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5th January 2017, Braunschweig

Lamb waves for structural health monitoring

Structural health monitoring (SHM) based on Lamb waves is a promising method for the in-service inspection of composite structures. Lamb waves can be excited and received using a network of actuators and sensors which are permanently attached to a structure. By analysing the sensor signals, different kinds of structural defects can be detected and located.

The DLR (Institute of Structures and Design) at the Technical University of Braunschweig in Germany has been involved in work with Airbus and its partners to prove that such damage detection and localisation can be achieved in complex and realistic structures.

The DLR (Institute of Structures and Design) at the Technical University of Braunschweig in Germany has been involved in work with Airbus and its partners to prove that such damage detection and localisation can be achieved in complex and realistic structures.

Due to its high structural complexity and the likelihood of it being damaged during aircraft operation, a special door panel surround was developed and manufactured for the testing. It consists of a skin, 44 stringers, four typical frames, a complete set of door frames and 584 piezoceramic sensors, including the wiring harnesses.

The robust sensor network was developed and integrated during the manufacture of the structure in order to keep manufacturing time and costs down. All 584 integrated sensors survived the different manufacturing steps involved.

Various kinds of realistic, barely visible impact defects were then induced by the use of a gas gun. The SHM network was employed to acquire acousto-ultrasonic data and detect the induced defects in the structure, using a probability-based imaging algorithm. The results have subsequently been compared with traditional non-destructive testing techniques.

The software successfully detected all of the induced damage, ranging from skin delaminations and stringer debondings, to clip detachments and damage to the frame area.

The wired door panel was displayed during Composites Europe 2016 in Düsseldorf.

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