Optical fiber sensors for smart composite materials and structures

Composite material structures [1] are widely used in the aerospace, marine, aviation, transport, sport/leisure, and civil engineering industries [1]. Such composite material structures are frequently subjected to external perturbations and varying environmental conditions, which may cause the structures to suffer from fatigue damage and/or failures, and thus require real-time structural health monitoring (SHM). Of necessity, the diagnosis process and condition monitoring of composite structures are usually carried out during their working life [2]. The goal of such diagnosis is to detect, identify, locate, and assess the defects that may affect the safety or performance of a structure. Sensors that are commonly employed for SHM are resistance strain gauges, optical fiber sensors 492(OFSs), piezoelectric sensors, eddy current sensors, and microelectromechanical systems (MEMS) sensors [3]. Traditional nondestructive evaluation (NDE) techniques such as ultrasonic inspection, acoustography, low-frequency methods, radiographic inspection, shearography, acousto-ultrasonic, and thermography are effective in SHM of composite materials and structures, but it is difficult to use them in an operational structure due to the size and weight of the devices [4].