SIMULTANEOUS SENSING OF THE STRAIN AND POINTS OF FAILURE IN COMPOSITEBEAMS WITH AN EMBEDDED FIBER OPTIC MICHELSON SENSOR

A fiber optic Michelson sensor was embedded in composite beams to sens e the internal strain and points of failure of the composite structure s. The bending deformation and matrix cracking were investigated by fo ur-point bending tests of cross-ply composite beams with the embedded fiber optic sensor. The failure points of composite beams were detecte d by using both a PZT sensor and a fiber optic sensor in order to inve stigate the fiber optic failure signals. The failure due to matrix cra cks in a composite beam was confirmed by the edge replica method. The digital processing of the fiber optic signal was carried out to determ ine the strains and failure points of composite beams. The failure poi nts were observed from the processed failure signal by high-pass filte ring. The initial failure strain of the composite beam was measured an d processed from the fiber optic strain signal after low-pass filterin g. (C) 1998 Elsevier Science Ltd. All rights reserved.