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Guided wave based SHM approach using SAFT-algorithm for impact detection in composite materials

: Schubert, L.; Schwerz, R.; Leibowitz, M.; Lieske, U.; Frankenstein, B.

Chang, Fu-Kuo:
Structural Health Monitoring 2011. Condition-based Maintenance and Intelligent Structures. Vol.2 : Proceedings of the Eighth International Workshop on Structural Health Monitoring; 13.-15.09.2011, Stanford University
Lancaster, Pa.: DEStech Publications, 2011
ISBN: 978-1-60595-053-2
International Workshop on Structural Health Monitoring <8, 2011, Stanford>
Conference Paper
Fraunhofer IZFP, Institutsteil Dresden ( IKTS-MD) ()

This work investigates the interaction of guided waves with low-velocity impact damage in carbon fibre reinforced plastics (CFRP) which are widely used in aerospace applications. The interaction of guided-waves with impact induced damage was already shown [1-2], but the defect localization is quite difficult because of anisotropic material behavior [3]. An adapted synthetic aperture focusing technique (SAFT) was used for defect localization in such anisotropic materials. In order to utilize the technique for composite materials the wave velocities have to be known. The velocities of different wave modes in CFRPs vary with frequency, mode order and the propagation angle. They can be computed from the stiffness coefficients of the material solving equation of motion for anisotropic case [4] or by the conduction of pitch catch or laservibrometric measurements and the subsequent computation of the angle dependent propagation velocities. This paper shows examples for both th e theoretical and experimental approach to obtain the lamb wave propagation velocities. In the experimental work, the velocity data obtained while using laservibrometric measurements are used by the localization algorithm. There for an anisotropic CFRP-plate was equipped with a network of distributed piezo disc transducers. Then a low velocity impact was introduced into the structure. The successful imaging of this damage will be demonstrated.