In this paper, a novel vibration-based methodology for detecting and identifying delamination damage in composite laminates was described. The approach does not require vibration measurements on the undamaged structure. Three alternative damage indexes, two of the Von Mises type and one based on the bending strain energy, were proposed and applied in several numerical studies concerning delaminated composite panels. Two smoothing techniques, GST and SEA, were used independently to smooth the discontinuities in the bending curvatures corresponding to a set of higher-frequency vibration modes of the damaged panels. The numerical examples were based upon Mindlin plate analysis that included delamination models of various sizes and spatial positions. Effects of random error in the curvature data were also studied in order to ascertain the sensitivity of the method to noisy experimental data. It was shown that the proposed damage indexes, combined with the SEA-based smoothing, provide the means for adequately identifying the delamination damage even near the panel boundaries. One difficulty associated with the use of a modal-curvature damage index is that when real test data are used, the differentiation process may compromise the quality of the results by amplifying the effects of measurement errors. Since the experimentally measured data are inherently noisy, the sensitivity of the considered technique to the noise affecting measured data is of primary concern. From an experimental point of view, the application of the Scanning Laser Doppler Vibrometer (SLDV) technique enables the non-contact curvature measurements to be performed with a high spatial resolution and a low degree of experimental noise within the broad frequency and amplitude ranges, where an acoustic source excitation can be used. In practical structural applications, the curvature data can be computed from surface strain measurements using high-density strain sensors based on optical fibers embedded with Bragg gratings. Fiber Optic Bragg Grating technology enables the distribution of thousands of sensors that are immune to moisture and electromagnetic interference and have negligible weight penalty. This technology can be conveniently coupled with the SEA-based computations that do not require strain measurements on a regular grid and provide robust interpolation/smoothing of the data relative to arbitrary locations.
Novel vibration-based method for detecting delamination damage in composite plate and shell laminates
Feststellung von Delaminierungsschäden in Platten und Schalen aus Schichtverbundwerkstoffen durch neue Vibrationsmessmethode
2005
8 Seiten, 9 Bilder, 1 Tabelle, 16 Quellen
Aufsatz (Konferenz)
Englisch
Abplatzen , akustischer Doppler Effekt , Balken , berührungsfreie Prüfung , Bragg-Reflexionsbedingung , Delaminierung (Schichtablösung) , Flugzeugrumpf , Krümmung , Laminat , Messaufnehmerfeld , numerisches Verfahren , optische Faser , Platte (Bauteil) , Schadenanalyse , Signalrauschen , Verformungsenergie , Vibrationsmessung
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