“…27 The gratings in FBG are characterized by their period, amplitude and length which typically lies between 1 and 25 mm. 28 It allows to reflect a narrow spectrum of incident light and transmits all others at the same time. This narrow spectrum is characterized by a peak centered on a particular wavelength called Bragg's wavelength ( λ B ) and is defined in equation (1) below.…”
A novel approach is developed to evaluate the property retention on prolonged ultra-violet exposure and hence, health monitoring of glass fiber reinforced polymer composite laminate. This is achieved in a non-destructive manner by mapping the strength retention with the established strain. Embedded fiber Bragg grating sensor and strain gauges are employed to monitor the strain evolution within the laminate. Tensile and flexural tests are conducted at regular intervals to estimate the mechanical strength retention with varying duration of ultra-violet exposure. Through this analysis, it is observed that the property degradation mechanism follows the first-order reaction kinetics. The degradation of matrix material along with the stress relaxation over time develops the stress–strain fields near the interfaces of matrix and fiber. Moreover, the established strain is interpreted by formulating the model that considers the unifying influence of stress relaxation and chemical degradation. This model has closely (R2 = 0.9810 and 0.9790) predicted the experimental data of strain than the existing ones (R2 = 0.9142 and 0.9119). Besides, property retention is mapped with the predicted strain. More importantly, FESEM and FTIR confirm the fact that ultra-violet radiation degrades the matrix material, and thus the mechanical property gets significantly deteriorated. This suggests that the strain measurement is an effective, non-destructive and health monitoring technique to assess the property degradation of the manufactured glass fiber reinforced polymer composites.
“…27 The gratings in FBG are characterized by their period, amplitude and length which typically lies between 1 and 25 mm. 28 It allows to reflect a narrow spectrum of incident light and transmits all others at the same time. This narrow spectrum is characterized by a peak centered on a particular wavelength called Bragg's wavelength ( λ B ) and is defined in equation (1) below.…”
A novel approach is developed to evaluate the property retention on prolonged ultra-violet exposure and hence, health monitoring of glass fiber reinforced polymer composite laminate. This is achieved in a non-destructive manner by mapping the strength retention with the established strain. Embedded fiber Bragg grating sensor and strain gauges are employed to monitor the strain evolution within the laminate. Tensile and flexural tests are conducted at regular intervals to estimate the mechanical strength retention with varying duration of ultra-violet exposure. Through this analysis, it is observed that the property degradation mechanism follows the first-order reaction kinetics. The degradation of matrix material along with the stress relaxation over time develops the stress–strain fields near the interfaces of matrix and fiber. Moreover, the established strain is interpreted by formulating the model that considers the unifying influence of stress relaxation and chemical degradation. This model has closely (R2 = 0.9810 and 0.9790) predicted the experimental data of strain than the existing ones (R2 = 0.9142 and 0.9119). Besides, property retention is mapped with the predicted strain. More importantly, FESEM and FTIR confirm the fact that ultra-violet radiation degrades the matrix material, and thus the mechanical property gets significantly deteriorated. This suggests that the strain measurement is an effective, non-destructive and health monitoring technique to assess the property degradation of the manufactured glass fiber reinforced polymer composites.
“…Hybrid materials, created by joining composites and metals using suitable adhesives, have shown promise as alternatives to mechanical fastening parts, offering several advantages, including high strength, high fatigue life, and better stress distribution [5][6][7]. It is well known that adhesive bonding offers several advantages, including welding, but due to reduced stress concentrations without suitable structural health monitoring (SHM), the integrity of adhesive joints is difficult to inspect [8].…”
Structural health monitoring of fiber-reinforced composite-based joints for automotive applications during their manufacturing and on-demand assessment for its durability in working environments is critically needed. High-definition fiber-optic sensing is an effective method to measure internal strain/stress development using minimally invasive continuous sensors. The sensing fiber diameters are in the same order of magnitude when compared to reinforcement (glass, basalt, or carbon fibers) used in polymer composites. They also offer a unique ability to monitor the evolution of residual stresses after repeated thermal exposure with varying temperatures for automotive components/joints during painting using an electrophoretic painting process. In this paper, a high-definition fiber-optic sensor utilizing Rayleigh scattering is embedded within an adhesive joint between a carbon fiber-reinforced thermoset composite panel and an aluminum panel to measure spatially resolved strain development, residual strain, and thermal expansion properties during the electrophoretic paint process-simulated conditions. The strain measured by the continuous fiber-optic sensor was compared with an alternate technique using thermal digital image correlation. The fiber-optic sensor was able to identify the spatial variation of residual strains for a discontinuous carbon fiber-reinforced composite with varying local fiber orientations and resin content.
“…However, the most widely used method to monitor real-time moisture diffusion in adhesives layers is optical fibres (OFs). 28 There are multiple techniques based on OF, 29 but most common are FBG sensors. 28…”
Section: Introductionmentioning
confidence: 99%
“…The periodic perturbation in the core refractive index ensures that a small amount of light is reflected. 28 The reflected light signals combine to one large coherent reflection with a particular wavelength as shown in Figure 1. Figure 1.Refraction principle of fibre Bragg grating sensors.…”
The increased joint efficiency, distribution of loads and decrease in stress concentrations have led to the increased use of adhesives for structural bonding. However, there are a limited number of techniques for verifying and monitoring the integrity and durability of adhesive bonds. This article studies the potential of estimating the curing and ageing of adhesive bulk samples with embedded fibre Bragg grating sensors through measuring the strain associated with hygroscopic expansion. This is achieved by relating the output of a fibre Bragg grating sensor to the deformation of the structure in which it is embedded. This work considers the possibility of mapping the changing structural resistance to mechanical loading (stiffness) of adhesive bonds as a function of time, under the influence of temperature and moisture as environmental factors. The goal is to map the influence of these environmental factors separately on the one hand, and their combined effect on adhesive bonds, on the other hand. This study subjects several bulk specimens to various environmental ageing loads. The swelling, associated to moisture absorption and that results in mechanical strain, is measured with fibre Bragg grating sensors. The moisture absorption behaviour at different temperatures and environmental relative humidity conditions determined in this way is verified using classical test methods (e.g. differential scanning calorimetry, gravimetric) on multiple fibreless specimens.
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