QUALITY PERFORMS. - Bond Laminates...2 LANXESS Teex ® Manal LANXESS Teex ® Manal 3TABLE OF...

QUALITY PERFORMS.

Information for processors

3LANXESS Tepex® Manual2 LANXESS Tepex® Manual

TABLE OF CONTENTS

04 1. ABOUT TEPEX®

06 1.1 Matrix systems

07 1.2 Reinforcingfibers

07 1.2.1 Glassfibers

08 1.2.2 Carbonfibers

09 1.3 Fiber-matrixadhesionanddivisionoftasks betweenfiberandmatrix

10 1.4 Semi-finishedtextileproducts

12 1.5 Tepex®laminatestructures

13 1.6 Tepex® family

13 1.6.1 Tepex®dynalite

13 1.6.2 Tepex®flowcore

14 1.6.3 Tepex®optilite

14 1.7 Nomenclature

16 1.8 PropertiesoftypicalTepex® materials

17 2. PROCESSES FOR MANUFACTURING TEPEX® COMPONENTS

17 2.1 Heating

19 2.2 Formingprocesses

19 2.2.1 Diaphragmprocess

20 2.2.2 Formingwithrubberstamps

21 2.2.3 Formingwithmetalmolds

21 2.2.4 FlowmoldingofTepex®flowcore

22 2.3 Combinationtechnologies

24 2.3.1 Insertmolding (combinationwithinjectionmolding)

25 2.3.2 Hybrid-Molding (combinationwithinjectionmolding)

26 2.3.3 Hybrid-Molding (combinationwithLFTflowmoldingcompounds)

26 2.4. Variothermalprocesscontrol

28 3. MOLD DESIGN AND HANDLING

28 3.1 DrapingofTepex®

30 3.2 Designinformationonthespecificforming behaviorofTepex®

32 3.3 Designingthemoldcavity

33 3.4 Integratingholes

34 3.5 DesigninformationonovermoldingTepex®

34 3.5.1 Ribdesign

35 3.5.2 Designingtheedges

36 3.5.3 Patching/overlappingofTepex®

36 3.6 GeneraldesigninformationonhandlingTepex®

37 4. JOINING TECHNIQUES FOR TEPEX®

38 4.1 Bonding

39 4.2 Joiningusinginjectionmolding

39 4.3 Mechanicaljoiningprocesses

40 4.4 Welding

41 5. RECYCLING TEPEX®

43 6. DESIGN AND CALCULATION OF TEPEX® COMPONENTS

44 6.1 FEMcalculations–conditionsandspecial characteristics

45 6.2 Drapingsimulation

46 6.3 Integrativesimulation

47 6.4 Simulationofcoolingbehavior

47 6.5 DesigningTepex®componentsindependently

48 7. HIANT® – SERVICE ALONG THE ENTIRE DEVELOPMENT CHAIN

50 8. ACKNOWLEDGEMENTS

5LANXESS Tepex® Manual4 LANXESS Tepex®Fibel

1. ABOUT TEPEX®

Our thermoplastichigh-performancecompositeTepex®hasestablisheditself as a lightweight constructionmaterial for a wide variety of appli-cations in large-scale series production. Its consistent quality and thethermoplasticmatrixmake it ideal for fullyautomatedand reproduciblemanufacturingandprocessingoperations.Tepex® isusedinautomotiveengineering,thesportsindustry,consumerelectronicsandvariousothersectors.

Tepex® isagroupofcompositesemi-finishedproductsthatarefully im-pregnated,consolidatedandplate-shaped.Theyaremadeofhigh-tensi-lecontinuousfibers (or longfibers in thecaseofTepex®flowcore)anda thermoplasticmatrix.Thesecompositesheetscanbeprocessed intocomplex components in short cycle times through heating and subse-quent forming.Continuousfibersaremainlyglassand/orcarbonfibersintheformoffabrics,inlaysorothersemi-finishedtextileproducts.Matrixmaterialsarethermoplasticssuchaspolypropylene,polyamide6,polya-mide66,polyamide12,polycarbonate,thermoplasticpolyurethaneandpolyphenylene sulfide.The strengths ofTepex® can be summarized asfollows:

Highstiffness

Veryhighstrength

Highlightweightconstructionpotentialthankstolowdensity

Veryshortcycletimesincomponentmanufacturing

Thermoplasticmatrixenablesover-moldingandwelding

Excellentdesignflexibility

Solvent-free

Recyclable

Verygoodenergyabsorptionproperties

Lowcoefficientofthermalexpansion

Gooddimensionalstabilityandchemicalandcorrosionresistance

ThisbrochureoffersanoverviewofthestructureofTepex®,itspropertiesanditsprocessingoptions.ItalsopresentsourHiAnt®services,whichweusetoprovideyouwithsupportinallstagesofdevelopingandmanufac-turingTepex®components.


The following thermoplastics are used as standard for Tepex®:

Polyamide(PA)6,6.6and12

Polypropylene(PP)

Thermoplasticpolyurethane(TPU)

Polyphenylenesulfide(PPS)

Flame-retardantpolycarbonate(PCfr)

1.2 Reinforcing fibers

Aswith all other fiber-plastic composites,Tepex® fibers need to absorbtheloadsonthecomponent.Todothis,theyneedtoofferhighstiffnessandstrengthandthelowestpossibledensity.Experienceshowsthatmostmaterialsexhibitmuchbettermechanicalpropertiesasfibersthanincom-pactform.Glassandcarbonowetheirexcellentcredentialsasreinforcingfiberstothisparadoxalthoughtheyarenotactuallyconsideredtobecon-ventionalstructuralmaterials.

1.2.1 Glass fibersAglassfiber isan inorganicfiberwhosehighstrength isbasedon thestrongcovalentbond(atomicbond)betweensiliconandoxygen(SiO2 = quartz).Glassfibersarecreatedfromameltthatiscooledquicklysoastopreventcrystallizationandproducea three-dimensionalnetworkwithanamorphousstructure.Glassfibersthereforehaveisotropicproperties.

Summary of glass fiber properties:

Goodcost-effectivenesswithexcellentmechanicalproperties

Veryhightensileandcompressivestrength

Outstandingthermalandelectricalinsulation

Completelynon-combustible

Verylowmoistureabsorption

Rot-proof

Varioustypesoffiberareavailabledependingonthechemicalcomposi-tion,withE-glassbeingbyfarthemostcommonlyused,alsoforTepex®. Glassfibershaveadiameterbetween9and24µm.Thefinenessofaglassfiberyarnorroving(strandsofparallelcontinuousfibers),referredtoasthetiter,isgivenintex(1tex=1g/1000m).

1.1 Matrix systems

OnlythermoplasticsareusedasamatrixmaterialforTepex®.Theirpro-pertiesareparticularlybeneficialforprocessing.Thermoplasticmatricesproduceveryshortcycletimes,whileworkhygieneisnotcritical.Thermo-plastic-basedfiber-plasticcompositescanalsobecombinedwithotherthermoplastics with the same matrix and their processing methods.Designfreedomforcomponentscanthusbeincreasedsignificantly.

Thereisawidespreadmisconceptionthatmatrixmaterialsareonlyusedasanadhesiveforreinforcingfiberswhiletheactualcompositepropertiesaredeterminedsolelybythefibers.

The matrix system performs key functions:

Transmittingforcesintothefibers

Transferringforcesfromfibertofiber

Protectingfibersagainstenvironmentalfactors

Fixingfibersintherequiredgeometricarrangement

Absorbingmechanicalloads,particularlyhighloadsperpendiculartothedirectionofthefibersandshearloads

1. S

TIF

FNESS &

2. LIGHTWEIG

HT

EN

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GY ABSORPTION

PROCESSIN

G

STRENGTH

DESIGN

3. D

YN

AMICS &

4. E

FFICIE

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1.3 Fiber-matrix adhesion and division of tasks between fiber and matrix

Acompositeonlyhasoptimumpropertiesiftheforcesoccurringaretrans-mittedtothefibersandcanbetransferredfromfibertofiber.Thisrequiresagoodbondbetweenthefiberandmatrix.InTepex®,optimumbondingofthefiberstothematrixisalwaysensuredbythetargetedselectionofafinishadaptedtoeveryplasticandappliedtothefibersaftermanufacture,and–wherenecessary–byaddingabondingagenttothethermoplastic.

