Ultrasensitive embedded sensor for composite joints based on a highly aligned carbon nanotube web

Abstract

Herein, we present a novel approach for damage sensing in adhesively bonded joints using a carbon nanotube single layer web (CNT-SLW) which marks a significant departure from the approach of dispersing CNTs within epoxy resins. In this work, a very thin, highly aligned CNT-SLW (densified thickness ~ 50 nm) with aerial density of 2.0 µg/cm 2 was horizontally drawn from a vertically aligned CNT forest, positioned over an adhesive film, which was, in turn, placed between two non-conductive composite adherents. This was followed by the application of heat and pressure to cure the adhesive. These joints were subjected to quasi-static and cyclic loading to investigate the damage sensing performance of a CNT-SLW. The CNT-SLW sensor, placed parallel to the load direction, exhibits remarkably high cyclic stability as well as exceptionally high sensitivity to damage initiation and accumulation. The resistance increase (∆R/R o % ∼1633%) is significantly higher than that of adhesive sensors with dispersed CNTs/graphene, reported in the literature. Morphological studies help to explain the sensing mechanism through interactions of the CNT-SLW with the evolution of micro-cracks. These results demonstrate the potential of

Mechanical and Strain-Sensing Capabilities of Carbon Nanotube Reinforced Composites by Digital Light Processing 3D Printing Technology

“…This is explained by the intrinsic piezoresistivity of CNTs [13,14], the contact conductive mechanism between CNTs and the tunneling effect that takes place between adjacent nanotubes. The combination of these factors leads to an enhanced strain sensitivity, much higher than those achieved for conventional metallic gauges [15][16][17][18][19].There are several studies of materials manufactured by 3D printing with CNTs as conductive fillers. Some specific examples are described below.…”

Electrical Monitoring as a Novel Route to Understanding the Aging Mechanisms of Carbon Nanotube-Doped Adhesive Film Joints

“…Their exceptional properties [5][6][7] and the enhancement of the electrical conductivity that they induce when added to an insulator resin [8][9][10][11] makes them very useful for multifunctional applications [12,13]. In fact, their use in structural health monitoring (SHM) applications is now of interest because of their piezoresistive and tunneling properties that lead to high sensitivities [14][15][16][17].…”

Mechanical and Crack-Sensing Capabilities of Mode-I Joints with Carbon-Nanotube-Reinforced Adhesive Films under Hydrothermal Aging Conditions

“…For example, the creation of percolating networks allows their use in structural health monitoring (SHM) applications by means of electrical conductivity measurements [ 9 , 10 ]. Their use is based on the fact that the electrical resistance between adjacent nanoparticles, which is called the tunneling resistance, increases in a linear exponential way with the interparticle distance [ 11 , 12 ], making these CNT nanocomposites very sensitive to the applied strain [ 13 , 14 , 15 , 16 ]. In addition, these materials have also demonstrated very good capabilities for determining damage, as the presence of cracks induces the breakage of electrical pathways inside the network, causing a related increase of the electrical resistivity [ 17 , 18 ].…”