1. Effect of Resonant Vibration on Defects in Carbon Fiber Based Polymeric Composites
Samuel Sellner, Mechanical Engineering
Dr. Rani Elhajjar, Civil/Environmental Engineering

2. Objectives
Determine the material properties of a carbon fiber composite bike frame and use this information to build a model to repeatedly predict defect propagation and resonant response in the frame.
Investigate and characterize a new failure mode for defects within carbon fiber composite parts that have been exposed to resonant vibration.
Investigate the distinct stages of composite fatigue failure related to initiation, propagation, and final growth.

3. Material Characterization
Figure 2: Samples taken from bike
Figure 1: CFRP composite bike frame cut into sections

4. Material Characterization
Figure 3: Tensile test
Figure 4: Three point bend test

5. Characterization Results
Tension Stress Strain
Bending Stress Strain
Figure 6: Example of results for tensile test
Figure 7: Results for three point bend test.
Comparison of stiffness in different sections.

6. Future Work Verify material property results
Apply material properties to finite element model of bike frame to predict failure

7. Figure 8: Forming a wrinkle
Wrinkle Manufacture
Use rods to form wrinkle in individual prepreg layers
Stack prepreg layers
Use vacuum bag to press prepreg layers together
Figure 8: Forming a wrinkle

8. Figure 9: Design of experiment
24 samples to test 4 variables:
Presence of wrinkle defect
Vibration mode
Composite thickness
Fiber layup direction
Figure 9: Design of experiment

9. Future Work Subject samples to resonant vibration
Test samples to failure
Determine affect of resonant vibration on the strength of the samples

10. Conclusion The goal of this study has not been met yet
More experimentation is required to make a conclusion

11. Acknowledgements Rani Elhajjar UWM Office of Undergraduate Research
College of Engineering and Applied Sciences