thermoset composite structures for automotive...

Thermoset Composite Structures for Automotive Lightweighting

Prof. Dr.-Ing. Frank Henning

Peter the Great, St. Petersburg, Polytechnic University

November 21st, 2016

© Fraunhofer ICT

Contents

Introduction

Motivation for lightweighting

The high pressure RTM process chain

Preforming - cutting, stacking and draping of fabrics

Reinforcement Draping simulation The challenges of processing

HP-RTM - infiltration and consolidation

Resins Mold filling simulation Curing characterization and modelling The challenges of processing

Future research and development goals

Summary

© Fraunhofer ICT © Fraunhofer ICT

Fraunhofer Institute for

Chemical Technology ICT

© Fraunhofer ICT

IntroductionKarlsruhe Institute of Technology KIT

We are a group of scientists developing methods for manufacturing and structural simulation of composite materials

Institute: Vehicle System Engineering

Department: Lightweight Technology

© Fraunhofer ICT

Collaboration between Fraunhofer ICT, KIT Institutes and Fraunhofer Project Center

Fraunhofer ICT - Polymer Engineering

KIT – FAST

KIT – IAM-WK

FPC Canada

FPC Korea

Technology Corridors

FPC@

FPC@

IntroductionCollaboration between the Institutions

© Fraunhofer ICT

Contents

Introduction




Reinforcement Simulation The challenges of processing




Summary

© Fraunhofer ICT

Motivation for lightweightingUse of FRP in Lightweight applications

High weight related performance

Highly integrated and “ tailored” design is feasible

» High geometrical design freedom

» Targeted use of the anisotropy

High weight related energy absorption potential

Excellent fatigue propertiesPicture: BMW-Group www.lightweight-design.de

Fixing and mounting elements

Targeted surface modifications

Structural Health Monitoring

Picture: Airbus

Fraunhofer ICT Fraunhofer ICT

Source: Roland Berger, VDMA

Source: Roland Berger, VDMA

© Fraunhofer ICT

Motivation for lightweightingUse of FRP in Lightweight applications

• Methods• Materials• Processes

technological advances

?

© Fraunhofer ICT

Motivation for lightweightingMethods - Materials – Processes (MMP) approach

C O M P O S I T E

S O L U T I O N S

P R O C E S S E S

Thermoplastic

RTM-/RIM

SMC

Fiber spraying

Tapes

Thermoset

T-RTM LFT

Preforming

Inject. molding

M E T H O D S

Engineering/Design

Structure Simulation

Process Simulation

M A T E R I A L S

Fiber

Matrix

Additives, Filler, (…)

In order to develop high-performance lightweight solutions which can be manufactured on an industrial scale, it is essential to concentrate and connect competences in the fields of methods, materials and production

© Fraunhofer ICT

Contents

Introduction








Summary

© Fraunhofer ICT

The High Pressure RTM Process ChainAutomotive applications

Side frames

Exterieurs

Body in white (BMW i3)

Back seat structure

BMW i3 Source: http://bmw-wiki3.de/

BMW i8 Source: http://bmw-wiki8.de/

Audi R8 Spyder Source: AUDI AG

Source:

http://evworld.com/press/bmw_i3_lifepod600x400.jpg

Source: BMW AG

Source: BMW AG

Leaf spring

Source: BMW AG

Source: Benteler SGL / Henkel

© Fraunhofer ICT

Motivation for the s imulation of the RTM process

Initial verification of the manufacturability of the part geometry

Virtual design and optimization of the process

Detailed knowledge of manufacturing effects and their influence on structural performance

Reduction of development time and costs

Requirements for Multi-Material-Design

V I R T U A L P R O C E S S C H A I N

F L O W O F I N F O R M A T I O N

O P T I M I Z A T I O N

Molding Curing /

cooling

Part Assembly

integral constructiondifferential

construction

Geometry Forming

The High Pressure RTM Process ChainVirtual process chain

© Fraunhofer ICT

The High Pressure RTM Process ChainProcess chain for HP-RTM

© Fraunhofer ICT

Continuous-fiber reinforced thermosetsResin Transfer Molding (RTM) process chain

Pre-cut partTextiles Final machining Preform RTM

Source: SGL Carbon Source: KIT wbkSource: BMW Source: Fraunhofer ICTSource: Dieffenbacher

