Composite Materials Sample Answers 20170716 KFL

Page|1 Sampleanswers–Compositematerials–RemSTEP(DeakinUniversity)

L A B O R A T O R Y L E A R N I N G A C T I V I T Y

Compositematerials

IntroductionToday’sLaboratoryunpackshowcompositematerialscanresponddifferentlytounbalancedforces.

VictorianCurriculumOutcomeChangetoanobject’smotioniscausedbyunbalancedforcesactingontheobject;Earth’sgravitypullsobjectstowardsthecentreofEarth(VCSSU103)

Checkouttheracingcarandsurfboard

GiedovanderGardedrivingtheCaterhamCT03atSepangInternationalCircuit.

AsurferattheCayucosPier,Cayucos,California.

Photo:"Mike"MichaelL.Baird.https://commons.wikimedia.org/wiki/File:Giedo_van_der_Garde_2013_Malaysia_FP1.jpg

https://commons.wikimedia.org/wiki/File:Surfer_at_the_Cayucos_Pier,_Cayucos,_CA.jpg


Whatcouldbethesamebetweenthematerialsusedamodernracingcarandsurfboard?(Hint:focusonthehoweachismade(manufactured).)

Thecarandsurfboardaremadefromlightmaterials,yetmadestrong.Thisallowsforshapingandrigidity.

CompositeMaterialsAcompositematerialismadefromtwoormorematerials,eachwithdifferentphysicalorchemicalproperties.Butwhencombined,thewholecompositehaspropertiesthataredifferentfromtheindividualmaterials.

Somecompositematerialsaremixtures,likecements,concrete,imitationgraniteandculturedmarblesinksandcountertops,andmetalalloys.

Somecompositematerialshaveonematerialembeddedinsidetheothermaterial,forexample,fiberglass,concretewithsteelreinforcement,andmudbrickswithstrawreinforcement.

Somecompositematerialshavetheindividualmaterialsinseparateanddistinctlayers.

Scientistsandengineersaredevelopingnewcompositematerialsbecausetheycanbestronger,lighter,orlessexpensivewhencomparedtotraditionalmaterials.

KeyideasForce–apushorapull

Compressionforce–apushthatsqueezesanobjecttotrytomakeitsmallerorshorter.

Tensionforce–apullstretchesanobjecttotrytomakeitbiggerorlonger.


AimThecompositematerialsactivityenablesyoutoexperienceandinvestigatethewaycombiningthepropertiesoftwomaterials(polystyreneandgaffertape)canresultinaparticulartypeofcompositematerial.Thepropertiesofthecompositeareverydifferentfromthepropertiesoftheoriginal.Intheprocess,youwilllearnabouttensionandcompressionforces.

Whydowemakecompositematerials?

Thesestructuresarestrongerandlighter.

(Note: this question and answer is to test the students’ understanding of theinformationthathasbeenpresentedtothem.)

Considerthesimilaritybetweenthesetwopictures

Abacon,lettuceandtomatosandwichontoastedbread.

Photo:StevenGrovesfromDenver(CO),USA.

GlassAluminumReinforced(GLARE)honeycombcompositesandwichstructure.

Photo:NASA.http://en.wikipedia.org/wiki/Sandwich#/media/File:BLT_sandwich_on_toast.jpg

http://ballistics.grc.nasa.gov/Photographic%20Data/Images/glare_honeycomb.jpg


Howdoyouthinksandwichcompositematerialsaremade?

Layersofmaterialsare“glued”together.

YourchallengeTodayyouareascientistwhohasbeenpaidtodesignastrongercompositeproductforaslittlecostaspossible.Thefollowingdemonstrationistoprepareyouforthetask.

Part1:Demonstrationoftheeffectivenessofsandwichstructures

Thingstonotefromthedemonstration:

• Apolystyreneplankisnotverystrong.(Footnote1)

• Whenadditionalmaterialsarelayeredontothepolystyreneitbecomesacompositematerialanditspropertieschange–itbecomesstronger.

1 Styrofoamisaparticularbrandnameforpolystyrene.


Drawandlabeltheequipmentandwhathappened.

(etcetra)

Part2:Comparisonofthreeproducts:polystyreneonitsownand2compositematerialswithdifferentstructures

Thinkaboutthedemonstrationyouhavejustseen.Canyouthinkoftwodifferentwaysofmakingsandwichcompositestructuresusingthematerialsandequipmentavailabletoyou?

Manypossibleanswershere.Someinclude:

• Puttingtapeonbothtopandbottom

• Puttingtapeonlyontop

• Puttingtapeonlyonbottom

• Usingpartialstripsoftape,etc


Re-dothedemonstrationwithyourgroup.Youwillneedtoworkoutawayofmeasuringtherigidityorhowmuchbendingthereisforeachindividualweightadded.Talkwithyourpartnertodecidehowyouwillmeasuretheamountofbendingandhowyouwillrecordthedatainanappropriatetablebelow.Yoursupportstructuresneedtobe21cmapart(Footnote2).

Recordthedatainanappropriatetabletoshowthedifferencebetweenthepolystyreneandthecompositematerialstructures1and2.

