optimization of a composite b-pillar

Optimization of a Composite B-Pillar

S. Menzel, Volkswagen Group Research

Dr.-Ing. T. Fuhrmann, Volkswagen

S. Beuermann, Altair HyperWorks

Dr.-Ing. B. Wiedemann, Altair Product Design

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Content

Situation, Task & Objective B-Pillar Audi A 8 Optimization Strategy Results Conclusion

SituationComposite materials allow to adapt structures to specific applications and loading conditions, to design lightweight, highly efficient structures.However, manufacturing may be costly and design processes complicated.

Task

Use a CAE based, optimization driven methodology to develop a composite car structure

Objective

get a composite design which is competitive wrt. performance, weight & costs identify a robust and efficient design methodology

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B-Pillar Audi A8 (D3)

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B-Pillar Aluminium

Reinforcement Steel

Reinforcement Aluminium

relevant load cases

roof crush

seat belt anchorage test

IIHS side impact Source: IIHS Status Report

initial design (series-production)

Problem Characteristics

highly nonlinear structural behaviour (large deformations, contact, failure,) large number of design variables (topology, number of layers, fiber orientation,)

Optimization Tools available: for large number of design variables: linear physics for nonlinear physics: small number of design variables

Engineering Approach: 2-Step-Strategy1.Concept Optimization with simplified (linearized) model

efficient methods are available and well-established 2.fine tuning considering nonlinear effects with reduced set of design variables

(if necessary)

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Strategy

Com

posite Optim

ization Process

Optimization Strategy

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Concept P

hase

Topology Optimization(isotropic material behavior)

new concept (CAD model) FEM model

Fine Tuning Phase

Tailoring?

Free Sizing!

Phase 1Laminate 1

Laminate 2

Number of Plies?

Discrete Parameter Opt.

Phase 2

Laminate Stacking?

Phase 3

Rule based

ply shuffling

0

45

-45

90

45 -45 0 0

45 -45 90 90 -45 45 0 0

-45 45

Patch InterpretationDiscrete Ply Thickness

Optimized Stacking Sequence

nonlinear physics

(if necessary)

Topology Optimization

topology optimization with linear isotropic material behaviour interpretation of reinforcement ribs

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design space ( > 30%) obtained by optimization

View of PSOLID-Elements with density > 30%

ConceptP

haseFine Tuning Phase

FreeSize-Optimization

B-pillar with ribs-structures patch interpretation

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Ply thickness [mm]

ConceptP

haseFine Tuning Phase

Parameter Optimization

Patch interpretation (considering manufacturing constraints) Patch definition with PCOMPG-cards Number of plies (still considering linear physics)

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Ply thicknes [mm]

Optimization

Concept P

haseFine Tuning Phase

Parameter Optimization

Variant with reduced number of patches (Layup for prototype)

Status static stiffness of composite and metal sheet B-pillar at same level

weight reduction approx. 40%

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5 patchesplus ribs

2 patchesplus ribs

Concept P

haseFine Tuning Phase

Testing

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exterior view

Composite-B-Pillar

interior view

Composite Prototype Original Design

Quasi-Static Component Crush Test

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test bench (serial B-pillar) test bench

Testing conditions:

- v = 1 mm/s

- smax = 500 mm

z-directionfree

rigidconnection

Impactor

B-Pillar

Quasi-Static Component Crush Test

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Deformation

Def

orm

atio

n En

ergy

mB-Sule 30%

Emax +25%

uintr +30%

B-pillar series

B-pillar composite

Quasi-Static Component Crush Test

Simulation: Strain rate dependent material properties not available. Validation of simulation model not

carried out

Test Result: Composite B-pillar with smaller force level and larger intrusion

reinforcement necessary to improve intrusion

significant weight advantages of composite

structure will disappear

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Loadcase: IIHS

Summary

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Significant weight reduction (up to 40%) for Composite B-Pillar at same level of

static stiffness

Effective weight reduction is limited by large intrusion (component crush test)

Optimization methodology very efficient for linear physics

Highly nonlinear effects need to be considered in sizing phase

Some project contents have been created within the BMBF-project BIOTEX. Therefore we would like to usethe opportunity to thank the BMBF for the financial support to realize the project.