Integration of carbon nanotube yarns into glass‐fiber reinforced composites for electrical self‐sensing of damage under cyclic bending and impact loading

Abstract Continuously long carbon nanotube yarns (CNTYs) were integrated into glass fiber weave/vinyl ester composites to act as electrical sensing elements to self‐monitoring damage. A grid comprising one longitudinal and three transverse CNTYs, running through the 125 mm long flexural specimen, was integrated into the top and bottom layers of glass fiber weaves to allow monitoring of the electrical resistance and locate damage. Four‐point bending specimens were tested under cyclic flexural loading, alternating with low‐velocity impacts to monitor damage initiation and progression. The electrical response of the CNTY grid is able to pinpoint the region where damage initiates, accumulates, and propagates under cycling loading, triggered or not by impact. The damage location identified by the electrical response of CNTYs is supported by in situ in‐plane and through‐thickness strain fields measured by digital image correlation (DIC). The correlation between the electrical technique and the DIC‐measured strain fields indicate that the majority of damage occurs through interlaminar stresses at or near the supports and/or loading introduction elements of the flexural test rig. Integrating CNTYs into structural composites enables online damage monitoring, leading to intelligent condition‐based maintenance for naval ships, aircrafts, and other structures, ultimately extending service life and reducing costs. Highlights CNTYs were integrated into composites for damage self‐sensing. Electrical response of CNTYs pinpoints the region of damage. Damage caused by cyclic bending and low velocity impacts were identified. Electrically identified damage is supported by DIC.