Lightweight and hard carbon fiber composite materials are important structural materials for automobiles, airplanes, and other transportation vehicles. However, damage in carbon fiber composite structures can be hidden beneath the surface and cannot be detected by visual inspection, which may lead to catastrophic accidents.

ORNL researchers Bowland and Amit Naskar have invented a roll to roll process that utilizes semiconductor silicon carbide nanoparticles to coat conductive carbon fibers. This composite material embedded with nanomaterials is more powerful than other fiber-reinforced composite materials and has a new ability to monitor the health of its own structure.

When enough coated fibers are embedded in the polymer, the fibers form an electrical network, and the composite material becomes an electrical conductor. Semiconductor nanoparticles disrupt this conductivity under applied external forces, adding electromechanical functionality to the composite material.

If the composite material undergoes deformation, the connectivity of the coated fibers is disrupted, and the resistance in the material changes, establishing a functional relationship between resistance and stress. If the turbulence of a storm causes the wings of a composite aircraft to bend, an electrical signal will alert the aircraft's computer that the wings have been subjected to excessive pressure and prompt for inspection.

The roll to roll process of ORNL has theoretically proven that this method can be used for the large-scale production of coated fibers in next-generation composite materials. Researchers have manufactured carbon fiber reinforced composite suspension beams for this purpose, with fibers aligned in one direction. Researchers attached electrodes on both sides of the cantilever for pressure testing.