fea analysis of carbon fiber failure
DESCRIPTION
Analysis of crack propagation in carbon fiber composite samples using ANSYS.TRANSCRIPT
April 28, 2010 – Slide 1ME612 – Finite Element Analysis
Analysis of Crack Propagation in Carbon Fiber Composite Laminate
PresentationApril 28, 2010
Paul Peavler and Jordan ReynoldsUniversity of Louisville
April 28, 2010 – Slide 2ME612 – Finite Element Analysis
1. Objective
2. Assumptions
3. Method
4. Results
5. Validation
6. Conclusion
Outline
April 28, 2010 – Slide 3ME612 – Finite Element Analysis
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.
April 28, 2010 – Slide 4ME612 – Finite Element Analysis
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.
April 28, 2010 – Slide 5ME612 – Finite Element Analysis
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.
April 28, 2010 – Slide 6ME612 – Finite Element Analysis
Method
• Iterative process to determine failed elements at a given load.
• For 1st 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.
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April 28, 2010 – Slide 7ME612 – Finite Element Analysis
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.
April 28, 2010 – Slide 8ME612 – Finite Element Analysis
Results
April 28, 2010 – Slide 9ME612 – Finite Element Analysis
Results
April 28, 2010 – Slide 10ME612 – Finite Element Analysis
Results
April 28, 2010 – Slide 11ME612 – Finite Element Analysis
Results
April 28, 2010 – Slide 12ME612 – Finite Element Analysis
Results
April 28, 2010 – Slide 13ME612 – Finite Element Analysis
Results
April 28, 2010 – Slide 14ME612 – Finite Element Analysis
Results
April 28, 2010 – Slide 15ME612 – Finite Element Analysis
Results-Complete Failure
April 28, 2010 – Slide 16ME612 – Finite Element Analysis
Validation
Measured Nxmax (lbs/in) Analytical Nxmax (lbs/in) Difference
5217 5750 8.046%
April 28, 2010 – Slide 17ME612 – Finite Element Analysis
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
April 28, 2010 – Slide 18ME612 – Finite Element Analysis
Questions?
April 28, 2010 – Slide 19ME612 – Finite Element Analysis
Equations
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