Long-Fiber Reinforced ThermoplasticsTailored for Structural Performance

Manfred Brümmer

Dr. Frank HenningDr. Wenzel Krause

ACCE5th Automotive and Composites ConferenceTroy, USA, 12.-14. September 2005

- Page 2

Outline

Introduction

Advantages of Dieffenbacher LFT-D-ILC technology

Continuous fiber reinforced LFT

Tailored LFT – material development

Conclusions

Future Perspectives

Presses & More - Teaming up in development

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Tailored

TailoredLFT‘s

Toughness

Stre

ngth

/ S

tiffn

ess

Rubber

Short fiber reinforced

plasticsLong fiberreinforced

plasticsParticle filled

plastics

Non reinforcedplastics

Why Long Fibers for Reinforcement ?

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Fiberglass rovingPolymer resin Additive/modifier

Product – LFT part

Glass Mat Thermoplastics(semi-finished product)

GMT oven+

Hydraulic press

Long Fiber Thermoplastic Granules(semi-finished product)

GMTCompression molding

Single screw extruder+

Hydraulic press

LFT-GInjection molding

LFT-GCompression molding

Injection molding machine

Product – LFT part Product – LFT part

Established Processing Techniques for LFT Semi Finished Products

- Page 5Quelle: AVK-TV 2005

Growth of LFT in Europe

0

5

10

15

20

25

30

35

40

45

19941995

199619971998

1999200020012002

20032004

kto

GMT LFT

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Product – LFT part

Polymer compound

LFI injection molding

equipment

LFT/SGInjection molding

LFT-D-ILC equipment+

Hydraulic press

LFT-DCompression molding

LFT-D-ILC compression molding

LFT-D extruder+

Hydraulic press

Product – LFT partProduct – LFT part

Fiberglass rovingPolymer resin Additive/modifier

In-Line Compounding

Technologies for LFT Direct Processing

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Compounding extruder suitable for: BlendingIn-line Stabilization and CouplingIn-Line coloringEngineering resins/polymersIn-line compounding of fillers or nanoparticles

Mixing unit (twin-screw)Extraordinarily low wear (screw/cylinder)Incorporation of different continuous fibersIncorporation of natural fiber matsIncorporation of chopped fibersComplete disintegration of fiber bundles

Dieffenbacher LFT-D-ILC technology basis for visible applicationsDisintegration of fiber bundles and homogenous dispersionReduced anisotropy and therefore low warpage

Advantages of Dieffenbacher LFT-D-ILC Technology (2 Extruders)

LFT strand

Mixing extruder

IL Compounder

Polymer Additive/modifier

Fiberglassroving

Compression molding

DIEFFENBACHER

LFT strandLFT strandLFT strand

Mixing extruderMixing extruder

IL CompounderIL Compounder

PolymerPolymer Additive/modifier

Additive/modifier

Fiberglassroving

Fiberglassroving

Compression molding

DIEFFENBACHERDIEFFENBACHERDIEFFENBACHER

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Advantages regarding material propertiesTailored LFT material Choice of matrix resin, additives and fibersAdjustable and reproducible fiber length distribution Continuously adjustable glass fiber contentExcellent homogeneity of LFT strandsCo-molding of continuous reinforcements at low thickness and weight compared to injection molding possibleSingle heat historyExcellent flow behavior Improved surface appearance (vs. GMT processing) Processing of recycled trimmings and even ELV material

Advantages regarding economical factsHigh productivityLow wall thickness possible compared to injection molding (material savings 25%)Low down time due to turnkey production cellSignificantly reduced expenses for total process energy consumptionHigh material output rates at constant and reproducible material propertiesExtremely short cycle times (22 seconds for VW Golf V underbody shield)Reduced mold and screw wear

Advantages of Dieffenbacher LFT-D-ILC Technology

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In-line compounder

LFT die

Conveyor belt forLFT strand

HydraulicPress

Provision of rovings

Mixing extruder

Fully automized material handling

AVK-TV Innovationspreis

2001

LFT-D-ILC Base Equipment

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What is Tailored LFT ?

LFT combined with local reinforcement by fabrics or continuous fiber structures

Next Generation of Composites in Automotive

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LFT (Long fiber reinforced thermoplastics – pellets, granules)

Tailored LFT (LFT-D-ILC with local continuous fiber placement –rovings, profiles, textiles or combination)

GMTex (GMT with one/several layers of woven fabrics)

GMT (Glass-mat reinforced thermoplastics)

LFT-D (LFT with direct incorporation of glass fibers)

Alternative to metal or metal hybrids

Development Path

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GMT + GMTexprecut

Ofen

Heated precut

PositioningIn mold

CrosswiseSheet placement

PartSource: Quadrant

Applications – Spare Wheel Tub

- Page 13

GMTex – Field of Applications

Source: QuadrantImproved crash performanceby combination of LFT and Fabrics

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GMTex – Tailored LFT - Field of Applications

previous model:GMT + steel brackets

new model:GMTex + integrated brackets

Source: Quadrant

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Production Technologies – Compression Molding of GMTexGMTex

