(The) signal characteristics of fiber bragg grating sensor embedded into composite structures and measurement of dynamic strain

Abstract

In this paper, signal characteristics of fiber Bragg grating sensor is investigated to monitor the response of composite structures during curing process and under external loading. The reliability of the FBGs embedded into composite materials was also studied using a microscope. The birefringence phenomena of embedded FBGs were observed during cure processing. Transverse contraction of the embedded sensor exhibits the birefringence due to the residual stress generated in composite laminates. The residual stress generated and released in composite laminates could be estimated by using the FBG with two spilt peaks. FBGs were applied to measure dynamic strain in the miniature half wing real-timely. The recoated FBG as longitudinal strain sensor was used as a dynamic strain sensor by the FBG sensor system with WSFLWI. The smart half wing embedded with two FBG sensors was fabricated. In the bench test, comparative results obtained in the half wing with three types of sensors (FBG, ESG, PZT) showed excellent agreements. The results measured from the optical fiber sensors showed good resolution in time domain and clear spectrum in frequency domain, as well as multiplexing capability and embedding ability. Finally, the wind tunnel test of the smart half wing demonstrated the suitability of FBG as an in-flight health monitoring sensor. FBG sensors could detect the flutter of the half wing during the wind tunnel test.