Impact localization in composite laminates by minimally intrusive piezoelectric nanostructured sensor

The development of Structural Health Monitoring (SHM) techniques is crucial to expanding the applicability of composite materials, particularly given their susceptibility to impact damage. Among SHM strategies, impact localization using elastic wave propagation plays a central role, yet conventional approaches often rely on embedded sensors that compromise the impact performance of the hosting laminate. In this work, we investigate a recently developed nanostructured sensor embedded in Carbon Fibre Reinforced Polymer (CFRP) plates for impact localization. The sensor, based on poly(vinylidene fluoride–trifluoroethylene) nanofibers, imparts self-sensing capabilities to the laminate while minimizing the detrimental effects of sensor embedment on mechanical properties. An experimental campaign was carried out to enhance the sensor's sensitivity, achieving 2.3 V/kN, while ensuring that the impact resistance of the host laminate remained unaffected. The proposed sensors were embedded in CFRP plates and benchmarked against plates instrumented with commercial lead zirconate titanate (PZT) disks. A data-driven Gaussian Process regression model was employed to determine a probabilistic map estimating impact locations. This approach uses time-of-arrival extracted from acoustic signals via the Akaike Information Criterion. The model achieved a negligible localization error of 2 cm, with the developed sensor performing on par with commercial PZT sensors in accuracy. Crucially, unlike PZT-based systems, the nanostructured sensors preserved the low-velocity impact resistance of the hosting laminate, offering a robust and reliable solution for SHM in composite structures.