Advantage- Synergy of co-molding (no high precision molds no

additional handling of textiles or organic sheets)- Local reinforcements just in areas where required- Reduced costs compared to the use of pure organic sheets

Disadvantage- Dependency on one material supplier- Costs of semi-finished products (incl. shipment and storage)- Co molding of standard GMT required- Fiber alignment is not optimal (0/90°)- No structural incorporation of inserts possible

Source: Quadrant

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Tailored LFT - Adjustment of Mechanical Properties by In-Line Assembly of Continuous Fiber Skeleton with LFT-D

LFT

Fabric

Important parameters are :

Fiber orientation of each layer (fabric and LFT)Volume ratio of fabric and LFT (thickness of each layer) Properties of each layerProcess parameters (processing window)

simplified approximation:

EC = EG*vG + ELFT*vLFT

Calculation of Modulus utilizing therule of mixture:

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75,7 89,9 90,9 91,8

130,1173,8

267,1

372

0

50

100

150

200

250

300

350

400

450

LFT-D30; 0° LFT-D30; +/-45°Gelege; 0°

LFT-D30;Twintex TPP601485AF; 1-lag;

0°

LFT-D40; 0° LFT-D40;Twintex TPP601485AF; 1-lag;

0°

LFT-D30;Twintex TPP60935BF; 2-lag;

0°

Twintexlaminat;TPP60

1485AF; 0°

Twintex laminatTPP60 935BF

4/1; 0°

Tens

ile s

tren

gth

[MPa

]

Fabric Reinforced LFT – Adjustment of Mechanical PropertiesThe variation of fabrics and LFT materials offers a material tailored for each application

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Elongation of a TWINTEX laminate 45° (7 layers of Twintex P PP60 745 AF)

Local Reinforcement Using TWINTEX Fabrics

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Textile Reinforcements - Tensile Strength PP/GF60 Laminates

Laminates of non crimped fabrics offer a high potential for energy absorption

0

50

100

150

200

250

300

350

400

0,00 5,00 10,00 15,00 20,00 25,00

Bruchdehnung [%]

Zugs

pann

ung

[MP

a]

Twintex 4/1 0°

Twintex 4/1 90°

Twintex +/-45° 0°

Twintex +/-45° 45°

Saertex +/-45° 0°

Saertex +/-45° 45°

Saertex 45°/90°/-45° 0°

Saertex 45°/90°/-45° 90°

Elongation [%]

Tens

ile S

treng

th [M

Pa]

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Advantages and Challenges of Local Textile ReinforcementsSignificant increase of Tensile Modulus and Strength

Significant increase of impact and energy absorption

Slight increase of flexural strength and modulus (low wall thickness!)

Material properties = properties of the component

but

Warpage…+

…Penetration of the fabric by LFT…+

…Influence of geometry =

= have to be considered in the design phase!

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30 c

m

7,9

27,830,5

134

44

144

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

LFT-D with-out rovingstructure

rovingstructure

Rovingstructureco-moldedwith LFT-D

Ten

sile

Stre

ng

th[k

N].

0

100

200

300

400

500

600

700

Part

wei

gh

t[g

]

ICT-DemonstratorContinuous fiberstructure co-moldedLFT-PP/GF

Tailored LFT – Light-Weight Composite Parts Made of Long Fiber Reinforced and Continuous Fiber Reinforced Thermoplastics

• Customized unidirectional continuous fiber structures for significant increase of part specific strength (increase of some 100%).

• Transmission of forces by part specific continuous fiber structures -fiber structures work as an superior integrated joining technology

Demonstrator:LFT-PP/GF

combined with continuous

fiber structure

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Filament woundreinforcement UD-profile reinforcement

Fabric reinforcement

Integration of Different Types of Local Reinforcements

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Fusion Bonding of LFT and Continuous Fiber Reinforcements

Cohesion and Adhesion

Fusion Bondingbetween

LFT and films

Cohesion force(equal join partners)

Interdiffusion atpolymer-polymer-interface

(LFT / Reinforcement)

Adhesion force(different join partners)

Form fit(surface roughness)

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Heating of thefabric in an infra-red oven

Transfer of fabric to the open mold

Two LFT-strandsare positioned inthe mold

Compressionmolding of fabricand LFT-material

Setup to Produce Co-molded LFT/Fabric Sample Plates

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Preheat temperature of reinforcement (important for handling)

mold LFT fabric mold

Preimpregnated fabric: PP/GF60LFT-D: PP/GF30

Example:TLFT = 230°CTInterface ≈ 185°CTFabric = 140°CTMold = 60°C

Tmold

TPPm

Interface temperature exceeds the melt temperature for a short time(Process window)

t1

t2

t3

t4

Temperature Curve at Non-Isothermal Bonding

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100µm

Uneven polymer-polymer interface

Filaments crossing thepolymer-polymer interface

Bond strength is based on interdiffusion, fiber bridging, andmechanical adhesion due to an uneven surface in the interface

