bmanuela aecher N I `ristina ianivschi O

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1 Structural Analysis of Historical Constructions Jerzy Jasieńko (ed) 2012 DWE, Wrocław, Poland, ISSN , ISBN TIMBER STRUCTURES REPAIR WITH WFRP (WOOD FIBRES REINFORCED POLYESTER) bmanuela aecher N I `ristina ianivschi O ABSTRACT `onsideringthedegradationsthatoccurintimberstructuresiincludingagingprocessesiaremedial measureiabletomitigatethesedegradationsaffectingbothstructuraltimbersystemandwooditself includestheuseofacompositesystemwithaninnovativeapplicationtechnologyk molyesterresiniwithitsviscousliquidaspectiimpregnatesthewoodibeingabsorbedonankr OKMmm depthifunctionofenvironmentalconditionskqheinterfacecomposedoftheimpregnatedwoodbecomes adistinctcompositematerial woodfibresspatiallyreinforcedpolyestertcomiwhichhavehigher physicalandmechanicalpropertiesthanwoodkqhisnewcompositemaybecreatedbylayingon impregnatedwoodacoatofwoodfibresialsoimpregnatedwithpolyesterresink qheremedialsystemmaybeappliedbothfortotalandpartialfracturedtimberstructuralelementsand consistsofcreatingsomepocâetswithdiametermeasurings NMmminwhichareintroducedsome pinsobtainedbyimpregnatingabundleofwoodfibreswithpolyesterresinkqheextremitiesofthepins fromwoodfibresaremouldedonthesurfaceofthestructuralelementiinanydirectioniandthen impregnatedwithresinkcinallyithedamagedzoneofthewoodelementsplicedwithlayersfromwood fibresiallimpregnatedwithpolyesterresiniformaspatialcleatiwhosesizesaredeterminedbydesign calculusk qhistypeofinterventionassuresacompleterehabilitationofthetimberstructuralelementibothfrom mechanicalandgeometricalpointofviewandalsomaintainstheestheticalandhistoricalvalueofthe structurek heywordsw Timber structuresi oepair technologyi `omposite materialsi tood fibres reinforced polyester 1. INTRODUCTION 1.1. General information qhestudyofcompositematerialsandtheireffectivenessinindustrialprocessesisfollowingan ascendingtrendibothonnationalandinternationallevelk`onsideringtheinformationdatabases presentlyavailableiadetailedanalysisofbiojcompositematerialsandtheirapplicationdomainsmay becarriedoutkfnburopeanrnionithedistributionofproductsinvolvingcompositematerialsshows thatconstructiondomainissituatedonthesecondplacewithapproxkpomthousandsoftonesixnzk toodfibresarebasicallyofcellulosicnatureandareextractedfromtreesistrawibambooicottoni hempijuteisugarcaneandothersourceskaependingonthedesiredfibrescharacteristicsithespecies thatisbestsuitedischosenandtherequiredfibreprocessingechemicaltreatmentiheattreatmenti mechanical±brushing orrefiningietckfiscarriedoutk cortimberelements rehabilitationiofgreatimportancearetheinvolvedmaterials`structureswwoodi jutefibresandunsaturatedthermorigidpolyester kbpqoamli4rmithetwolatterbeingusedto obtainthehybridcompositematerialproposedhereink N AssocKmrofKI±dheorgheAsachi qechnicalrniversityicacultyof`ivilbngineeringandbuildingpervicesi fasiioomaniaidecher]cektuiasikro O mhastudenti±dheorgheasachi qechnicalrniversityicacultyof`ivilbngineeringandbuildingpervicesi fasiioomaniaickeklanivschi]gmailkcom OMOM