Main cost driver:

Lack of automation during preforming High cutting rate during preform manufacturing High scrap rates due to lack in process understanding

Research areas at Fraunhofer ICT

Cost overview

25% 50% 20% 5%

© Fraunhofer ICT

Continuous-fiber reinforced thermosetsResin Transfer Molding (RTM) process chain

© Fraunhofer ICT

The High Pressure RTM Process ChainCase Study – Automotive Trunk Lid Component

Demonstration part:

Preform made of three Sub-preforms

Minimizing of the geometrical com-plexity in the areas of the light pots

„light pod left“

„light pod right“

„inner part“

© Fraunhofer ICT

Contents

Introduction




Reinforcements Simulation The challenges of processing




Summary

© Fraunhofer ICT

Preforming - ReinforcementFibers

Fiber Structure Features

Carbon fiber 2D covalent bonds

Para crystallin (100%)

High orientation

Glas fiber 3D crosslinking leads to isotropic properties

Amorphous

Covalent bonds between silicon and oxygen

Aramid fiber 1D covalent bonds

Hydrogen bonds and Van der Waals bonds

Para crystallin (100%)

Very high degree of orientation

Carbon fiber: High strength and modulus, low density, electrical conductive, small diameter

Glass fiber: Low price, good strength, chemical resistance, electric insulator, medium diameter

Aramid fiber: High strength, lowest density, high impact strength, low pressure resistance

© Fraunhofer ICT

Preforming - ReinforcementSemi-Finished Products

Continuous fiber

1D semi-finished

products

2D semi-finished

products

3D semi-finished

products

Non stich-forming Stich-forming Mats and Fleeces

Non-woven fabrics

Woven fabrics

Braided fabrics

Mesh ware

Knitted fabrics

Non-crimp fabrics

Continuous Mats

Long fiber Mats

Fleece

Roving

Yarns

Plied Yarns

3D-braided fabrics

3D-knitted fabrics

Preform

Bild

Source: sgl.de Source: toray.comSource: saertex.com

Source: sglacf.com Source: sgl-kuempers.com

© Fraunhofer ICT

Preforming - ReinforcementFabrics for HP-RTM process chain

Linen Köper Atlas

Most relevant weaving styles for FRP‘s:

Standard non-crimp fabric (NCF), stitched with trickot-style

Multi-axial non-crimp fabric

Examples for different braiding styles

Litze

„Round“

Tri-axial

Upper sideBottom side

© Fraunhofer ICT

Contents

Introduction




Reinforcement Draping s imulation The challenges of processing




Summary

Virtu

al P

roce

ssC

hain

Geometry

Curing / cooling





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

Molding





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

Forming





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

© Fraunhofer ICT

Preforming: Separate textile forming process to transform the 2D engineering textiles in a complex double-curved 3D geometry

Goal: Processing, that transforms the 2D textile in an 3D geometry without manufacturing defects like winkling in consideration of the textiles specific forming behavior:

Low shear and bending stiffness

High stiffness the direction of the fibers

Shear and bending are the main forming mechanisms

Wrinkling occurs due to low bending stiffness

shearing bending

Preforming - SimulationGoal of process simulation

© Fraunhofer ICT

Simulation of the sequential preforming process

High shear strains in the double curved area

Preforming - SimulationCase Study - Lamp Pot Draping Simulation

© Fraunhofer ICT

Contents

Introduction




Reinforcement Draping simulation The challenges of process ing




Summary

© Fraunhofer ICT

Preforming - The Challenges of ProcessingSequential Draping Process

Stack supply over

heated draping-belt

Input:

2D-LayupStack handover

to Draping mold

Stack fixation in Draping-

mold with Draping-stamp

Mold completely closed,

Curing of the binder

Output:

3D-Preform Initial state of the mold,

Demolding of the

Preform

Partly/sequential closed

draping mold while

continues stack handover

© Fraunhofer ICT

Preforming - The Challenges of ProcessingDraping (d)effects

Manufacturing (D)effects

Various fabric deformation modes

Multi-scale deformation

(D)effects:

