Towards an Ultrasonic Guided Wave Procedure for Health Monitoring of Composite Vessels: Application to Hydrogen-Powered Aircraft

International audienceThis paper presents an overview and description of the approach to be used to investigate the behavior and the defect sensitivity of various ultrasonic guided wave (UGW) modes propagating specifically in composite cylindrical vessels in the framework of the safety of hydrogen energy transportation such as hydrogen-powered aircrafts. These structures which consist of thick and multi-layer composites are envisioned for housing hydrogen gas at high pressures. Due to safety concerns associated with a weakened structure, structural health monitoring techniques are needed. A procedure for optimizing damage detection in these structural types is presented. It is shown that a finite element method can help identify useful experimental parameters including frequency range, excitation type, and receiver placement

Suivi d'endommagement par EA dans un composite obtenu par pultrusion et soumis à un chargement en flexion 3 points

Dans ce travail, un matériau composite à fibres de verre et à matrice vinylester, obtenu par pultrusion, est soumis à un chargement en flexion 3 points, d'abord sous chargement quasi statique, et ensuite en fatigue à fréquence relativement faible. La technique d'émission acoustique est utilisée lors des essais afin de préciser le seuil d'endommagement et de suivre son développement. Les résultats ont montré que le seuil d'endommagement survient bien avant la fin de proportionnalité permettant de préciser l'intervalle de contrainte le long duquel les essais de fatigue sur ce matériau seront pratiqués, à savoir entre la contrainte correspondant au seuil d'apparition d'endommagement et la contrainte de fin de proportionnalité. Jusqu'à la fin de proportionnalité, le scénario d'endommagement du matériau étudié suggère un mode d'endommagement gouverné principalement par les divers micro mécanismes d'endommagement de la matrice (microfissuration de la matrice longitudinalement et transversalement aux fibres). A un niveau de contrainte plus élevé, les ruptures de fibres en nombre engendrent l'activation concomitante de multiples autres mécanismes d'endommagement. Le réarrangement du matériau composite lors du rechargement s'accompagne d'une activité acoustique importante. Ceci est prouvé par une distribution très large des amplitudes des événements acoustiques

A Semi-Supervised Based K-Means Algorithm for Optimal Guided Waves Structural Health Monitoring: A Case Study

This paper concerns the health monitoring of pipelines and tubes. It proposes the k-means clustering algorithm as a simple tool to monitor the integrity of a structure (i.e., detecting defects and assessing their growth). The k-means algorithm is applied on data collected experimentally, by means of an ultrasonic guided waves technique, from healthy and damaged tubes. Damage was created by attaching magnets to a tube. The number of magnets was increased progressively to simulate an increase in the size of the defect and also, a change in its shape. To test the performance of the proposed method for damage detection, a statistical population was created for the healthy state and for each damage step. This was done by adding white Gaussian noise to each acquired signal. To optimize the number of clusters, many algorithms were run, and their results were compared. Then, a semi-supervised based method was proposed to determine an alarm threshold, triggered when a defect becomes critical