Strain-Dependent Electrical Resistance Response to Fibre Fragmentation in Thin-Ply Carbon/Glass Hybrids for Structural Health Monitoring

Thin-ply carbon/glass hybrid composites exhibit sharply amplified and simultaneously continuous, strain-dependent electrical resistance increases exceeding 40,000% upon carbon fibre fragmentation under tensile loading. Resistance remains stable during elastic deformation up to fibre failure strain, rising significantly only as fragmentation initiates. Through in situ electrical and visual monitoring, a direct correlation between fibre fragmentation and resistance response has been clearly demonstrated for the first time. Cyclic loading produces pronounced hysteresis and a persistent memory effect in the resistance–strain loops, reflecting cumulative damage detected by the piezoresistive response. Contrary to the assumption of total conduction loss after fibre fracture, fragmented fibres maintain partial conductivity via residual fibre-to-fibre contacts, even after extensive ply-level cracking. These contacts drive resistance changes during unloading and reloading and the resistance relaxation post-unloading. Combining quantitative electrical sensing with visual indicators enables earlier and more sensitive detection of progressive damage than conventional carbon fibre reinforced polymer (CFRP) composites. These findings introduce a novel, strain-dependent multifunctional self-sensing material that can be used for structural health monitoring (SHM) for real-time overload and damage tracking in high-value advanced composite structures.