Journal of Industrial Textiles/Optimization of Parameters for the Production of NeedlepunchedNonwoven GeotextilesAmit Rawal, Subhash Anand and Tahir Shah2008 37: 341Journal of Industrial TextilesDOI: 10.1177/1528083707081594The online version of this article can be found at:/content/37/4/341Published by:can be found at:Journal of Industrial TextilesAdditional services and information for /cgi/alertsEmail Alerts:/subscriptionsSubscriptions:/journalsReprints.navReprints:/journalsPermissions.navPermissions:/content/37/4/341.refs.htmlCitations:- Mar 28, 2008Version of Record >>What is This?Downloaded fromOptimizationofParametersfortheProductionofNeedlepunchedNonwovenGeotextilesAMIT RAWAL,* SUBHASH ANANDANDTAHIR SHAHTheUniversityofBolton,DeaneRoadBolton,BL35AB,UKABSTRACT: Needlepunchednonwovengeotextilesarewidelyusedforvariouscivil engineeringapplications.Theseapplicationsarerequiredtoperformmorethanone function,i.e.,filtration,separation,protection,drainage,andreinforcement. Reinforcementisacomplexphenomenonandstronglydependsuponthefabric dimensionalandmechanicalpropertiesinadditiontothesoilCgeotextileinteraction Inthisstudy,theeffectofprocessparametersincludingwebareadensity,punch density,anddepthofneedlepenetrationhasbeeninvestigatedondimensional (areadensityandthickness)andmechanical(punctureresistanceandtensile strengthsinthemachineandcross-machinedirections)propertiesofneedlepunched nonwovengeotextiles.Theseprocessparametersarethenempiricallyrelatedwiththe fabricpropertiesusingmultipleregressiontechnique.Theanisotropiccharacteristics ofneedlepunchednonwovengeotextilestensilepropertieshavealsobeendiscussed. KEYWORDS: geotextiles,needlepunchednonwoven,tensile,dimensional, mechanical,punctureresistance.INTRODUCTION EEDLEPUNCHEDNONWOVENGEOTEXTILES arewidelyusedforvarious civilengineeringapplicationsincludingroadandrailwayconstruction,N*Authortowhomcorrespondenceshouldbeaddressed.E-mail:amitrawal77@,amitrawal77@ Figures1C12appearincoloronline:http://jit.sagepub.co341JOURNALOF INDUSTRIALTEXTILES, Vol.37,No.4!aApril2001528-0837/08/040341C16$10.00/0DOI:10.1177/152808********* SAGEPublications2008LosAngeles,London,NewDelhiandSingaporeDownloaded from342A.RAWALETAL.landfills,slopestabilization,etc.Suchapplicationsrequirecertainfunctional characteristicsinthestructure,besidesbasicproperties,whicharerequired tobeengineeredbyjudiciousoptimizationoftheneedlepunchingprocess. Theseapplicationsarerequiredtoperformmorethanonefunction,i.e.,filtration,separation,protection,drainage,andreinforcement. Anexampleofusingnonwovengeotextilesasreinforcementincludesslope stabilizationinwhichthestabilityoftheslopedependsonthestressesthat thegeotextilecansustainandtransmittheloadswithinthenonwoven structure.Theprincipleofusinggeotextilesasreinforcementistointroduce thegeotextilesintothesoilstructurethatincreasethecohesionbetweenthe grains[1].Thismodifiesthetransmissionoftheloadandtheresulting compositeisabletosustainhigherloads.Theforcesexertedonthestructure asaresultofvariousloadsaretransferredintotensilestresseswhichfurther