On-line health monitoring of smart composite structures using fiber polarimetric sensor

Abstract

The sensitivity of the fiber polarimetric system for smart structure applications depends on various parameters such as pre-stress, input azimuth, fiber turns etc. The presence of the smart structure modifies the output characteristics of the highly birefringent (HiBi) fiber due to elastic properties of the structure. This differential lateral strain will produce a change in the birefringence of the fiber over this length, which manifests as the state of polarization change in the fiber output. These concepts are used in the defect detection of smart composite structures. Experimental procedures are repeated for bow-tie HiBi fibers with different optical configurations. A parameter sensitivity factor 'Q' is proposed to characterize defects. A significant variation in Q-factor can be attributed to the presence of defects/delamination. This paper deals with the on-line defect detection of smart composites based on such concepts.

Experimental Study and Analysis of a Polymer Fiber Bragg Grating Embedded in a Composite Material

“…Among the different fiber optic sensors, the most researched fiber optic sensors for application in composite materials were silica fiber Bragg grating sensors [7][8] and polarimetric fiber sensors [9][10]. However most of the studies were focused on the use of fiber sensors to measure the temperature and strain during the curing process and also during structural tests [7][8][9][10].…”

“…However most of the studies were focused on the use of fiber sensors to measure the temperature and strain during the curing process and also during structural tests [7][8][9][10]. Our recent studies established that the thermal expansion effects of the composite material considerably affect the performance of the embedded sensors and result in a cross sensitivity in sensing parameters [11][12][13].…”

Crack monitoring using multiple smart materials; fiber-optic sensors & piezo sensors

“…If the longitudinal strain is produced increasingly in the Hi-Bi fiber, the polarization of the light coming out of the fiber changes sinusoidally. Since the light finally passes through an analyzer, the output intensity (or voltage V) of the light which is measured by the photodiode also changes sinusoidally [15]. In the loading test conducted with FOPS, a normalized output parameter called state of polarization (SOP) is calculated, which is given by…”

“…The increased strain due to the damage or crack in a structure is picked up by FOPS irrespective of the damage location in the structure. Thus, FOPS monitors damages in different structures globally [14][15][16]. However, the location of the damage might not be achieved using FOPS.…”

Interaction between optical fibre sensors and matrix cracks in cross-ply GFRP laminates. Part 2: Crack detection

“…Some of the early work on damage detection concentrated on using the attenuation of the intensity of the optical output due to fibre failure or bending losses induced in an area of damage (see e.g. Udd 2 Takeda et al [3]; Okabe et al [4,5]; Kwon et al [6]; Tsuda et al [7]; Murukeshan et al [8], Ussorio et al [9] ). Of these techniques, only Fibre Bragg grating (FBG) optical sensors possess the potential to detect matrix cracking damage, as both Takeda and colleagues and Ussorio and colleagues have shown recently (e.g.…”