In-plane fiber waviness gaps between fiber bundles Out-of-plane fiber waviness large-scale wrinkling In-plane fiber waviness out-of-plane fiber wavinessgapping

Complex 3D-preform Large-scale wrinkling

Complex 3D-Preform with arising manufacturing effects

© Fraunhofer ICT

Contents

Introduction








Summary

© Fraunhofer ICT

HP-RTM – ResinsResin System Requirements

Resin System Requirements

Component specific

Temperature behavior

Mechanical properties

Structural integrity

Resistance to diff. medium

Environmental requirements

Long-term behavior

Legal requirements

Viscosity

Shrinkage

Curing behavior

Car body specific

Ref.: Derks, Martin (BMW AG )- 2007

Process specific

Compatibility to other components:

Elongation metal-composite, adhesives, sealing compounds, vibration absorbing materials, etc.

Compatibility to coating processes (assembly):

Heat and form resistance, good mechanical properties, etc.

Future requirements:

Reduced curing time, high Tg , no need for post curing

© Fraunhofer ICT

HP-RTM – ResinsIndustry Overview

Epoxy Resin Systems

Polyurethane SystemsProtective Coatings

11%

Automotive8%

Powder

Coating

16%

Construction18%

ElectricalApplications

24%

Aviation and Aerospace11%

Others4%

Ships 8%

© Fraunhofer ICT

Automotive

Wind energy

Sports

Molding + Compound

Pressure Tanks

Construction

Marine

Others

Aerospace & Defense

Global Demand [%] 2014 (Application based)

http://composites-germany.org

HP-RTM – ResinsComposites Market

Global demand for Carbon fibers [kT] 2009 – 2014 and outlook


(*Estimation)


Breakdown of Manufacturing Processes for Composites [%]

© Fraunhofer ICT

HP-RTM – ResinsPolyurethanes - Chemistry

Polyaddition of Polyol and Isocyanate („gel reaction“) Thermoset resin

A second reaction („foam reaction“) leads to foaming of resin system

Well adjustable material properties for HP-RTM

For HP-RTM application a mixture of different Polyols and MDI (Methylendiphenyldiisocyanate) is used

Polyol (based on polyether or polyester)

Reactive OH-groups Material properties

Isocyanate

TDI or MDI

Reactivity

Additives

Accelerator Catalyst Propellant Release agent

Urethane-groupIsocyanate-group

© Fraunhofer ICT

HP-RTM - ResinsEpoxy Resin Systems – Resin Chemistry

Resin component is a product of Epichlorhydrine and Bisphenol A or F

~90% of epoxy resins are based Bisphenol-A (~ double viscosity compared to Bisphenol-F)

High energetic epoxy ring

Bisphenol A ….or….

Bisphenol F + 2 NaOH

Epichlorhydrine

+ +

Diluent for

- Reduced viscosity,- Changed reactivity and Tg

and physical strength- Mainly for Bisphenol A resins

© Fraunhofer ICT

Aminecuring agents

aliphatic cycloaliphatic,

aromatic:

Anhydridecuring agents

- Monoanhydrides- Dianhydrides

Examples for HP-RTM hardeners(based on aliphatic amines):

Triethylentetramine (TETA) 70-95%Triethylendiamine (TEDA) 2-20%Polyethylenpolyamine (PEPA) 1-8%2-Piperazin-1-ylethylamin 0.1-1.4%

(UV , Tg )

(Tg , UV , reactivity , health )

Not common for HP-RTM, accelerated with catalysts

Amine curing agents (aliphatic) are used in different formulations (know-how of resin suppliers)

Anhydrides often used in Pultrusion (insulation of power lines)

HP-RTM - ResinsEpoxy Resin Systems - Hardener Chemistry

© Fraunhofer ICT

Resin

HardenerB- Component Diamine

Poly-addition

Epoxy resin

A- Component Epoxy

Cure reaction of an epoxy resin with a diamine hardener

Degree of cure as function of time:

High curing temperature decreases curing time In HP-RTM: 100-120°C

Resin/hardener formulation is the key for processing & curing behavior + material properties

Fast demolding and postcuring possible (shouldbe avoided)

