The high specific strength and stiffness of composite materials have resulted in a widespread introduction of composite structures in the commercial aviation industry. Although composite materials offer the possibility to design lightweight structures, they also suffer from complex failure modes of which damage progression is badly understood. This thesis research is about Structural Health Monitoring (SHM) for composite aircraft structures. By permanently attaching a sensor network to a structure, maintenance activities can be improved by reducing costs and by optimizing maintenance scheduling. SHM could furthermore be used to increase the understanding of composite behavior. This research focuses on investigating an image reconstruction algorithm which can be used to visualize impact damage on a composite plate using piezoelectric (PZT) sensors. The relationship between the reconstructed images and damage growth is analyzed using different excitation frequencies and different formulations of a damage index while also assessing the influence of sensor failure on the algorithm. Moreover, an experimental campaign is performed during which composite plates are subjected to Quasi-Static Indentation (QSI) testing in order to create impact damage and monitored to obtain data.