The division of tasks between fiber and matrix can be summarized as follows: Figure 1: Illustration of the relevance of the components

in the composite

It isworthunderliningthattheprocessingpropertiesaredeterminedal-most exclusively by thematrixmaterial.Thiswill be examined inmoredetailinthefollowingsectionsofthisbrochure.

Thisparameter is ameasureof thediameterandnumberof individualfilamentsinaglassfiberstrand(yarnorroving).Finetypeswithatiteroflessthan68texaredescribedasfilamentyarns,whileheaviertypesaretermedrovingyarns.ThetiterofthefibersusedinTepex®areshowninthecorrespondingdatasheets.

1.2.2 Carbon fibersCarbonfibersareindustrialfibersmanufacturedinatemperaturerangefrom1,300to3,000°Cfromaprecursor(usuallyPANfiber)andwhichhaveacarboncontentbetween92and99.90%bywt.Carbonfibersaremadeupofindividuallayers(graphitestructure).Theirhighstrengthand highmodulus of elasticity are based on the strong covalent bond(atomicbond)between the individualcarbonatoms in these layers.Bycontrast,thebondsbetweentheindividuallayersareweak,withtheresultthatpropertiesperpendicular to thedirectionof thefibersare lesspro-nounced.Carbon fiber stands out from all reinforcing fibers due to itsextremeproperties.

Summary of carbon fiber properties:

Verylowdensity

Extremelyhighstrengthandveryhighmodulusofelasticity

Virtuallylinear-elasticproperties

Pronouncedanisotropy

Verylowcoefficientofthermalexpansion,actuallynegativeinthedirectionofthefibers

Resistancetomostacidsandalkalis,tolerabilityinthehumanbody

Goodelectricalconductivity

Varioustypesofcarbonfiberarealsoavailable,andthesemayvarysig-nificantlyintheirmechanicalproperties.Themosteconomicallyattractivefiberand theonemostcommonlyused forTepex® ishigh tensilefiber,whichhasveryhigh strength andgood stiffness.Carbon fibershave adiameterbetween5and10µm.Aswithglassfibers,carbonfibersareusuallysuppliedasacontinuoustoworrovingwoundonacoil.

These towsconsistofanumberof individualfilaments.Thenumberoffilaments in a tow is indicatedby theKnumber (1K=1,000filaments/tow).CarbonfiberswithaKnumbergreater than24arereferredtoas“heavytows.”

Fiber

Matrix

Mechanicalproperties

Stiffness

Strength

Impactresistance

Technical&chemicalproperties

Electricalproperties

Temperatureresistance

Chemicalresistance

Corrosionbehavior

Processing characteristics


Aninlayisreferredtoasanonwovenifitconsistsofoneormorelayersofparallelstretchedthreads.Thereinforcingdirectioncanbesetwithincertainlimitsinalmostanywayusingthissemi-finishedtextileproduct.

The various types of reinforcement are also shown by the Tepex® code:

C;RG;FG:carbonfabric,rovingglassfabric,filament glassfabricCUD;RGUD:carbonfabricuni-directional, rovingglassfabricuni- directionalRGUDm:rovingglassfabricuni-directional,suitableformultiaxialstructures

1.4 Semi-finished textile products

Specialsemi-finishedtextileproductsareusedinproducingfibercompo-sitematerialstooptimizetheirdesignwithregardtothenecessaryfiberorientationandtoensureefficientandreproduciblecomponentmanufac-turing.Primarilythreedifferenttypesofsemi-finishedtextileproductsareusedforTepex®:

Textileswith0/90degreefiberorientation: Bidirectionalfabrics

Textileswithunidirectionalfiberorientation: Unidirectionalfabricsorinlays

Textileswithquasi-isotropicproperties: Randomfibermats(nonwovens)

Thefabricsareflatmaterialsmadeupofwarpandweftthreadscrossingat rightangles,givingabidirectional reinforcingeffectat0and90de-grees.Varioustypesofweaveexistforfabrics,withplainweaveandtwillweaveusuallybeingusedforTepex®(Figure2).Twillweavesareagoodcompromisebetweenachievablemechanicalproperties,formabilityandhandling,whichiswhythisweavetypehasbecomewidelyestablishedinfibercompositetechnology.However,plainweavesarealsousedformanyapplicationsduetotheireaseofhandling. Figure 2: Diagram of a plain weave (left) and a twill weave (right)

Plain weave Twill weave

Iffabricshaveaveryhighproportionofwarpandweftthreads,theyarereferredtoasunidirectionalfabricsandhaveareinforcingeffectmainlyat0or90degrees.

Leinwandbindung Köperbindung


1.6 Tepex® family

1.6.1 Tepex® dynalite

Tepex®dynalitematerialsconsistofoneormore layersof semi-finishedtextileproductswithcontinuousfibersembeddedinamatrixofindustrialthermoplastics.Thisgradeisfully impregnatedandconsolidated.Allthefibersare thussheathedwithplastic,and thematerialdoesnotcontainanyairpockets.Tepex®dynalitethereforeprovidesmaximumstrengthandstiffnesscombinedwithverylowdensity.

1.6.2 Tepex® flowcore

Thefibers inTepex® flowcorehaveafinite length,making thismaterialsuitableforflowmoldingandthusenablinggreaterdesignfreedom.Here,too,thefibersarefullyimpregnatedandconsolidated.Theflowcorefam-ily also includes structures consisting of a combination of continuous

1.5 Tepex® laminate structures

Inveryrarecases,fibercompositestructuresareonlysubjectedtounaxialstress,sothatjustonefiberdirectionisneeded.Thefrequentlymultiaxialstressonthematerialthususuallycallsformultiplefiberorientations,re-sultinginvariouslaminatestructures(multilayercomposites).

Inprinciple,alltheabove-mentionedsemi-finishedtextileproductscanbecombined inTepex®.Thisoffersdesigners theopportunity toconfigurethelaminatetomeetthespecificloadrequirements.Aswellasconven-tional fabricfiber-reinforced laminates, thisalsoenables theproductionofmultiaxial structures andquasi-isotropicproperties, as shownby theexamplesinFigure3.

a) RGUD600(4) b) RGUDm317(8)

RGUD600

RGUDm317-45°

RGUDm317+45°RGUD600

RGUDm317+45°

RGUDm317-45°RGUD600

RGUDm317-45°

RGUDm317+45°RGUD600

RGUDm317+45°

RGUDm317-45°

0°

180°

90°

45° 315°

135° 225°

270°

600

400

200

0

0°

180°

90°

45° 315°

135° 225°

270°

600

400

200

0

c) RGUD600(2) - RGUDm317(4) d) RG600(2) - RGUDm317(4)

0°

180°

90°

45° 315°

135° 225°

270°

600

400

200

0

0°

180°

90°

45° 315°

135° 225°

270°

600

400

200

0

RGUDm317+45° RGUDm317+45°RGUDm317-45° RGUDm317-45°RGUD600 RG600

RGUD600 RG600RGUDm317-45° RGUDm317-45°RGUDm317+45° RGUDm317+45°

Figure 3: Examples of laminate structures with Tepex® (strength of a glass-fiber-reinforced PA6 as a function of the angle, displayed as a polar graph incl. the relevant laminate structures)


As Tepex®isfullyimpregnatedandconsolidated,thismakesitpossibletocalculateallothervaluessuchaslaminatethicknessandfibercontentbyweight.AllrelevantinformationcanbederivedfromtheTepex® material code:

Figure 4: Breakdown of the Tepex® material code

(Tepex® dynalite) and long fibers (Tepex® flowcore).Typically, the con-tinuousfibersareplacedontheoutsideof the laminate,while the longfibers are placed in the center. This produces a fiber composite withmaximumflexuralstrengththatalsosupportsmoldingofcomplexcom-ponents.