influencesothermechanicalproperties,suchaspunctureresistance[2]. Thereinforcementisacomplexphenomenonandresultsfromthecombined behaviorofsoilCgeotextileinteractions[3C5].However,theperforman characteristicsofgeotextilesarestronglydependentuponraw-material, manufacturingprocess,anditsrelatedparametersthatalsoinfluencethe structuralmechanicsofthefabrics.Thereareseveralmaterialandprocess parameters(fiber,web,needle,needlepunching,andfinishing)thatcanaffecttheperformancecharacteristicsofgeotextiles.Inaddition,the structuralcoherenceinaneedlepunchedfabricdependsuponthefrictional characteristicsandinteractionofconstituentfibers[6C8]Recently,RawalandAnandjiwala[9]havedemonstratedtheeffectof processparametersincludingfeedrate,strokefrequency,anddepthofneedle penetration(NP)onvariousgeometrical,mechanical,andhydraulicproper- tiesofneedlepunchednonwovengeotextiles.Inthispaper,theeffectofmore thanoneprocessparameter,namelypunchdensity(PD),webareadensity (WAD),andNPhasbeeninvestigatedondimensionalandmechanical propertiesofneedlepunchedgeotextiles.Theseprocessparametersarerelated tothedimensionalandmechanicalpropertiesofneedlepunchednonwoven structuresusingmultipleregressiontechnique.EXPERIMENTALWORK Afullfactorialdesignwasemployedwiththreedesignfactorsatthreelevels,WAD,PD,andNPusingTaguchistechnique[10],asshowinTable1.Here,thefactorlevelswereselectedsuchthatthelower,middle, andupperlevelscorrespondto1,0,and1,respectively.Thecodedlevels andtheactualvaluesofthesefactorsaredefinedinTable2.Following theexperimentaldesign,pre-needledcross-laidwebswereproducedusingDownloaded fromOptimizationofParametersforProductionofGeotextiles 343Table1.Experimentaldesignforproductionof needlepunchednonwovengeotextiles.SampleID NP PD WAD1111201131114101500161017111801191111011011 010121101310014 0 0 0151001611017 010181101911120 011211112210123 0 01241012511126 01127111NPdepthofneedlepenetration;PDpunchdensity;WADweb areadensity.Table2.Codedandactualvaluesofthe processparameters.Parameters1012) 400 800 1200WAD(gm2 aPD(cm) 150 225 375NP(mm)81012WADwebareadensity;PDpunchdensity;NPdepthofneedle penetration.aAccordingtotheexperimentaldesign,themiddlevalueofPDshould2 correspondto262.5cmhowever,problemshavebeenencounteredin producingthefabricsexperimentallyontheneedlepunchingline.Therefore,2 .Inaddition,thesevaluesthenearestvalueofPDwasfoundtobe225cm werematchedwiththeindustrialdatasets.Downloaded from344A.RAWALETAL.polypropylenefibers(10dtexand100mm)atthecollaboratingcompany (GeofabricsLtd,Leeds,UK).Aseriesofneedlepunchednonwoven structureswassubsequentlyproducedonalaboratoryneedlepunchingline attheUniversityofBoltonbasedupontheexperimentaldesign,asshownin Table1.Thestandardtestswereperformedontheneedlepunched geotextilestodeterminefabricareadensity(EN965,1995),thickness(EN964-1,1995),punctureresistance(EN-ISO12236,1996),andtensile strengthsinthemachineandcross-machinedirections(EN-ISO10319, 1996).RESULTSANDDISCUSSIONTable3showsthedimensionalandmechanicalpropertiesofneedle- punchednonwovengeotextilesproduced,tested,andfullyanalyzedusing theexperimentalmatrix(asshowninTable1). EffectofProcessParametersonDimensionalPropertiesofNeedlepunched NonwovenGeotextilesHearleandSultan[11]suggestedthatWADandtypeofstructurehave amajoreffectonneedlepunchedfabricareadensity(FAD)andfabricthickness(FT).Later,themachineparameters,suchasamountofneedling andNPweretakenintoaccount[12].Rakshitetal.