Optical fiber sensor systems for simultaneous monitoring of strain and damage in smart composites

Abstract

To perform the real-time health monitoring of the smart composite structures, two fiber optic sensor systems are proposed, that can measure the strain and detect the moment of fracture simultaneously. The two types of the coherent sources were used for fracture signal detection - EDFA with FBG and EDFA with Fabry-Perot filter. These sources were coupled to extrinsic Fabry-Perot interferometer sensors imbedded in composite specimens to monitor the fracture behavior of composites. To understand the characteristics of matrix cracking signals, at first, we performed tensile tests using surface attached PZT sensors. This paper describes the implementation of time-frequency analysis such as short time Fourier-transform for the quantitative evaluation of the fracture signals like matrix cracking. From the test of tensile load monitoring using optical fiber sensor systems, the measured strain agreed with the value of electric strain gage and the fracture detection system could find out the moment of damage with high sensitivity to recognize the onset of micro-crack fracture signals.