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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 (ρ > 30%) obtained by optimization
View of PSOLID-Elements with density ρ > 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
ΔmB-Säule≈ −30%
ΔEmax ≈ +25%
Δuintr ≈ +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.