Multifunctional nanocomposite assessment using carbon nanotube fiber sensors

Abstract

Here, we propose a novel application of carbon nanotube fibers (CNTFs) for the one-step, dual-stage, non-destructive monitoring of multifunctional conductive nanocomposites. Hierarchical nanocomposites were created by embedding CNTFs into carbon nanotube (CNT) - modified matrices during their manufacturing to assess production variables. CNTFs are then left embedded in the structure for monitoring during nanocomposite application. We investigated the dependence of detection sensitivity and reliability on the CNTF diameter (~ 40–700 µm), electrical conductivity (~ 10²-10⁴ S/m), and the choice of measurement technique (2- and 4-point) for single-walled and multiwalled CNT fillers at different concentrations. The sensors showed promising sensitivity to CNT type and concentration, the results were independent of CNTF diameter and contact resistance, and showed low noise. For application monitoring, nanocomposites electrical and mechanical (tensile and cyclic) properties were tested to determine sensitivity to static and dynamic conditions. CNTFs did not cause any reduction in mechanical properties, unlike the losses observed for metallic electrodes (up to 60% reduction in ultimate tensile strength). CNTF-based evaluation of the electrical resistivity (between 10² — 10⁶ Ohm∙cm) and dynamic electrical response (gauge factor between ~ 2 — 12) matched values from a standard electrode material. Microstructural analysis proved that this unique performance was due to the surface and internal volume infiltration of the nanocomposite matrices into the CNTFs, causing interconnection of the CNTs of the matrix and CNTFs. These findings show that CNTFs may be used to accurately monitor nanocomposite multifunctional properties both during manufacturing and application using one-step integration, regardless of the sample size and manufacturing technology.