No abstract

The multiple advantages presented by Fiber Bragg Grating (FBG) sensors, if compared with other sensor typologies, are strengthening the development of Structural Health Monitoring (SHM) systems based on this technology. The application fields include a wide variety of industries, highlighting those where safety and reliability are key aspects, as aerospace and civil. In this paper, two examples are shown where FBG networks have been implemented for monitoring of structural tests, including composite aircraft cockpit during pressurization tests, and a concrete/CFRP pillar subjected to compression tests.

Structural health monitoring consists of structural integrity assessment by means of data acquisition and analysis from on-board sensors. Fiber Bragg grating–based monitoring is increasingly attracting the scientific community working on structural health monitoring due to its multiple advantages such as electromagnetic immunity, negligible weight and size, and multiplexing availability. However, the integration of fiber optics within a structure still requires new procedures and signal treatment techniques for increasing technology reliability and exploiting its full potential. In this article, five embedded Fiber Bragg grating sensors are installed in an unmanned aerial system wing for correlating operational conditions with structural strain in real time. Sensor locations are determined by a finite element model accounting for manufacturing limitations of the fiber line. The developed Fiber Bragg grating system and processing techniques are used in static and dynamic tests showing the capacities of this powerful technology. The assessment includes deflection shape estimation, strain cycles counting, audible and visual strain alarms, aileron control based on strain levels, and structural resonance response detection.

In the last decade, many low-cost monitoring sensors and sensor-networks have been used as an alternative air quality assessment method. It is also well known that these low cost monitors have calibration, accuracy and long term variation problems which require various calibration techniques. In this work PM2.5 and PM10 low cost sensors (Plantower and Nova Fitness) have been tested in five cities under different environmental conditions and compared with collocated standard instruments. Simultaneously, particle composition (organic and black carbon, sulfate, nitrate, chloride, ammonium, and chemical elements) has been measured in the same places to study its influence on the accuracy. The results show a very large variability in the correlation between the low cost sensors and collocated standard instruments depending on the composition and size of particles present in the site. The PM10 correlation coefficient (R2) between the low cost sensor and a collocated regulatory instrument varied from to 0.95 in Temuco to 0.04 in Los Caleos. PM2.5 correlation varied from 0.97 to 0.68 in the same places. It was found that sites that had higher proportion of large particles had lower correlation between the low cost sensor and the regulatory instrument. Sites that had higher relative concentration of organic and black carbon had better correlation because these species are mostly below the 1 μm size range. Sites that had higher sulfate, nitrate or SiO2 concentrations in PM2.5 or PM10 had low correlation most likely because these particles have a scattering coefficients that depends on its size or composition, thus they can be classified incorrectly.