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SVENSSON JOSEF

1 3 4 6 1 1 3 7

Building Science A C S S 4 0 0

22 02 2012

John Begg

E3

CW2 Lab Report

Svensson, Josef

Szelag, Marlena 133685081

Ten, Stanislav 133184171

Wang, Xu 136072501

Woods, Nicholas 133795461

E3

ACSS400 E3 22/02/12

1

YoungsModulusofElasticity

BySvenssonJosef,SzelagMarlena,TenStanislav,WangXu,WoodsNicholas

ACSS400 E3 22/02/12

2

Contents:

1. Objectivespg.32. Procedurepg.33. Observationspg.34. Resultspg.45. Discussion pg.66. Conclusion pg.107. References pg.118. Bibliography pg.119. CertificatesofAttendance

andSignedDeclaration pg.12

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Objective:TodetermineEforsoftwood(ParanaPine)andonehardwood(Mahogany[Keruing])usingathreepointbendingjig.

TodetermineEforoneferrousmetal(LowCarbonSteel0.3%)andonenonferrous(Brass60/40)usingaanelectronicextensometer.

Procedure:AsLabSheet.

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Observations:TogetYoungsModulus,E,formetals,suchasBrassandMildSteel,thetestinvolvesloadingthespecimenintensionandmeasuringtheresultingextension.Duringtheexperiment,therewasnovisiblechange.Themetalsamplestestedintension,didnotchangevisiblyinanyway,normadeanysound.

SincemetalshaveahighYoungsmoduli,largeforcesmustbeappliedtoproducemeasurableextensionsinsmallspecimens,howevernoneofthemodificationswerenoticeableaswedidnotgopasttheYoungsmodulus,thereforenotcausinganyvisibledeformation.

YoungsModulus,E,fortimberismeasuredbycarryingoutthetestincompressionmodeusingtestingmachinefittedwithathreepointbendingjig.Inthiscase,howeverthechangesweredetectible,asthetimbersamplesdidslightlybendundertheappliedloadandsprungbackwhentheloadwasremoved.

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Results:

60/40Brass87x25.74600=F=1639.4N0.0180.002=x=0.016mm1639.4/pix(7.97/2)^20.016/50=102690Nmm^2102690x10^6=102690000000Pa=102.69GPaYoung'smodulusof70/30BrasshasYoung'smoduluswithavalueof100GPa.Ourcalculatedvalueisthereforerelativelycorrect.

0.3%CarbonSteelMildsteel(110x80)(110x22)=F=6380N0.040.01=x=0.03mm6380/pix(7.97/2)^20.03/50=213138.99Nmm^2213139x10^6=213139000000Pa=213.139GPaTheYoung'smodulusofourmildsteelisapproximately213GPa,thevaluethatwearegivenaccordingtothetableis210whichisthereforerelativelycorrect.

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TimberParanaPine(120^3/419.637.63^3)340/3.96 =4254Nmm^24254110^6=4254000000Pa

=4254MPa

TimberMahogany(120^3/4x20.08x7.55^3)290/2=7248Nmm^27248x1x10^6=7248000000Pa=7248MPa

Material Published value CalculatedvalueMildsteel 210GPa 213.139GPaBrass 100GPa 102.69GPa

Mahogany 010000MPa 7249MPa

Pine 1120020000MPa 4253MPa

Toconclude,inmosttheresultsfromtheexperimentpresenteduswithaYoung'sModulusclosetothegivenvaluesforthematerials.Thefindingspresentediswith3GPaincaseofthetestedmetalsandtimberpublishedvaluescouldonlybefoundinthetermsofMPa.Mega=1x10^6Giga=1x10^9

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Discussion:

Question1:CompareyourresultswithpublishedvaluesofE.Comment.

Material Published value CalculatedvalueMildsteel 210GPa 213.139GPaBrass 100GPa 102.69GPa

Mahogany 010000MPa 7249MPa

Pine 1120020000MPa 4253MPa

ThetableaboveshowsthevaluesofEthatwegotfromourexperimentandtheprovidedvaluesthatarequotedonvariousinternetandbooksourcesastowhattheactualvalueis(Kermani1999,andMatbase).

Thetableshowsthatthemildsteelandbrassvaluesarerelativelyclose,withonlyasmallvariationfromthepublishedvalues,howeverthetimbermaterialsofParanaPineandMahoganyseemtobeoutbyalargeamount,pineinparticular.Thiscanindicatethatthemetalshavelessvariationinqualityofthematerial,asthesamplestestedwasclosetotheindustrystandardsone,whereasthePinematerialmayhavebeenanolderorweakerdespitebeingofthesameorigin.

