Perforated piezoresistive film-based flexible bidirectional strain sensors for large bending deformation detection and health monitoring of glass fiber-reinforced polymers

Monitoring the structural health of fiber-reinforced composites under bending loads is crucial for ensuring their long-term performance and reliability in practical applications. Herein, we propose a novel perforated piezoresistive film sensor (PPFS) made of one- and two-dimensional (1D and 2D) hybrid nanomaterials for in-situ monitoring of the bending damage of glass fiber-reinforced polymers (GFRPs). The PPFS is fabricated using a template-sacrificial method combined with mechanical scraping and photolithography. The PPFS exhibits several key advantages. It can detect curvatures over a wide range, from 0 % to 90 %, this is attributed to its elliptical mesh structure, which effectively disperses external stress through geometric deformation. The sensor shows outstanding cyclic stability as it is capable of withstanding over 500 cycles at 70 % curvature while maintaining high sensitivity. This excellent performance is due to the incorporation of MXene nanosheets as spacers, which reduce the aggregation of carbon nanotubes (CNTs), transforming point-to-point contacts into point-to-line contacts and enhancing both the conductivity and stability of film sensors. The elliptical mesh structure design also enables the PPFS to detect bidirectional bending strains as fractures occur at mesh intersections along conductive paths under strain. Embedding the PPFS into composites improves the resin permeability and interfacial adhesion without compromising the mechanical properties of the host material. These findings demonstrate that these PPFSs can be effectively used for non-invasive sensing and hold significant potential for the health monitoring of GFRP structures across a wide range of applications.