International Automotive Congress 2016 · 2017. 10. 21. · Stiffness varies between layers Each layer as individual shell mesh ... Torsional Stiffness Safety Requirements on Vehicle

© ika 2016 · All rights reserved2016/11/30Slide No. 1#133160 · 16su0074.pptx

Shanghai, 30th November 2016

Thorolf Schulte, M.Sc., Institute for Automotive Engineering, RWTH Aachen University

Dipl.-Ing. Michael Gerkens, Dipl.-Ing. Christopher Schmal, LWF Paderborn

Dr. rer. nat. Frank Meißen, Dr. rer. nat. Sebastian Wiedemann, inpro, Berlin

Dr.-Ing. Christian Paul, Tech Center Carbon Composites, thyssenkrupp AG

Lightweight Automotive Floor Structure usingMetal-CFRP Sandwich Materials

International Automotive Congress 2016


0

50

100

150

200

1995 2000 2005 2010 2015 2020

CO

2 e

mis

sio

ns [k

/km

]

Voluntary TargetsTargets by EU ComissionActual Fleet Emission in EU

Need for Lightweight Design and Materials in Automotive Industry

Diminishing reserve of fossil fuels

Increasing legislative environmental constraints

Electric vehicle: optimising range (compensate weight of battery)

Reduce mileage independent of powertrain by lightweight design

Current Situation

Powertrain42%

Total weight23%

Air resistance

19%

Roll resistance

13%

Misc.3%

Sources:

Ahrens, M.: Leichtbaupotenziale von Leichtmetallguss-Metallhybriden. Leichtbaugipfel 2015, Würzburg, March 2015

European Environment Agency: “Monitoring CO2 emissions from new passenger cars and vans in 2014”, EEA Technical report No 16/2015

140 (g/km)

95 (g/km)


Aluminium-Sheet

Aluminium-Cast

Aluminium-Extrusion

Steel

Hot-rolled Steel

Magnesium-Sheet

Magnesium-Cast

Glass fibre-Thermoplastic

Multi-Material-Design in Automotive Applications on Different Levels

… in materials

… in body-in-white

Multi-Material Design

… in components

SuperLightCar [SAH10]

Mercedes-Benz C-Class [EUR14]

[EUR14] EuroCarBody 2014, Benchmarkdaten, Bad Nauheim

[SAH10] Sahr et. al. „Systematische Werkstoffauswahl für die Karosserie des SuperLight-Car“, ATZ - Automobiltechnische Zeitschrift, Mai 2010

LSS

HSS

AHSS

UHSS

PHS

Al 6xxx

Al 5xxx

Al Profile

Al Guss

FVK

Al Cast

FRP


CFRP (UD/MD)


[BIM15] http://www.bimmertoday.de/2015/04/18/bmw-7er-g11-carbon-leichtbau-spart-bis-zu-130-kilogramm-ein/, visited 30. April 2015

[ICK14] Ickert, „FVK-Metall-Hybridbauweise für die automobile Großserie“, Dissertation, RWTH Aachen, 2014

[MIL12] Mildner, „Numerische und exp erimentelle Untersuchungen des Crashverhaltens von FVK-verstärkten Metallstrukturbauteilen“, Dissertation, TU München, 2012

BMW 7 series [BIM15]

[ICK14]

[MIL12]

… in materials



… in components

MetalMetal

GFRP (UD/MD) Adhesive-

layer


GLARE [TUD]


[ROG]

[ATZ14] „Das Projekt ThyssenKrupp InCar plus“, ATZ extra, 2014

[ROG] „Airbus A380 overfly“ von Roger Green from BEDFORD, UK

[TUD] www.lr.tudelft.nl

… in materials



… in components

Aluminium

Prepreg

thyssenkrupp LITECOR® [ATZ14]