WehavedoublecheckedtheEvaluesfortimbertomakesurethatourvalueswerecorrectandhaveresearchedseveralotherwebsitesthatmayprovideuswiththepublishedvaluesofE,inallcasesParanapinewasoutbyalargeamountwhereasmahoganyfellwithintheapproximaterange,showingthatthesamplethatwehadwouldnothavemettheindustrystandardsastheEvalueisconsiderablylessthanthosethathavebeenpublished.

ThepublishedvalueofBrassthatwehaveusedwasintheexperimenthandbook,thegivenvaluewasgivenfor70/30brass,meaningthatitwas70%copperand30%zinc,whereasoursamplewas60/40.DuetocopperhavinghigherYoungsmodulusthanzinc,thatwouldmeanthattheoreticallyourvalueof60/40shouldhavebeenlowerthanthatof70/30,itwasinfacthigher,butstilllikelywithinarationalmarginoferror,ourvaluesmayhavebeendifferentduetoerrorincalculationoftheareaorcalculationofthegradientofthegraphthatwewereprovidedwith.

Insummary,thevaluesthatwehaveattainedhavebeenrelativelyclosetothepublishedvalueswiththeexceptionoftheParanapine,itmayhavebeenduetofaultysampleorotherunknownvariationthatcausedtheEvaluetobeconsiderablylowerthanthepublishedvaluesfoundontheinternet.

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Question2:Distinguishbetweencomponentstiffnessandmaterialstiffness.

Stiffnesscanbedescribedastheabilityofamaterialtomaintainitsshapewhenacteduponaload(CraneandFurness1997p.92)anddependsontheYoungsmodulusofthematerial,howtheloadisperformingonitandbythegeometricalshapeofthespecificpieceofthatmaterial.

Thecomponentstiffnesswillchangedependingontheshape,size,lengthandapplicationofthematerial.IllustratedinFigure1itisevidentthatasthesampleismodified,itisabletowithstandmoreload.However,thecomponentstiffnessdoesnotonlydependontheyoungsmodulusofthematerialusedbutalsoonhowthematerialisloadedwhetherthroughtensionorbending.

Figure1:Showingthreebeamswithequalcrosssectionarea.(CraneandFurness1997p.94)

Therefore,duringthedesignstage,componentstiffnesscanbeimprovedamaterialcanbeusedtodeflectundermoreloadsbeforedeformingpermanently,whereasitisimpossibletochangethematerialsinheritedstiffnessalsoknownastheYoungsmodulus,whichisuniquetoallmaterials.Forexample,changingthecarboncontentcanimprovethestiffnessofamaterial,allowingittowithstandmoreweightthroughreinforcementofmoleculesbutthecomponentstiffnesscanbechangedwithoutmodificationonmolecularlevelbyjustvaryingthesizeorlengthofthesamematerial.AmaterialwithalowEvaluethatbysomereasonispreferredoveranothermaterial,byaestheticreasonsorotherproperties,cantherebyhaveitsstructuraldesignmodifiedsoitcanovercomeitsdisadvantagesofhavingalowmaterialstiffness.Forinstanceatimberjoistofaspecifictimbercanbeproduceswithdifferentdimensionstobeabletowithstanddifferentload.Thestiffnessofthetimberitselfwillnotchangebutthemanipulationofthegeometricalshapewillhavechangedthetimberjoistscomponentstiffness.

Question3:Onthebasisofresults,whichmetalismostsuitableforstructuralapplications?Explainwhy

Onthestressstraindiagramofourexperimentresults,itshowsastraightlinebetweenstressandstrain.Itmeansanincreasestressoccursaproportionateincreasestrain.This

ACSS400 E3 22/02/12

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factisknownasHookesLaw.Itcanbeexpressedmathematicallyas=E.TheconstantofproportionalityEistheYoungsmodulus(Hibbeler,2011)p.156.Youngsmodulusisameasurementofmaterialsstiffnessorresistancetoelasticdeformationunderload(WilliamD.Callister,2010).Hence,thehigherEvalue,thestifferthematerial.Inthetable6.1somemetalsyoungsmodulusispresented.

