FEM Impact Simulation: Fan Blade Out Event for a Composite Fan Containment Case

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Impact simulation of composite components is an active field of research and development. While many FEM codes provide tools for such simulations, the main challenge remains in defining the model and material parameters appropriately such as to arrive at an objective and reliable prediction of the structural response to the impact event. In engineering practice, parameters like mesh refinement and material formulations are often adapted in order to obtain desired simulation results. Although this common procedure is able to reproduce experimental results that have previously been tested, it is hardly appropriate to predict beforehand how a structure will actually behave under given impact conditions and is therefore of limited use during the design process.

In this presentation, the current status of reliable impact simulation is discussed by example of a composite fan containment case subjected to a blade out event. The objective is to develop sound modeling techniques for structural analysis that are based on parameters determined by experimental testing on the material level without the need for subsequent ‘tweaking’ of the model. Also, they need to be simple enough for efficient evaluation of larger structures, yet refined enough to capture all mechanisms relevant to structural failure.

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FEM Impact Simulation: Fan Blade Out Event for a Composite Fan Containment Case

  1. 1. WWW.LUXNER-ZT.COM FEM Impact Simulation: Fan Blade Out Event for a Composite Fan Containment Case FEM Impact Simulation: Fan Blade Out Event for a Composite Fan Containment Case Dr. Clara Schuecker, Dr. Mathias Luxner,Dr. Clara Schuecker, Dr. Mathias Luxner, Dr. Martin Fleischmann, DI(FH) Jürgen TauchnerDr. Martin Fleischmann, DI(FH) Jürgen Tauchner 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC)
  2. 2. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 22 Luxner Engineering ZT GmbHLuxner Engineering ZT GmbH  Engineering consulting firm  Organisation Founder & Owner: DI Dr.techn. Mathias H. Luxner Locations: Imst & Vienna, Austria  Expertise Finite Element Analysis Lightweight design & composite materials Methods development Software implementations  Focus: Research and Development „Bringing Science and Engineering together“  Imst  Wien
  3. 3. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 33 DefenCE ProjectDefenCE Project  3 Year Research Projct Funded by FFG – Austrian Research Promotion Agency  3 Project Partners  FACC AG  Luxner Engineering ZT GmbH  Vienna University of Technology Institute of Light Weight Design and Structural Biomechanics  Goals:  develop composite fan containment case  reliable analysis methods for composite impact simulation Fan-Blade Off (FBO)
  4. 4. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 44 FBO – problem definitionFBO – problem definition  Geometry  Material Parameters  Boundary conditions  Load application Mounting Composite casing Titanum blade Rotation Contact
  5. 5. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 55 Results FBO analysisResults FBO analysis
  6. 6. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 66 Different results FBO analysisDifferent results FBO analysis
  7. 7. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 77 ??  so which one is correct? So which one's realistic?
  8. 8. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 88 Analysis ingredientsAnalysis ingredients  Blade material  damage degradation  Casing material(s)  damage degradation, element deletion ...for each direction  failure criteria  Property formulation  hourglassing, shell formulation, …  Contact formulation  gap definition, penalty stiffness, …  Modeling approach  UD-analogy, Solid vs Shell, CZE, ADM, … Mesh refinement numerical parameters physical parameters
  9. 9. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 99 Simplified test problemSimplified test problem  Standard droptower test ISO 6603-2, ASTM 3763  impactor adjusted to blade-like geometry
  10. 10. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1010 Mesh density effectMesh density effect coarse (3750 el) fine (15000 el) extra fine (60000 el)
  11. 11. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1111 Sources of mesh density effectSources of mesh density effect  resolution of stress distribution (geometry / contact) → convergence  damage material law softening leads to localization (ill-posed problem) no convergence→ (without regularization) localization in 1 element row
  12. 12. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1212 Damage mechanics and localizationDamage mechanics and localization  fracture mechanics: dissipation related to crack formation energy release rate („toughness“)→ … energy dissipated per cracked area  damage mechanics: homogenized material law … energy dissipated per volume element micro cracking crack propagation fully cracked fracture damage homogenized damage law
  13. 13. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1313 Softening with characteristic lengthSoftening with characteristic length  Bažant crack band model [Materials and Structures 16, pp.155-177, 1983]  adjusted material law /Mat/Law25 with ...area associated with integration point ...constant dependent on element type ...characteristic length for quadratic elements (reduced integration): general formulation brittle material requirement for minimum element size:
  14. 14. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1414 Results including characteristic lengthResults including characteristic length  adjusted damage law gives (almost) mesh independent result coarse (3750 el) fine (7500 el)
  15. 15. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1515 Conclusions – mesh size dependencyConclusions – mesh size dependency  issue of mesh size dependency has beed identified  adjustment with characteristic length gives objective results  for full scale analysis an automated solution is required (mesh size & mesh type dependent ) varying mesh sizes→ adaptive meshing→ εm = f (Gc , Lch ) e.g. /Fail/user
  16. 16. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1616 mesh pattern dependencymesh pattern dependency  cracks tend to follow mesh pattern → aligned mesh if crack direction is known a-priori → random mesh to allow for realistic crack pattern Consistent (~15.000 elem) Locally refined (~17.000 elem) Random (~19.000 elements) t=0.6ms t=0.9ms t=0.6ms t=0.9ms t=0.6ms t=0.9ms
  17. 17. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1717 modeling strategiesmodeling strategies  solids / shells  Composite model  UD-analogy  CZE / delamination  adaptive meshing  X-FEM
  18. 18. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1818 sensitivity analysessensitivity analyses  sensitivity analyses:  element formulation / deletion options  number of thickness integration points  interface formulations IOFF=4 IOFF=5 IOFF=6 Note: dissipated energy shown for fabric material model effect much more pronounced for UD-material!
  19. 19. June 26, 2014June 26, 2014 2014 European Altair Technology Conference (EATC)2014 European Altair Technology Conference (EATC) 1919 Further workFurther work  quantitative evaluation of modeling approaches → determine which mechanisms need to be captured for reliable prediction → determine how these mechanisms can be modeled efficiently on a structural level  verification by experiments  material tests  small scale tests  full scale prototype test  development of feasable analysis strategies for full scale simulation

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