1.6.3 Tepex® optilite

Tepex® optilite is tailor-made for applications that require anestheticallyappealingdesignandminimum thicknessalongsidemaximumstrengthand stiffness.Tepex® optilite canbeadapted to specificdesign require-mentsintermsofcolorandfabricarchitecture.

1.7 Nomenclature

Afiber composite isdescribedunambiguouslywith the following infor-mation:

Typeoffiber(glass,carbon..)

Typeofsemi-finishedtextileproduct(fabric,inlay...)

Plastic(PP,PA6..)

Numberoflaminatelayers

Fibervolumecontent

Directionoffiberorientation

Tepex® dynalite 108-FG290(4)/45 % – 1.0 mm

Laminate thickness

Fiber volume content

Number of fabric layers

Area weight (g/m²)

Fabric code (see below)

Polymer type: 1: PA66, 2: PA6, 4: PP, 6: PA12, 7: PPS, 8: TPU, 10: PCfr

Fiber type: 100: glass, 200: carbon, 400: glass/carbon

Fabriccode:FG = Filament glassFGAL =FGaluminumcoatedsilverFGc =FGcoloredRG =Rovingglass

RGUD=RGuni-directionalRGR =RGrandomfibersC =CarbonCUD =Cuni-directional


2. PROCESSES FOR MANUFACTURING TEPEX® COMPONENTS

The process for manufacturing Tepex® components comprises the following steps:

1. Heatingthecompositesheetblankabovethemelttemperature* ofthethermoplastic

2. Transportingtheheatedblanktothemold

3. Incorporatingandpositioningtheheatedblankinthemold

4. Formingusingappropriatemoldtechnology

5. Ifnecessary,pressingormoldingonafurtherthermoplastic component(combinationtechnologies)

6. Coolingandremovingfromthemold

On account of this process sequence, the forming of Tepex® is also often referred to as thermoforming. However, the following must be noted in this regard:

Composite sheets are not formed in the rubber-elastic temperaturerange, unlike conventional thermoforming, but above the melt tem-perature*.

Usingappropriatemoldtechnologyandprocesscontrolduringformingand cooling, theTepex® semi-finished product is subject to uniformpressureonallsides.

The heating and individual forming processes/techniques are outlinedbrieflybelow.Further informationon the formingmechanisms forcom-positesheetsandtheresultingmolddesigncanbefoundinSection5.

2.1 Heating

Heating Tepex®reducestheviscosityofthermoplastictoalevelthatgivestheindividualfiberssufficientfreedomofmovementduringtheformingprocess.This is the onlyway to produce the drapingmechanisms ex-plainedinSection3andtopreventwrinklingandcracksinthematerial.

1.8 Properties of typical Tepex® materials

Fiber-plasticcompositesarecharacterizedinparticularbytheirexcellentstiffnessandveryhighstrengthcoupledwithverylowdensity.Thesearethepropertiesofanideallightweightconstructionmaterial.ThefollowingtableshowsthekeyparametersofanumberofstandardTepex®grades:

Figure 5: Material parameters of selected Tepex® materials

1L=longitudinal;T=transversal

STANDARD MATERIALS

Fast response time in material selection and manufacturing

TEPEX®

dynalite101

E-glassRoving

PA 66 1,81 47 380 23 560 20 (–) 260

TEPEX®

dynalite201

Carbon PA 66 1,46 50 700 55 840 48 (–) 250

TEPEX®

dynalite102

E-glassRoving

PA 6 1,80 47 390 23 580 20 (–) 220

TEPEX®

flowcore102

E-glassRoving

PA6 1,80 47L=260T = 220

(1)

L=19T = 14

(1)

L=450T = 300

(1)

L=18T = 14

(1)

(–) 220

TEPEX®

dynalite104

E-glassRoving

PP 1,68 47 430 20 370 17 (–) 165

TEPEX®

dynalite108

E-glassFilament

TPU 1,82 45 440 23 650 21 94 (–)

TEPEX®

dynalite210fr

Carbon PC(fr) 1,47 45 550 48 750 44 100 (–)

TEPEX®

mate

rial

Fiber

Polymer

Density(kg/dm

3 )

Fibervolumecontent(%byvol.)

Tensilestrength(MPa)

Tensilemodulus(GPa)

Flexuralstrength(MPa)

Flexuralmodulus(GPa)

Glass t

ransit

ion

temperature(°C)

Crystal

lite

meltingpoint(°C)

*Tobemoreprecise:temperaturerangeabovethecrystalllitemeltingpointinthecaseofsemi-crystallineplasticsorabovetheglasstransitiontemperatureinthecaseofamorphousplastics.


The following conditions must be complied with:

Tepex®mustalwaysbeformedabovethemelttemperatureofthether-moplasticused.

Theheatingtemperatureshouldbehighenoughfor thefiberstostillhavesufficient freedomofmovementevenafter transportation to themoldwhen themold closingmovement occurs (keep transportationtimeandrouteasshortaspossible).

Theheatingtemperatureandtimeshouldbeselectedsoastopreventoxidativedamage.

Theheatingprocessshouldbedesignedsothattemperaturedistribu-tioniscompletelyuniformacrosstheentireTepex®surface.

Thetemperaturecontrolsshouldbedesignedsoastopreventexces-sivelyhightemperatures/temperaturepeaks.

To ensure efficient process control, heating must not be allowed todeterminethecycletime.

In principle, the following heating methods are available:

Heatingthroughradiation(infrared)

Heatingthroughconvection(airflow)

Infrared radiation involves electromagneticwaves in the spectral rangebetweenvisiblelightandmicrowaveradiation.Thesemi-finishedproductblanksabsorbtheIRlightandheatupasaresult.Heatconductionalsocauses the inside of the composite to heat up. As thermoplastics andfibers have a high absorption capacity in the IR range, heat transfer ishighlyeffective.

An equallywidespread heatingmethod in plastics technology is circu-latingair technology.Convectionovenswithmaterial feedingbasedonthepaternosterprinciplehaveexisted foravarietyofapplicationssincethe1980s.

2.2 Forming processes

A wide range of different forming processes are available for formingTepex®.Decidingwhich to use is basedprimarily on component com-plexityandthenumberofpartsbeingproduced.Theindividualprocessesarebrieflydescribedbelow.

2.2.1 Diaphragm processDiaphragmformingistheoldestprocessforproducingthin-walledcom-ponentsfromcontinuouslyfiber-reinforcedthermoplastics.

Indiaphragmforming,thesemi-finishedproductisplacedbetweentwohighly elastic films, the entire structure is heated above themelt tem-perature*ofthematrixusingradiationorconductionandthentransportedtotheformingstation.Theclampingbellisclosed,withthediaphragmsactingasseals.Theheatedlaminatepackageisplacedonthemoldandthencompressedairisappliedtoit.Anadditionalvacuumcanbeappliedtothemoldtosupporttheformingprocess.

Figure 6: Diagram of Tepex® diaphragm forming

Thebenefitsofthisprocessincludelowinvestmentcostsandthepossi-bilityofformingvariousmaterialthicknesseswithonemold.Theprocessrequiresrelativelylongcycletimesandismoresuitedtosimplecompo-nentgeometries,eventhoughminorundercutsarepossible.

P PPP

Siliconefilm=diaphragm

Tepex®

Hotplate

Stationary moldhalf



2.2.2 Forming with rubber stampsInthiscompressionmoldingprocess,themoldconsistsofasolidbottommoldhalf,correspondingtotheoutsideofthecomponentgeometry,anda topmoldhalfmadeof silicone.Byclosing themoldat lowpressure,Tepex®ispressedtocreatecomponents.

Figure 7: Diagram of Tepex® forming using rubber stamps

Thanks to its high elasticity, the silicone stamp enables sequential for-ming,whichmeansthenecessary,uniformpressuredistributioncanbeensuredduringforming(seealsoSection3).Formingwithrubberstampsis suitable forprototypesand smaller seriesdue to the low investmentcostsandeasyoptimizationofthestamps.However,themethodhasalsodemonstrated its suitability in large-scale series production for simplergeometries.