(WilliamD.Callister,2010)p.157

Onthebasisofourexperimentresults,theYoung'sModulusofcarbonsteelis213.139GPa.ItismuchhigherthantheYoung'sModulusofbrass,whichis102.69GPa.Inotherwords,thecarbonsteelisrelativelyastiffermaterial.Astiffmaterialmeansitchangesitsshapeonlyslightlyunderelasticloads(UniversityofCambridge,DepartmentofEngineering,2002).Inrealitythestructuralapplicationsarerequiredtobeasstiffaspossible,sothatitisabletowithstandtheloadsappliedtobuildings.

Furthermore,carbonsteelalsoisahighlyductilematerial.Itmeansitisabletoreturntoitsoriginaldimensionwhenthestressisreleasedwithinitselasticlimit.Ifthestresscarriesonbeyondtheelasticlimit,itwillnotbeabletoreturntoitsoriginaldimensionwhenthestressisreleased,butitwillnotbefracturedimmediately(Leslie,2007).

Inconclusion,carbonsteelhashighstiffness,highductilityandelasticlimit.Thesepropertiesmeettherequirementsofstructuralapplicationsneedsaswellasitcanbeusedtocalculatetheloadbearingcapabilities.Thereforeitcanbeusedpreciselyandeconomically.Thatiswhycarbonsteelisthemostsuitableforstructuralapplicationsofthemetalstested.

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Conclusion:Inconclusion,theseseriesofexperimentstofindoutyoungmodulusofvariousmaterialshelpedustounderstandthateachmaterialhasadifferentloadbearingcapacitybeforeitbeginsdeformingpermanently.Asaresult,itiswisetoselectmaterialsappropriateforthespecificstructurebeforebeginningconstruction.Ifweknowwhatthetotalsumofallloadswouldbeonthebuilding,wecanuseappropriatematerials,suchasusingmetalswithhighcarbonpercentageforthebuildingswhichareexpectedtosustainbigloadstomakesurethatthebuildingdoesnotcollapseasaresultofmaterialdeformation,whichcanoccuraftertheEvaluehasbeenreached.

Wehavealsodiscoveredthecomponentandmaterialstiffness,andidentifiedthedifferencesinboth,whereascomponentstiffnesscanbeimprovedthroughmodificationofsizeofthesampleorlength,thematerialstiffnessremainsthesameunlessthematerialitselfismodifiedinawayourswere,suchasthebrassbeingcombinationofcopperandzinc,changingthe%wouldhaveadirectimpactupontheyoungsmodulus.

Theexperimentalsoshowedthateverymaterialhasauniqueyoungsmoduli,notallmetalshavethesameEvalue,nordoalltimber.Insomecasescombiningthematerialssuchasthebrassbeingcombinationofcopperandzinc,theyoungsmoduluswasactuallylowerthanthosematerialswouldhavehadindividually,despitetheloweryoungsmodulus,itislikelythatthecomponentstiffnessofthematerialwasgreaterthaniftheyweretestedindividually.

Wehavealsoworkedwithwhatappearedtobeafaultysample,asthequotedbookvalueofEwasconsiderablyhigherthanwhatwehadattained;thissortofexperimentisusefulindeterminingwhetherthematerialprovidedbythesupplierisingoodenoughconditiontobeusedfortheplannedconstruction;decreasingthechanceofaccidentsorcollapseofthebuilding.

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References:CraneF.A.A.andFurnessJ.(1997)SelectionandUseofEngineeringMaterials,3rdEd,ElsevierScience&TechnologyBooks

KermaniA.(1999)StructuralTimberDesign,Cambridge:Blackwellscience

LESLIE,J.A.A.T.(2007).Designtech:Buildingscienceforarchitects..1stEdition.Oxford:ElsevierLtd.

MatbaseMECHANICAL,PHYSICALANDENVIRONMENTALPROPERTIESOFMATERIALS,[online]Availablefrom:http://www.matbase.com/material/wood/

WILLIAMD.CALLISTER,J.D.G.R.(2010).Materialsscienceandengineering:anintroduction.8thEdition.USA:JohnWiley&Sons,Inc.

Bibliography:

HIBBELER,R.C.(2011).MechanicsofMaterials.8thEdition.USA:PearsonPrenticeHall

UniversityofCambridge,DepartmentofEngineering,(2002).PropertyInformationYoung'sModulusandSpecificStiffness[online]Availablefrom:[Accessed30Jan2012]

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AnisotropyofTimber

BySvenssonJosef,SzelagMarlena,TenStanislav,WangXu,WoodsNicholas

ACSS400 E3 22/02/2012

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Contents:

1. Objectivespg.192. Procedurepg.193. Observationspg.204. Resultspg.225. Discussionpg.286. Conclusion pg.337. References pg.34 8. Bibliography pg.349. CertificatesofAttendance pg.35

AndSignedDeclaration

ACSS400 E3 22/02/2012

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Objectives: Samplesofstraightgrainpine,plywoodandchipboard,at0,45and90aregiventoexaminehowtheyareaffecteddifferentlywhencompressionforceisapplied.Forthemaininvestigationweareaimingtoestablishtherelationshipbetweenstrengthandgraindirection.Twospecimensofeachmaterialateachorientationweretested.

