The application of laser generated ultrasonics was first
demonstrated in the mid-seventies and has shown good potential
when applied to isotropic materials. However, its use with
composite materials is still in the early stages of development.
This study explores the potential for application of laser
generated Rayleigh and Lamb waves in graphite/epoxy composites.
Numerical results are obtained by the solution of the wave equations
using assumed solutions, and enforcing the boundary conditions.
Experimentally, Rayleigh and Lamb waves were generated by a Q-switched
ruby laser in the ablation regime and detected by piezoelectric
pinducers which permitted accurate phase velocity
measurements.
The Rayleigh wave velocity was measured at various directions
relative to the fiber direction and results were found to agree closely
with numerical predictions. The increase of surface wave velocity
using thin plates could be useful for the application of delamination
detection in thick composites and an increase of Rayleigh wave
attenuation could indicate damages caused by impact. Also, surface
waves can reflect from small surface cracks. Therefore, laser
generated surface waves, particularly along the fiber direction, have
high potential for application in non-destructive testing.
Lamb wave experiments were conducted in aluminum plates
and gave distinctive signals, but there were some difficulties in
detecting the precise arrival of each Lamb wave mode for the
graphite/epoxy composite plates. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36263 |
| Date | 12 December 1991 |
| Creators | Park, Heeyong |
| Contributors | Calder, Clarence A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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