Welding or riveting of structures is state of the art for metallic materials. However, the joining of polymers with polymers or with other materials requires reliable bonding techniques which achieve a more homogeneous distribution of mechanical stress. The paper presents methods for non-destructive inspection where bonding defects may be revealed within a short time: air ultrasound, non-linear acoustics, thermal and interferometric methods, all of them providing images. The methods are based on the fact that bonding defects are areas of mechanical weakness resulting in stress concentration, enhanced losses, lack of mechanical contact, or non-linear transfer of load. The examples relate to aerospace-relevant problems, e.g. loose rivets, loss of adhesion, delaminations, stringer disbond, and shape adaptive structures. Non-linear behaviour is a general property of most defects. As an example, the out-of-plane movement of loose disbonded interfaces behaves non-linearly and results in 'clapping'. The higher harmonics can be generated by injecting a sinusoidal wave into the damaged sample. As the higher harmonics appear only at the damaged area they may be used for defect selective imaging based on non-linear scanning laser vibrometry or non-linear air-coupled ultrasound.
Non-destructive inspection of bonding quality in aerospace materials and shape adaptive structures
Zerstörungsfreie Prüfung der Bindungsqualität in Luft- und Raumfahrtwerkstoffen und in formadaptiven Strukturen
2004
6 Seiten, 5 Bilder, 10 Quellen
Conference paper
English
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