Procedure:AsLabSheet.

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Observation:Duringtheexperiment,wehavetestedstraightgrainedtimber,plywoodandchipboardinturns,withcutsparallel,45degreesandperpendiculartothegrainineachofthesamples.Thedifferentsampleshaveallexperiencedsomesortofvisibledamage,insomecasesitwasseveresuchastheexamplefallingapartcompletelybutinmosttherewerevisiblecracksandloudcreakingwhenthepressurewasappliedonthem.

StraightGrainedtimberwasthefirstsamplestested,slightcreakingcouldbeheardduringtheapplicationoftheweightanddeformationofthesampleshasbecomeevidentafterweremovedthesamples.

Theplywoodsampleshaveexperiencedconsiderablymoredamagethanthetimber,althoughthedamagewasnotapparentuntilweveremovedthepressurefromthesamples,audiblecreakingcouldbeheardassamplesbeganbreakingasaresultoftheload.

Figure2:Plywoodaftercompression,Fromrighttoleft:04590

Figure3showshowthechipboardhasbeenaffectedbythepressure,inthecaseonfarright,thesamplehascrackednoticeably,whereasthesamplesthathaveparallelandthe45degreecuthavenotexperiencedasdrasticofachangeintermsofdamage.Duringtheexperiment,loudaudiblecreakingcouldbeheard,butlikeinthecaseofPlywood,visibledamagewasnotapparentuntilafterthe

Figure1:StraightGrainedTimber(BritishColumbianPine)aftercompression.Fromrighttoleft:04590

Figure3Chipboardaftercompression,Fromrighttoleft:04590

ACSS400 E3 22/02/2012

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sampleshavebeenremoved.

Duetoourinexperiencewithusingthisparticulartestingequipmentwefailedtocorrectlyadjusttheequipmentbetweensamplesonafewoccasionswhichledtoinconclusivedataasaresult.Thesesampleswerereplacedwithsamplesofthesamepropertiesandthetestingwasredone.Allresultspresentedbelowarefromsamplestestedcorrectly.

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Results:FailureStress=FailureLoad/OriginalCrosssectionalarea

FailureStress/Area=FailureLoad

TabulateddimensionsandresultsforAnisotropyofTimber.StraightGrainedTimber(BritishColumbianPine).

Timberat0

1. Area:14.9915.31=229.5mm75.1229.4969=17,235N(FailureLoad)

2. Area:14.8715.13=225.0mm59.8225=13455N

Timberat45

1. Area:15.7615.03=236.9mm13.1236.9=3103.39N

2. Area:15.6615.16=237.4mm21.3237.4=5056.74N

Timberat90

1. Area:15.4715.23=235.6mm7.2235.6=1696.32N

2. Area:15.1015.68=236.8mm6236.8=1420.60N

Table1

TimberStraightGrainedTimber[BritishColumbianPine]

Width(mm)

Thickness(mm)

Originalcrosssectionalarea(mm)

Maximumload(N)

FailureStress(N/mm)

FailureLoad(N)

At0degrees 14.99 15.31 229.5 17,244 75.1 17,235

At0 14.87 15.13 225.0 13,458 59.8 13,455

At45 15.76 15.03 236.9 3,107 13.1 3,103

At45 15.66 15.16 237.4 5,064 21.3 5,057

At90 15.47 15.23 235.6 1,702 7.2 1,696

At90 15.10 15.68 236.8 1,413 6.0 1,421

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Resultsinaverage,calculatedfromtableabove

Table2

Graph1:ShowingThefailurestressofBritishColumbiaPinesamplestested

TabulateddimensionsandresultsforAnisotropyofTimber.Plywood.

