On Tuesday, November 28, VTechWorks will be unavailable due to an upgrade. Please do not plan to use the repository or deposit files in Elements on the 28th. Login attempts may result in inaccurate error messages. Email firstname.lastname@example.org if you have questions.
An investigation of the excitation frequency dependent behavior of fiber reinforced epoxy composites during vibrothermographic inspection
Russell, Samuel Stephen
MetadataShow full item record
This investigation concerns the frequency related behavior of delaminations in fiber reinforced composites during vibrothermography, the use of active thermography with a mechanical excitation for the nondestructive evaluation of a structure or part. Two models, one where the size and geometry of the flaw control a local resonance and the other where the part or panel is undergoing structural resonance with the flaws dissipating the mechanical energy, are proposed for this frequency related behavior and tested on simulated and service produced delaminations in coupons, panels, and a machine part of complex geometry. The behavior predicted by the local resonance model is compared with experimental observations. The vibration state of the panels or coupons is determined during the vibrothermal tests, and compared with the frequencies which cause vibrothermographic heating of the flaws as a test of the structural resonance model. The usefulness of vibrothermography is demonstrated in glass and graphite reinforced epoxy components. Impact damage sites are located in graphite epoxy panels using vibrothermography. The size of the damage is indicated not only by the size of the hot region but also by the temperature rise in the center of the flawed region. A glass epoxy machine part, which was damaged during service, was subjected to interrogation by ultrasonic C-scans, X-ray radiography, and then compared with the vibrothermographic NDE.
- Doctoral Dissertations