Baseline-free delamination detection in CFRP composites using guided wave-based virtual sensing paths

In this study, a novel baseline-free damage localization method, multipath reflected wave reconstruction algorithm for probabilistic inspection of damage (MRW-RAPID), is proposed for detecting delamination in carbon fiber-reinforced polymer (CFRP) composites. Virtual sensors, created by mirroring actuator-receiver positions at panel boundaries, generate virtual sensing paths that incorporate boundary-reflected guided waves into the damage localization process. These virtual paths simulate boundary reflection effects without requiring actual wave measurements along those paths. By combining these virtual sensing paths with direct sensing paths, the proposed MRW-RAPID significantly improves damage localization performance without requiring the baseline. Additionally, a multipath baseline-free damage index calculation method is developed based on the reciprocity principle and ray tracing theory, and it is integrated into the MRW-RAPID by fusing the damage indices of multipath for the detection and localization of composite delamination damage. Experimental validation on composite laminates demonstrates the MRW-RAPID's effectiveness, with accurate and reliable baseline-free damage localization achieved using only four sensors. These advancements establish a practical, scalable approach for structural health monitoring and enhance the state-of-the-art in baseline-free delamination detection.