Impact damage detection in CFRP using fiber Bragg gratings

Abstract

A fiber-optic ultrasonic sensing system was constructed with fiber Bragg gratings based on the intensity modulation of light reflected from fiber Bragg grating sensors. This fiber-optic system consists of fiber Bragg gratings for sensing and filtering, a broadband light source as well as a photo detector. The feasibility of damage monitoring using the fiber-optic system was investigated. Transient ultrasonic Lamb waves generated with a piezoceramic pulser were propagated in a cross-ply CFRP with visible impact damage. The response of the fiber Bragg grating sensor to the Lamb wave propagated through the damaged area was compared with a reference response in an intact area. Frequency characteristics of the response signal were analyzed in order to evaluate Lamb wave interaction with damage. Moreover, Lamb wave detection using a piezoceramic sensor was performed to compare with the response of the fiber Bragg grating sensor. The experimental results demonstrated that fiber Bragg grating sensors are comparable to piezoceramic sensors in ultrasonic detection and the fiber-optic system proved to be effective in impact damage detection of CFRP.

Development of smart composite structures with small-diameter fiber Bragg grating sensors for damage detection: Quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing

“…After the wave propagates in the laminate, the transmitted wave is received by an FBG sensor embedded in or glued on the laminate. Some high-speed FBG demodulation systems have been developed by other researchers [27][28][29][30][31][32]. Since it is difficult to use mechanical moving parts for the systems to detect high-speed change in Bragg wavelength of FBG, the techniques of transformation from the wavelength shift to the optical power are of key importance.…”

“…From the transmitted power ratio of the two waves, the Bragg wavelength can be detected. A uniform FBG or a Fabry-Perot tunable filter was also used for the wavelength filter [30][31][32].…”

Ultrasonic Excitation – Fiber Bragg Grating Sensing Technique for Damage Identification

“…Duck et al proposes the theory of two cylindrical model and studied the strain transfer characteristics of the fiber Bragg grating sensor from the base material to the fiber core [2].Hang-Yin Ling et al proposes a four cylinder strain transfer model for symmetric structures, and studies the strain transfer characteristics from the substrate to the fiber core through the adhesive layer and the coating one [3]. Tsuda et al verifies fiber Bragg grating (FBG) response sensitivity for ultrasonic wave on the composite materials [4]. Jang, Byeong-Wook uses multiplexed FBG sensor to study positioning algorithm for composite structures [5].…”

Instrumentation of integrally stiffened composite panel with fiber Bragg grating sensors for vibration measurements

“…One direction has been to instrument stiffened composite airframe structures with fiber Bragg grating (FBG) sensors for strain measurements. These measurements have provided information for condition monitoring of the airframe, impact damage detection, quality assurance during curing of the composite laminates, and buckling of airframe components [1][2][3][4][5][6][7]. The main benefit to using FBG sensors is the fact that FBGs can be multiplexed in large numbers on a single optical fiber, significantly reducing the weight of instrumenting the structure with a large number of sensors.…”

“…The first is the use of strain anomalies to detect buckling of the stiffened panel, a critical failure mode in skinstiffener airframe structures [1,2,[4][5][6][7]. The second approach is to measure the FBG strain due to an acoustic signal in the composite due to propagating Lamb waves, for example, through acoustic emission or active actuation of the structure with piezo-electric (PZT) elements [15].…”