Electromechanical characterization of an innovative painted carbon nanotube strain sensor under dynamic loading

Piezoresistive strain sensors can be manufactured by embedding carbon nanotubes (CNTs) in an insulating polymer matrix, by taking advantage of CNTs superior electromechanical properties. In particular, the electromechanical properties find their roots in the conductive network formed by the randomly dispersed CNTs, through which the current can flow. When a mechanical strain occurs the conductive network configuration varies, changing the overall material conductivity. In this study this concept is being exploited to form a CNTs-based functional paint that allows to monitor ultra-large structural areas, in multiple directions, with an easy to assemble and processing approach. In particular, CNTs are dispersed in a PolymethylMethacrylate (PMMA) matrix following a carefully designed process to achieve a proper viscosity for direct painting onto a large in scale structure. Electromechanical tests are performed to characterize the piezoresistive behaviour of the coating in static and dynamic loading conditions. The results showed the great sensitivity of the coating to strain. The proposed approach to directly paint a sensitive coating onto the structure to be monitored has the advantages of: ultra-low weight, direct contact with the structure to be monitored and an extremely simple installation procedure.