2.2.3 Forming with metal moldsIn most cases, Tepex® is formedusingmetalmolds.Bothmold halvesaremadeofmetal/steelandaretemperature-controlledinrelationtothepolymerinquestion–i.e.matchedmetalmolding.Indesigningthemold,specialattentionshouldbepaidtothecavity.Duetothespecialformingmechanism of composite sheets, basic factors need to be taken intoaccount–seeSection3.

Thisformingtechniqueincombinationwithappropriateautomationenab-lesveryshortcycletimesandahighlyreproducibleprocess.Componentsmanufacturedusingthisprocessalsoexhibitonlyaverylowtendencytowarp.However,thesebenefitsmustbeweighedupagainsthigherinvest-mentandgreaterworkloadforthedesign.Themethodisthusparticularlysuitableforlargeseries.

2.2.4 Flow molding of Tepex® flowcoreAsnotedabove,Tepex®flowcore issuitable forflowmoldingdue to itsreinforcementwithfinitefiberlengthsfromapproximately30to50mm.Thisthereforeenablesproductionofevenmorecomplexcomponentgeo-metries.Moldingof ribsand functionalelements is alsopossible.Flowmolding is awidelyusedmethod inplastics technologyand is charac-terizedbyveryhighreproducibilityandshortcycletimes.

Figure 8: Flow molding of Tepex® flowcore

1.Centralbeadformed 2.Allbeadsformed

3.Completelyformed

metalmold

metalmold


AswiththeestablishedGMTandLFTthermoplasticflowmoldingcom-pounds,apreciselydefinedquantityofTepex®flowcoreisfirstheatedandthenplacedinanappropriatelocationinthemold.Formingthemoldedpart/fillingthemoldiseffectedbyclosingthemold,whichinducesflowinthemelt.Compressionmoldsaregenerallyusedforthispurpose.

2.3 Combination technologies

CombiningTepex® withplasticsreinforcedwithshortorlongglassfiberswiththesamematrixsystemandtheirinjectionandflowmoldingproces-sesalsoofferstheexcellentoptionofusingbothlightweightmaterialsanddesign,forexamplebyinjecting

reinforcingandstabilizingribs

force transmission elements

functionalelements

contoursattheedgeofthecomponent

An appropriate selection ofmaterials and process control produce acomponentwithahomogeneousbondbetweenthetwosections(seeFigure9).

Thisprocessinnovationoutlinedbelowhasitsrootsinthe“SpriForm”re-searchanddevelopmentprojectfundedbytheGermanFederalMinistryofEducationandResearch(BMBF).Sincethen,thistechnologyhasbeencontinuously optimized. Machine manufacturer Krauss-Maffei marketsthiscombinationtechnologyunderthe“FiberForm”name,whilemachinemanufacturerEngelusesthename“Organomelt.”Abasicdistinctionismadebetweenatwo-stepprocess(referredtointhisbrochureasinsertmolding) andaone-stepprocess (referred tohereashybridmolding).Thetwomethodsofferthefollowingbenefits:

Greaterdesignflexibility

Optionofintegratingfurtherfunctionsandthusreducing subsequentsteps

Combinationoflightweightmaterialsanddesign

Shortcycletimes

Reproducibleandfullyautomatedprocesses

Availableandmanageableplanttechnology

Figure 9: Diagram of combination options for Tepex® with compounds

Regardlessofthetechnologyselected,goodadhesionmustbeensuredbetweenthetwocomponentsbymeansoffusing.Adhesiondependspri-marilyon the temperatureof thecompositesheetand the temperatureof themeltat thetimeof injection.Thisresults inthefollowingprocessengineeringconclusions,whichmaybeconfirmed throughappropriatetests:

1. Thehigherthetemperatureofthecompositesheetandthehigherthetemperatureoftheinjectionmelt,thebettertheadhesion.Asinjectionisperformedatrelativelyhighmelttemperatures*andacontacttem-peratureatthejointisproduced,compositesheettemperaturesbelowthemelttemperature*arealsousuallysufficient.

2. Thetransfer timebetweenheatingthecompositesheetandformingshouldbeasshortaspossibletopreventcooling(asageneralrule).

3. Theinjectionspeedhasasignificantinfluenceonadhesion.Thehigherthespeedselected, thegreater thesheareffect in themelt,and thelowerthecoolingeffects,whichhasapositiveimpactonfusing.Thiseffectisparticularlynoticeableinareasfurtherawayfromthegate.

4. Ahighholdingpressurealsohasapositiveeffectonadhesion.



Tepex®

2.3.2 Hybrid molding (combination with injection molding)Inhybridmolding,bycontrast,formingofthecompositesheetandinjec-tion takeplace together in the injectionmold.Theclampingunitof theinjectionmoldingmachineisusedasaformingpressinthisprocess.Themold,whichthushasvarioustaskstoperform,needstobespeciallyde-signedforthisprocess.InformationondesigncanbefoundinSection3.Toproducemoldedpartsinasinglestep,semi-finishedcompositesheetsareprovidedasblanksthatapproximatethefinalcontour.Theseblanksofferdraping-compatiblecomponentproduction thatcanbecalculatedusingadrapinganalysis(seealsoSection6:“Designandcalculationofcomponents”).

Figure 11: Hybrid molding with Tepex®

F

2.3.1 Insert molding (combination with injection molding)Intheinsertmoldingprocess,formingofthecompositesheetandover-molding/injectionwithplasticsreinforcedwithshortorlongglassfiberstakeplaceinseparatemoldsandmachines.Toachieveahomogeneousbond/fusingwiththeinjectedplasticmelt,itisadvisabletoheatthepre-formedcomponent(insert)onceagainbeforepositioningitintheinjec-tionmold.Thisistheonlywaytoachievetherequiredfusingofthetwocomponents.

Figure 10: Insert molding with Tepex®

Heating

Thermoforming Injection molding

Forming

Transfer/insertion

Injectmelt

Cooling Removal Overmolding Cooling Removal

Injectmelt

Heating Forming Overmolding Cooling Removal


2.3.3 Hybrid molding (combination with LFT flow molding compounds)LFT stands for long-fiber thermoplasticswhose reinforcing fibers are atleast4mmlong. In thismostpopulardirectmethod, themoldingcom-poundconsistingoffibers,matrixand,whereappropriate,additivesispro-ducedusingextrusiontechnologyimmediatelybeforethemold.Thecom-poundproducedusingthismethodisthenprocessedusingflowmoldingwithcompressionmolds.Thenecessaryflowofthemeltisachievedbytheclampingpressureoftheappropriatelydesignedmold.

Combining thismethodwithpreheated composite sheets enables easyproductionof large, extremely strong anddistortion-free components inveryshortcycletimes.Thekeycharacteristicofcomponentsproducedinthiswayistheirextremelyhighimpactresistance. Figure 12: Tepex® hybrid molding in combination with LFT or Tepex® flowcore

2.4 Variothermal process control

Ifnecessary,thesurfacequalityofTepex® componentscanbefurtheren-hancedusingvariothermalprocesscontrol.Withvariothermaltemperaturecontrolofthemold,themoldwallsaretemporarilyheatedtoatemperaturebetween the glass transition temperature andmelt temperature* of theplasticused.Themoldisnotcooledagaintillafterformingofthemolded

part has been completed. This increase in the mold wall temperaturedelays solidificationof themelt,with the result that the surfaceof com-ponentsproducedusingthismethodcandevelophighlyeffectively.Figure13shows theprocess including the temperaturecycles forTepex® andthemoldwallforhybridmolding(combinationofcompositesheetformingandinjectionmolding,seestartofthissection).

