b integrated optic fibre sensors

ABSTRACTAn optic fibre sensor based on the intermodal interference principle was integrated in a composite materialstructure to detect impacts and vibrations. Six fibres were integrated at the top of a carnJepoxy composite panel and arranged to form a regular network on the structure. A series of impacts at various positions on the plate were performed using an instrumented hammer. The spectral responses of the optic sensors werecompared to a reference piezoelectric accelerometer. Moreover a determination of the impacts position was performed with the arrival times measure of the generated acoustic wave front to the optic sensors. These tests proved the great sensitivity of this type of sensor, its integration easiness and the possibility to localize an impact on composite structures with a very simple device. 1.INTRODUCTIONDuring the last twenty-five years, there was a considerable increase in the use of composite materials for aeronautical structures. In spite oftheir various qualities: weight saving. properl.ies optimization and in-servicebehaviour which has contributed to generalize their use, composite materials present some inconvenients and