LEIKA – Efficient Multi-Material Design for Lightweight Bodies

Project Partners

Funding

Project Duration

Start: September 2013

End: December 2016

Project Targets

Manufacturing of steel/magnesium-CFRP sandwich materials in

near series production

Development of new design approaches utilizing the benefits of

metal/CFRP sandwich materials in crash applications

Simulation models for crash and forming simulation including the

transfer of forming information into crash simulation

Virtual development of an automotive floor structure

(with integrated battery system)

Installation of an integrative process chain for a combined

processing of metal/CFRP sandwich materials and overmoulding


Manufacturing Process for Semi-Finished Metal-CFRP Sandwich Materials

2. Press loading,

Heating and pressurisation

3. Transportation and

post production

2a. Heating 2b. Consolidation and cooling

adhesion agent metal cover layer

polyamid foilsCFRP layers

heating

heatingF F

FF difference in thermal expansion

residual stress

tension

compression

tension

1. Stack-up

(Film stacking-principle)


Demonstration of Material Behavior on Vehicle Floor Structure

PA-GF

Steel-Thermoplastic

Magnesium-CFRP

Steel-CFRP

CFRP-Magnesium

Magnesium

CFRP

CFRP

CFRP

Steel

Steel

CFRP

Magnesium

Magnesium


Joining Techniques for LEIKA-Sandwich Materials

SW-materials lead to

high challenges for the

joining technique!

Solutions for structural

joining were found:

• Blind riveting,

• Flow drill screwing,

• Friction/ Resistance

element welding,

• Self pierce riveting


Blind Riveting of Different SW-Combinations

a)

Litecor®

(1.5 mm)

+

DP-K60/98

(1.2 mm)

b)

Litecor®

(1.5 mm)

+

SW SCS_Tun

(2.0 mm)

c)

SW SCS_Tun

(2.0 mm)

+

SW SCS_Tun

(2.0 mm)

1.982 2.088 3.6210

500

1000

1500

2000

2500

3000

3500

4000

Fmax©LWF

Type of specimen

Lap shear specimen acc.

to DIN EN ISO 14273

F

F

Material combination

1 Litecor® (1.5 mm)

2 DP-K60/98 (1.2 mm)

3 LEIKA-sandwich with

woven CFRP (2.0 mm)

Joining process

Blind riveting

Testing machine

Zwick Z100

Displacement

measurement

Extensometer

Testing speed

v = 10 mm/min

Ma

x t

es

t f

orc

e F

max

[N]

Joining element

a) DIN 7337 4.8x6

b), c) DIN 7337 4.8x8

b)

a)

©LWFc)Maximum value

Average value

Minimum value

Average value2.5

1 1 3

3 32

SW-material enables

exploitation of blind rivet

strength!15 mm 15 mm15 mm

F

F

0

500

1000

1500

2000

2500

3000

3500

4000

0 2 4 6 8 10 12 14

Fo

rce

F [

N]

Displacement s [mm]


Forming Simulation of Sandwich Material

Melted CFRP core during forming

Stiffness varies between layers

Each layer as individual shell mesh

Contact definition between the layers

Large parts to be computed

Metal

CFRP

Metal

Metal

CFRP Plies

Metal

Contact

Contact

Contact

CFRP Plies

Insertion of blanks

Closed tool

Forming simulation model in

PAM-FORMLEIKA sandwich

material stack-up


Simulation Chain from Forming to Crash Simulation to Include Residual Stresses

Mapping of forming results onto cooling model

Mapping of cooling results onto crash model

Initial stress after cooling for tensile test improves simulation results

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

0,00 0,50 1,00 1,50 2,00

Str

es

s (

2n

d P

iola

-Kir

ch

off

) [G

Pa

]

Strain (engineering) [%]

Experimental dataSimulation without initial stressSimulation with initial stress

Initial state

Before rupture

von Mises

Stress [MPa]

500,0450,0400,0350,0300,0250,0200,0150,0100,050,00,0

Steel/CFRP-UD/Steel

0,25 1,5 0,25 [mm]


