frequency of excitation is varied in such a way that local flawed regions are set into local resonance, and serve as generators of heat. The purpose of this work is to compare some experimental results obtained by vibrothermography with those obtained by X-ray tomography in the characterization of impact damage in composite materials. The X-ray tomography data will serve as reference to evaluate the possibilities offered by vibrothermography.

42714 Maldague, X.; Krapez, J.C.; Cielo, P.; Poussart, D. Processing of thermal image for the detection and enhancement of subsurface flaws in composite materials Signal Processing and Pattern Recognition in Nondestructive Evaluation of Materials, Proceedings of the NATO Advanced Research Workshop, Lac Beauport, Quebec (Canada) 19-22 Aug. 1987, pp. 257-286 Springer Verlag, Berlin Heidelberg (1988)

Subsurface imaging using thermal wave generated either by line heating with lateral displacement of the part to be inspected or full-field heating with no displacement is an attractive approach for the NDE of composite materials. Proper detection of flaws, such as delaminations or unbonds require dedicated thermographic image processing. In this paper we will present recent work done at our Institute on the detection and enhancement of unbonds in aluminum to foam laminates. Also quantitative characterization of flaws in graphite-epoxy laminates using specially developed image processing and modelling will be presented. Emphasis will be given to either time-domain image processing methods for precise and reliable defect visualization.

42509 Jones, R.; Heller, M.; Lombardo, D.; Dunn, S.; Paul, J.; Saunders, D. Thermoelast ic assessment of damage growth in composites Composite Structures, Vol. 12, No. 4, pp. 291-314 (1989)

This paper examines, experimentally and numerically, the use of thermal emission measurements as a means of assessing severity of damage and monitoring damage growth in composite materials. In contrast to most traditional methods the thermal emission profile reflects the interaction of load, geometry, material and damage in a non-destructive fashion. It represents a possible method for the scaling of test data, obtained from coupon tests, to tests on full scale structures.

42506 Vikstrom, M.; Backlund, J.; Olsson, K.-A. Non-destruct ive testing of sandwich constructions using thermography Composites Structures, Vol. 13, No. 1, pp. 49-65 (1989)

Thermography with an infrared (IR) scanner has been used to detect prefabricated defects within sandwich panels. The sandwich panels had faces of glass/polyester composite laminates (GRP) and a core of rigid cellular PVC foam. Different types of disbonds were simulated, perpendicular and parallel to the faces. All disbonds were successfully detected and it is particularly interesting that a simulated disbond centred in the core, parallel to the faces, was found. Cavities within the core were also simulated and detected.

42505 Vikstrom, M. Thermography of foam-core sandwich structures Materials Evaluation, Vol. 47, No. 7, pp. 802,804 (Jul. 1989)

Thermography with an infrared (IR) scanner has been used to detect prefabricated defects within sandwich panels. The sandwich panels had faces of glass/polyester composite laminates (GRP) and a core of rigid cellular PVC foam. Different types of disbonds were simulated, perpendicular and parallel to the faces. All disbonds were successfully detected and it is particularly interesting that a simulated disbond centred in the core, parallel to the faces, was found. Cavities within the core were also simulated and detected.

42312 Platonov, V.V.; Dymchenko, V.V.; lvanova, E.G. Evaluat ion of the sensitivity of contact thermal inspection methods Soviet Journal of Non-Destructive Testing, Vol. 24, No. 11, pp. 726- 732 (Jul. 1989)

Variants of the active thermal nondestructive method of inspection (ANTI) by processing the signal recorded by the heat flow sensor are examined. The sensitivity of the amplitude, differential, time, and integral methods of ATNI is evaluated.

ND T abstracts

42085 Maldague, X.; Krapex, J.C.; Cielo, P.; Poussart, D. Processing of thermal images for the detection and enhancement of subsurface flaws in composite materials Signal Processing and Pattern Recognition in Nondestructive Evaluation of Materials, Proceedings of the NATO Advanced Research Workshop, Lac Beauport, Quebec, Canada, 19-22 Aug. 1987. Edited by C.M. Chen, pp. 257-286. Springer-Verlag (1988)

Subsurface imaging using thermal wave generated either by line heating with lateral displacement of the part to be inspected or full-field heating with no displacement is an attractive approach for the NDE of composite materials. Proper detection of flaws, such as delaminations or unbonds require dedicated thermographic image processing. In this paper we will present recent work done at our Institute on the detection and enhancement of unbonds in aluminum to foam laminates. Also quantitative characterization of flaws in graphite-epoxy laminates using specially developed image processing and modelling will be presented. Emphasis will be given to either time-domain or space- domain image processing methods for precise and reliable defect visualization.

41719 Leung, W.P.; Tam, A.C. Noncontact measurement of thermal conductivity of epoxy bonds by pulsed photothermal radiometry International Business Machines Corporation, San Jose, California (United States), AD-AI99064FIIGAR, 5 pp. (21 Dec. 1987)

Pulsed photothermal radiometry relies on the flash heating of a surface and the detection of the time-depeodence of the surface cooling by infrared radiometry. This is useful as a non-destructive and non- contact technique to quantify the thermal conductivity of a subsurface epoxy bond underneath an opaque surface. The degree of curing of the epoxy can also be monitored.

41716 Smith, R.L. Applications of thermal pulse video thermography Anglo-Finnish Joint Symposium on Advances in Nondestructive Testing, Espoo (Finland), 9-11 May 1988, pp. 26-32. Edited by T. Astron, Technical Research Centre of Finland (VTT) (1988)

Thermal pulse video thermography has been pioneered by the National NDT Centre at Harwell for the remote inspection of composite, ceramic and metallic components. The combination of scanning infra-red cameras, fully compatible with "IV video standards, with fast heat sources allows such inspections to be carried out very rapidly. The technique can be applied to a wide range of materials and problems. Originally developed for the detection of delaminations in carbon fibre reinforced plastic (CFRP) the versatility of the system has enabled the technique to be applied to materials of widely different thermal properties, including metals and ceramics. Examples of the application of the technique are discussed.

41714 Inglehart, L.I. Photothermal characterization of ceramics Nondestructive Testing of High-Performance Ceramics, Conference Proceedings, Boston, Massachusetts, (United States), 25-27 Aug. 1987, pp, 163-176. Edited by A. Vary and J. Snyder. The American Ceramic Society (1987)

Various photothermal detection methods are discussed, and results are presented for near surface characterisation of Alsub(2)Osub(3) with varying densities using the photoacoustic detection method, and an SiC- SiOsub(2) composite material with distributed damage using Mirage Effect detection method (optical beam deflection).

40909 Delouard, P.; Marin, J.-Y.; A venas-Payan, I.; Tretout, H. Infrared thermography development for composite material evaluation Proceedings of the 12th World Conference on Non-Destructive Testing, Amsterdam (Netherlands) 23-28 Apr. 1989, Vol. 1, pp. 567-572. Edited by J. Boogaard and G.M. van Dijk, Elsevier, 1989

The increasing use of fibre reinforced composite materials in structural components, mainly in the aircraft industry, has induced manufacturers to acquire appropriate non destructive testing means for larger production rates and tighter quality control. A large assessment program has been carried out in order to demonstrate the applicability and reliability of infrared thermography as a method for the inspection of composite materials.

40203 McLaughlin, P.V. Jr. Defect detection and quantification in laminated composites by EATF (Passive) thermography Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7B, pp. 1125-1132. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988.

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