9 th European Workshop on Structural Health Monitoring July 10-13, 2018, Manchester, United Kingdom Analytical solutions for active and passive monitoring of structural damage in fibre-composite laminates L R Francis Rose 1 , Wing K Chiu 2 , Nithurshan Nadarajah 2 , Benjamin S Vien 2 1 Aerospace Division, Defence Science and Technology Group, Melbourne 3207, Australia francis.rose@dst.defence.gov.au 2 Department of Mechanical & Aerospace Engineering, Monash University, Clayton 3168, Australia Abstract The acoustic emission due to various forms of crack-like damage can be represented by an integral involving the emission due to appropriately defined crack elements, which in turn can be represented as particular combinations of force dipoles. These same fundamental solutions can also be used to represent the scattered field due to crack-like damage, which can be regarded as being due to an induced source at the damage location, activated by an incident wave. It is shown that the elastodynamic reciprocal theorem can be used in conjunction with a judiciously defined ansatz to derive a compact analytical form for these fundamental solutions in isotropic plates. The only calculations required are to determine the plane-wave dispersion curves and through- thickness mode functions. The radiation and scattering patterns for fibre breakage and delamination cracking are presented, based on the analytical solutions for Mode I and Mode II crack elements. These analytical results are compared with both finite element simulations and experimental measurements. The practical implications for active and passive structural health monitoring of composites are briefly discussed. 1. Introduction Damage detection techniques can be broadly classified as active or passive, where the former rely on some form of interrogation of the damaged structure, and recording the response, whereas the latter rely on detecting signals generated by the damage process itself. Examples of active approaches include ultrasonics, X-rays, and optical techniques such as shearography [1-3]. The best-known passive approach is acoustic emission (AE) monitoring, which is primarily used as a qualitative technique for detecting and locating impact events [4]. However, there is currently a resurgence of research interest in quantitative AE monitoring, driven in part by recent advances in sensor technology, signal processing and computer modelling [5], but also in part by the attractiveness of in situ structural health monitoring (SHM) based on built-in sensor networks [6,7]. The failure mechanisms in composites have been extensively documented [8]. The ones of principal interest as AE source mechanisms are fibre breakage, delaminations, transverse matrix cracking and splitting. These failure mechanisms all involve crack- like sources of AE. The resulting AE can be represented theoretically as a convolution of (i) a source function, characterised by the displacement discontinuity across the More info about this article: http://www.ndt.net/?id=23241