FEA analysis of carbon fiber failure

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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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

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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

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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?

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Equations

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