HP-RTM - Raw MaterialsEpoxy Resin Systems – Curing

© Fraunhofer ICT

Contents

Introduction

Motivation for Lightweighting

The High Pressure RTM Process Chain

Preforming - Cutting, Stacking and Draping of fabrics

Raw materials Simulation The Challenges of Processing

HP-RTM - Infiltration and Consolidation

Raw materials Mold Filling Simulation Curing Characterization and Modelling The Challenges of Processing

Future Research and Development Goals

Summary

Virtu

al P

roce

ssC

hain

Geometry

Curing / cooling





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

Molding





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

Forming





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

© Fraunhofer ICT

The mold filling process during RTM manufacturing is often modelled as

incompressible flow through porous media

A first approach to calculate the flow was formulated by Henry Darcy in 1856:

Darcy's law describes the average volume-flow velocity 𝒗 as function of:

permeability K, viscosity 𝜂 und pressure gradient 𝛻𝑝

The weight force (𝜌𝒈) is often neglected because of its small impact compared to

the pressure gradient

HP-RTM - SimulationMold Filling Simulation, Fluid Mechanics

𝒗 = −𝑲

𝜂(𝛻𝐩 − ด𝜌𝒈

≪𝛻𝐩

)

© Fraunhofer ICT

HP-RTM - SimulationMold Filling Simulation, Fluid Mechanics

When Darcy´s law is combined with equation of continuity:

𝛻 𝒗 = 0

A second order partial differential equation is obtained:

0 = 𝛻𝑲

𝜂𝛻𝐩

This equation can be solved by using numerical methods like finite difference, finite element, finite volume or spectral methods.

There is an important modification of Darcy´s law, where instead

of volume-averaged velocity 𝒗 the seepage velocity 𝒗 is calculated:

𝒗 = −𝑲

𝜙𝜂𝛻𝐩

𝒗𝒗 =

𝒗

𝛟

𝒗

𝛟: Porosity

© Fraunhofer ICT

The local changes in fiber structure (fiber orientation and fiber volume fraction), that result from preforming process, should be considered in the model for the mold filling simulation

HP-RTM - SimulationMold Filling Simulation: Import of Local Fiber Structure

© Fraunhofer ICT

HP-RTM - SimulationMold Filling Simulation: Material Parameters

The permeability K of the textile (here: unidirectional fabric) depends on fiber orientation and fiber volume fraction

© Fraunhofer ICT

Because of the higher fiber volume fraction at the tip of the saddle, there is a delay at the beginning of the mold filling

HP-RTM - SimulationMold Filling Simulation: Influence of Local Fiber Structure

with draping simulation

without draping simulation

Legend█ = Air█ = Resin

© Fraunhofer ICT

Contents

Introduction

Motivation for Lightweighting

The High Pressure RTM Process Chain

Preforming - Cutting, Stacking and Draping of fabrics

Raw materials Simulation The Challenges of Processing


Raw materials Mold Filling Simulation Curing Characterization and Modelling The Challenges of Processing

Future Research and Development Goals

Summary

Virtu

al P

roce

ssC

hain

Geometry

Curing / cooling





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

Molding





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

Forming





Molding Curing /

cooling

Part Assembly


construction

Geometry Forming

© Fraunhofer ICT

Monitoring of cross-linking reactions with Differential Scanning Calorimetry (DSC):

Measuring heat flow of curing reaction

Various temperatures / heating rates

Evaluation of data (integrating heat flow over time)

𝛼 𝑡 =0𝑡 ሶ𝑄 𝑡 − 𝐵 𝑡 𝑑𝑡

Δ𝑄

HP-RTM - SimulationCuring Characterization and Modelling

𝛼 = degree of cure; ሶ𝑄 = heat flow; Δ𝑄 = heat of reaction of fully cured resin; 𝐵 = baseline (if no exothermal reaction would occur)

© Fraunhofer ICT

HP-RTM - SimulationCuring Characterization and Modelling

Example: DSC of epoxy resin at different heating rates

Temperature dependency: Faster heating leads to higher curing rates

Kinetic model is needed for process simulation

-0,5

0

0,5

1

1,5

2

0 50 100 150 200

Temperature T [°C]

Hea

tfl

ow

ሶ𝑄

[W/g

]

higherheatingrate

Heating rate

Enthalpy

5 K/min 512 J/g

10 K/min 465 J/g

20 K/min 433 J/g

© Fraunhofer ICT

Modelling of cross-linking using the Kamal-Malkin kinetic model:

𝑑𝛼

𝑑𝑡= 𝐾1 + 𝐾2 ⋅ 𝛼

𝑚 ⋅ 1 − 𝛼 𝑛 with 𝐾1|2 = 𝐴1|2 ⋅ exp −𝐸1|2

𝑅⋅𝑇

Model parameters (𝐴1|2, 𝐸1|2, 𝑚, 𝑛) are identified by curve-fitting against DSC data

using genetic algorithms

HP-RTM - SimulationModeling of reaction kinetics

© Fraunhofer ICT

Viscosity is measured using rheometry for different temperatures:

Viscosity is influenced by temperature and curing

Behavior is modeled using a Williams-Landel-Ferry (WLF) approach

HP-RTM - SimulationModeling of viscosity

© Fraunhofer ICT

Contents

Introduction

Motivation for light-weighting



Reinforcement Simulation The Challenges of processing


Resins Mold filling simulation Curing characterization and modelling The challenges of process ing


Summary

© Fraunhofer ICT

HP-RTM - The Challenges of ProcessingHP-RTM Equipment

HP-RTM machine (KraussMaffei) Mixing head principle

Maintenance-free mixing head

Hydraulic press with press force (max. of 3200kN)

Equipment necessary for HP-RTM process:

Precise press with parallel holding feature

HP-RTM equipment with mixing head connected to mold cavity

Mold with vacuum function, injection gate and fiber clamping

feature

© Fraunhofer ICT

25 30 35 400

10

20

30

40

50

60

0.5

Time [s]

Near injection port

Middle of flow length End of

flow length

0

1

0

500

1000

90 95 100 105

0

10

20

30

40

50

60

Middle of flow length

End of

flow length

Time [s]

Near injection port

1

0.5

0

0

500

1000

HP-IRTM:

Constant press force

Mold gap increase

Mold gap [mm]

Press force[kN]

Ref.

: R

ose

nb

erg

, P., C

hau

dh

ari

, R

., A

lbre

cht,

P., K

arc

her,

M., H

en

nin

g,

F.,

“Eff

ect

s o

f p

roce

ss p

ara

mete

rs o

n c

avi

ty p

ress

ure

an

d c

om

po

nen

t p

erf

orm

an

ce i

n H

igh

-Pre

ssu

re R

TM

pro

cess

vari

an

ts”

HP-RTM - The Challenges of ProcessingCharacterization of the process variants

HP-CRTM:

Constant injection gap

Press force increase

Cavity pressure[bar]

© Fraunhofer ICT

Viscos ities at process temperature

ResinTemper-

ature [°C]Dynamic

viscosity [mPas]

EP - Mixture* 69.3 74.5PU - Mixture* 59 67.3EP - Mixture* 120 10.3PU - Mixture* 90 19.1

*Viscosity of the mixture calculated by mixture law of Arrhenius

Rheological characterization of highly reactive resin systems by measuring of single components

Calculation of mixing viscosity using mixture law of Arrhenius

Viscosity of PU is 85% higher at mold temperature than Epoxy viscosity

Viscosity in mixing head

Viscosity at mold temperature

Viscosity at mold temperature

HP-RTM - The Challenges of ProcessingEpoxy and Polyurethane - Processing Viscosities

© Fraunhofer ICT

Pressure increase rate [bar/s]:

Epoxy 5.1

PU 8.1 (+59%)

Higher PU resin system viscosity leads to higher pressure increase rate

Increasing the flow rate further, the high pressure increase can cause fiber distortions

HP-RTM - The Challenges of ProcessingEpoxy and Polyurethane Behavior During Injection

84 86 88 90 92 94 96 98 100 102

10

20

30

40

50

Injection

start

Cavity p

ressure

[b

ar]

Time [s]

Injection

end

0 0

100

200

300

400

500

600

700

800

Epoxy

Polyurethane

Pre

ss fo

rce [

kN

]Press force

© Fraunhofer ICT

Epoxy resin system

Polyurethan resin system

0µm 10µm 20µm

HP-RTM - The Challenges of ProcessingEpoxy and Polyurethane - Fiber Push-Out Test

