© Fraunhofer LBF

Seite 1HEV

201

4 –

Frau

nhof

er L

BF

Requirements regarding Fatigue Tests of a Composite Wheel with Integrated Hub Motor

Functional and Innovative Lightweight Concepts and Materials for HEVsSwitzerland, Oct. 09th-10th 2014

A. Büter, D. Laveuve, O. SchwarzhauptFraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBFwww.lbf.fraunhofer.de

© Fraunhofer LBF

Seite 2

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFSummary

Example: Design and manufacturing of FRP-wheel with integrated hub motor

Workflow

Design methodology

Manufacture

Special considerations regarding durability-tests for FRP-wheels

Influencing parameters

Challenge: Damage equivalence

Outlook

Testing of combined functionality of hub-motor driven wheel

© Fraunhofer LBF

Seite 3

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFExample:„Fraunhofer Systemforschung Elektromobilität“

© Fraunhofer LBF

Seite 4

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFMultifunctional design of an FRP wheel with hub-motor

1. CAD-design

2. Identification of critical areas

3. Optimization

Load case analysis

4. Mold design & fabrication

Requirements:

strength, space, mass,

integration of electric drive

5. Manufacturing

6. Testing

Lay-up definition

© Fraunhofer LBF

Seite 5

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFMultifunctional design of an FRP wheel with hub-motor

electric motor

Motor Power: 4kW(Voltage: 2*24,5V)

© Fraunhofer LBF

Seite 6

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFComposite Wheel With Integrated Hub-motor - Summary

Wheel size: 6,5 x 15”

Wheel mass:

Basic wheel: ca. 3.5kg

Motor-housing: ca. 1.4kg

Wheel load: 450kg (static)

Load cases:

“Straight driving”

Fv = 10,2 kN

Fh = ± 3,15 kN

“Cornering”

Fv = 8 kN

Fh = 6,2 kN

© Fraunhofer LBF

Seite 7

chas

sis.

tech

201

3 –

Frau

nhof

er L

BF

Area, Area Location and Fiber Orientation

Calculation and Identification of the Optimal Ply Layup

© Fraunhofer LBF

Seite 8

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFSimulation and Visualization of Draping in CAD

Spoke 45°-ply Spoke 0°-ply

Offset 45°-ply Offset 0°-ply

© Fraunhofer LBF

Seite 9

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFTooling - Design of the Mold

Part 2Spoke region

Part 1Rim region

© Fraunhofer LBF

Seite 10

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFPatches for the Spokes

Cut prepregFlat-patterns

© Fraunhofer LBF

Seite 11

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFCFRP-Wheel With Hub-motor: Manufacturing

© Fraunhofer LBF

Seite 12

chas

sis.

tech

201

3 –

Frau

nhof

er L

BF

© Fraunhofer LBF

Seite 13

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFClassification of Components Considering Safety And Functionality

Depending of component-class, different requirements for design and testing apply.

© Fraunhofer LBF

Seite 14

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFLoading of Safety-components And Possible Effects

Structural durability of safety-components

Operational loading

Fatigue strength / stiffness-/strength-evolution

Eigenmodes / eigenfrequencies

Special event / misuse

Buckling

Yielding

Impact behavior

Environmental conditions

Ageing

© Fraunhofer LBF

Seite 15

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFMechanical Failure Criteria

Fracture

No failure due to cyclic loading during design-life (approx. 300000km)

Stiffness degradation

No exceedance of allowable deformation (usability)

Residual strength

Endure the maximum operational load at any time (also at the end of design-life time; No „Sudden Death“)

Quelle: Grubisic

© Fraunhofer LBF

Seite 16

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFRequirements For A Reliable Durability Proof

Service-like deformation of the entirely assembly, including the influences from environmental conditions, wear and long term service

Service-like load program with typical load cases (e.g. cornering, straight driving, bad road driving, breaking operations, temperature, centrifugal forces etc.)

Correct load correlations for individual load-cases

Damage equivalence between test load program and usage under operational conditions

Therefore: Fatigue test on component must be checked, if the design, the material or the manufacturing technique changed!

Standard of Valuation: Damage Equivalence

© Fraunhofer LBF

Seite 17

chas

sis.

tech

201

3 –

Frau

nhof

er L

BF

Test Spectra: “Standardized Load Spectra” (damage equivalent synthetic test spectra)

Challenge: Test spectra (originally developed for metal wheels) need to be adapted for FRP to ensure damage equivalence.

Zweiaxialer Radprüfstand (ZWARP)

© Fraunhofer LBF

Seite 18

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFMultiaxial Stress-states + Inhomogenous and Anisotropic Material (Composite)

Fx

FzF

Different local stress-spectra for running wheel (simplified)

Load Spectrum

Requirement: For each point of the wheel the accumulated damage caused by test spectrum must be similar to the damage due to design spectrum!

Node x Node y

© Fraunhofer LBF

Seite 19

chas

sis.

tech

201

3 –

Frau

nhof

er L

BFOutlook: Electro-mechanical System-reliability

© Fraunhofer LBF

Seite 20

chas

sis.

tech

201

3 –

Frau

nhof

er L

BF

For multifunctional composite parts,

test-methods need to be reconsidered.

© Fraunhofer LBF

Seite 21

chas

sis.

tech

201

3 –

Frau

nhof

er L

BF

Thank you for your attention!

Questions?

© Fraunhofer LBF

Seite 22

chas

sis.

tech

201

3 –

Frau

nhof

er L

BF

Mean Areas of LBF

• Load analysis and -monitoring considering fatigue

• Characterisation of new lightweight materials considering the manufacturing methods

• Design and Structural Optimisation

• Stability, Durability and Reliability Investigations based on testing and numerical calculations

• Functional expansion such as Adapronics and Structural Health Monitoring

Services and Products

• Determination of fatigue life

• Development of adapted failure models and strength theories

• Optimisation of components and Structural Systems

• Design of Fail Safe Structures

• Evaluation of Joints

• Evaluation of manufacturing and repair techniques

• Durability tests of lightweight structures & components (exp. & num.)

• Development of adapted SHM Systems for lightweight structures

Fraunhofer LBF - Lightweight Structures

LBF Wing Mock-Up with18 DMS; 16 FOBGs, Sensor coating, 8 Piezo-Modules

© Fraunhofer LBF

Seite 23

chas

sis.

tech

201

3 –

Frau

nhof

er L

BF

Prof. Dr.-Ing. Andreas BüterHead Light-Weight DesignFraunhofer-Institute for Structural Durabilityand Systemreliability LBFBartningstr. 47, 64289 Darmstadt, GermanyTel.: +49 6151 705-277Fax.: +49 6151 705-214andreas.bueter@lbf.fraunhofer.dewww.lbf.fraunhofer.de/