Fiber Bragg grating sensing in smart composite patch repairs for aging aircraft

Residual strain measurement in bonded composite repairs for aging aircraft by embedded fiber Bragg grating sensors

“…In this paper we use our previously reported findings [5] in order to demonstrate how FBG sensors can track the initiation of structural bonding and measure the residual strains during bonded composite patch curing. The experimental procedure and the analytical model used in order to obtain the mechanical residual strain are described in Secs.…”

“…The recently introduced smart repair concept [2][3][4][5] is aimed towards real-time assessment of bonded repair integrity, based on direct measurements, using embedded sensors. In such an approach, the residual strains may be accurately measured during the repair application, leading to a better assessment of the repair long term durability.…”

“…Embedded Fiber Bragg Gratings (FBG), as well as extrinsic Fabry-Perot interferometric sensors, have been used extensively to monitor strain and temperature in composite structures, during curing or service [4][5][6]. An FBG sensor has many advantages such as: low weight and small size, high sensitivity, long life, resistance to extreme environmental conditions, simplicity of fabrication, and easy embedding into a composite patch.…”

Damage detection under a composite patch using an embedded PZT-FBG ultrasonic sensor array

“…Moreover, for composite structures, such optic fibers sensors can be easily embedded into the structure, eliminating the need for sensor protection, and can be also used to monitor strain and temperature during curing or service [2,3]. Unlike the omnidirectional sensitivity of the commonly used piezoelectric discs, FBGs have directional sensitivity [4], which can be advantageously used for damage detection and location.…”

Interrogation of interferometric sensors with a tilted fiber Bragg grating

“…These are the most widely used devices in the field due, mainly, to their versatility (first case) and high sensitivity (second case). Thus, FBGs have been and still are extensively used in civil engineering applications and in the aerospace industry [4], and interferometers are gaining an increasing popularity as hydrophones [5]. So, taking these facts into account, and reckoning the demand for multi-transducer interrogation units, the authors have very recently presented a technique that can be used for recovering the measured information from both FBGs and interferometers.…”