Single fiber filaments were pushed-out of a 50 µm thick sample and analyzed in SEM

Upper side Lower side

brittle resinbehavior

ductileresinbehavior

© Fraunhofer ICT

Fiber volume content analysis (biaxial carbon fiber reinforced test samples):

Epoxy resin system: 52.9 ± 1.2%

PU resin system: 51.5 ± 1.2% Material properties can be compared directly

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80

700

750

800

850

900

950

1000

1050

1100

1150

1200

+ 2%

EP-CF 969 38 MPa / 66.9 3 GPa

PU-CF 950 14 MPa / 63.9 4 GPa

+ 4.7%

Bendin

g s

trength

[M

Pa]

Bending modulus [GPa]

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80

500

550

600

650

700

750

800

850

900

950

1000

+ 5.1%

EP-CF 741 51 MPa / 66.9 4 GPa

PU-CF 783 37 MPa / 63.6 3 GPa

Ten

sile

str

en

gth

[M

Pa

]

Tensile modulus [GPa]

+ 5.6%

Mechanical properties on equal level:

Tensile: EP: 741 MPa PU: 783 MPa Bending: EP: 969 MPa PU: 959 MPa

HP-RTM - The Challenges of ProcessingEpoxy and Polyurethane - Quasi-Static Properties (Test Plate)

Fiber dominated – quasi-static test

© Fraunhofer ICT

HP-RTM - The Challenges of ProcessingEpoxy and Polyurethane - Impact Tests

Impact testing following the compression after Impact test standard Results show the force measured during impact on sample

Raise of impact energy causes more delamination

Epoxy samples had significant drop at lower energy (37J) compared to PU laminates (45J)

24J 37J 45J

© Fraunhofer ICT

Future Research and Development GoalsPreforming Process

Automated Preforming Process for complex structural parts

Current situation: Sub-Preforming Approach

Assembly of different sub-preforms before resin infiltration (usually in manual process)

Single-lap joint design vs. stepped-lap joint design

Stepped-lap joint designs contribute to higher mechanical performance

Performance can be optimized to maximize light-weighting potential

tc

2x tc

Single-lap joint

Stepped-lap joint designs

Ref.

: N

iu,

Mic

heal

C.Y

.: C

om

po

site

Air

fraim

eSt

ruct

ure

s. T

hir

d E

dit

ion

, 2010.

© Fraunhofer ICT

Future research and development goalsHP-RTM - Infiltration and Consolidation

Current situation :

High injection pressure & limitation of maximum flow rate

Fiber distortion effectsInjection and curing

Future requirements:

High speed infiltration (high flow rate) & precise control of cavity pressure

Low cavity pressure process profiles for pressure sensitive foam cores

HP-IRTM

Risk of fiber washout (gap injection leads to low clamping force) during injection

High cavity pressure after injection HP-CRTM

Injection and curing

New process variants

Processing of “1min cure” resin systems Complex and functions integration Maximized light-weighting

Hollow sections/Foam cores Use of recycled fibers

© Fraunhofer ICT

Summary

Structural performance Economic efficiency

I N T E R AC T I O N S W I T H I N L I G H T W E I G H T D E S I G N AP P R O AC H E S

QUALITY

TIME

COSTS

PROCESSES

METHODS

MATERIALSE F F I C I E N T L I G H T W E I G H T

D E S I G N O N S Y S T E M L E V E L

MMP-approach

© Fraunhofer ICT

Thank you very much for your attention

Fraunhofer Institute for Chemical Technology

Prof. Dr.-Ing. Frank HenningJoseph-von-Fraunhofer-Straße 7

76327 Pfinztal - Germany

Phone: +49 (721) 4640-711

Fax: +49 (721) 4640-730

Email: [email protected]

Internet: http://www.ict.fraunhofer.de/

Karlsruhe Institute for Technology (KIT)

FAST Institute for Vehicle System Technology

Rintheimer-Querallee 2

76131 Karlsruhe

Germany

Phone: +49 (721) 608-45905

Fax: +49 (721) 608-945905

http://www.fast.kit.edu/

mailto:[email protected]

http://www.ict.fraunhofer.de/

http://www.fast.kit.edu/

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