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Application of Optical Fiber Sensors for Damage Accumulation Monitoring in Composite Structures

In this paper a study of damage accumulation evaluation of highly stressed composite layer using acoustic emission method and local strain measurements by optical fiber based sensors in form of Fiber Bragg Grating (FBG) is presented. The study was carried out using composite NOL-ring specimens. These kind of specimens can simulate behavior of the cylindrical part of the pressure vessel. Quasistatic and creep tests of CFRC made NOL specimens were performed. It has been shown that there is a correlation between changes in the strain field of composite material, detected by FBG optical sensors, and changes in acoustic emission signals. The possibility of a kind of calibration of composite material strain state monitoring system by AE measurements and at the same time evaluation of damage accumulation was confirmed.