2 1.2. Some aspects concerning wood toodisanaturalfibrouscompositematerialiasacombinationofcelluloselongfibresbondedtogether bylignink`ellulosefibresensurethestrengthofwoodiwhiletheligninplaystheroleofmatrixwhich stabilizesthefibresintothematerial`sstructurexoj4zkqhetree`schemicalstructureistheresultof biosynthesisreactionsofnaturalpolymerswcelluloseiligninihemicellulosesandtheirtransformationsk qhechemicalcompositionofwoodstructure`smaincomponentsarew cellulosew nh (C 6 H 10 O 5 ) OH (n-1) H 2 O + H (C 6 H 10 O 5 ) n OH(C)W4Oto4RBIanatural polymerbeingthemaincomponentofthevegetalcellularmembranekqhestructuralunityof cellulosemacromoleculeisconstitutedbytheanhydrousjajglucosekqhevegetalcellmembrane representsamassofdifferenttypesof`arbonhydratesthatbasicallyconstituteacellulosic fibresreinforcedplasticgelitheproportionbetweenthetwocomponentspresentinglittle variationsk`elluloseisapolymerwithrigidchainandquasijcrystallinemonojphasesfibrillar structurek`ellulosebiosynthesisinsidetheplantislimitedbytheinfluenceofstericformations andthevitalactivityofthecellk hemicellulosesisresponsibleforthebiodegradationimicroabsorptionandthermaldegradation ofthefibresasitshowsleastresistanceiwhereasligninisthermallystablebutpronetors degradationx4zk ligninwn(c 10 H 12 O 3 ) + 1/2 no 2 nh 2 O + (C 10 H 12 O 3 ) n (L)WNUtoPPBIisthemainaromatic componentofvegetaltissuesandintegratesagroupofchemicallybondedamorphous macromolecularcombinationskqhelignincomplexpresentssomecharacteristicfunctional groupsserieswmetoxilihydroxylandcarbonylk 2. CONSTITUTIVE MATERIALS OF WFRP 2.1. Jute fibres gutefibresbelongto±vegetalnaturalfibres groupinwhichthemaincomponentisrepresentedby celluloseiwhosestructuralunitisxrzw `e O le e le l e e e l le e l le e e l e e l e le `e O le wherestructuralelementsarebondedbetweenthemiinachainibyaidofoxygenbridgesnumdegrees rotatedtoeachotherk `hemicalcompositionandthemoisturecontentofjutefibresissnkntotnkrttbcelluloseinpksto OMK4ttBhemicellulosesINOtoNPttBligninandNOKRtoNPKTttBmoisturecontentK gutefibrespresentsomeadvantagesasbeingecologicalifullybiodegradableiabundantlyavailableand renewableiwithreducedcostsinonjabrasivenatureandsafehandlingigivingthepossibilitytobeused forrepairingtimberelementskftalsopresentsgoodworâabilitywithreducedenergyconsumptioni reduceddensityifactorsthatareextremelyimportantforbeingacceptedonthemarâetswithhigh materialconsumptioniasconstructionindustryk qhedisadvantagesofthesetypesofmaterialsarethelimitedthermalstabilityistrengthdecreasing withincreasinghumidityandthevariationofthematerialqualitydependingonthegrowthseasonof theplantiwhichconsiderableaffectsthepossibilityofusethesefibresforreinforcingpolyesterskeigh humidityabsorptionofvegetalfibresandthepresenceofvoidsintheinterfaceeporoussurfacesf decreasethemechanicalpropertiesandreducethedimensionalstabilityofcompositematerials reinforcedwiththesetypesoffibresk qhephysicalandmechanicalpropertiesofjutefibresarethereduceddensityofaboutnkpglcm P Ithe fibrelengthofnrmmmmtoptmmmmivoungjodulusofoskrdma;tensilestrengthofpvpjmato TTPjmaandelongationofNKRtoOBK 2.2. Polyester resin rnsaturatedpolyesterresinikbpqoamli4rmjsmiisanunsaturatedpolyesterssolutionin amonomeriwiththeroleofreactivesolventitowhichcojpolymerizationformsareticularstructure polymershardeningxszk OMON

