FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

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well-bonded region, because of the linear thermal expansion as well as the
elastic deformation of the relatively compliant epoxy interface. It is
interesting to note that the 3 mm underlying honeycomb structure can be seen
only when the heating laser beam diameter is smaller than the cell size, in
agreement with the thermoelastic considerations illustrated in Fig. 9 . '
CONCLaSION
The optothermal approach to the nondestructive inspection of layered materials
appears to be an attractive alternative to conventional materials inspection
techniques. Its main advantages are that it is fast, non-contact, does not
require sample preparation nor access from both sides of the laminate, and
provides information about the mechanical bonding properties of the layer.
Two inspection techniques are presented in this paper, and the results of our
experimental investigation are discussed. The infrared technique appears to
be a relatively inexpensive method for the inspection of high emissivity
materials such as graphite-epoxy laminates, while the interferometric approach
is more appropriate for the inspection of metal-honeycomb structures and for
quantitative analyses of bonded laminates.
REFERENCES
1. Scott, I.G. and Scala, CM.- A review of NDT of Composite Materials, NDT
Int. Vol. 15, p. 75, 1982.
2. Segal, E. and Rose, J.L., NDT Techniques for Adhesive Bond Joints, in
"Research Techniques in NDT", R.S. Sharpe ed., Academic Press, London,
1980.
3. Chaskelis, H.H., and Clark, A.V., - Ultrasonic Nondestructive Bond
Evaluation: an analysis of the problem, Mater. Eval. Vol. 38, p. 20,
1980.
A. Birnbaum, G. and Vest, CM. - Holographic NDE: status and future, in
International Advances in NDT, vol. 9, p. 257, 1983.
5. Vavilov, V.P. and Taylor, R. - Theoretical and practical aspects of the
thermal NOT of bonded structures, in "Research Techniques in NDT", R.S.
Sharpe ed., Academic Press, London, 1982.
6. Vogel, P.E.J., - Evaluation of bonds in armorplate and other materials
using infrared NDT techniques, Appl. Opt. Vol. 7, p. 1739, 1968.
7. Lawson, W.D. and Sabey, J.W. - Infrared Techniques, in "Research
Techniques in NOT", R.S. Sharpe ed., Academic Press, London, 1970.
8. Trezek, G.J. and Balk, S. - Provocative Techniques in Thermal NDT
Imaging, Mater. Eval., Vol. 34, p. 176, 1976.
9. Engelhardt, R.E. and Hewgley, W.A. - Thermal and Infrared Testing, in
"Nondestructive Testing, a Survey", NASA-SP-5113, 1973.