Aligned carbon nanotube-based sensors for strain monitoring of composites

Abstract

This paper presents a proof of concept of an aligned carbon nanotube (CNT) based strain sensor tested on the surface of a conventional aeronautic laminate. Two type of strain sensors were produced, type S and type T, in which the CNT alignment was parallel (Y) and transversal (X) to strain direction, respectively. Their electrical resistance response was thoroughly evaluated during cyclic tensile tests. Despite some disparities of the relative electrical resistance behavior in specific strain cycles, probably due to one-off interferences in the CNT conductive mechanism, the obtained gauge factor (GF) values were quite stable. Also, the electrical resistance anisotropy was evaluated and its opposite behavior when the samples were strained in Y- and X-directions may be used as strain direction indicator. Being able to quantify and indicate strain direction with just one 10 x 10 mm CNT patch, this sensor has proven to be suitable for strain sensing applications, namely for structure health monitoring of advanced composites.