Challenges in the Simulation of Car Body Structures made from Composite Materials

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Challenges in the Simulation of Car Body Structures made from Composite Materials

  1. 1. Challenges in the Simulation of Car Body Structures madefrom Composite MaterialsJochen Döll, Nico Feindler, Audi Lightweight Design Center5th European HyperWorks Technology Conference,Bonn 7.-9. Nov. 2011
  2. 2. Agenda► Trend towards Multi-Material-Design including CFRP applications► Challenges for the simulation process► Characteristics of composites - methods and quality of prediction► Progresses in the simulation of FRP body structures ► Simulation of CFRP-crash-structures in full vehicle models ► Ply book definition of a front bonnet► Summary Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made2 from Composite Materials, 09.11.2011
  3. 3. Trend towards Multi-Material-DesignReversal of the weight spiral • Initiation by lightweight • Downsizing body design Power Train Weight Reduction • Secondary effects e.g. Fuel tank etc. • Lightweight design measures in detail (all - kg • light, sportive, departments) less fuel consumption Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made3 from Composite Materials, 09.11.2011
  4. 4. Trend towards Multi-Material-DesignFlexible material architectures driven by product and demands Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made4 from Composite Materials, 09.11.2011
  5. 5. Challenges for car body design processNew tasks to develop composite car body structures► Predictive material models for the virtual rating and advance computing of body functions, especially in crash situations: ► A precondition for establishment of the material in series projects► Selection of FRP and assessment of suitability in body structures with a flexible material policy, in particular with regard to crash disciplines ► Target: Lighter than Audi-Space-Frame - ASF► A suitable CAE-CAD data interface► Optimization tools with regard to the wide variety of design parameters► Delta Alpha simulation and forecasting of critical construction methods► Continuous simulation of processes and properties Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made6 from Composite Materials, 09.11.2011
  6. 6. Modeling composites - behavior and quality of predictionAnisotropy und Stiffness (linear elastic) Stiffness and anisotropy high Quality of prediction► Covered by CLT, included in most FE-Solvers► Additional effort for defining fiber orientations► Methods for optimization fiber orientation and stack up are established and in use (Altair, Optistruct) high Time and effort Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made7 from Composite Materials, 09.11.2011
  7. 7. Modeling composites - behavior and quality of predictionPly Failure Ply Failure high Quality of prediction► Essential for any crash simulation► Needs extensive material characterization► Know how for fitting and use of suitable material models (combined damage and ply failure models in use) high Time and effort Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made9 from Composite Materials, 09.11.2011
  8. 8. Modeling composites - behavior and quality of predictionFailure between plies - Delamination Delamination high Quality of prediction► Failure mode leads to significant reduction of load carrying capacity and structural integrity► Modeling in full vehicle models possible but moderate accuracy (coarse discretization)► Needs FE-discretization through the thickness and high Time and effort characterization of additional material parameters Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made10 from Composite Materials, 09.11.2011
  9. 9. Modeling composites - behavior and quality of predictionExample – Pole test of an Al/CFRP floor structure (Ply failure + Delamination) Simulation Test Contactforce Pole Intrusion pole Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made11 from Composite Materials, 09.11.2011
  10. 10. Modeling composites - behavior and quality of predictionCrushing / Fragmentation Crushing high► Classic FE-modeling doesn’t work on macroscopic Quality of prediction level for that failure mode► Most state-of-the-art approaches are not satisfying (non predictive, many complex hardware tests)► New efficient numeric method with simple material testing developed and in use at Audi high Time and effort Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made13 from Composite Materials, 09.11.2011
  11. 11. Ply book definition using OptistructEngineering of a lightweight front bonnet ► Task ► Ultra lightweight design ► Meet pedestrian protection requirements ► Design same properties compared to aluminium version (series) for stiffness, deformation under wind load and HIC ► Adopt geometry of aluminium concept (tooling was fix) Explosion view of CFRP-concept bonnet Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made15 from Composite Materials, 09.11.2011
  12. 12. Ply book definition using OptistructSensitivity analysis of fibre orientation using free size optimisation 0° 90° Specific fibre orientations are sensitive when matching the orientation of an existing load path 45° - 45° Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made16 from Composite Materials, 09.11.2011
  13. 13. Ply book definition using OptistructInterpretation and engineering of an optimal fabric 90° +x° • Triax Fabric for optimal stiffness • Thickness sizing according HIC- Targets Realisation via simple Triax-NCF Fibre orientation fits load paths Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made17 from Composite Materials, 09.11.2011
  14. 14. Ply book definition using OptistructPerformance of manufactured CFRP front bonnetsHead Impact Deformation at Wind Load [mm] P05L Test / Simulation Simulation: Test 1-3: ► Good correlation between simulation and test ► CFRP-bonnet concept fulfils all requirements and functions ► 30 % lighter than full-aluminium bonnet (series) Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made18 from Composite Materials, 09.11.2011
  15. 15. Summary► Realization of advanced Multi-Material-Concepts including composite materials needs suitable simulation tools useable within industrial development routine► Aspects like anisotropy and ply failure important for basic design process are well covered with current FE-Codes and simulation techniques► Simulation and prediction of delamination and especially crushing mode in full vehicle models is a challenge (not state of the art in many FE-Codes)► At Audi a new method is developed and used to design and predict the behavior of new CFRP crash structures► To ensure maximum lightweight potential composite materials have to be designed anisotropic as much as possible by using composite optimization tools (Altairs Optistruct) Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made19 from Composite Materials, 09.11.2011

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