
3.5. SEMmicrographfracturesurfaceshowingmicrostructurallayers 31
3.6 Singleedgenotchedbeamconfigurationtodeterminefracturetoughnessof
Strombusgigasfor(a)theweakerinnerlayerand(b)thestrongermiddlelayer 34
3.7. Opticalmicrograph(400x)showingthecoastlineofapolishedreplica 37
3.8. Plotoflogtotallengthversuslogsteplength. Theslopeisthenegativevalueofthe
fractaldimensionalincrement 38
vi
3.9 Representativeimageofthefractaldimensionobtainedusingtheatomicforce
microscope 39
4.1. DensityofStrombusgigasasafunctionofenvironmentinmonolithicand
powderform 41
4.2. Vickershardnessasafunctionofindentationloadforfiveenvironment/temperature
conditions 42
4.3 Opticalmicrographofindentationwithrespecttpa)shellmicrostructure(1OOx)and
b)crushzone(400x)aroundtheindentation 43
4.4. ElasticmoduliandPoisson'sratiovaluesforfullthicknessStrombusgigasspecimen
obtainedbyultrasonicmeasurements 44
4.5 ElasticmoduliandPoisson'sratiovaluesforsinglelayerStrombusgigasspecimen
obtainedbyultrasonicmeasurements 45
4.6. X-raydiffractionspectraforStrombusgigas powderstoredinair. Aragonitecrystal
structureistheonlyphasepresent 47
4.7. X-raydiffractionspectraforStrombusgigaspowderheattreatedat200°Cfor24h.
Aragonitecrystalstructureistheonlyphasepresent 48
4.8. X-raydiffractionspectraforStrombusgigaspowderheattreatedat300°Cfor24h.
Aragonitecrystalstructureistheonlyphasepresent 49
4.9. MeanstrengthforStrombusgigasspecimenstoredinair,storedindeionizedwater,
andheattreatedat200°Cfor24hcalculatedusinglinearbeamanalysis,linearbeam
analysisusingmiddlelayerthickness,andcompositeanalysis 52
4.10 Meanstrengthcalculatedusinglinearbeamanalysis,middlelayerlinearbeam
analysis,andcompositeanalysis. Specimenswerestoredinsixenvironments: air
(Air),deionizedwater(DI),naturalseawater(SW),pH4buffersolution(pH4),pHlO
buffersolution(pHlO),andartificialseawatersolution(ASW) 53
4.11.Meanstrengthcalculatedbylinearbeamandmiddlelayerlinearbeamasafunction
ofincreasingstressingrate 54
4.12 Meantoughnessdeterminedusingsingle-edgenotchedbeamforthreeconditions:
storedinair,storedindeionizedwater,andheattreatedat200°Cfor24h 55
4.13.Workoffractureforspecimenstoredinair,storedindeionizedwater,andheat
treatedat200°Cfor24h 56
vii
4.14 Workoffractureforspecimensstoredinsixenvironments: air(Air),deionized
water(DI),naturalseawater(SW),pH4buffersolution(pH4),pHlObuffersolution
(pHlO),andartificialseawatersolution(ASW) 57
4.15.Workoffractureasafunctionofstressingrateforgroupsstoredinairandin
deionizedwater 58
4.16 SEMmicrographofthefracturesurfaceofaStrombusgigasatamagnificationof
20xdisplayingtwodistinctfracturesurfaces 59
4.17 SEMmicrographoftheinnerlayerofafracturesurfaceofaStrombusgigasata
magnificationof5Ox 59
4.18 SEMmicrographofthetoughmiddlelayerofafracturesurfaceofaStrombusgigas
atamagnificationof50x 61
4.19 SEMmicrographofasecondorderlamellaofStrombusgigasatamagnificationof
2500x 61
4.20 Representativestress-straindiagramsforStrombusgigasforthreeconditions 63
4.21.SEMmicrographatamagnificationof20xshowingbothfirstorderlamellaof
Strombusgigas storedindeionizedwaterpriortofracture. Thepresenceofthe
proteinaceousmatrixispervasive 65
4.22 SEMmicrographatamagnificationof50xofasecondorderlamellaofStrombus
gigasshowingtheinterconnectingprotein 66
4.23.SEMmicrographatamagnificationof2000xshowingthestrongbondingofthe
proteinwiththearagonitecrystalsofStrombusgigas 66
4.24.SEMmicrographatamagnificationof20xshowingthepresenceoftheproteinon
theinterfacebetweentheinnerandmiddlelayersoftheStrombusgigas 67
4.25 SEMmicrographatamagnificationof200xshowingthehighorganizationof
proteinmatrixwiththearagonitecrystalsofStrombusgigas 68
4.26 SEMmicrographatamagnificationof800xshowingthestrongbondingofthe
proteinwiththearagonitecrystalsofStrombusgigas 69
4.27.Representativestress-strainplotsforgroupsstoredinair:
(a)stressingrateof0.02MPa/s 71
(b)stressingrateof0.5MPa/s 71
(c)stressingrateof20MPa/s 72
(d)stressingrateof500MPa/s 72
viii
4.28.Representativestress-strainplotsforgroupsstoredindeionizedwater:
(a)stressingrateof0.02MPa/s 73
(b)stressingrateof0.5MPa/s 73
(c)stressingrateof20MPa/s 74
(d)stressingrateof500MPa/s 74
4.29.Fractaldimensionalincrementasafunctionofenvironmentasmeasuredbythe
modifiedslitislandanalysis 75
4.30 Fractaldimensionalincrementasafunctionofstressingrateasmeasuredbythe
modifiedslitislandanalysis 76
4.31.Fracturetoughnessversussquarerootofthefractaldimensionalincrementforboth
theinnerandmiddlelayersforthreeconditions: storedindeionizedwater,storedin
airandheattreated. Opensymbolsareinnerlayerandfilledsymbolsaremiddle
layervalues. Diamond-heattreated,Cross-air,andSquare-water 77
4.32 Fractaldimensionalincrementobtainedforinnerandmiddlelayersusingbotha
macroscopictechnique(modifiedslitisland)andamicroscopictechnique(atomic
forcemicroscopy) 78
ix
AbstractofDissertationPresentedtotheGraduateSchoolofthe
UniversityofFloridainPartialFulfillmentoftheRequirementsforthe
DegreeofDoctorofPhilosophy
QUANTITATIVEFRACTUREANALYSISOFA
BIOLOGICALCERAMICCOMPOSITE
By
ThomasJeraldHill
August,2001
Chairman: JohnJ.Mecholsky,Jr.
Cochair: KennethJ.Anusavice
MajorDepartment: MaterialsScienceandEngineering
Thepurposeofthisstudywastoanalyzetheimprovedmechanicalpropertiesof
theStrombusgigasovernon-biogenicaragonite(CaCOs)bycontrollingandanalyzing
thepresenceoftheproteinaceousmatrixandwater.
Thespecificobjectivesofthisstudywereto1)estimatetherelativeincreaseof
mechanicalpropertiesfromstructureandproteinaceousinterfaceoftheStrombusgigas,
2)determineifionsinaqueous solutionofstressredistributionfromthepresenceof
waterwastheprimarymechanisminincreasingworkoffracture,3)identifyifwater
activatesanyviscoelasticeffectsfromtheproteinaceousmatrix,and4)identifyifthe
fractal dimension can discern iftoughening mechanisms are present in the complex
composite.
TheStrombusgigassystemwaschosenforthisstudybecauseithasdemonstrated
a10000-foldincreaseintheamountofenergytocausefailureovermonolithscomposed
X