[13]havealsostudiedthe influenceofPDandNPonthephysicalpropertiesofneedlepunched nonwovensmadefrompolyesterandpolypropylenefibers.However,they didnotreportsimultaneousinfluenceofmorethanoneparameter.Figure1showsthecombinedeffectofWADandNPontheFAD.Ithas beenobservedthattheNPhasanegligibleeffectontheFAD.However,the FADincreasessharplywiththeWAD.Ontheotherhand,theFADinitially increasesandsubsequentlydecreaseswithfurtherincreaseinthePDas showninFigure2.Thisisbecausehighernumberoffibersarearranged inthethicknessdirectionthatyieldshigherresistancetodraftingbetween bedandstripperplates.FurtherincreaseinthePDcausesthefiberdamage thatreducestheFAD.SimilareffectscanbeobservedforPDandNPon FADasshowninFigure3.Ingeneral,theincreaseinFTisrelativelylessthanthecorrespondingincreaseinFAD[11,12].Since,itisacombinedeffectofhigherfrictional resistanceofferedbythehigherdensitywebsandgreatereffectivefiber entanglementinthestructure.Figure4showsthecombinedeffectofWAD andNPontheFT.ItcanbeseenthattheFTdecreaseswithincreasingNPDownloaded fromOptimizationofParametersforProductionofGeotextiles 345Table3.Dimensionalandmechanicalpropertiesof needlepunchedgeotextilesproducedonlaboratorymachine.Parameters PropertySampleIDWADNPPDFADFTCBRTMDTXMD1 400081505236.484.6122.6655.412 400101505025.435.0025.2050.083 400121505264.584.8624.5056.264 400082255406.125.3226.6550.765 400102255354.794.9529.8250.076 400122255614.004.5629.6150.907 400083754805.384.4324.5139.878 400103755684.225.4130.0943.589 400123756054.174.4540.0454.1010 80008150105611.1511.4943.7581.6711 8001015010858.5511.0446.9895.4912 8001215010306.9610.8156.07107.5813 8000822511989.2412.8157.9781.2314 8001022512157.7011.8955.6198.1115 8001222512896.6810.3865.8397.2216 8000837511588.3611.4542.6560.0117 8001037511456.269.9458.1075.3918 8001237512856.217.6855.2278.9019120008150144611.3317.5467.05100.2820120010150167710.7119.0181.39144.642112001215017399.7416.8676.37148.5722120008225176811.1617.5468.5990.252312001022518759.9516.1988.22126.532412001222518849.2215.1279.43145.8225120008375177210.2217.3345.2259.732612001037518698.3014.7167.1192.162712001237518957.5813.5574.68123.522WADwebareadensity(gm );NPdepthofneedlepenetration(mm);22 PDpunchdensity(cm);FADfabricareadensity(gm );FTfabricthickness(mm);CBRpunctureresistance(kN);TMDtensilestrengthinmachinedirection11 );TXMDtensilestrengthincrossmachinedirection(kNm ).(kNmatlowerWADs.AsimilarrelationshiphasbeenobservedforFTby increasingthePDatlowerWADs,asshowninFigure5.Itshouldbenoted thattheeffectofNPismoresignificantthanthePDontheFT.Figure6 illustratestheeffectofNPandPDontheFT.Sinceatlowerneedle penetrations,theneedlesmaynotbeabletoreorientatethefibersfromthe surfacelayertothethicknessdirectionwhichmayleadtothefullrecoveryof thefibersonremovaloftheneedles.Downloaded from346 A.RAWALETAL.2600 only2328¨2600¨232820562600260023282328¨20561784205620561512¨17841784178415121512¨15121241 