Structural health monitoring of smart composite materials by using EFPI and FBG sensors

Structural health monitoring (SHM) including the real-time cure monitoring and non-destructive evaluation (NDE) in-service is very important and definitely demanded for safely working of high performance composite structures in situ. It is very difficult to carry out by using conventional methods. A unique opportunity was provided to real-time monitor the health status of composite structures by using embedded fiber optic sensors (FOSs). In this paper, the extrinsic Fabry-Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors are real-time employed to simultaneously monitoring the cure process of CFRP composite laminates with and without damage. The results show that both embedded EFPI and FBG sensors could be used to monitor the cure progress of composite materials and detect the occurred damage on-line during the fabrication of composite structures. Furthermore, the NDE of smart composite laminates embedded both EFPI and FBG sensors are performed by using the three-point bending test. The experimental results present that the flexural strain of CFRP composite laminates with damage is more than that of CFRP laminates without damage under same load as we expected. Both EFPI and FBG sensors also show the excellent correlation during the cure monitoring and bending test. (C) 2002 Elsevier Science B.V. All rights reserved.