Plywoodat0

1. Area:14.6715.16=222.40mm30.3222.4=6738.7N

2. Area:15.1214.50=219.24mm39.9219.24=8747.7N

75,10

13,107,20

59,80

21,30

6,000

10

20

30

40

50

60

70

80

Failu

reStress(N/m

m)

Graindirection

BrittishColumbiaPine sample1 sample2

0 degree 45degeree 90degree

TimberStraightGrainedTimber[BritishColumbianPine]

Width(mm)

Thickness(mm)

Crosssectionalarea(mm)

MaximumLoad(N)

FailureStress(N/mm)

FailureLoad(N)

At0 14.93 15.22 227.3 15,351 67.45 15,345

At45 15.71 15.1 237.2 4,086 17.2 4,080

At90 15.29 15.46 236.4 1,558 6.6 1,559

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Plywoodat45

1. Area:14.6514.77=216.38mm10.1216.38=2185.4N

2. Area:14.7214.65=215.70mm9.9215.7=2135.4N

Plywoodat90

1. Area:14.9814.91=223.40mm29.5223.4=6590.3N

2. Area:14.9814.62=219.00mm28.4219=6219.6N

Table3

Resultsinaverage,calculatedfromtableabove

Table4

Plywood Width(mm)

Thickness(mm)

Originalcrosssectionalarea(mm)

Maximumload(N)

FailureStress(N/mm)

FailureLoad(N)

At0degrees 14.67 15.16 222.4 6,733 30.3 6,739

At0 15.12 14.50 219.2 8,757 39.9 8,748

At45 14.65 14.77 216.4 2,183 10.1 2,185

At45 14.72 14.65 215.7 2,127 9.9 2,135

At90 14.98 14.91 223.4 6,587 29.5 6,590

At90 14.98 14.62 219.0 6,222 28.4 6,220

Plywood Width(mm)

Thickness(mm)

Crosssectionalarea(mm)

MaximumLoad(N)

FailureStress(N/mm)

FailureLoad(N)

At0 14.9 14.83 221.0 7,745 35.1 7,744At45 14.69 14.71 216.1 2,155 10 2,160At90 14.98 14.77 221.3 6,405 29 6,405

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Graph2:ShowingThefailurestressofPlywoodsamplestested

TabulateddimensionsandresultsforAnisotropyofTimber.Chipboard.

Chipboardat0

1. Area17.6917.80=314.90mm19.9314.9=6267N

2. Area17.7017.66=312.60mm20312.6=6252N

Chipboardat45

1. 17.7517.74=314.90mm19.3314.9=6078N

2. 17.7317.62=312.40mm19312.4=5937N

30,30

10,10

29,50

39,30

9,90

28,40

0

5

10

15

20

25

30

35

40

45

Failu

reStress(N/m

m)

Graindirection

Plywood sample1 sample2

0 degree 45degeree 90degree

ACSS400 E3 22/02/2012

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Chipboardat90

1. 17.9617.69=317.70mm18.9317.7=6005N

2. 17.6817.84=315.40mm17.7315.4=5583N

Table5

Resultsinaverage,calculatedfromtableabove

Table6

Chipboard Width(mm)

Thickness(mm)

Originalcrosssectionalarea(mm)

Maximumload(N)

FailureStress(N/mm)

FailureLoad(N)

At0degrees 17.69 17.80 314.9 6,216 19.9 6,267

At0 17.70 17.66 312.6 6,241 20.0 6,252

At45 17.75 17.74 314.9 6,080 19.3 6,078

At45 17.73 17.62 312.4 5,933 19.0 5,937

At90 17.96 17.69 317.7 5,998 18.9 6,005

At90 17.68 17.84 315.4 5,574 17.7 5,583

Chipboard Width(mm)

Thickness(mm)

Crosssectionalarea(mm)

MaximumLoad(N)

FailureStress(N/mm)

FailureLoad(N)

At0 17.7 17.73 313.8 6,251 19.95 6,260

At45 17.74 17.68 313.6 6,007 19.15 6,008

At90 17.82 17.77 316.7 5,786 18.3 5,794

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Graph3:ShowingThefailurestressofChipboardsamplestested

19,90

19,30

18,90

20,00

19,00

17,70

17,5

18

18,5

19

19,5

20

20,5

Failu

reStress(N/m

m)

Graindirection

Chipboardsample1 sample2

0 degree 45degeree 90degree

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Discussion:

Question1:Explainthevariationincompressivestrengthoftimberwithtestdirection.Anisotropyisthestateorqualityofhavingdifferentpropertiesalongdifferentaxes.Theanisotropyoftimbercanbetestedusingacompressiontest;thisconsistsoftwoplatescompressingtogethertotellustheboundsatwhichamaterialcantakebeforeeventuallyfailing.Wecanthenunderstandthematerialsstructuralpropertiesanditscompressivestrength.Compressivestrengthistheabilitytosupporttheforcesexertedontoamaterialatdifferentdegrees.Thematerialthenreachesalimittowhichitcanwithstandandthenbucklesundertheload.Atalternatedegreesamaterialhasdifferentcapacitiesatwhichitisabletosupportacompressiveload.

