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FEA analysis of carbon fiber failure

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

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FEA analysis of carbon fiber failure

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

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