Response of fiber Bragg gratings bonded on a glass/epoxy laminate subjected to static loadings

Abstract

Response of fiber Bragg gratings bonded on a glass/epoxy laminate subjected to static loadings, Composite Structures (2015), doi: http://dx.doi.org/10. 1016/j.compstruct.2015.04.015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractFiber Bragg gratings (FBG) may be used to monitor strain over the surface of a structure as an alternative technology to conventional strain gauges. However, FBG bonding techniques have still not been established to yield satisfactory surface measurements. Here, two adhesives were investigated, one with low viscosity and the other with high viscosity for bonding FBGs on glass/epoxy sandwich skins. First, instrumented elementary specimens were tested under tension. FBG strain results were analyzed together with digital image correlation (DIC) measurements. The influence of the bonding layer on the measured strain and on the integrity of the sensor was investigated by considering different regions of interest. Next, an instrumented structural sandwich beam was tested under four-point bending. FBG rosettes were compared to conventional strain gauge rosettes. The high viscosity adhesive demonstrated behaviors that affected FBG accuracy. Brittleness of the bonding layer and poor interface adhesion were observed using DIC and X-ray tomography. By contrast, the low viscosity adhesive demonstrated satisfactory results. The FBG strain measurements appeared to be consistent with those of DIC. The accuracy is also adequate as the FBGs and the conventional strain gauges had similar results in three directions, under tension and under compression.

Mode I interlaminar fracture toughness of carbon‐epoxy coupons with embedded ceramic sensors

“…[1][2][3][4][5][6][7] Nevertheless, the major drawback that composites instrumentation finds is that sensors are not inherently fail-safe. Currently, the sensor's integration has been made with the aim of monitoring the phenomena caused by the in-service conditions.…”

“…[2,[8][9][10] These are the reasons why composites instrumentation has not been applied at full scale in the industry. [1][2][3] On the other hand, the embedded sensors have proven their value added to survey the inner physical phenomena. On the one hand, the surface sensors have been employed widely because they do not have a significant influence on the mechanical properties of the structure.…”

“…In the last two decades, the development of intelligent structures has involved the implementation of sensors on the surface and inside composite structures. Currently, the sensor's integration has been made with the aim of monitoring the phenomena caused by the in‐service conditions …”

“…On the one hand, the surface sensors have been employed widely because they do not have a significant influence on the mechanical properties of the structure. However, these sensors are only sensitive to the physical phenomena on the external face of the structure . On the other hand, the embedded sensors have proven their value added to survey the inner physical phenomena .…”

Strain Modal Analysis of Small and Light Pipes Using Distributed Fibre Bragg Grating Sensors

“…Unlike conventional electrical techniques, Fibre Bragg Grating (FBG) sensors adopt light as a sensing signal, which gives FBG sensors various attractive characteristics, such as small size, light weight, immunity to electromagnetic interference, and large multiplexing capability [7,8,9]. In recent years, FBG sensors have been investigated and applied for dynamic strain measurement and modal analysis [10,11,12,13].…”