Timberisanaturalmaterial,whichhasuniquecharacteristicsandstructuralproperties;thisisduetothenatureofthegrain.Thegraingivesthetimberitsstrength.Tounderstandthis,thenatureofthegrainwassubjecttoacompressivestrengthtest,twiceat0paralleltothegrain,twiceat45,andtwiceat90perpendiculartothegrain.Inordertotryandachievearoughaveragethetestwascarriedouttwice,thisalsocatersforfailedtests.

Wecanclearlyseefromtheresultspresentedearlierthattestdirectionproducesdifferentresults.Itshowsusclearlythattestingparalleltothegrainiswherethetimberhasmostofitsstructuralproperties.Overthetworesultsofeachspecimenwecanalsounderstandthata90degreesturnofthetestdirectioncandecreasethestructuralpropertiesbyanaverageof13,794N.Thecompressivestrengthoftimberat0isgreaterthantimberat90tothegrain.Thevariationincompressivestrengthcouldbeduetothecellalignmentinthetimber.Thegrainismadeupoftimbercells,towhich90%ofthesearealignedvertically.Sowhenthespecimeniscompressedtheverticallyalignedtimbercellsresistthebendingmoment,actinglikeawebofasteelbeam.Theverticalcellsrequiremoreforcetocompresswhereaswhenthespecimenisrotated90thecellsareverticallyalignedmakingthemeasytocompressandeventuallycausingthematerialtobuckleundertheload.Oncethegrainisrotatedto45and90theresistancedecreases.Thisissincecovalentbondingispresentalongthedirectionofthemicrofibersintimber,whilsthydrogenbondsisactiveinbetweenthemicrofibers.Thusitwillrequirelessforcetobreakthebondingbetweenthecellwallsiftheforceisappliedperpendiculartothefibredirectiontheniftheforceisappliedalongthegraindirection.

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Question2:Itisnotpossibletocomparemeaningfullythemagnitudesofthefailurestressesforthedifferentmaterials.Whyisthis?

Itisnotpossiblesincewoodcomesfromalivingorganism.Therewillbedifferentpropertiesofdifferentsamplesdependingonthespecifictreethatthespecificpieceoftimberoriginatesfrom,independentofwhatgrainangleitiscut.Thereforeseeminglyidenticaltestpiecescanhavedifferentproperties.Anumberofcontributingfactorswilldeterminetheindividualpropertiesofthetestedsamplessuchasdensity,knots,otherdefectsandgrowthrate.Alsowhenusedinconstructionandstructurestimberisusedindifferentsizes,temperaturesandenvironmentsthenthosepresentinthisexperiment.Thiswillhavevaryingeffectonthepropertiesofthematerialsused.Evenifweassumethatallthesamplestestedwereofequalmoisturecontentandstoredinthesameenvironmenttherearefactorsthatcanhaveanimpactonthepropertiesofthematerials.

Thedensityoftimbervariesnotonlybythemoisturecontentandtemperatureofthesamplebutcanalsobedependentontheamountoflatewoodandearlywoodinasample.Sincetreesgrowindifferentratesatdifferentstagesitaffectsthepropertiesofthewood.Strengthanddensitywillbelowestatthelowercenterofatreeandwillincreaseslightlyupwardsandoutwards(Desch&Dinwoodie1996).Theoriginofthetreewillalsoaffectthepropertiesofaspecificpieceoftimber.Twosamplesofidenticalsizethatarecutinthesameangletothegraincanhaveslightlydifferentpropertiesdependingonwhereonthetreetheyoriginatefromaswellasfromwhichtree.

Sinceknotsareanirregularityinthegrainandaffecttheangleofthegrainsitwillhaveanimpactonthestrengthofthematerial.Knotsvaryinsizeandcanoccuranywhereinapieceoftimberandtheeffectswillthereforevary.Iftheknotforinstanceispositionedontheedgeofapieceitwillhaveadifferentimpactonthepropertiesofthepiecethenifitispositionedinthecenterofthepiece.Itisthereforedifficulttoquantifytheeffectofknotsinspecificpiecesoftimber(Desch&Dinwoodie1996).

