Coupled carbon nanotube network and acoustic emission monitoring for sensing of damage development in composites

Material and structural reliability is crucial for the potential use of composite materials in a variety of structural applications. As a result, damage detection and health monitoring of fiber-reinforced composites are attracting progressively more attention in the field of materials research. In this work, small amounts of carbon nanotubes are added into traditional fiber composites to form electrically conductive networks throughout the polymer matrix. The electrical response of the carbon nanotube network to accumulated damage combined with the acoustic emission (AE) technique is utilized to sense damage initiation and evolution in laminated composites. The parameters which correspond to the resistance change of the specimen due to damage in quasi-static and cyclic tests are used to evaluate the damage state in the material. There exists a bi-linear relationship between the resistance change and AE signal cumulative counts which gives insight toward the damage state of the material during quasi-static and cyclic tests.