Advancement of long-gauge carbon fiber line sensors for strain measurements in structures

This article proposes a new technique that advances long-gauge carbon fiber line sensor technology, with and without post-tensioning of the sensor, to measure changes in strain levels in structural areas. Carbon fiber line sensors were fabricated to produce a slim high-strength sensor with a diameter of less than 1.4 mm using a carbon fiber tow with a width of 6 mm. A theoretical analysis of these sensors as well as several series of experiments was conducted to investigate the effect of fiber arrangement on the error compensation of the carbon fiber line sensors. The results revealed that using two sets of carbon fiber line sensors, one as an active sensor and the other to compensate the errors of the first, is an effective method when both sensors have a convergent fiber arrangement and change in resistance. A post-tensioning method was implemented to enhance the overall behavior of the sensor. The results showed that the post-tensioning method yields significant improvement in the linearity and cyclic ability up to 6000 microstrains and reduces the fluctuation errors in the change in resistance from ±0.031% to ±0.007%. Finally, the possibility of repairing damaged carbon fiber line sensors is also discussed.