Structural health monitoring of stitch repaired composite structure with Buckypaper sensors and MXene sensors

With the increasing application of composite materials in the industry, the repair of damaged composite materials has gradually become a research focus. In this article, the traditional scarf repairing laminate was stitched with carbon fiber line to check the influence of stitch on repair efficiency. The traditional Buckypaper sensors and the novel MXene sensors were used to conduct real-time structural health monitoring of the specimen, and the results were compared with X-ray monitoring. The experimental results show that the breaking strength of the stitch repaired specimen is 21.2% higher than that of the traditional scarf repaired specimen. Both kinds of sensors can monitor the load of the specimen in real-time. As the force is transferred, the resistance change rate ( increment R/R0$$ \Delta \mathrm{R}/{R}_0 $$) of the Buckypaper sensors varies by up to 0.045, while the increment R/R0$$ \Delta \mathrm{R}/{R}_0 $$ of the MXene sensors varies by up to 0.7. The resistance change of the sensors can also reflect the initiation of damage. The sudden change in increment R/R0$$ \Delta \mathrm{R}/{R}_0 $$ of 0.01 can be monitored on the specimen in the crack initiation stage. Through the X-ray nondestructive testing method, it can be confirmed that both kinds of sensors are suitable for structural health monitoring, and the sensitivity of the MXene sensors is much higher.