3 rnsaturatedpolyestershavelinearstructureiwithfewlateralchainswhichhaveintheirstructure dicarboxylacidsanddiolskpomeoftherawmaterialsusedinpolyesterification containdouble chemicalbondej``jfwhichgiveunsaturatedcharacterandcomefromtheeα-βf unsaturated dicarboxylacids maleicanhydrideieasytobesynthesizedincomparisonwithunsaturateddiolsk qoobtainthepolyesterchainipolyesterificationofdicarboxylacidswiththediolsandaddingthe diepoxyanhidrideisdonek molyesterificationisachemicalreactiontoreachtheequilibriumandrepresentsthemainchemical reactionxtzw ell` o `llehel o N leell` o `l lo N lehe O li whichcontinueswhilethewaterisremovediassecondaryproductk rnsaturatedpolyesterresinikbpqoamli4rmjsmiisoforthophthalictypeiwithhighviscosityand reactivityihavingmaleicanhydrideiphthalicanhydrideandpropylenejglycolcomponentsk eardeningoftheseresinstaâesplacebycojpolymerizationofmonomershavingdoublechemical bondintheunsaturatedpolyesterchaink `oldhardeningonunsaturatedpolyesterresinisfrequentlyappliedformanualprocessingforrepairs andisensuredbyusingaredoxsystemformedbycobaltsalt âetoneperoxidekfnthiscaseithe polyestershavelongergellingtimeandthehardeningprocessproceedsmoreslowlyk mostjpolymerizationofhardenedresinwithcobaltacceleratorsubstantiallyshortensitsmaturation periodk 2.3. Wood fibre reinforced polyester segetalfibresreinforcedcomposites maybeconsideredintheframeofcompositematerialsinwhich thefibresensurethestrengthandstiffnessofthematerialandunsaturatedpolyesterresinrepresents thematrixiwhichtransfersthestressesbetweenfibresandthroughoutthecompositekqhematrixalso rejdistributesthestressesinthecompositewhensomeofthefibresarebroâenk qhecriteriaofchoosingthejutefibresforrepairingtimberconstructionelementsarebasedonthe similarmechanicalpropertiesandcompatibilityofthesetwomaterialsk qheproposedrepairsolutionisbasedontherelationbetweenresinlwoodandresinlvegetalfibres respectivelykqhusithewoodfibreseofcellulosicnaturefandpolyesterresinisconsideredtohave goodcompatibilitybecausetheresiniasitislessviscousimaybeabsorbedbywoodicreatinga compositematerialwoodjsyntheticresinkqhismaterialcreatedatthewoodjresininterfacehas superiorshearbondstrengththanwoodfibresjlignininterfaceklntheotherhanditheexistenceof somedegreeofcompatibilityemechanicalichemicaliphysicalfbetweenthejutevegetalfibresealsoof cellulosicnaturefandpolyesterresiniallowthecreationofanindependentcompositematerialwith unitarystructureandwithajpriorideterminedmechanicalpropertieskcorthistypeofmaterialithree pointsbendingtestwereperformedispecifictocompositematerialplatesiconsideringthattherepaired timberelementisalsoloadedinbendingk Associatingwood syntheticresinforobtainingahybridcompositeisomedisadvantagesofnatural woodiliâenaturaldefectsidimensionalinstabilityireducedresistancetophotojbiojchemicalattacâi maybepreventedxvjnnzk mroducingandprocessingtechnologiesofhybridcompositematerialismanual contacttechnologyk 3. TESTING PROGRAM qhemainobjectiveofthetestingprogramistodeterminethemechanicalpropertiesofthehybridbioj compositematerialobtainedbyimpregnatingjutefabricwithpolyesterresinandtheeffectofrepair appliedtothebroâennaturaltimberiusingthistypeofmaterialk qheexperimentalprogramiscarriedoutinthreestepswthreepointsbendingtestofthehybridbioj compositeofpolyesterresin jutefabrictype;thebehaviouroftheresinlwoodrespectively resinljutefabricinterface;applicationofthehybridbiojcompositeontwosprucetimberelements bothofthembeingloadedinfourpointsbendingioneofthembeingfracturedandthesecondloaded withaforceofnsâkk 3.1. Three points bending test of the hybrid bio-composite specimens corthehybridbiojcompositespecimensithreejutefabriclayersimpregnatedwithpolyesterresinwere usedkftisstatedthatjutefabricismadeofuntwistedyarnsandisofunbalancedtypewthewarpis OMOO

