Embedded Piezoresistive Sensor Network for Multi-Failure Mode Monitoring in CFRP Bolted Joints

Carbon fiber-reinforced polymer (CFRP) bolted joint structures are susceptible to multiple failure modes during service, including net-tension, shear-out, and bearing failures, which present risks to structural integrity and operational performance. While piezoresistive sensing technology has the potential for monitoring CFRP structures, existing approaches still need to be improved in their ability to detect these diverse failure modes simultaneously. This study introduces an embedded piezoresistive sensor network based on carbon nanotube/graphene nanoplatelet (CNT/GNP) nanocomposites for the in situ monitoring of multiple failure modes within CFRP bolted joints. The proposed sensor network integrates CNT and GNP fillers into a polyvinylpyrrolidone (PVP) matrix, utilizing sodium dodecylbenzene sulfonate (SDBS) as a dispersant. The experimental results for the embedded integration method indicated that the proposed nanocomposite piezoresistive sensor network effectively detected the initiation and propagation of bearing, net-tension, and shear-out failures within CFRP bolted joints. In addition, the embedded integration demonstrated reliability and a significant increase in monitoring sensitivity compared to surface integration methods. This research advances the methodology for real-time structural health monitoring (SHM) of composite materials by proposing a methodology with potential applications improving the safety and maintenance strategies of high-performance engineering systems.