Figure 13: Variothermal process control for hybrid molding

F

Heating Forming Cooling Removal

PlasticizedLFTorTepex®flowcore

Tepex®

Temperature

F

Tepex® Temperature

Time

Tmelt

Tmelt =melttemperature*

Tg

Tg =glasstransitiontemperature

Tepex®

Moldwalltemperature

Heating Forming Overmolding Cooling Removal

Injectmelt



Thesetwomechanisms,eitherindividuallyorincombination,enableveryhigh degrees of forming. In areas of the componentwith pronouncedthree-dimensionaldeformation,thefiberorientationchangestoagreaterorlesserextentrelativetotheoriginalstate.Thisresultsinitiallyinanuna-voidablethickeningofthematerial,whichneedstobetakenintoaccountinmolddesign(seeSection3.3“Designingthemoldcavity”).Ifdrapingisincreasedfurther,blockingofthetextilemayoccur,resultinginunwant-edwrinkling.Adrapingsimulationprovides informationonsuchcriticaldegreesofformingsothatappropriatecountermeasurescanbetaken.

Figure 15: Results of a draping simulation (shear angle as a mea-sure of fabric shear strain)

3. MOLD DESIGN AND HANDLING

There is now awealth of experience about how to optimally structuremoldsforprocessingTepex®andhowthehandlingcomponentscanbedesignedaccordingly.With itsHiAnt®customerservice,LANXESSsup-portscustomers’projectsinallmattersinvolvingmolddesign.Numerousmachineandmoldmanufacturersnowalsospecializeinprocessingcom-positesheets.Afundamentalunderstandingoftheformingmechanismsofplasticsreinforcedwithcontinuousfibersiskeytodesigningandhand-ling Tepex®.

3.1 Draping of Tepex®

Thespecial formingbehaviorofTepex®hasamajor influenceonmolddesign.Forming,alsoknownasdraping,onlyrarelyusesflowprocessesas in conventional plastics processing methods, and instead is basedlargelyonformingthesemi-finishedtextileproduct(draping).Thereareessentiallytwodifferentdraping/formingmechanisms,whichareshowninFigure14(fiberelongation,fiberstretchingandfiberslippagearedis-regardedhere):

Anglechanges/fabricshearstrainofthesemi-finishedtextileproduct,alsoreferredtoasthetrelliseffect

Movements of individual layers relative to eachother, also knownasinterplyshear(inmultilayerlaminatestructures)

Figure 14: Tepex® forming mechanisms; left: trellis effect; right: movement of individual layers


3.2 Design information on the specific forming behavior of Tepex®

Aswellastheformingmechanismsdescribedabove,knowledgeofthespecial kinematics of formingTepex® is particularly important formolddesign.Toensurereproducible,consistentformingofthecomponent,theheated compositemust be able to slide freely from the outside to themiddleofthemoldduringforming.

Figure 16: Sliding of Tepex® during the mold closing movement

Inmore complexgeometries, anunfavorablemolddesignmay lead tostressesoccurringbetweenneighboringareasofthecomponent,whichmayresultinthematerialjammingoreventearing.Here,too,adrapinganalysiscoverssuchareasandprovidesvaluableinformationfordesign-ing themold. Several design solutions are available to solve this prob-lem.Theanglesoftheflanksshouldincreasefromthecenterofthecavitytoward the edgeof themold, as canbe seen in the illustrationbelow.Slides ormoving stamps can also be used to ensure staggered entryof thematerial into themoldand thussequential forming. Ifnecessary,checksshouldbemadetoseewhethercomponentareaswithverysmallanglescanbeformedusingactiveelementssuchasslides.

Figure 17: Solutions to prevent stress during forming (left: adjus-ting the angles, right: integrating a slide)

ToensurethatTepex®componentscanbeshapedeffectivelyasshownabovebutalsodemoldedquicklyandreliably,openingangles/draftsof≥5degreesarerecommendedforverticalareasofthemoldindependentlyofthematerialthickness.Contourswithdraftsof≥2degreescanalsobeusedtoalimitedextent.

Figure 18: Design of radii

If possible, the inner and outer radii of angular contours should bedesignedaccordingtothefollowingrules–partlytoensurethatthefibersarenotdamagedduringformingduetoexcessivelysharpmoldedges:

InnerradiusRi≥Tepex®wallthickness,butatleastR1(1mm)OuterradiusRa≥innerradiusRi+Tepex®wallthickness

Nachrutschen

Thermoformen mit Metallwerkzeugen

1. Problemstellung

Tepex® wird zwischenoberer und untererWerkzeughälfteeingeklemmt undkann nicht „nachrutschen“.

2. Lösungsansatz

Werkzeug mit Entformungs-schrägen, um ein „Nachrutschen“des Organblechs zuermöglichen.

3. Lösungsansatz

Werkzeug mit Voreiler,der die Mitte des Werkzeugesausfüllt, bevor das restlicheWerkzeug schließt.

a ß

12 2

Thermoformen mit Metallwerkzeugen

1. Problemstellung

Tepex® wird zwischenoberer und untererWerkzeughälfteeingeklemmt undkann nicht „nachrutschen“.

2. Lösungsansatz

Werkzeug mit Entformungs-schrägen, um ein „Nachrutschen“des Organblechs zuermöglichen.

3. Lösungsansatz

Werkzeug mit Voreiler,der die Mitte des Werkzeugesausfüllt, bevor das restlicheWerkzeug schließt.

a ß

12 2

3-5°

Auslegung von Radien

R i

R a

R a

R i


3.3 Designing the mold cavity

Tepex® is supplied fully impregnated and consolidated. The individualfibersofthesemi-finishedtextileproductarethusenclosedbythethermo-plasticmatrix,andthelaminatecontainsvirtuallynoairinclusions.Whenheatedabovethemelttemperature*ofthethermoplasticmatrix,thethick-ness of Tepex® increasesbyup to20percent.This is largelyexplainedby the increase in thevolumeof theplastic and the releaseof internalstresses in thesemi-finishedtextileproductbyheating.During forming,thesemi-finishedproductmustthereforebepressedbacktothenominalwallthicknesssothatacompact,smoothsurfacewithoutimperfectionsiscreatedandidealpropertiesareachievedinthecomponent.

Asabasicprinciple, it isadvisable todesignthemoldcavityareawhe-re Tepex® is formed in linewith therequiredwall thicknessof thecom-ponent.However,specialattentionshouldbepaid toareaswithahighdegreeofdraping(highshearangle).Asbrieflyexplainedintheprevioussections,thickeningoccurshereduetoabuildupofmaterial.Thisoftencannotbepressedbacktotherequireddimension,despiteelevatedmol-dingpressures,whichmeans that adjacent areas cannot be subjectedfullytopressurebecausethemoldisblockedandthuscannotbeformedcorrectly(seeFigure19).Thecavityintheseareasthenneedstobecor-respondingly thicker toensureuniformpressuredistributionacross theentirecomponent.

Figure 19: Shear angle distribution projected onto an actual com-ponent; red area indicates a local thickening

Inprinciple,auniformandsmoothlyformedsurfaceonthemanufacturedcomponentmaybeviewedasanindicatorofgoodmolddesign,asthisisasignofuniformpressuretransfer frommoldtocomponentsurface.However,inadditiontoawelldesignedmold,processcontrolalsohasasignificantinfluenceonsurfacequality:

TemperatureoftheTepex® insert

Surfacetemperatureofthemold (seealso“Variothermalprocesscontrol”)

Moldingpressure

Surfacequality/propertiesofthemold

Insummary,itmaybenotedthattheprecisionofthecavitygapiskeytocomponentdesign.

3.4 Integrating holes

Inprinciple,holesandbreakthroughscanbeintegratedintwoways:

1. HolesaremadewhenproducingtheTepex®insertbycuttingordrilling

2. Holesarecreatedduringformingbypushingbackthefibers

Thesecondoptionappearsadvantageousparticularly forhighstressesonthefacesofholes,asitispossibletodiverttheflowofforcesaroundtheholes.Figure20illustratesthissituation.