Thepropertiesofplywoodandchipboardalsodepend,inthesamewayastimberpieces,greatlyonthespecificpiecesoftimberusedandnotonlyonthepropertiesoftheadhesiveorresinused.Sincebothplywoodandchipboardiscomposedofdifferentpiecesoftimberofdifferentkind,factorssuchasknotsandirregularitiesindensityhaveasmallereffectonthemechanicalpropertiesofthesematerials.Butthepropertiesoftheusedtimberwillreflectonthepropertiesonthemanufacturedplywoodorchipboard.Youcouldintheorycalculatethestrengthpropertyofplywoodwithdetailedinformationofthetimberpiecesandadhesiveused.(Illston1995).

Sinceonlytwopiecesofeachgrainandcutanglewastesteditisnotpossibletodrawameaningfulconclusionsbasedonthetestsperformed.Andasseeninthegraphspresented

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earliertherearevaryingdifferencebetweenthetwosamplestested.Anumberoftimberpiecesfromdifferentoriginandsuppliersofthesamekindandstandardwouldhavebeennecessarytobetterindicatethevariationsofthesamekindsofwood.

Gradingoftimbernowadaysisdonewithstructuralsizedpiecesoftimbertobetterdeterminethepropertiesofdifferenttimbersinthewaytheywillperforminstructures.Thereforetheresultsintheexperimentwillbedifferentcomparedtostructuralsizedtesting.

Inadditiontomeasuringthetestsamplesitcouldhavebeeninterestingtoweighthemtodeterminethedensityoftheindividualsamplesofthesamegrainandcutangletoidentifyanydifferences.Ifalargeramountofsamples,orlargerpieces,wastestedandweighedperhapssomeabnormalitiescouldhavebeenidentifiedandmoreaccuratelyindicativeresultscouldhavebeenpresentedforthedifferentpiecesoftimber.

Question3:Comparethevariationinpropertiesfortimber,plywoodandchipboardandoutlinethesignificancefortheuseofthesematerials.Asstatedpreviously,wehavebeengiventimber,plywoodandchipboardsamplestotestthemintermsofcompressionresistance,andanalysethem.

Timberasanaturalsourcehasclearlyvisibledifferencesthanplywoodandchipboard.Asshowninthetable1,timbercutparalleltothegraincanwithstandmuchmoreload(average15,351N)andittakesmoreFailureload(average15,345N)thancutat45or90.ItsbeenfoundthattheTensileandCompressionstrengthsisreachingmaximumatparallelpositiontothegrain,andminimumatperpendicular.Tocomparethistotheplywoodandchipboardresults,Timberhasthebestcompressionresistancecutparalleltothegrainthananyofthematerialatdifferentangles.Totakethesefactorsunderconsideration,Timberishighlyanisotropic,whichmeanhasdifferentpropertiesindifferentdirections.

LookingattheTable4,whereplywoodresultsareaveraged,itcanbeassumedthatthismaterialcanbeslightlyanisotropic,whileitsmaximumloadisvisiblydecreasedwherethesampleswerecutat45,thanat0and90.

ComparingtheconclusionsabovetotheTable6,wherethechipboardresultsaretabulated,thismaterialisnotanisotropic,asithasthesamepropertiesindependentontheanglecut.

Beingatimberbasedmaterial,plywoodhastheabilitytoaccommodatetheoccasionalshorttermoverload;uptotwicethedesignload.Thismeans,thatwhenloadingisapplied

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forashortterm,anelasticresponseispresent.Longtermloadingcancausecreep,whichfollowonfailureofthematerial.

Particleboard isareconstitutedwoodpanelproductmanufacturedfromwoodparticles. Itcanalsobemanufacturedusingwoodflakesorstrands.

Amatof individualwoodparticles iscoated inadhesiveresinandpressedtogether intoafinishedpanel.Asthewoodfibresintheparticlesarerandomlyoriented,thefinishedpanelhasuniformpropertiesineachdirection.

Thismeans, that thepropertiesof thematerial,dependson its contents. Looking at thetable6,chipboardhassimilarmaximum loadand failure loadat thedifferentangles. It ispossibletogetthechipboardresistanttomoisture,ifadequateresinisusedtomanufacturethematerial.

Althoughtimbersmechanicalpropertiesarefixedbythegrowthcycle,plywoodandchipboardspropertiesarefixedbyresinbywhichtheywereglued,andwhichtimberpartstheyaremadeof.Examiningclosureanatureoftimer,betweenhardwoodsandsoftwoods,thereisadifferenceinstructure,butnotinmechanicalproperties.

