Safety and reliability of aircraft structures are of main concern within the aerospace industry, preferably without influencing the availability of the aircraft and maintenance and operation costs. As damages in composites can be hard to detect, methods are being developed to detect damages which can potentially lead to a (catastrophic) failure of a (sub)system. Interest in structural health monitoring (SHM) has thus gained a strong interest within aerospace engineering, with the development of new systems or optimising existing ones to contribute to a safe and reliable aircraft. This research focuses on the development of an impact damage detection and quantification method for composite structures. The main research objective of this thesis is to investigate the capabilities of a PZT and a state-of-the-art FBG sensor system for passive impact damage detection and quantification on a simple composite panel and a complex stiffened composite structure.