4 representedbyonejuteyarniwhilewefthastwojuteyarnsithedifferencebetweenthesetwobeingof RRBweftto4RBwarpIgravimetricallymeasuredKqherarefabrichasO PmmmeshsizeIthesmall differenceoffibresonthetwodirectionsbeingexplainedbytheuseofonebiggerwidthstrandsin warpiandtwosmallerwidthstrandsinweftithewarploosingsomeofthefibresquantityduring weavingprocessbyfrictionk cromthehybridbiojcompositeplateiofrmm PSMmmINSspecimenswerecutandprocessedin accordancetoapqjptandardatos4jmti±clexuralpropertiesofmolymerjatrix`omposite jaterials Kqhespecimens`lengthandthedistanceareestablishedfunctionofthewidthoftheplateKcor theplateitmvgofkbpqoamli4rmjsmpolyesterresinandn4mgofjuteyarnfabricwereusedi resultingareinforcingpercentofombkqheplatewasâeptinstandardconditionsirespectivelyom N ` temperatureandsrbinteriormoistureiforhardeningandmaturationoftheresiniforn4daysk qhetestingequipmentisa`omputer`ontrolblectroeydraulicpervorniversalqestingmachinewith amaximumappliedloadofsmmâkkqheappliedloadingspeedwasofmkrâklseckqhespecimens wereloadeduntilfailureandtheforcejdisplacementresulteddiagramswereobtainedecigknfk AfterprocessingthedataIthestressesandstrainsatfailureandtheelasticmoduluswerecomputedK cromthediagrampresentedinecigknfiitmaybeseenthatibyincreasingloadisomeofthejute strandswithsmallercrossjsectionssuccessivelybreaâifactthatisemphasizedbyabruptchangesin thediagramskqhepolyesterresinovertaâesandredistributesthestressestothestillworâingstrandsk cinallyithefailureoccurssimultaneouslybybreaâingthefibresandcrushingoftheresinkko detachmentorpulloutofthefibresfromthematrixareobservedk corthetestedbiojcompositematerialtheresultsobtainedarewmaximumnormalstressfuof TUKNORkLmm O andthemaximumstrainofpkmosbkqhemaximumobtainedmodulusofelasticityis 4TMOKTMOkLmm O K Fig. 1ioad displacementdiagramofthehybridbiojcompositespecimens qhemeanvaluesofthenormalstressistrainandmodulusofelasticityareofspkuurklmm O IOKRUSB andpvovknsuklmm O IrespectivelyK 3.2. Shear bond strength of the wood bio-composite material interface qhesecondstageoftheexperimentalprogramconsistsofdeterminingtheshearbondstrengthofthe biojcompositematerialtothesupportemeaningwoodfkanumberoftenspecimensofsprucewood werecarriedoutandprocessediwiththedimensionsofom OM PMMmmKAtthemiddlethirdIon alengthofnmmmmithetwopiecesofwoodwerebondedtogetherbyaidoftwolayersofjutefabric impregnatedwithpolyesterresinithesamematerialusedfortherepairtechnologykafterbondingithe elementswerepressedandâeptintopositionforhardeningandmaturationforn4dayskqhespecimens weretestedintensionwithanapplicationloadspeedofmknâklseck OMOP

5 afbfcf Fig. 2 toodspecimenstestedinshearbondstrength;aftestsetup;bfcftypeoffailure qheobjectiveofthetestingprogramistodeterminetheshearbondstrengthattheinterfacebetween woodlbiojcompositematerialskqheexperimentalresultsobtainedareplottedinaloadjdisplacement diagramipresentedinecigkpfk Fig. 3ioad displacementdiagramofthewoodlbiojcompositematerialspecimensloadedintension BythetestsetuppresentedhereIattheinterfacebetweenthetwomaterialsIshearstressesoccurIwhich describethemechanicalpropertiesofbondstrengthofthetwophaseskbyprocessingtheobtained resultsiforthemaximumappliedloadofpktsrâkepsfashearstressofnkuuorklmm O was computedk qhefailuremodesarepresentdinadetailedviewinecigk4fk Fig. 4cailuremodesofwoodLbioJcompositespecimenssubjectedtotension OMO4

