Residual strain measurement in bonded composite repairs for aging aircraft by embedded fiber Bragg grating sensors

2007 ◽  
Author(s):  
U. Ben-Simon ◽  
I. Kressel ◽  
Y. Botsev ◽  
A. K. Green ◽  
G. Ghilai ◽  
...  
Keyword(s):  
Fiber Bragg Grating ◽  
Residual Strain ◽  
Strain Measurement ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors ◽  
Aging Aircraft ◽  
Bonded Composite ◽  
Composite Repairs

Experimental analysis of the response of fiber Bragg grating sensors under non-uniform strain field in a twill woven composite

2018 ◽  
Vol 53 (7) ◽  
pp. 893-908 ◽  
Author(s):  
M Kharshiduzzaman ◽  
A Gianneo ◽  
A Bernasconi
Keyword(s):  
Composite Materials ◽  
Digital Image Correlation ◽  
Fiber Bragg Grating ◽  
Digital Image ◽  
Strain Measurement ◽  
Strain Field ◽  
Image Correlation ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors ◽  
T Matrix

Fiber Bragg grating optical sensors are nowadays widely employed for strain measurement for structural health monitoring and in experimental mechanics. Compared to other techniques, i.e. electrical strain gauges, fiber Bragg grating offer immunity to electromagnetic interference and allow for long transmission lead lines. Moreover, thanks to multiplexing interrogation, several sensors can be photo-imprinted into a single fiber core allowing for strain evaluation at multiple locations simultaneously. They have high adaptability to composite materials, particularly because it is possible to be embedded into laminates without affecting their strength and stiffness. Fiber Bragg grating strain measurements are based on the detection of the wavelength shift of their peak reflected spectrum. However, subjected to strain gradients, the spectral response of fiber Bragg grating sensors may be distorted and the sharp peak may not be retained. In this work, the response of fiber Bragg grating sensors having different grating lengths and bonded to the surface of a carbon fiber-reinforced twill woven laminate was analyzed. The analysis combined transfer matrix (T-matrix) with digital image correlation methods. Digital image correlation technique was used to capture the non-uniform strain fields in the woven composites and measured strains were employed in T-Matrix algorithm to simulate fiber Bragg grating response. Using this approach, the effect of the length of the fiber Bragg grating on the strain measurement is assessed and results discussed. Moreover, it is shown that T-matrix formulation combined with a non-contact strain field measurement technique, as DIC, is an appropriate technique to simulate the behavior of fiber Bragg grating bonded to composite materials of complex microstructure.

Differential strain measurement using multiplexed fiber Bragg grating sensors

2004 ◽  
Vol 43 (2) ◽  
pp. 195-204 ◽  
Author(s):  
Peter G. LoPresti ◽  
Dilip Jali ◽  
Christopher Shrock
Keyword(s):  
Fiber Bragg Grating ◽  
Strain Measurement ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors

STRAIN MEASUREMENT AT CANTILEVER BEAM WITH FIBER BRAGG GRATING SENSORS AND COLLIMATORS AND ITS CORRECTION METHOD

2012 ◽  
Vol 06 ◽  
pp. 576-582
Author(s):  
Seung Min Tak ◽  
Min Kyu Kang ◽  
Dong Jin Park ◽  
Seok Soon Lee
Keyword(s):  
Optical Fiber ◽  
Fiber Bragg Grating ◽  
Cantilever Beam ◽  
Strain Measurement ◽  
Wave Length ◽  
Correction Method ◽  
The Other ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors ◽  
Fbg Sensors

Recently, Fiber Bragg Grating(FBG) sensors are being used in various fields. However, it has difficulty to measure at the place where it is not possible to connect fibers each other physically. In this study, using FBG a collimator, we have measured strains with a single optical fiber with many FBG sensors where FBG sensors on one optical fiber line is installed on the beam and the other optical fiber line is connected with an optical interrogator installed at stationary side. The optical fiber lines between an optical fiber line with FBG sensors on the beam and the other optical fiber line on the stationary part are connected by the collimator which makes the use of light's unique characteristic - light travels through space. The experiment showed that the wave length of the light were changed to be linear as strains increased, and the accurate strains were measured by applying the collimator collection factor, which was proposed in this paper.

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