Figure 20: Making holes – left, by cutting or drilling; right, by for-ming and pushing back the fibers in the mold



Figure 22: Diagram of rib design

Sharpedges in the areaofmounting the ribbaseonto the compositesheetalsoneedtobeavoided.Roundedcornerspreventdamagetothefiberswhenmountingthemold.

3.5.2 Designing the edgesIndesigning force-transmissionand functionalelementsand theedgesofacomponent,acombinationoffrontalandoverlappingmoldingonisrecommended,asshowninthefollowingdiagram.

Figure 22: Diagram of edge design

An optimum bond can be produced in this way, in combination withappropriateprocesscontrol.

3.5 Design information on overmolding Tepex®

AsalreadyexplainedinSection2.3,ahomogeneousbondcanbeachiev-edbyinjectingaplasticreinforcedwithshortorlongfibersandthesamematrixasthatofTepex®.Thisenablesthedesignofcomplexcomponentswithhighstrengthandstiffness.Figure21showsasectionofsuchacom-ponent.Atypicalribstructurecanbeseenthatalsostiffensandstabilizesthecomponent.Typicaledgeovermoldingisalsovisible.

Figure 21: Example of rib structure and edge overmolding

3.5.1 Rib designTwofactorsmustbetakenintoaccountindesigningribsforovermoldingTepex®.Firstly,theribbaseshouldcoveralargearea,asinthediagrambelow.Goodexperiencehasbeengainedusingawidthofapproximately10mm,whichachievesaverygoodbondbetweentheribandcompositesheet,providedthereisoptimumprocesscontrol(seeSection2.3).

Injectionmoldingmaterial(rib)

Approx.10mm

Tepex®

RR

Injectionmoldingmaterial(rib)Tepex®

Approx.7mm


3.5.3 Patching / overlapping of Tepex®

Usingtailoredblanktechnologyasabasis,differentcompositesheetscanalsobecombinedtoadaptthecomponenttolocalcomponentstressesusingdifferentsheetthicknesses.Thesesheetsarepreferablyfirstheatedseparatelyandonlythencombinedandformedinorbeforethemold.

3.6 General design information on handling Tepex®

ThehandlingoftheTepex®insertplaysanimportantroleinensuringhighreproducibilityofthemanufacturingprocessandthecomponentproper-ties.Itleavestheheatingstationinahotandplasticizedstateandisthuslimp.Thismustbetakenintoaccountwhentransportingthematerialtothemold,closingthemoldandduringtheactualforming,aswellaswhenovermoldingandback-injecting.Thehandlingsystemhastoperformthefollowingfunctions:

Securegrippingduringandafterheating

Preventinglocalcoolingbygrippers

Fasttransportationtothemoldbytheshortestpossibleroute

Reproducibletransfertothemoldinthecorrectposition

Inthemold,itthenneedstobeensuredthat

theblankismountedinthecorrectpositionwithoutheatloss,and

theblankisapprovedforformingduringthemoldclosingmovement

Thefollowinggrippermethodsforhandlingarerecommendedfortrans-portationbetweentheheatingstationandmold:

Needlegrippersincl.stripperbushes (arestuckintothecompositesheet)

Clampingpins,pointgrippers(double-sidedclamping)

Vacuumsuctiondevice

Pins(theyholdthecompositesheetinpreviouslymadeholes)

Forincorporationintothemold,usecanbemadeof

needlestofixtheblank

swivelingretainingfingers

clampingpinsinbothmoldhalves,whichareusedtoinserttheblankcentrallybetweenthetwomoldhalves

Vacuumsuctiondevice

TopreventcoolingofTepex®inthemold,earlycontactwiththerelativelycoldmoldwallsshouldbeavoidedindesigningthetransfersystem.The-semountsalsoneedtobedesignedinsuchawaythatwhenthemoldis closed, theTepex® is kept in a reproducible state and in the correctpositionduringformingwithoutimpairingthedraping.

4. JOINING TECHNIQUES FOR TEPEX®

Tepex®componentsareoftenpartofcomplexassembliesthat,inextremecases,combinedifferentmaterials, includingsteel, lightmetalssuchasaluminumandmagnesium,plastics reinforcedwith short or longglassfibers,orcarbon-fibercompositematerials.Tomanufacturesuchassem-bliesquickly,automatically,toahighlevelofqualityandatlowcost,Tepex® mayneedtobejoinedwithitselforwithothermaterials.Todothis,proces-sesmaybeusedthatarelongestablishedforthermoplasticcomponentsinindustrialseriesproduction.

Thevarious joiningprocessesdifferaccording to thephysicalprincipleofaction: Homogeneousbonds(welding,adhesion) Non-positiveprocesses(fasteningwithscrews,pressing,riveting) Positiveprocesses(catches,locks,brackets)

There is also a differentiation between separable (screws, pins, wed-ges) and inseparable connections (adhesion,welding, riveting).Whileweldingcanonlybeused for thermoplasticsemi-finishedproducts,byusingadhesionandmechanicaljoiningitispossibletoconnectvariousmaterial combinations, even plastics, to completely differentmaterialssuchasmetal.


Aconcreteconfigurationforajoiningprocessshouldalwaysbeproducedon a component- and application-specific basis. In this regard, pleaserefer toadhesivemanufacturers,manufacturersofconnectingelements(screws, rivetsetc.),machinemanufacturers(welding)andengineeringservice providers,who can reliably assess and design such processesusingtheirexpertiseandexperience.

4.1 Bonding

Componentbondingisanestablishedhomogeneousjoiningtechnologythatalsomakesitpossibletocombineincompatiblematerialswitheachother.Awiderangeofadhesivesystemsareavailableonthemarketthatareinsomecasestailoredtospecificmaterialcombinations.

Userscanemployestablishedsystemstoselectanappropriateadhesivesystem for Tepex®.Knowledgeofthecompositematrixandbondingpart-nerisgenerallysufficient–adhesivesystemsspeciallytailoredtoTepex® arenotnecessarilyneeded.

Systems made of two-component epoxy adhesives, two-componentacrylate adhesives and two-component polyurethane adhesives havealreadybeenseries-testedassolvent-free,low-shrinkageadhesives.

Thecomponentsmustbedesignedinawaythatisconducivetoadhe-sion.Thefollowingtypesofloadmayoccurwithadhesivebonding:

Tensilestress–shouldbeavoided,asthetensilestrengthofadhesivesisoftenlessthanthestrengthoftheadherends.

Tensileshearstress–overlappingadhesivebondsenabletheformationoflargerjoiningsurfacesandthusthetransferofgreaterforcesunderrelativelylowshearstressinthebondingjoint.Theidealscenario.

Peeling – peel forces trigger stresses perpendicular to the bondingjoint.Unclearstressconditions,estimationofprotectionagainstdam-agealmostimpossible.Ifpeelstressesareunavoidable,theyshouldbereducedthroughappropriatemeasures.

Bendingandgapstresses–shouldalsobeavoided,astheymayleadtohighstresspeaks.

Cleaning,rougheningthesurfacesand/oractivatingorusingspecialpri-mersincreasesadhesivestrength.

Tepex®canalsobejoinedwithcommercialstructuraladhesivesthatcureatcathodicdipcoating(CDC)temperatures.Thisincreasesthepossibleapplicationsforthecompositematerialinthemanufactureoflightweightbodyworkparts,asnoadditionalenergyisneededforheatingandcuringtheadhesive.

4.2 Joining using injection molding

Asalreadydescribed inSection2.3, joiningusing injectionmolding isanefficient,versatile joiningprocessfor thermoplasticcompositessuchas Tepex® that has become established in series production. If the in-jectionmoldingmaterial and compositematrix are polymer-chemicallycompatible, theresult isahomogeneousbondwithexcellentadhesion.This techniquecanevenbeusedto joinseveralcompositeblankswithmetalcomponentsinasingleprocesssteptocreatecomplexassemblies.Whiletheconnectionbetweenthethermoplasticcompositeandinjectionmoldingmaterialisgenerallyahomogeneousbond,theconnectionwithincompatiblebondingpartnerssuchasmetalsismadeeitherbyaposi-tive connection mechanism (injecting breakthroughs or anchoring thepolymertosurfacefeatures)orbyusingprocessingaids.AnappropriatebondingagentthatenablesasecondaryadhesivebondbetweenTepex® andmetalcanthusbeappliedtosheetmetal.

