Multifunctional MXene/carbon nanotubes coated glass fiber sensors for in-situ monitoring of curing process and structural health of polymeric composites

Monitoring the structural health of fiber-reinforced composites from fabrication to in-service is important. Herein, two types of glass fibers (GF) coated with hybrids carbon nanotubes (CNTs) and Ti₃C₂T_X (MXene) were developed for life-long structural health monitoring. Two conductive layers consisting of CNTs and MXene laminated structure (LS) and randomly mixed structure (MS) were constructed on the single glass fiber surface by electrophoretic deposition (EPD). Compared to pristine GF, LS and MS improved the tensile strength of single fibers by 20.2% and 25.4% for GF with LS (GFL) and GF with MS (GFM), respectively. They also enhanced the interfacial shear strength of the GFL-based and GFM-based composites by 10.11% and 34.22%, respectively. This enhancement was attributed to multiple interactions between CNTs and MXene, such as the mechanical interlocking effect and chemical bonds. Additionally, they could detect the in-situ curing information of the resin, effectively capturing the resin phase change, enabling the monitoring of resin flow, and detection of dry spots. The porous mixed CNTs/MXene layer, which had more voids for resin infiltration, resulted in a superior peak of ΔR/R₀ change (1000%) for MS. Furthermore, both conductive layers could monitor the damage and warn of failure, accurately reflecting the details and crack growth under tensile action. The continuous laminated MXene nanosheets in LS enabled GFL to exhibit excellent cyclic stability and high sensitivity to tensile strain. In sum, by rationally designing the conductive structures, the unique requirements of the sensing fibers for life-long structural health monitoring at different stages were satisfied.