0

20

40

60

80

100

120

0 5 10 15 20 25

Kra

ft [kN

]

Weg [mm]

Versuch Stacked Shell

Fo

rce

[kN

]

Material Modelling in Crash Simulation

Stacked Shell (Cohesive)LEIKA-Sandwich Layered Shell

Shell Layer per material

+ failure between layers

- effort (characterisation,

modelling, computation)

Schematic representation

sandwich material

Simplified model of the material

+ undemanding modelling

- No failure between layers

Metal

Adhesion Agent

CFK

0

5

10

15

20

25

30

35

0 20 40 60 80 100 120

Kra

ft [kN

]

Weg [mm]

Versuche Stacked Shell Layered Shell

dyn. 3-point-bending steel-CFRP dyn. compression magnesium-CFRP

Displacement [mm] Displacement [mm]

Fo

rce

[kN

]

Experiments


Relevant Loadcases for the Floor Assembly

With the project InCar®plus thyssenkrupp provides a fully validated

vehicle structure as lightweight steel reference.

Euro NCAP Frontal Crash ODB

Bending Stiffness

Euro NCAP Side Impact Pole

Torsional Stiffness

Safety Requirements on Vehicle


Crash Simulation Euro NCAP Pole Impact

Development Targets Protection of battery compartment

No critical intrusions in battery packageCriteria Target Reference LEIKA

Intrusion < 335 mm

Acceleration < 30 g

Survival Space > 350 mm

Intrusion Battery < 15 mm

-400

-350

-300

-250

-200

-150

-100

-50

0

Intrusion [mm]

LEIKA

Reference


Crash Simulation Euro NCAP Front Impact

Development Targets

Criteria Target Reference LEIKA

Intrusion < 100 mm

Acceleration < 45 g

-160

-140

-120

-100

-80

-60

-40

-20

0

Intrusion [mm]

LEIKA

Firewall

Reference

Firewall


„Oneshot“ Manufacturing ConceptCombination of Forming and Overmoulding


Lightweight Result in Floor Structure

15%

52%

8%

25%

<400 400-500 500-600 >600

Reference

46,3 kg

PA-GF

Steel-ThermoplasticMagnesium-CFRPSteel-CFRP

CFRP-Magnesium

Reference: InCar®plus BIW

Yield Strength [MPa]

37%

7%20%

9%

2%

25%

Steel MagnesiumCFRP PA-GFThermoplastics Mass Reduction

LEIKA

34,7 kg


Conclusion and Outlook

Lightweight solutions in automotive industry still needed to achieve decrease in emissions

Investigation of sandwich material with steel or magnesium sheet (cover) and thermoplastic

CFRP for application in structural parts

Development of simulation methods for forming, cooling, joints and full vehicle crash

Inclusion of forming/cooling results in crash simulation (residual stress)

Demonstrator vehicle floor structure can bear crash loads and fulfils requirements regarding

passenger and battery safety (according to simulation)

By the end of the year: floor structure testing

Bending stiffness

Torsional stiffness

Front crash

Pole side crash

Validated development with Metal-CFRP

sandwich materials and simulation models


Phone

Fax

Email

Internet www.ika.rwth-aachen.de

Institute for Automotive Engineering (ika)

RWTH Aachen University

Steinbachstr. 7

52074 Aachen

Germany

Contact

Thorolf Schulte, M.Sc.

+49 241 80 25688

+49 241 80 22147

[email protected]

This research and development project is funded by the German Federal Ministry of

Education and Research (BMBF) within the framework “Innovations for the production,

service and labor of tomorrow” (funding numbers 02PJ2770 – 02PJ2781) and

managed by the Project Management Agency Karlsruhe (PTKA). The author is

responsible for the contents of this publication

Documents

International Automotive Congress 2016 · 2017. 10. 21. · Stiffness varies between layers Each layer as individual shell mesh ... Torsional Stiffness Safety Requirements on Vehicle