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
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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.