Multi-mode real-time strain monitoring in composites using low vacuum carbon fibers as a strain sensor under different loading conditions

Abstract

Structural health monitoring is a vastly growing field consisting of sensors embedded in or attached with the structure which respond to the strain or other stimuli to monitor the deformation in real-time. In this study, a multi-mode strain detection is carried out in composites using nanomaterial-based sensor technology. A Carbon fiber (CF) sensor was developed using unidirectional carbon filaments aligned straightly together and its sensitivity was calculated experimentally, with gauge factor (GF) in 10.2–10.8 range. Then, this CF sensor is embedded gradually at different directions i.e. 0°, +45°, 90°, −45° between the plies of composite for real-time/in-situ strain monitoring. The composite specimen was then cut in star profile, each leg demonstrating the direction of the CF sensors. These composite samples are then tested under tensile and flexural cyclic loading. There is a good reproducibility in the results and the mechanical response of composite correlated perfectly with the electrical resistance of the CF sensor. It can also be noted that the sensors, depending on their respective position, manage to faithfully reproduce the mechanical behavior of the specimen tested (traction/compression). The results established that the CF exhibited good potential as flexible reinforcement for in-situ monitoring of composites and can provide detection over large sections and unapproachable locations. This study also showed that direction and position of the sensor plays a vital role in the detection, identification (whether its tensile or compressive) and quantification of the deformation experienced by the structure under different loading conditions.