Composite panel structural health monitoring and failure analysis under compression using acoustic emission

Abstract

This paper documents an application of the acoustic emission (AE) method for structural health monitoring (SHM) of an integrally stiffened composite panel. The panel consists of a skin and two T-stringers and represents a typical part of the wing or fuselage structure. Similar design is used in civil structure parts. Quasi-static loading under compression was carried out to determine the initiation of the buckling modes. Two pieces of integral panels were tested up to failure. Both panels were monitored using 9 AE sensors in the same configuration throughout the test. The final stage of the test was recorded with a high-speed camera to obtain a detailed view of failure development. The velocity of the propagated AE elastic waves was determined experimentally before the test based on the best match of the computed and real positions of the Hsu–Nielsen sources. The determined velocity was subsequently used for AE source localization during the compression test. Different failure mechanisms were directly linked to different sources of AE using cluster analysis. Visualization of the AE location clusters was performed via the Kernel density estimation. High-speed camera images confirmed that the location of failure corresponds with the localization of a specific cluster of AE events. The AE method demonstrated the detection capability of the critical spot at 87% of the panel strength in compression. In conclusion, AE is suitable as an SHM method for damage monitoring of aerospace composite structures as well as for applications in civil structures.