6 ftmaybeobservedthatthespecimensfailureoccursbypullingoutofthewoodfibresinthematerial withweaâermatrixeligninfkkoneofthespecimensshoweddetachementofthewoodfrompolyester resinorfromthehybridcompositeandalsothehybridcompositeisnotaffectedbyanydeteriorationk qhisisduetothefactthattheresingetsintothewood`smassonacertaindepthiformingatransition zonebetweenwoodandthebiojcompositematerialkqhefailureoccursbypullingoutthewoodfibresi seespecimenspnippipriptandpvrespectivelykthenthelongitudinalshearstressesinwoodare smallerthanthestressesatlevelofthewoodlresininterfaceithespecimensfailedinthewoodsectioni seespecimenspoip4andpukfnonlyonecasethedetachmentofthecompositematerialfromthe woodtooâplacebecausetheresindidn`tsufficientlyimpregnatedthewoodispecimenpnmk Aspecialbehaviorwasthatofspecimenp4wherethebondedzoneremainedintactIwhilethefailure occuredinthewoodsectionasaresultofthetensionstressesparaleltothegraink AsaconclusionIthegoodcompatibilitybetweenwoodIjutefabricandkbpqoAmli4RMJSM unsaturatedpolyesterresinmaybeemphasizedk 3.3. Four points bending test of timber beams repaired with WFRP qhethirdstepoftheexperimentsconsistedofassessmentoftheeffectoftheproposedrepairmethod onstructuraltimberelementsusingthehybridbiojcompositematerialkcourtimberbeamswiththe crosssectionof4r NRMmmandthelengthofOSMMmmwereusedKqhetestingdevicehastheroller supportsato4mmmmdistanceandtheloadsareappliedsymmetricallytothebeamsmiddlecross sectioniatummmmbetweenthemk qhetestingprogramconsistedintwostagesw cirststage thefourtimberbeamsidntod4iwereloadedinbendinguntilfailureoccurredifor estimatingtheultimateforceandthemaximumdisplacementk Fig. 5ioad displacementdiagramfortimberstructuralelements qhehighnohomogeneityofthewoodledtochoosingforcontinuationoftheexperimentonlytwo beamswithalmostidenticalevolutionwdpbeamloadeduntilfailureandd4beamloadeduntil reachingnsâkialoadlevelwheresomeofthewoodfibresstartedtobraâeibutthefailureofthe elementdidn`toccurkqheloadingspeedwasofmknâklskfnecigksfareshowedfailuremodesofeach timberbeamiintheorderinwhichtheyweretestedk Fig. 6courpointsbendingtestoftimberbeams;testsetupandfailuremodes qhesecondstageconsistedofrepairingthetwodpandd4beamsbyapplyingabiojcompositesystem onalengthwhichcoveredthedeterioratedzonewithnmmmmonesideandanotherandforthed4 beamthesystemwasappliedontheentirezoneofmaximumbendingmomentiwithnmmmmoneside andanotheriecigktfk OMOR

7 qherepairtechnologyofthedpbeamconsistedinfillingthecracâswithpolyesterresinand straighteningthebeamtocomeascloselyaspossibletotheinitialshapekqhedetachedpartsofwood werefixedwithsteelnailskaftero4hoursionthecrosssection sheightialongthebeamisomesmm diameterholesweredrilledeveryommmmstartingfromrmmmfromtherepairedzoneendskqhrough theseholessomebunchesofjuteyarnseo4strandsfwereintroducedandleftnmmmmoutsidetheholes onbothsidesoftheelementkqheyarnswerethenimpregnatedwithpolyesterresinandtheextremities ofthusobtainedpinsaremouldedonthesurfaceofthestructuralelementipreviouslycoveredwith