4.3 Mechanical joining processes

Self-tappingscrewsthathavethreadflankswithanangleofbetween20and30degreesshouldbeusedtofastenTepex®components.Giventhatthe fiber structuresgenerally need tobepenetratedby introducing joi-ningelements,theseelementsshouldeithernotbeintroducedintotheprimary loadpathsof thecomponent,oralternatively thefiberscanbedisplaced in the plasticized semi-finished product so that they traversearoundtheholeintowhichthejoiningelementislaterintroducedwithoutbeing damaged (seeSection3.4 Integratingholes).Alternatively, load-introducinggeometries suchas screwdomescanbemolded inplaceduringcomponentproduction.


Ingeneral,forceshouldbetransmittedlessviathefaceoftheholeandmoreatthesemi-finishedproductorcomponentlevelasappropriate.Thiscanbedonebyusinglargejoiningelementheadsandappropriatepre-tension.

4.4 Welding

As Tepex® isbasedonathermoplasticmatrix,appropriateweldingpro-cesseslendthemselvestothispurpose.Inwelding,useismadeprimarilyof physical adhesionmechanisms so as to generate a connection be-tweentwoormorebondingpartners.Thisinvolvesthebondingpartnersbeingtransformedintoameltedstateatleastonalocalbasisandthenbrought intocontactwitheachotherunderpressureandcooledagainunderthe joiningpressure.Duringthe joiningphase, theadhesionpro-cessesareactivatedandgenerallyremainreversiblewhencooled.

Avarietyofprocessesareavailablethathavealreadylongbeenusedinconventional thermoplastic processing. The processes are suitable forseries production and have been thoroughly testedwith thermoplasticcomponents.Amongotheraspects, theydifferaccordingtoweldseamstrength,cycletimesandsuitabilityforsmallorlargebatchsizes.

Theweldingprocessescanbeclassifiedaccordingtotheapplicationofheat.Thefollowingtypesaredistinguished:

Heatingthroughheatconduction Heatingthroughradiation Heatingthroughmovement Heatingthroughconvection

Averygoodoverviewoftheindividualweldingprocessesandtheirsuit-abilityforthermoplasticfibercompositesisgivenin“HandbuchVerbund-werkstoffe”(HanserVerlag)byNeitzel,MitschangandBreuer.

5. RECYCLING TEPEX®

Whencuttingoutapplication-specificblanks,acertain levelofwaste isproduced,ascanbeseenintheexampleinFigure24.Tominimizethiswaste, the relevant geometries are nested in theTepex® semi-finishedproduct toobtain anoptimumyield, taking into account thenecessaryfiberorientation.DuringthedevelopmentphaseofTepex®components,everyoneinvolvedshouldthereforepaygreatattentiontooptimizingtheblankgeometrywithregardtoreducingmaterialloss.Eventhesmallestadjustmentscanincreasetheyieldconsiderably.

Figure 24: Example of waste after cutting the component geometry to size

Inthecaseofcurvedgeometriesthatareverydifficulttonest,thepossi-bilityof thecomponentalsobeingdesignedusinganumberofTepex® blanksthatarethencombinedinthemoldshouldbeexamined.Thisoftenresultsinmaterialbeingusedmuchmoreeffectively.


Unavoidablewaste can be sent for recycling. AsTepex® is a fiber-rein-forcedthermoplastic,thefollowingrecyclingmethodscanbeused:

Materialrecyclingusingmechanicalprocessing

Feedstock/chemicalrecycling,i.e.separationintoindividual componentsusinghydrogenation,hydrolysisandpyrolysis

Energyrecyclingtorecovertheenergycontainedintheplastic

Materialrecyclingoffersthegreatesteconomicbenefitsinrecyclingresid-ualmaterialandwaste.Inthisprocess,theTepex®wasteisfirstgroundtoadefinedparticlesizeusingcuttingmillsormulti-shaftcrushers.Theresult-inggranulatedmaterialcanthenbesentdirectlytoatypicalplasticspro-cessingoperation.Duetothegranulatedmaterial’slowbulkdensity,forceddispensingshouldbeusedinordertopreventbridginginthehopper.

Byaddingnon-reinforcednewmaterial,therecycledmaterial’sfibercon-tentcanbecontrolledprecisely toproduceregranulate.WithPP-basedTepex®, diluting the granulatedmaterial to a fibermass content of 30percent is recommended.OtherTepex® gradescanalsobeprocessedundiluted.Themechanicalproperties (strength,stiffness, toughness)ofthe recycledmaterial are comparablewith standard plastics reinforcedwithshortfiberswithappropriatefibercontent.

Figure 25: Value chain: Tepex® granulated material regranulate component made from recycled material

6. DESIGN AND CALCULATION OF TEPEX® COMPONENTS

Tepex® offers designers tremendous freedom in the load-optimizeddesignofheavy-dutyyet lightweightcomponents.Thecharacteristicsofthesecomponentsdependonthethermoplasticforthematrix,thetypeof continuous fiber (glass, carbon) and the typeof fabric or inlayused(unidirectional,bidirectional,multiaxial).

One of the key factors in the engineering process is the directionaldependency(anisotropy)of themechanicalproperties that results fromreinforcement with continuous fibers. Unidirectional continuous fibersembeddedinathermoplasticmatrixexhibitthepropertiesofthefibrousmaterial inthedirectionofthefibers(onedirection),whereasperpendi-culartothefibers(twoandthreedirections),theytendtoexhibitthepro-pertiesofthematrix.

WithTepex®components,thelengthofthefiberscorrelateswiththatofthe components.Wherever possible, designers should therefore orientthefibers inthedirectionoftheappliedloadssothattheflowofforcesbetweenpointsof forceapplicationtakesplacethroughthecontinuousfibers.However,amorecomplexstateofstress in thecomponent (e.g.combinedshearandtensilestress/compressivestressinthecurvedpro-file)mayalsorequireacombinationofvariousfiberorientations.Asym-metricallayerstructureisbeneficialinensuringlow-distortioncomponentdesign.Theforcesshouldalsobeabsorbedoveraslargeanareaaspos-sibletoavoidexcessivestressandnotcheffectsasfaraspossibleandtoalwaysapplyaloadtomultiplefiberrovings.


Figure 26: The diagram shows the influence of fiber orientation on component behavior

6.1 FEM calculations – conditions and special characteristics

Computer-aided engineering (CAE) ofTepex® components is essentialtoachieveshortdevelopmenttimes,cost-effectiveproductionprocessesandcomponentdesignthat isoptimizedfor the loadcases. In thispro-cess, thedesignrelatesspecifically toboththeproductionprocessandthemechanicalbehaviorofthecomponentandtheinteractionbetweenproductionandcomponentproperties.

Asnotedintheintroduction,theanisotropy– i.e.directionaldependen-cy– is themost importantpropertyof the semi-finishedproduct in thedesignprocess.Themorphologyofthereinforcingfabricgivesrisetoatension-compressionasymmetry,adependencyonthepositionintermsofthethroughplane(layerstructure)and,forthemanufacturingprocess,thedrapability.Thematrixpropertiesgiverisetothetemperatureand,insomecases,moisturecontentdependency,aswellas–dependingonthetypeof load–time-dependentcreep.The layerstructurealsoproducesrelativelylargedifferencesbetweentensileandflexuralproperties.

Boththemanufacturingprocessandcomponentbehaviorcanbechar-acterized highly effectively using standard FEmethods and calculationprograms(solvers),withprecisionandforecastqualitydependingonthemodel-basedapproachused,thescopeoftheunderlyingmeasuringdataandthespecificaspectstobecalculated.

