Abstract:

In order to develop carbon nanoyarn sensors used in three-dimensional braided composites in-situ structural health monitoring, a carbon nanoyarn strain sensing experiment system was established. By the longitudinal tensile experiment, the correlation between the mechanical properties (stress and strain) and the electrical properties (initial resistance and strain sensitivity coefficient) of carbon nanoyarns was investigated, and Weibull statistical analysis on performance parameters was conducted. The strain sensing characteristics of carbon nanoyarns were systematically studied.The results show that the relative resistance variation and the strain of carbon nanoyarns under longitudinal tensile load have a good linear correlation. Besides, carbon nanoyarns provide a strain sensitivity coefficient equivalent to conventional strain monitoring, which is very suitable for monitoring composites whose failure strain limit is far less than the strain of carbon nanoyarns(carbon nanoyarns damage strain mean of 10% and the minimum value of 2.5%). Therefore, carbon nanoyarns become a good candidate material of sensors for composite structural health monitoring.

Key words: structural health monitoring, carbon nanoyarn sensor, three-dimensional braided composite, linear correlation, strain sensitivity coefficiency