polyesterresiniinanydirectionkbyintroducingtheseimpregnatedyarnsitheresinfilledtheholesand wasabsorbedinthewoodmassiasdescribedinthepreviousparagraphicreatingsomepinswiththe roletoovertaâeandtransmitthestressesfromthewoodtothehybridbiojcompositek Fig. 7dPandd4beamsrepairedwiththebioJcompositesystem lnthesurfacethuspreparedithetimberelementwaswrappedwiththreelayersofjutefabricsi impregnatedoneaftertheotherwithpolyesterresinusingthemanual±contacttechnology Kqoâeep thejutelayersinthedesiredpositioniafterimpregnationieachlayerwastightenwithjutestrandsand slightlytensionedforensuringauniformcontactbetweenthetimberelementandthelayersof impregnatedjutek qherepairedelementwasloadedinbendingiinthesameconditionsaspreviouslyandtheloadj displacementdiagramswererecordedkfnecigkufthediagramsofthetimberelementandtherepaired onearecomparativelypresentedk Fig. 8ioadJdisplacementdiagramfordPbeam ByapplyingthesystemproposedhereinIitmaybestatedthatthehybridbioJcompositecompletely restoresthebehaviourofthetimberbeaminbendingbyovertaâingthestressesandreleasingthe deterioratedwoodkqhemaximumloadatfailurerecordedforthedpbeambothfornaturaltimberand therepairedelementisofnuk4âkkqhemaximumdisplacementoftherepairedbeamcorrespondingto themaximumloadisof4skuotmmicomparedtor4knurmmofthenaturaltimberbeamkqhefailure occurredintheappliedbiojcompositematerialk fnthecaseofd4beamibyassociatingtimberwiththehybridbiojcompositeithebearingcapacityof thetimberelementwasobtainedkqheappliedtechnologyisthesameasforthedpbeamkfnthe originaltimberelementiforthensâkloada4pkonummdisplacementisrecordedkcortherepaired beamithefailureoccurredatorkuâkwithacorrespondingdisplacementofsvktt4mmiecigkvfkft maybeseenthatinthetwosituationsid4naturalandd4repairedithebeamsworâbasicallyinthe samewayuntiltheloadsreachesnmâkwiththecorrespondingdisplacementofopksmmktithload OMOS

8 increasingthenaturaltimberelemententerstheelasticjplasticdomainiwhiletherepairedd4beam reachesthenonjelasticdomainataloadofomâkwithacorrespondingdisplacementof4sknsrmmk qheloadingwasstoppedwhenthedisplacementexceededtheavailablespaceforthedeformationto taâeplacek Fig. 9ioad displacementdiagramofd4beam ByprocessingtheobtaineddataIthecontributionofthehybridbioJcompositemadeofthreelayersof jutefabricissignificanticonsideringthepmbincreaseoftheloadbearingcapacityofthetimberelementk 3.4. Conclusions of the experimental program `onsideringtheresultsofthetestscarriedoutsomeconclusionmaybementionedw thehybridbiojcompositeappliedinthreelayersonthebroâentimberstructuralelementshasthe capacitytorestoreitsinitialbearingcapacity; analysingthefracturemodesitmaybeconsideredthatresultedstressesdescribemorethe adherenceofpolyestermatrixbothonwoodandvegetaljutefibres; repairedspecimensdemonstratehowiinafirststageithewoodsplitintheinitialbroâensectioni thefailureofspecimensoccurringmainlyinthehybridbiojcomposite; italsomaybeobservedthehighcompatibilitybetweenwoodandthehybridbiojcomposite materialk 4. CONCLUSIONS `onsideringthebiodegradableandrenewablecharacterofthewoodfibresitheybecameanimportant alternativeforcreatingcompositematerialsusedinconstructiondomaink qhebiojcompositematerial±unsaturatedpolyesterresin jutefibres givethepossibilitytorepair