FAD FAD 1241 1241 968.65 968.65 ¨1241 968.65 696.79 696.79 424.92 424.92 ¨968.65 696.79 153.05 153.05 ¨696.79 424.92 12 1200¨424.92 153.05 10800 4008 118.81 ¨153.05 WADNP2FIGURE1. Effectofwebareadensity(gm )anddepthofneedlepenetration(mm)22 onfabricareadensity(gm)atapunchdensityof225cm .2503 only2211¨C2501920¨C22125032503221122111629¨C192192019201338¨C162162916291338FAD FAD13381047¨C1331047 1047755.68755.68755.68¨C104464.53464.53173.38173.38464.53¨C755.6117.77117.77173.38¨C464.51200375117.77¨C173.3800225400150WADPD22FIGURE2. Effectofwebareadensity(gm )andpunchdensity(cm )onfabric2 areadensity(gm)ataneedlepenetrationof10mm.Downloaded fromOptimizationofParametersforProductionofGeotextiles3471298 only1237¨12981175¨123712981298123712371113¨1175117511751051¨11131113111310511051FAD FAD989.04¨1051989.04 989.04927.16927.16927.16¨989.04865.28865.28803.39803.39865.28¨927.16741.51741.51803.39¨865.2837512741.51¨803.39102251508679.63¨741.51NPPD679.63 only2FIGURE3. Effectofpunchdensity(cm )anddepthofneedlepenetration(mm)on22 fabricareadensity(gm)atawebareadensityof800gm .14.62 only13.19¨C14.611.76¨C13.1 14.6214.6213.1913.1910.34¨C11.711.7611.768.912¨C10.3 10.3410.348.9128.912FT FT 7.486¨C8.91 7.4867.4866.0596.0596.059¨C7.48 4.6334.6333.2073.2074.633¨C6.05 1.7811.7813.207¨C4.63 812001.781¨C3.2010400120.354¨C1.78NP WAD0.354 only2FIGURE4. Effectofwebareadensity(gm )anddepthofneedlepenetration(mm)2 onfabricthickness(mm)atapunchdensityof225cm.Downloaded from348 A.RAWALETAL.12.65 only11.38¨12.6510.10¨11.3812.65 12.6511.3811.388.831¨10.1010.1010.107.559¨8.8318.8318.8317.5597.559FT FT6.286¨7.5596.2866.2865.0135.013¨6.2863.7413.7412.4682.4683.741¨5.0131.1951.1952.468¨3.74112001501.195¨2.4688002254003750.0774¨1.195WADPD0.0774 only22FIGURE5. Effectofwebareadensity(gm )andpunchdensity(cm )onfabric thickness(mm)ataneedlepenetrationof10mm.13.16 only12.37¨C13.111.57¨C12.313.1613.1612.3712.3710.78¨C11.511.5711.579.980¨C10.710.7810.789.9809.9809.184¨C9.98 FTFT9.1849.1848.3888.3888.388¨C9.18 7.5937.5936.7976.7977.593¨C8.388 6.0016.0016.797¨C7.59 15086.001¨C6.79 22510123755.206¨C600PDNP5.206 only2FIGURE6. Effectofpunchdensity(cm )anddepthofneedlepenetration(mm)on2 fabricthickness(mm)atawebareadensityof800gm.Downloaded fromOptimizationofParametersforProductionofGeotextiles349 EffectofProcessParametersonMechanicalPropertiesofNeedlepunched NonwovenGeotextiles Themechanicalpropertiesincludingtensilestrengthsinthemachineandcross-machinedirections(TMDandTXMD)andpunctureresistance(CBR) werealsostudied.ItisexpectedthatTXMDwouldbehigherthanthe correspondingstrengthinthemachinedirectionbecausethepreferential orientationoffibersisinthecross-machinedirection(cross-laidwebswere usedinallexperimentalfabrics).Inthepast,thetensilepropertiesofthe needlepunchednonwovenstructureshavebeenrelatedtothefabric dimensionalpropertiesandprocessparametersincludingNP,numberof barbs,etc.