Micrograph of the Interface LFT/ Reinforcement

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Penetration in the demonstrator part (beam structure)

No penetration

Standardmold filling

Penetration,

Mold-fill trough the fabric

LFT-Material

Mold withrib cavity

Function integration on bothsides of the fabric

molding

Fabric

Penetration of Fabrics with LFT-Material

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Functional Integration in a Front-End Carrier (by Penetration)

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highly oriented fibers

Reduction of glass content from 29,9 wt.-% to 26,9 wt.-%

(Fabric: Twintex P PP60 935 BF 4/1)

Rib structure of demonstrator part (LFT PP/GF30)1. Row no Penetration2. Row penetrated areas

X-ray Images of Penetrated Areas

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020406080

100120140160

0 10 20 30 40 50Torsion Angle [degree]

Torq

ue [N

m]

180

LFT-beam structure with continuous fiber reinforcementLFT-beam structure without continuous fiber reinforcement

1,5 °/s

350 mm

Improvement of Torsional Strength by Local Reinforcement

Adding an roving reinforcement:Beam weight increase by 4% compared to pure LFT-PPGF30

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Filament woundroving reinforcement

Metal insert

LFT-part with co-molded reinforcement

(with and without metal inserts)

Part dimensions: Length: 300 mmPart weight: 150 gAdditional weight for UD-Reinforcement: 10 g

Loop Reinforcement Between Fixtures – Load Path

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Number of layer

X

Y

ZTesting directions:

0

10

20

30

40

50

0 10 20 30 40 50Number of layers (glass-roving)

Froc

e at

bre

ak [k

N]

Test in X-directionTest in Y-directionTest in Z-direction

The part strength is improved by a factor of 10 in all three directions

Mechanical Properties of a Co-molded Continuous Loop Structure

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Filament woundreinforcement

LFT forfunctional integration

Rovingstructure

Fabric-reinforce-ment

PressLFT-material

Robot

UD-reinforcement is preheated as a tailored Preform LFT-material and UD-reinforcement are assembled in-line to the compression molding step

Production Concept for a Tailored LFT Composite Frontend Carrier

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Process Development and Modification for Tailored LFTPrototype Manufacturing

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Tailored LFTAdvantage- Synergy of co-molding (no high precision molds no

additional handling of textiles or organic sheets)- Local reinforcements just in areas where required- Reduced costs compared to the use of pure organic sheets- Reduced costs compared to the use of semi-finished products (GMTex)- Independency from material supplier- Optimimum fiber alignment and structural integration of inserts- Combination of geometrical stiffening (ribs) and material stiffening (continuous fiber)- Improvement of impact by additional fabric possible if necessary (integrity after crash)

Disadvantage- Higher degree of automation due to profile positioning / equipment (not cycle time

relevant)- New development – not state-of-the-art, some development necessary

Production Technology – Tailored LFT

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Bumper Beam madeof Tailored LFT

Advantages of automised local fiber placement:

Reduced material cost

Economical use of continuous fiberreinforcements

Reinforcement is tailored to thespecification

High level of functional integration

Advancements of Tailored LFT

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LFT-D Technology avoids the use of semi-finished products

LFT-D parts can be reinforced withcontinuous fiber reinforcements

Wide processing window allows goodbonding of LFT and reinforcement

Co-molding combines high functionalintegration and the performance of continuous fiber reinforced composites

Source :Quadrant

Door modules

Front ends

Spare wheel pan:Fabric reinforcement (GMTex)

Conclusion

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Future/Perspectives

LFTs with engineering plasticsApplication of technical plastics (ABS, SAN, PA 6, PA 6.6, PBT, etc.)

LFTs with other fibers/filling materialsApplication of natural fibers (Flax, Sisal, Hamp, etc.)Application of additional filling materials (Talc, hollow glass beads, etc.)

Exterior body panels - „LFTs and PFM“Back compression molding of films (PFM – Paintless Film Molding)

Development of process technology, material and equipment for the use of:

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Dieffenbacher „Engineering Area“

Equipment consisting of features that areClose to real production and different ways oftreatment:

Hydraulic High Speed Press 36.000 kN (End 05) with an active parallel levelling systemLFT-D PlantLFT-G Extruder for granulesConveyor and dosing plants for various plasticsgranules and recyclesAdjustable die for tailored plastificates

Research and DevelopmentDevelopment of new process technologies and modifications suitable for the processing of longfiber-reinforced thermoplastics and -setsSupport for part design by Dieffenbacher Competence Team Simulation of Mold filling by Fraunhofer ICTMatching and prototype productionMaterial development in cooperation withFraunhofer ICT

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Closing Words

The In-line Compounding-Compression Process is an established technology for long fiber reinforced components which offers a high development potential for future applications especially for structural and semistructural parts as well as for car body parts aiming at class „A“ surface quality.

www.dieffenbacher.dewww.ict.fraunhofer.de