Impact analysis of fiber-reinforced composites by means of carbon nanotubes

Carbon nanotubes (CNT) can be profitably embedded into the matrix of composite structure to obtain a distributed sensor able to estimate deformations due to vibrations, impacts or high load applied. In this paper electrical measurements of carbon nanotube multiscale GFRPs have been carried out to monitor low velocity impacts and to estimate the severity of corresponding damages. The work has been developed experimentally, by monitoring the variation of the structure electrical impedance as a consequence of impacts. Electrical measurements show that there is an initial decrease of electrical resistance due to plate compression, followed by an increase due to tunneling effect of carbon nanotubes. Criteria based on the dynamic variation of electrical impedance were proposed and their correlation with the impact energy was studied. Severity of damages has been estimated with different approaches, by measuring the damage extends through the microscope. The analysis shows that CNT can properly describe the dynamics of impact. Synthetic indexes proposed in this work to estimate the severity of damages from CNTs electrical measurements have some limitations and, at now, only partially fit with experimental data.