[11C13].However,itisinterestingtocharacterizetheisotropyi thetensilestrength,expressedastheratiooftensilestrengthsinthecross- machinedirectiontothemachinedirectionbaseduponthecombinedeffect ofprocessparameters.Figure7showsthecombinedeffectofWADandNP ontheratiooftensilestrengthsinthecross-machinetomachinedirections. Ithasbeenfoundthatthedesiredisotropiccharacteristicsintensile strengthscanbeachievedathigherWADwithlowerNP.Ontheotherhand,thestructurewouldbelooseastheentanglementofthefiberswould2.831 only2.652¨C2.832.473¨C2.65 2.8312.8312.6522.6522.294¨C2.47 2.4732.473 TXMD/TMD 2.115¨C2.29 2.2942.2942.1152.1151.937¨C2.11 1.9371.937 TXMD/TMD 1.758 1.758 1.758¨C1.93 1.5791.5791.4001.4001.579¨C1.75 1.2221.2221.400¨C1.579 124001.222¨C1.4010800120081.043¨C1.22WADNP1.043 only2FIGURE7. Effectofwebareadensity(gm )anddepthofneedlepenetration(mm) onratiooftensilestrengthsinthecross-machinetomachinedirectionsatapunch2 densityof225cm.Downloaded from350 A.RAWALETAL.3.479 only3.262¨C3.473.045¨C3.263.4793.4793.262 3.2622.829¨C3.043.0453.045TXMD/TMD2.612¨C2.822.8292.8292.6122.6122.395¨C2.612.3952.3952.1782.178TXMD/TMD2.178¨C2.391.9611.9611.7451.7451.961¨C2.171.5281.5281.745¨C1.9615012001.528¨C1.742258003754001.311¨C1.52PDWAD1.311 only22FIGURE8. Effectofwebareadensity(gm )andpunchdensity(cm )onratio oftensilestrengthsinthecross-machinetomachinedirectionsataneedlepenetration of10mm.notbesubstantial.TheothercombinationwhichmayyieldhigherisotropiccharacteristicsishigherPDatagivenrangeofWADs.Figure8shows thecombinedeffectofPDandWADontheratiooftensilestrengthsinthecross-machinetomachinedirections.Thehigherisotropiccharacteristicsincross-laidnonwovenstructurescanalsobeachievedatahigherPDwith lowertohigherNP,asshowninFigure9.Thismaybeattributedtothefact thatpreferentiallyorientedfibersinthecross-machinedirectiontendto reorientateinthemachinedirectionathigherpunchdensities.Theseeffects havealsobeenobservedbyRawalandAnandjiwala[9]asthefiber orientationdistributionwascharacterizedbyvaryingtheprocessparameters includingNPandstrokefrequency.Punctureresistance(CBR)hasalsobeencharacterizedasitisof paramountimportanceintheapplicationswherethegeotextileissubjected totheconcentratedforcesperpendiculartoitsplane.Theseconcentrated forcescanresultinthepuncturefailureofthegeotextilematerial.Figure10 showsthecombinedeffectofWADandNPonthefabricpunctureresistance.IthasbeenobservedthattheWADhasasignificanteffectonthe punctureresistancewhereastheNPhasanegligibleeffect.Thisisbecause thepunctureresistanceishighlydependentupondimensionalproperties suchasFADandFT[14,15].ThishasalsobeensupportedbyformulatingDownloaded fromOptimizationofParametersforProductionofGeotextiles3512.797 only2.650¨C2.792.503¨C2.652.7972.7972.650 2.6502.356¨C2.502.503 2.5032.3562.3562.209¨C2.35TXMD/TMD2.209 2.2092.0622.0622.062¨C2.201.915 1.9151.768 1.768TXMD/TMD1.915¨C2.061.621 1.6211.621 1.6211.768¨C1.911.4741.4741.621¨C1.7681501.474¨C1.6210225123751.327¨C1.474PDNP1.327 only2FIGURE9. Effectofpunchdensity(cm )anddepthofneedlepenetration(mm)ontheratiooftensilestrengthsinthecross-machinetomachinedirectionsatawebarea2 densityof800gm.24.60 only21.86 ¨C 24.619.11 ¨C 21.824.6024.6016.37 ¨C 19.121.8621.8619.1119.1116.63 ¨C 16.316.3716.3713.6313.63CBRCBR10.88 ¨C 13.610.8810.888.1428.1428.142 ¨C 10.85.3995.3992.6565.399 ¨C 8.140.08710.08712.656 ¨C 5.39120080.0871 ¨C 