Self-sensing of Viscoelastic Phenomena in Multiscale Composites by Using the Electrical Resistance Approach

Abstract

The potential use of multiscale carbon nanostructures to sense viscoelastic phenomena in polymer composites using the electrical resistance method is explored, including glass fibers modified with multiwall carbon nanotubes (MWCNTs) and carbon nanotube yarns embedded in a vinyl ester matrix. Conventional carbon fibers are used as reference material. The intended application demands detailed knowledge of the electrical behavior of the investigated fibers. To this aim, DC current-voltage measurements of individual glass fibers covered with MWCNTs, carbon nanotube yarns, and conventional carbon fibers were conducted. The MWCNTs are deposited on glass fibers following an electrophoretic method assisted by ultrasonic MWCNT dispersion in distilled water, and a parametric analysis of the main factors affecting such electrophoretic deposition is carried out. The electrical resistance of 20 mm long- CNT-modified glass fiber tows is between 42-200 kΩ/cm, and the best conditions were achieved with a deposition time of 30 min and an electric field intensity of 4.5 kV/m. Overall, current-voltage measurements of MWCNT-modified glass fibers, carbon nanotube yarns and carbon fibers shows a rather Ohmic behavior in a range of 0.1-2.5 μA, but the measurements present local variations from linearity. These local variations from linearity are larger for carbon nanotube yarns (up to 90 %) and MWCNT-modified glass fibers (52 %). Preliminary tests of relaxation-induced piezoresistivity of monofilament composites showed that the electrical resistance of carbon fiber/vinyl ester specimens increases with elapsed time, while it decreases with time for carbon nanotube yarn/vinyl ester composites.