Acoustic Emission Source Identification in Large Scale Fibre Reinforced Composites

Within the last decades many approaches have been proposed to perform source identification in fibre reinforced composites. Some of them have been validated using skilled micromechanical experiments or by using reference specimens in combination with imaging methods, leaving strong evidence that these approaches are valid tools to perform source identification tasks. Lately, also numerical methods have been applied to validate the applicability of source identification methods to fibre reinforced composites for reasonably small size specimens as typically used in materials testing. However, the implementation of the same approach for a real composite structure as used in an industrial environment is still challenging. The reasons for this are manifold. To name just a few reasons, the frequency dependent attenuation starts to compromise frequency information with distance of propagation, directivity effects in a composite laminate may cause distinct differences of frequency spectra when detected at different angles to the source and changes in material and thickness will influence the guided wave modes. The aim of this contribution is to present and discuss the current limitations of source identification procedures in large scale composite structures and to highlight the challenges to overcome when attempting to use such approaches. Influence of signal attenuation, directivity effects, laminate stacking and thickness, presence of existent damage, load configurations and component geometry are discussed and recommendations are given how to estimate the applicability of a source identification approach for a specific application.