2.658001040012NPWAD2FIGURE10. Effectofwebareadensity(gm )anddepthofneedlepenetration(mm)2 onpunctureresistance(kN)atapunchdensityof225cm.Downloaded from352 A.RAWALETAL.Table4.Relationshipbetweengeotextiledimensionalandmechanicalproperties. Mechanicalproperty Regressionequation Correlationcoefficient(R)CBR(kN) CBR0.0052FAD1.03FT3.14 0.981TMD(kNm) TMD0.0372FAD0.816FT14.87 0.891TXMD(kNm )TXMD0.0478FAD1.243FT18.460.8124.38 only821.56¨C24.18.73¨C21.624.3824.3821.5615.90¨C18.3 18.7318.7313.08¨C15.0 15.9015.9013.0813.08CBR CBR 10.25¨C13.8 10.2510.257.4257.1257.425¨C10.5 4.5994.5991.7721.7724.599¨C7.45 1.0541.0541.772¨C4.59 15012001.054¨C1.72 225800400WADPD22FIGURE11. Effectofwebareadensity(gm )andpunchdensity(cm )onpuncture resistance(kN)ataneedlepenetrationof10mm. therelationshipbetweenpunctureresistanceandfabricdimensional properties.Table4showsalinearrelationshipbetweenpunctureresistance andFADplusFTandhasyieldedanexcellentcorrelation.Furthermore,the combinedeffectofWADandPDhasbeenanalyzedonpunctureresistance, asshowninFigure11.However,theeffectofPDismoresignificantin comparisontothatofNP.Figure12showsthecombinedeffectofPDand NPonpunctureresistance.IthasbeenobservedthatathigherPDs,the punctureresistancesignificantlydecreaseskeepingtheotherparameters constant.Thismaybeattributedtothefactthathigherpunchdensities causesignificantfiberdamagewhichdecreasesthepunctureresistance values.Downloaded fromOptimizationofParametersforProductionofGeotextiles35311.82 only10.98¨C11.810.13¨C10.911.82 11.8210.98 10.989.285¨C10.110.1310.138.440¨C9.289.2858.4408.440CBR CBR 7.594¨C8.44 7.5947.5946.7196.7496.749¨C7.59 5.9045.9045.0585.0585.904¨C6.74 4.2134.2135.058¨C5.90 37584.213¨C5.05 10225121503.368¨C4.21 NPPD3.368 only2FIGURE12. Effectofpunchdensity(cm )anddepthofneedlepenetration(mm)on2 punctureresistanceatawebareadensityof800gm.DevelopmentofEmpiricalModels Theempiricalrelationshipsbetweenthemainprocessparameters,namely, WAD,PD,andNP,andthefabricpropertieswereformulatedusing multipleregressiontechnique.Theanalysishasalsoincludedinteraction andquadraticeffectsasshowninEquation(1).Y aa xa xa xa x xa x x0 1 1 2 2 3 3 12 1 2 13 1 32 2 2a x xa xa xa x ;123 2 3 11 22 331 2 3, x , x areindependentvariables, a isawhere, Y isadependentvariable, x1 2 3 0regressionconstant, a, a , a areregressioncoefficientsofindependent1 2 3variables, a, a , a areinteractioncoefficientsofindependentvariables,12 13 23and a, a , a arequadraticcoefficientsofindependentvariables.11 22 33Table5showsthecoefficientsoftheempiricalmodelsbaseduponEquation(1)alongwiththeirrespectivecoefficientsofdetermination. Thesemodelsarebaseduponthecodedvaluesoftheparameters,i.e.,theminimumandthemaximumvaluesare1and1,respectively. Itisconcludedthattheprocessparameters,namely,NP,PD,andWADhaveasignificanteffectonthevariousdimensionalandmechanical propertiesas p-valueis<0.0001.Downloaded from354 A.RAWALETAL.Table5.Regressionconstantsandcorrelationcoefficientsofempiricalmodelsfor needlepunchedgeotextilesproperties. NeedlepunchedgeotextilespropertiesConstantsFADFTCBRTMDTXMD1220 7.7311.3160.4713.54aaNP 48.501.130.7925.7111.821aPD 