Proyecto de Investigación: RESISTENCIA Y TOLERANCIA AL DAÑO POR IMPACTO DE BAJA VELOCIDAD EN ESTRUCTURAS DE MATERIALES COMPUESTOS PROCESADOS MEDIANTE FABRICACION ADITIVA
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PID2021-122491OB-I00
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Study of the transverse strain effect on the Fiber Bragg Grating Sensor (FBGS) response with polyimide coating under experimental biaxial tests
(Elsevier, 2023-12-15) Martínez Vicente, Juan Luis; González Gallego, Manuel; Terroba, Félix; Frövel, Malte; López Cela, Juan José; Junta de Comunidades de Castilla-La Mancha; Agencia Estatal de Investigación (AEI); Ministerio de Ciencia e Innovación (MICINN)
The aim of this research work is to study the behaviour of Fiber Bragg Grating (FBG) sensors to interpret their response more accurately in a structural monitoring system. In the presence of a complex stress state, a structure is subjected to strain fields in multiple directions simultaneously and the sensors used for its structural monitoring are affected as well. However, the traditional procedure to calibrate FBG sensors consists of uniaxial tensile tests to calculate a strain sensitivity factor () that relates the sensor response to the strain measured during the test. In this study, a polyimide coated FBG sensor is embedded in a cruciform composite specimen to analyse its response to biaxial strain states. The experimental methodology has consisted of carrying out a campaign of biaxial tests on this specimen in which the longitudinal strain () has been kept constant and the transverse strain () has been varied by means of a triaxial testing machine to reproduce different plane stress states. Biaxial tests have allowed to study experimentally the influence of the on the longitudinal measurement of the FBG sensor and therefore on the calibration procedure. Finally, the experimental results obtained in both uniaxial and biaxial tests have been compared to the strain-optic theory.
Fiber bragg gratings sensor strain–optic behavior with different polymeric coatings subjected to transverse strain
(Multidisciplinary Digital Publishing Institute (MDPI), 2024-04-27) González Gallego, Manuel; Terroba, Félix; Martínez Vicente, Juan Luis; González del Val, Miguel; López Cela, Juan José; Frövel, Malte; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Ciencia e Innovación (MICINN)
This research work is based on a previous study by the authors that characterized the behavior of FBG sensors with a polyimide coating in a structural monitoring system. Sensors applied to structural health monitoring are affected by the presence of simultaneous multidirectional strains. The previous study observed the influence of the transverse strain (ey) while keeping the longitudinal strain constant (ex), where the x direction is the direction of the optical fiber. The present study develops an experimental methodology consisting of a biaxial test plan on cruciform specimens with three embedded FBG sensors coated with polyimide, acrylate, and ORMOCER®. Applying the Strain–Optic Theory as a reference, a comparison of the experimental values obtained with the different coatings was studied. This experimental work made it possible to study the influence of the transverse strain (ey) on the longitudinal measurements of each FBGS and the influence of the coating material. Finally, the calibration procedure was defined as well as K (strain sensitivity factor) for each sensor.