Sometypicaldata

load(g)

bendingnotape(mm)

bendingtapetopandbottomfullwidth

bendingtapebottomandhalftop

0 0 0 0300 3 0400 5 0500 6 2 0600 8 2 1700 14 2 2750 50 2800 (break) 2 3900 3 4

1000 4 61100 6 71200 7 81300 10 91400 13 101500 13 121600 14 14

load(g)

bendingnotape(mm)

bendingtapetopandbottomfullwidth

bendingtapebottomandhalftop

1700 14 161800 15 221900 15 242000 16 262100 20 302200 20 322300 21 352400 22 (break)2500 222600 232700 242800 502900 (break)3000

2 21cmhasbeenchosenbecauseiotisthewidthofanA4cpageandiseasytosetup.Ifyouwish,youcouldusesomeotherseparationdistance.


Graphthedatatoshowthedifferencebetweenthepolystyreneandthecompositematerialstructures1and2.(Hint:putallthedataonasinglegraph.)

0

10

20

30

40

50

60

0 500 1000 1500 2000 2500 3000 3500

defle

ction(m

m)

massloadedontostructure(g)

Deflectionversusload


Describeinwordswhatwasrevealedthroughthedataanalysisofthegraph.

The graph shows the typical deflection of the polystyrene (vertical axis) as load(weights,horizontalaxis)areappliedtothecentreofthepolystyrene.

The left-hand-mostdataare forpolystyrenewithnotape.The lastdatapoint isat750g.Thepolystyrenebrokewithaloadof800g.

Theright-hand-mostdataareforpolystyrenewithfull-widthtapeonthebottomandtop.Thelastdatapointisat2800g.Thepolystyrenebrokewithaloadof2850g.

Part3:AnalysisofforcesRoofsandbridgeshavetospanlargegapswhilesupportingmassiveweight.

Considerthebridgebelow.Theschematicdiagramfollowingisofasimilarlydesignedbridge.

Steelframetrussbridge,locatedontheSouthernHighway,Belize,CentralAmerica.

Photograph©JohnReid&Sons(Strucsteel)Ltd.http://www.steel-bridges.com/under-truss-bridge.html

Steelframetrussbridgedesign.Theconcretedeckandthesteelstrussesformacomposite

structure.Diagram©JohnReid&Sons(Strucsteel)Ltd.


http://www.steel-bridges.com/under-truss-bridge.html

Considertheroof/ceilingbelow.Theschematicdiagramfollowingisofasimilarlydesignedroof.

Compositetrussroof,TahoeRidgeHouse,California.Photograph©WADesignInc

http://www.wadesign.com/newbuilding#/tahoe-ridge-house/

Simplecompositetrussroof

Alltheseroofsandbridgeshaveoneelement(orpart)thatspansthetopofthestructureandoneelementthatspansthebottomofthestructure.


Canyourepresentthemainforcesthatyouthinkareactingonthesetwoelementsofthestructures?

Howmanyelementsspanyourpolystyrenestructure?Whydoyouthinkthepolystyrenestructureisrelativelyweak?

Thepolystyrenestructureonlyhasasingleelement.

Somestudentsmightrealizethatthetopofthepolystyrene isundercompression,whilethebottomisundertensionasweightisapplied.

Howmanyelementsspanyoursandwichstructure?Canyourepresentwhyyouthinkthesandwichstructureworkstoalterthestrengthandrigidity?

Effectivelyonly2elementsspanthesandwichstructure.

Thetapeonthebottomisundertensionasweightisapplied.

Like the roof andbridges, the (mostly) toppolystyrene is under compression. Thetapeonthetopiseffectivelydoingnothing.


Whatistheroleofthetapeandwhatpropertiesmakeitworkwell?

Thetapeprovidesthefibreandagluetofusethelayeredsandwichmaterials.Thetapeisstrongundertension.

Wouldonepieceoftapeaboveorbelowthepolystyrenebeaseffectiveastwopiecesoftapeinabridgestructure?

Onepiecebelowisallthatisneeded. Thetoplayeris ineffectiveat increasingthestrengthofthelayeredstructure.Thebottomlayercouldbereducedtoanoptimalamount(ofstrengthforcost).


Discusswithyourteam,howacompositematerialmightbeusedinboathulls,swimmingpools,racecarbodies,surfboards,spacecraftandaircraft.Canyourepresentwhyyouthinkan“open-sandwich”structure(similartotapeonlyononesideofthepolystyrene)wouldperformbetterorworsethanaregularsandwichstructure(similartotapeonbothsidesofthepolystyrene)?

Inabridge,thegravitationalforcesactdownward.Hencethebottomlayerisalwaysunder tension, and putting tape on the top does nothing as the top layer alwaysundercompression.

However,inboathulls,swimmingpools,racecarbodies,surfboards,spacecraftandaircraft,panelsarebeing flexed: forcespushagainst thepanels inbothdirections.Hencethereinforcinglayerisneededonbothsides.

Part4:ChallengeYourjobasaScientististocreateastrongercompositematerialusingtheleastamountofmaterial(polystyreneandtape)toreducecost.

Workwithyourgrouptodesigntostrongestsandwichstructurecompositematerialusingtheleasttape.Testeachdesignforstrengthandrigiditytodecidethebestdesign.

Decidehowyouwillcollectyourdataforeachtrialandproduceareportthatdescribesthedesignthatworksbest.Includeevidence(data)andanexplanationastowhy(usingdiagramsandwords).




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Composite Materials Sample Answers 20170716 KFL

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