66.280.790.6820.3532.252aWAD 615.832.395.79221.91.823a a 8.750.140.5352.8412.71 2aa 31.920.0780.5332.447.821 3a 47.670.250.6375.003.89a2 32a10.390.380.3053.576.3612a76.060.110.4086.773.8222a8.720.490.1973.5113.543Coefficientof 0.990.970.980.950.982determination(R )F-value 275.9468.65148.439.8380.75NPdepthofneedlepenetration;PDpunchdensity;WADwebareadensity;FADfabricareaden sity;FTfabricthickness;CBRpunctureresistance;TMDtensilestrengthinmachinedirection;TXM Dten-silestrengthincrossmachinedirection.CONCLUSIONSAseriesofcross-laidneedlepunchednonwovengeotextileswasproduced baseduponTaguchisexperimentaldesigntechniquebyvaryingtheproces parameters,i.e.,WAD,PD,andNP.Theeffectofmorethanoneparameter hasbeeninvestigatedondimensionalandmechanicalpropertiesof needlepunchednonwovengeotextiles.ItwasfoundthatWADandPD havesignificanteffectsonFADwhereasthemajorparametersaffectingthe FTareWADandNP.Furthermore,isotropicneedlepunchednonwoven structurescanbeproducedathigherpunchdensitiesforagivenrangeof webareadensities.Punctureresistance(CBR)hasalsobeenrelatedtothe processparametersanditwasconcludedthatpunctureresistanceishighly dependentuponFADandFT.Theseresultswerealsosupportedby obtaininganexcellentcorrelationbetweentheexperimentalandmodeledresults,i.e.,byformulatingthelinearrelationshipbetweenCBR,FAD,andFT.Theempiricalmodelsrelatingtheprocessparameterstothedimensional andmechanicalpropertieshavealsobeendevelopedusingmultiple regressiontechnique.Downloaded fromOptimizationofParametersforProductionofGeotextiles355ACKNOWLEDGMENT Theauthorsgratefullyacknowledgethesupportprovidedbythe DepartmentofTradeandIndustry(DTI)andGeofabricsLtd.,Leeds,UK. 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APrimerontheTaguchiMethod,SocietyofManufacturing Engineers,NewYork.11.Hearle,J.W.S.andSultan,M.A.I.(1967).AStudyofNeedledFabricsPartI: ExperimentalMethodsandProperties, JournalofTextileInstitute, 58(6):251C26512.Hearle,J.W.S.,Sultan,M.A.I.andChoudhari,T.N.(1968).AStudyofNeedled Fabrics,PartCII,EffectsoftheNeedlingProcess JournalofTextileInstitute,59(2):103C116Downloaded from356 A.RAWALETAL.13.Rakshit,A.K.,Desai,A.N.andBalasubramananian,N.(1990).Engineering NeedlepunchedNonwovenstoAchieveDesiredPhysicalProperties, Indian JournalofFiberandTextileResearch, 15(1):41C4814.Wilson-Fahmy,R.F.,Narejo,D.andKoerner,R.M.(1996).Puncture ProtectionofGeomembranes,PartI:Theory, GeosyntheticsInternational,3(5):605C62715.Narejo,D.,Koerner,R.M.andWilson-Fahmy,R.F.(1996).PunctureProtection ofGeomembranes,PartII:Experimental, GeosyntheticsInternational, 3(5): 629C653BIOGRAPHYAmitRawalreceivedhisPhDdegreein advancedmaterialsfromTheUniversityofBolton.HecompletedhisMasterofPhilosophy degreeintechnicaltextilesattheUniversityofManchester.HehasbeenawardedaYoung ResearcherFellowshipfromtheprestigious MassachusettsInstituteofTechnology,Cambridge,USAforexemplaryresearchin computationalmechanics.Recently,hehasbeen involvedindevelopingthemechanicalmodelsfor variousnonwovenstructures.Hisresearchinter- estsincluderheologicalpropertiesofpolymers, polymerflowmodellingandstructuralmechanicsofwovenandnonwoven fibrousassemblies.。