In recent years carbon nanotubes (CNTs) have been widely used for the realization of polymeric matrix nanocomposites for strain monitoring applications in civil, biomedical and aerospace engineering. In fact, by embedding CNTs in an insulated polymer matrix, it is possible to realize a conductive nanocomposite with piezoresistive behaviour which allows to monitor the occurring strains through an electrical resistance change. In this work a conductive coating made of Multi-Walled Carbon Nanotubes (MWNTs) and PolymethylMethacrilate (PMMA) is fabricated and is applied onto a fiberglass structure surface. In order to characterize the electrical behaviour of the coating and its capability to sense strain, an experimental campaign is carried out by applying a voltage to the manufactured coating. Its variations throughout the surface in the longitudinal and transverse directions are then evaluated to identify the electric field distribution and its dependence on strain.

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.