FEA analysis of carbon fiber failure

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Analysis of crack propagation in carbon fiber composite samples using ANSYS.

Analysis of crack propagation in carbon fiber composite samples using ANSYS.

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  • 1. Analysis of Crack Propagation in Carbon Fiber Composite Laminate Presentation April 28, 2010 Paul Peavler and Jordan Reynolds University of Louisville
  • 2. Outline
    • Objective
    • Assumptions
    • Method
    • Results
    • 5. Validation
    • 6. Conclusion
  • 3. Objective
      • Construct a 16 ply carbon fiber composite using SHELL99 elements.
      • Analyze crack propagation and failure of plies with increasing load through an iterative process.
      • Compare ANSYS results to measured results from graduate research study.
  • 4. Assumptions
      • Material Properties and failure strengths were determined/assumed from graduate research.
      • Part length has no effect on stress/failure of part under tensile load.
      • Ply failure is ignored, and instead, failure throughout the entire thickness of the element is determined for any given iteration.
  • 5. Method
      • Input file asks user to input the parameters for part length, part width, hole radius, and load step values in tension (lb/in).
      • Part is modeled with ¼ symmetry using SHELL99 elements which is defined as Linear Layered Structural Shell Elements.
      • This allows the user to input individual plies and fiber orientation as separate layers within each element not exceeding 250 layers.
  • 6. Method
      • Iterative process to determine failed elements at a given load.
      • For 1 st iteration or solution, a *DO loop determines the first load step when an element(s) failed.
      • Element is considered to have failed when Inverse Tsai-Wu failure criterion index (STWR)>1.
  • 7. Method
      • Another *DO loop then analyzes each individual element and assigns that element a new real constant, material property, and failure strength.
      • The new material properties are 70% less than the original material properties.
      • In addition, the failure strength properties for the failed element(s) are increases to extremely large value.
      • This is done so that further failure iterations do not calculate failure in elements that have already failed.
      • The model is then solved again and the next failed elements are determined.
      • Process is repeated until complete failure has occurred.
  • 8. Results
  • 9. Results
  • 10. Results
  • 11. Results
  • 12. Results
  • 13. Results
  • 14. Results
  • 15. Results-Complete Failure
  • 16. Validation Measured Nx max (lbs/in) Analytical Nx max (lbs/in) Difference 5217 5750 8.046%
  • 17. Conclusion
      • The difference between the measured load and analytical load for complete failure is 8.046%
      • Data obtained from ANSYS compares favorably with that obtained from experimental analysis
      • Assumption of near instantaneous failure is shown by rapid propagation of failed elements over small load variations
      • ANSYS can be used to determine ultimate failure load of a composite laminate with an open hole under tension
  • 18. Questions?
  • 19. Equations