Condition monitoring in composite materials: An integrated systems approach

This paper presents the results of a collaborative project, the objective of which was to investigate the potential offered by combining ultrasonic Lamb wave interrogation of composite material structures, insonifying the whole structure, with a single wavefront integrating optical fibre detector. The system, which was designed primarily for condition monitoring rather than defect imaging, proved to be capable of detecting small (centimetre square) delaminations, millimetre-sized holes and impact damages of a few joules, all with insonification wavelengths of the order of 2 cm. Data extraction proved to be extremely important since the damage-detection process relies essentially on analysing scattering signatures rather than attempting to image defects and damage. The system—dubbed SISCO (Structurally Integrated Systems for comprehensive evaluation of COmposites)—indicates that self-monitoring structures can be efficiently designed using controlled insonification and a relatively sparse sensor array, presenting a contrast to the more conventional imaging approach involving far more complex sensing arrays and detection and signal processing algorithms.