Strain sensing and progressive failure monitoring of glass-fiber-reinforced composites using percolated carbon nanotube networks

This paper presents a study on incorporation of carbon nanotubes (CNTs) in fiber-reinforced plastics for real-time structural health monitoring. CNTs dispersed in a solvent were uniformly spray-coated on the surfaces of glass fiber fabrics, which were then layed-up and impregnated with an unsaturated polyester resin using vacuum-assisted resin transfer molding to form composite samples. Prior to resin infusion, electrodes were embedded on the periphery as well as between the plies for electrical resistance monitoring. The composite sample was subjected to three-point bending, during which the changes in resistances between various electrode pairs were measured and recorded. Experimental results revealed the dependence of resistance change on the loading conditions, amount of CNTs coated, measured directions, and presence of structural failure. In particular, the percolated CNT networks enabled real-time identification of various failure modes, including delamination, fiber breakage, and in-plane compression. The proof-of-concept was demonstrated by fabricating and testing with a scaled-down wind turbine blade.