Fiber optic sensors (FOSs) in smart structures provide a special opportunity for real-time-multiplexed monitoring of the health status of infrastructure using surface-bonded or embedded sensors. FOSs are very important sensors used in smart materials and structures because of their advantages compared with commonly used NDE technologies [1]. FOSs used for the NDE of advanced materials and structures have been demonstrated to be feasible for the measurement of material changes during fabrication, the in-service lifetime measurement of strain, temperature, and other physical perturbations, and the eventual detection of damage or material degradation [2].
Smart materials and structures provide the real possibility of structural integrity monitoring on-line, in situ or in vivo.
FOSs in smart structures are an enabling technology that will allow engineers to establish a nervous or feedback system in their designs, in which the system performs structural damage monitoring and assessment, whereas it is difficult to accomplish the above tasks with common NDE technologies [3].The advantages of fiber optic sensors include light weight, small size, geometrical versatility, immunity to electromagnetic interference (EMI), large bandwidth, environmental ruggedness, and electrical and optical multiplexing. Thus, fiber optic sensors are ideal sensors for potential smart structure and material applications.
In recent years, the technology of fiber optic sensors has been applied to the field of structural monitoring, infrastructure assessment, and some industrial sectors [3�C6].
The most attractive feature of fiber optic sensors is their Brefeldin_A inherent ability to serve as both the sensing element and the signal transmission medium, allowing the electronic instrumentation to be located remotely from the measurement site. This is especially useful for remote monitoring of the condition of infrastructures.In this work, a reference dual-wavelength grating FBG and LPFGs were examined to evaluate typical infrastructure materials, such as Portland cement concretes and asphalt mixtures, for temperature, strain, and liquid-level measurements as these three Drug_discovery physical measurements are the common measurands for infrastructure materials regarding thermal effects, mechanical response, and liquid-level monitoring.
The experimental results presented here include temperature fluctuation and stability tests using both FBG and LPFG, respectively. An indirect tensile strain test using a FBG sensor as well as finite element modeling were carried out for comparative analysis. Liquid-level measurements using a sensor constructed by cascading five different wavelength LPFGs are presented.