Conversion de modes de Lamb à l'extrémité d'une plaque immergée

This paper deals with an experimental study of the conversion of an incident Lamb wave on the extremity of an immersed plate. This wave gives rise to one or several different Lamb waves propagating in the opposite direction. The converted waves are observed only after a distance from the end of the plate. Non guided waves are also observed backward in the plate. An interpretation is proposed, based on the description of Lamb waves by the Debye series

SCATTERING BY A SEMI-INFINITE ELASTIC PLATE IMMERSED IN WATER

We present an experimental study of the acoustic scattering by a semi-infinite plate embedded in water, using short pulse signals. The damping coefficient of Lamb modes and their retroreflection coefficient at the extremity of the plate are investigated. The results are presented for four different Lamb modes. We show that the modes with a stronger "transversal" character have a higher retroreflection coefficient

Discrimination between weak adhesion, delamination and kissing bond at the interfaces of composite bonded assemblies

International audienceIn this work, the impact of delamination, weak adhesion and kissing bond defects at the interfaces of trilayer composites structures, are numerically investigated in order to differentiate these three phenomena that are usually encountered in composite bonded assemblies. The structure is composed by two carbon-epoxy composites with 1.8 mm bonded by an adhesive epoxy of 0.5 mm. The Stiffness Matrix Method (SMM) is used to calculate the transmission and reflection coefficients of bulk waves likely to propagate in a trilayer structure immersed in water. Then, the behaviors of the symmetric and antisymmetric Lamb modes are analyzed. Four different states of interfaces are considered: (a) nominal interfaces with good adhesion, (b) interfaces with weak adhesion, (c) interfaces with delamination and (d) interfaces containing kissing bond defects. The carbon-epoxy composite is considered as an orthotropic layer and the epoxy adhesive interface as an isotropic layer. Results show that, only the antisymmetric Lamb modes are affected by the presence of kissing bond defects while the symmetric and antisymmetric Lamb modes are affected by the presence of delamination at the interfaces. In addition, weak adhesion only partially preserves the symmetric modes (with a shift in their frequencies) and introduces a reduction in amplitude compared to kissing bond like defect. The potential of the proposed method for the qualification of bonded composite structures is clearly demonstrated, with the ability to discriminate among three categories: weak adhesion, delamination and kissing-bond-like defect

Effets de rugosités d'interfaces dans une structure métal/colle/métal sur la propagation des ondes SH : résultats numériques et expérimentaux

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Etude du Couplage des Modes dans une Structure Bicouche Aluminium/Epoxy

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Lamb Modes for the Characterization of Bonded Structures

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