damagedstructuralelementsuntillrestoringtheoriginalbearingcapacityandiontheotherhandito considerablyincreaseepmbftheloadbearingcapacityinthecaseofundeterioratedstructuraltimber elementskbyassociatingwood jutefabricreinforcedpolyesterthestiffnessofthestructuraltimber elementalsoincreaseswithanrbpercentk fntherepairmethodproposedhereinithepinshavetheroletoreplacesteelboltscurrentlyusedfor woodjointskqheadvantageofthecompositepinistorestorethenaturalwoodstructurebyremoving localstressconcentrationssurroundingtheholeskasdemonstratedintheworâbytestsconductedon wood tcomitheproposedrepairtechnologydoesn`tinducesupplementarystressesintheinitial structurekbystressanalysismaybestatedwhethertherestoringofbearingcapacityoftheelementis desiredorincreasingtheloadbearingcapacityoftheelementisnecessarykqherepairsolution proposedisefficientandeasytoapplyforhighlydamagedstructuraltimberelementsk auetothesimilarityofthestructureofwoodandrespectivelyjutefibresreinforcedcompositeithe unsaturatedpolyestermatrixensurestheadherencebetweenthecomponentmaterialsasforwooditselfk AsaconcludingremarâIthistypeofmaterialmaybesuccessfullyappliedforrehabilitationofhystoric structuresiforstructuraltimberelementswhicharedifficulttoreplacekqhistypeofinterventiondoes notinducesupplementarystressesintheoriginalelementianddoesn tsignificantlyinfluencethe behaviouroftheentirestructurek OMOT

9 ACKNOWLEDGEMENTS qhetestswerecarriedoutinthe`ivilbngineeringoesearch`entreicacultyof`ivilbngineeringand BuildingpervicesofthedheorgheAsachiqechnicalrniversityoffasiK REFERENCES xnz ButnaruoKIjurariu`KEOMMUFoesearch of composite materialsk Technical reporti dheorghe Asachi qechnicalrniversityoffasiicacultyofqextilescieatherbngineeringandfndustrial janagementioomâniaeinoomanianfk xoz aecherbkeommpftimber `onstruction solume fi ptudy of woodi jateijqeiubotez Academic pocietyeedfifaşiioomaniaeinoomanianfk xpz katterergkieerzogqkenvv4ftimber `onstructions 2Imressemolytechniquesetrniversitaires oomandeseedfi`e NMNRiausanneIpuisseEincrenchFK x4z Timber bngineeringibditedbypvenqhelandersson iundrniversityipwedenandeansgk iarsen qechnicalrniversityofaenmarâiiyngbyiaenmarâiomm4k xrz jâlcometelkeommsfpectionfcoordinatoroftextile fibresi dheorgheasachi qechnical rniversityoffaşiicacultyofqextilescieatherbngineeringandfndustrialjanagementi oomâniaeinoomanianfk xsz joţoiujkimaladeqkenvutfrnsaturated polyester resiniqechnicalbditoreedfibucureştii oomâniaeinoomanianfk xtz aecheribkenvvufiblements and structures of composite materials for the buildings` roofsimha qhesisi dheorgheasachi qechnicalrniversityoffaşiioomâniaeinoomanianfk xuz BarbujK`KENVVVFItood composite materialsiiuxiibriseedfibrasovioomaniaeinoomanianf xvz milaâoutashkicom `omposites materials and `onstitutive oelationshipsi aepartamentof`ivil andptructuralbngineeringirniversityofpheffield `fssntmk xnmz BismarcâAKIBaltazarJvJgimenezAKIparlâaâishKEOMMSFdreen composites as manacea?pocioeconomic aspects of green materialsk bnvironmenti aevelopment and pustainabilityuepfi44rj4spk xnnz `uivkiptepheniikeommufcabrication and interfacial modification of woodlrecycled plastic composite materialsi`ompositesw mart AIPVISRRJSSNK xnoz aecher bki oepair and strengthening method applied for highly deteriorated timber barsi fnventioniicensenoknnvtmmbnloukmokommreinoomanianfk OMOU