Abstract
The interest of the aerospace industries in structural health and usage monitoring systems is continuously increasing. Among the techniques available in literature those based on Fibre Bragg Grating sensors are much promising thanks to their peculiarities. Different Chirped Bragg Grating sensor configurations have been investigated in this paper. Starting from a numerical model capable of simulating the spectral response of a grating subjected to a generic strain profile (direct problem), a new code has been developed, allowing strain reconstruction from the experimental validation of the program, carried out through different loading cases applied on a chirped grating. The wavelength of the reflection spectrum for a chirped FBG has a one-to-one correspondence to the position along the gauge section, thus allowing strain reconstruction over the entire sensor length. Tests conducted on chirped FBGs also evidenced their potential for SHM applications, if coupled with appropriate numerical strain reconstructions tools. Finally, a new class of sensors—Draw Tower Grating arrays—has been studied. These sensors are applicable to distributed sensing and load reconstruction over large structures, thanks to their greater length. Three configurations have been evaluated, having different spatial and spectral characteristics, in order to explore possible applications of such sensors to SHM systems.
Highlights
Nowadays, structural health monitoring represents one of the major concerns for modern aeronautical structure maintenance and aircraft fleet management [1]
Starting from the implementation of a numerical strain reconstruction program, this paper has shown how this can be used together with different types of FBG sensors for the development of a complete structural health monitoring (SHM) system
The coupling between the developed program and a chirped grating sensor yielded excellent results for simple strain profiles applied to the sensor
Summary
Structural health monitoring represents one of the major concerns for modern aeronautical structure maintenance and aircraft fleet management [1]. As a matter of fact, the progressive ageing of the aircraft fleet can make questionable their durability, affordability and profitability, as well as the conventional preventive maintenance philosophy, based on a scheduled-based approach and non-destructive inspection techniques Such uncertainties become even more alarming when the structures are made of composite materials [2]. The structures become smart structures and the philosophy is called structural health monitoring (SHM), usually implemented in modern aircraft through health and usage monitoring systems (HUMS) Such methodology is very promising and is going to be adopted by most modern aircraft, provided some major concerns can be successfully tackled, such as sensor and actuator integration, data processing and storage, noise and false signals filtering, environmental and variable operational conditions management [3,4]. Three array configurations have been tested in order to identify the most suitable one(s) for strain monitoring applications
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