17 June 1998 High-frequency vibrations of sandwich plates and delamination detection
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Abstract
In multi-hull marine vehicles assembled by FRP sandwich composite materials problems with delamination and skin/core debonding are reported. High frequency vibrations in foam core sandwich materials are investigated to see if it was possible to apply them, together with bending vibrations, in an early damage warning system for delamination detection in marine vessels. This manuscript presents a theory for high frequency vibration in sandwich plates and beams. The core is modeled as a two parameter foundation with shearing interaction effects as well as normal stress effects in the core included. The skins are modeled as ordinary plates or beams on a foundation. Expressions for both anti-symmetric and symmetric modes are given. In addition to the theoretical development, experiments with a simply supported sandwich beam, using a TV-Holography technic, were performed and good accordance between theory and experiments were achieved. The results indicates that disappearance of symmetric modes may be used a parameter for delamination detection. The anti-symmetric modes may be interchangeable with higher bending modes by an early damage warning system. To avoid this, the theory presented may be applied to determine the anti-symmetric frequency values in forehand.
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Alf Egil Jensen, Alf Egil Jensen, Fridtjov Irgens, Fridtjov Irgens, } "High-frequency vibrations of sandwich plates and delamination detection", Proc. SPIE 3325, Smart Structures and Materials 1998: Smart Systems for Bridges, Structures, and Highways, (17 June 1998); doi: 10.1117/12.310616; https://doi.org/10.1117/12.310616
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