Damage identification using guided waves on a composite skin-stiffener structure

The potential of using guided waves for damage detection in composite materials has been proven by many researches in the past few years and in particular by the cases studies of the European project SARISTU. In that project integration methods for the piezoelectric wafer active sensors (PWAS), algorithms and a graphical user interface were developed, to allow for an easy to access analysis of the measured data. Despite the proven potential, there is still a large number of questions to be answered before the guided wave based damage identification can be extended from detection to a fully automated, robust and reliable damage identification. This requires a further understanding of the behaviour of guided waves travelling through a multi-layered composite material. To this end, a 16 layer carbon fibre reinforced PEKK thermoplastic, with cobonded T-shaped stiffeners, panel is instrumented with 16 PWAS. An impact is applied to the structure, after measurements of the pristine structure, to inflict a delamination damage underneath one of the stiffeners. Previous research has revealed impact causes first ply failure and skin-stiffener debonding.