Optimization of a Composite B-Pillar

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  • 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

  • 2

    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

    3

  • B-Pillar Audi A8 (D3)

    4

    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)

    5

    Strategy

  • Com

    posite Optim

    ization Process

    Optimization Strategy

    6

    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

    7

    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

    8

    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)

    9

    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%

    10

    5 patchesplus ribs

    2 patchesplus ribs

    Concept P

    haseFine Tuning Phase

  • Testing

    11

    exterior view

    Composite-B-Pillar

    interior view

    Composite Prototype Original Design

  • Quasi-Static Component Crush Test

    12

    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

    13

    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

    14

    Loadcase: IIHS

  • Summary

    15

    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.

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