In order to sufficiently predict themanufacturingprocess, the resultingfiber orientation and the component properties through to fracture be-havior,LANXESShasdevelopedtoolsbasedontheFEsolverABAQUSthatcharacterizethepropertiesandinfluencesreferredtoandcanthusbeuseddirectlyinthedevelopmentprocessforTepex®components.TheseFEtoolsusematerialdatathatarecalculatedusingdirection-dependenttensiletests,sometimeswithahighexpansionrate,andvariousshearandflexuraltests.

Figure 27: Stress distribution and deformation in three-point flexural testing with the HiAnt® beam

6.2 Draping simulation

Forminganddrapingsimulationsservetwoaimsthatareindependentofeachother:

Determiningthedistributionoflocalfiberorientationsandshearanglesin the fabric.Theseareneeded in themechanicalcalculationto takeintoaccounttheanisotropicmaterialbehavior.Thiscalculationisoftenneededearlyintheprojectintheconceptphasetomechanicallyana-lyzevariousconceptproposalsatthisstage.Simulationoffiberorienta-tionsmustthereforebeperformedquicklyandeasilyandrequireaslit-tleinformationaspossibleaboutthemoldthatisnotyetavailableatthistime.Todothis,LANXESSusesanFE-basedcalculationmethodthatdeterminestherelevantblankandthedistributionoforientationsforagivenTepex®geometryveryquickly(approximatelyonehour).Thepro-cessisnotexact,butisgenerallysufficientlyprecise(one-stepdraping).

Complete representationof thedrapingprocess, taking intoaccountblank geometry, mold geometry, slides, retaining needles, handlingsystemetc.Thetaskhereistomaptheprocess,identifyanyerrorsatanearlystage,developsuggestionsforimprovementandassesspro-cessreliability.Calculationoffiberorientationissomewhatintheback-groundinthiscase.Acompletedrapingstudyis ideallycarriedout if

> 372,1

318,9

265,8

212,7

159,5

106,4

53,2

< 0,1

Str

ess

[MPa

]

Def

orm

atio

n [m

m] > 142

122

10,1

8,1

6,1

4,1

2,0

< 0,0

3-Punkt-Biegung3-point bending

Fiberorientation1paralleltothecomponentaxis

Fiberorientation1at45°tothecomponentaxis

Distance [mm]

Force[kN]


Figure 29: The illustration shows the key influences on integrative simulation of Tepex® hybrid components

6.4 Simulation of cooling behavior

LANXESShassupplementedtheformingsimulationandthenewmateri-almodelforTepex®withamodelingapproachthatalsosupportssimula-tionofthermalprocessesinheatedTepex®duringforming.Thissimulati-onmodelessentiallymakesitpossibletoexamineunevencoolingunderslides,forexample,anditsreverseeffectondrapability,whichresultsfromthetemperature-dependentmaterialbehavior.

As this simulation process requires precise information on the heatingprocessandallthethermalconditionsandismuchmorecomplexoverallthantheisothermalapproach,itisnormallyonlyusedforanalyzingveryspecificquestionsandproblems.

6.5 Designing Tepex® components independently

LANXESSusesintegrativesimulationinjointdevelopmentprojectssoastoprovidecustomerswithsupportindevelopingcomponents.Yetitisalsoimportanttogiveourcustomerstoolstheycanusetodesignnewapplica-tions in Tepex®aspartoftheirownCAEworkflow.Tothisend

amaterialmodelhasbeenvalidatedforthecommercialprogramDigi-matfrome-Xstreamandpopulatedwithdata.Ourcustomerscanusethisprogram in combinationwith anumberof calculationprograms.AnappropriateprogramlicenseisneededtousetheDigimatsolution.

Draping simulation

Injection molding simulation

Processing parameters

Fabric orientation

Tepex®

Durethan®

Short fiber orientation

Adhesion

thecomponentgeometryisessentiallyfixedandmolddataarealreadyavailable(atleastformoldsurfaces),yetsomeflexibilitystillexists.

ThesimulationmodeldevelopedbyLANXESSforthedrapingofTepex® components is basedon theFE solverABAQUS. It takes into accountthefactthatthermoplasticfabric-basedcompositesdonotallowplasticthermoformingbut insteadareadded to thecomponent’s three-dimen-sionalgeometryasaresultoffabricshearstrainfromtheflatmold(trelliseffect).Ifthesheareffectwhichisnecessaryforformingissolargethatthefiberslocktogether,thematerialswitchestothenormaldirectionandwrinklesareproduced.Thiseffectcanalsobereproducedinthecalcu-lationmodel. Figure 28: Shear angle distribution in a mock-up component

6.3 Integrative simulation

ThecompositematerialmodelforTepex®developedbyLANXESS,com-binedwiththefiberorientationsdeterminedforthecomponentgeometryintheone-stepdrapingprocess,enableshighlyeffectiveprecalculationofthecomponent’sstiffness,strength,crashpropertiesandvibrationchar-acteristics.ThetoolscanbeusedbothforpureTepex®componentsandthoseproducedusing insertmolding, hybridmolding or flowmolding.Designerscanthusreacttoaweaknessinacomponentatthecomputerstage–forexamplebyusinggreaterwallthicknessesorreinforcingribs

Bothtoolshaveproventheirsuitabilityandprecisioninthedevelopmentofnumerousprototypeandseriescomponents–suchasinthecaseofafrontendupperbelt,brakepedal,airbaghousing,seatshellandinfotain-mentbracket(load-bearingstructureofthesoundsysteminavehicle).

Shearangle[rad]

> 0,8

0,7

0,6

0,5

0,4

0,3

0,2

0,1

< 0,0


astandardmaterialmodel forLS-Dyna(MAT58)hasbeenidentifiedwithwhichmanydifferentdesignproblemscanbedealtwitheffectively.

linearmaterialdatasetsthatenableasimplestiffnessanalysisregard-lessofthecodeusedhavebeenprovidedformostTepex®grades.

Anexpandingreserveofmaterialparametersisavailableforallmethods.Allcasesrequiretheorientationdistribution,whichLANXESScancalcula-tebyusingtheone-stepdrapingprocess,forexample,andmakeavailableforaspecifiedcalculationmodel,tobesaved.

7. HIANT® – SERVICE ALONG THE ENTIRE DEVELOPMENT CHAIN

TheHiAnt®brandrepresentsthecompleteknow-howthatLANXESSpos-sesseswhen itcomes tomaterials,composite technologies, simulationmethods, component testing,processingandmanufacturing.We intro-ducethisexpertisetoourpartnershipswithourcustomers.

HiAnt®servicesforTepex®include:

Assistanceinselectingmaterials,takingaccountofcomponentrequirements

Provisionofcustomizedpolymergradesforinsertmolding,hybridmoldingandflowmolding

Materialstestingtodeterminematerialparametersformechanicalstructuralanalysisandcomponentdesign

Simulationofforming(draping)ofTepex®

Integrativesimulationfortheload-optimizeddesignofcontinuous-fibercompositecomponents

Reproductionofcustomers’manufacturingprocessesinourfully automated,production-qualitydemocellstodetermineprocesspara-metersandforqualitycontrolandimprovement

Componenttestingsuchasmechanicalcomponentandclimatechangetests

COMPONENT TESTING

MATERIAL DEVELOPMENT

COMPUTER-AIDED ENGINEERING

State-of-the art testing equipment

Suitable material solutions

Simulation processes developed for our materials

PROCESS DEVELOPMENT

CONCEPT DEVELOPMENT

Material / process combinations for new applications

Expertise in lightweight design


8. ACKNOWLEDGMENTS

Thefollowingcompaniesanduniversities(inalphabeticalorder)havegenerouslysupportedtheproductionofthisbrochurewithimagemateri-alandadditionalinformation:

ENGELAUSTRIAGmbH,Ludwig-Engel-Strasse,14311Schwertberg,Austria

RosenheimUniversityofAppliedSciences (Prof.Schemme,Prof.Karlinger)

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KraussMaffeiTechnologiesGmbH,Krauss-Maffei-Strasse2, 80997Munich,Germany

LANXESSDeutschlandGmbHHighPerformanceMaterials50569 Cologne, Germany

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