Durability

Whileitisunlikelyincoolerenvironments,particleboardisstillsusceptibletofungiandtermites;howeveramoisturecontentofover18%wouldneedtobeachieved.Particleboardflooringisthemostcommonapplicationtoencountermoistconditionsandfungusresistantandtermiteresistantflooringisavailabletohelppreventdeterioration.

Particleboardwillperformsatisfactorilyinareasofhighhumidityandcanalsoaccommodatetheoccasionalwaterspillagebutitisnotdesignedtobecontinuallywet.

Particleboardshouldbeconditionedtohumidityleveloftheenvironmentitwillbeusedin,withanormalmoisturecontentrangeof1012%

Thedurabilityofplywoodwillinpartdependonthebondqualityusedinmanufacturing.Althoughtheuseofadurableadhesiveprovidesabondoflongtermeffectiveness,itdoesnotguaranteethattheveneersbeingbondedtogetherwillhaveanylongtermdurability.

Asstructuralplywoodismanufacturedfromarangeofhardwoodandsoftwoodspecies,itmaynotbedurableinexposedweathersituationssomustbetreatedwithpreservativetoensureitsfullservicelifecanbereached.

Uses

Plywoodisnotrecommendedforfullyexposedhorizontalapplicationslikedeckingbecauseseverecheckingcanoccur,butitisagoodsubstrateformembranesinthisapplication.Faceveneersarealsopronetocrackingifleftunprotectedinunsuitableweatherconditions.

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Doors,ExteriorStairs,ExternalCladding,Flooring,Framing,InteriorRailsandBalustrades,InteriorStairs,InternalPanelling,InternalPanelling,TimberJoineryProductsandTimberPortalFramesareexamplesofpotentialuses.

Timberisoneofthemostversatilematerialsforbothinternalandexternaluses.Whethermanufacturedfromsolidorengineeredtimber,therearemanyoptionsinfinishesthatwillnotcompromiseonstrengthandstructuralperformance.

Materialswhichwehavebeengiventotestandanalysearemostlyusedinnonforce,orlittleforceappliedobjects.Timberandtimberlikesuppliesareknownofitsstrength,durability,flexibilityandeasyworkability.HoweverChipboardismainlyusedasafloorboard,itisalsostrongandnaturalmaterial.

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Conclusion:Inconclusion,asdiscussedabove,timberishighlyanisotropic,duetoitsnaturalstructure.Itshowsgreatcompressivestrengthparalleltothegrainandleastperpendiculartothegrain.

Thefailurestressoftimberisinconclusivetocomparesince,evenifthepiecestestedderivedfromthesametree,eachindividualpieceofthetimberhastheirownpropertiessuchasgrainangle,cellstructureanddensityetc.allofthesefactorsaffectthestrengthofthetimber.Forthevarietiesofthecharacteristicoftimberitisusedwidelyinourlifesuchasstructuralbeams,flooring,furniture,frameetc.

Plywoodandchipboardaremanufacturedproducts.Plywoodisproducedbymeansofcrossbindingtimberveneers,thereforethecompressivestrengthparalleltothegrainandperpendiculartothegrainareapproximatelyequal.Thefailurestressdependsonthetypeofadhesiveusedandqualityoftheveneers.Itcanbeusedasconstructionstructurematerial,fordecorationorgeneralpurposeaccordingtothedifferenceofbondingperformance.

Chipboardhassimilarmaximumloadandfailureloadatthedifferentangles,asitisproducedbypressingthewoodparticlesbondedtogetherwithadhesiveandithasuniformpropertiesineachdirection.Thepropertiesofchipboardwillvarybecauseitdependsonthesizeofthechip,densityoftheboardandthetypeoftheresinused.Chipboardismostlyusedasflooringandforfurniturepurposes.

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References:DeschH.E.&DinwoodieJ.M.(1996)Timber,Structure,Properties,ConversionandUse,SeventhEd,London:Macmillan

IllstonJ.M.(1994)ConstructionMaterials,TheirNatureandBehavior,SecondEd,Suffolk:E&FSpon

Bibliography:FindlayW.P.K(1975)Timber,PropertiesandUses,London:CrosbyLockwoodstaples

MerrittF.RickettsJ.(2000)BuildingDesignandConstructionHandbookSixthEd,McGrawHill

WoodSolutions(2011)[online]Availablefrom:http://www.woodsolutions.com.au/WoodProductCategories/[Accessed10022012]

CA1youngs in progressTimber in progress)