Exploring nanoscale organic piezoelectric coatings for in -situ non destructive structural health monitoring of carbon fibre reinforced composites

This study develops the integration of piezoelectric sensors into carbon fibre reinforced polymers (CFRPs) for non-destructive health monitoring. A uniform, continuous coating of Poly(vinylidene fluoride) (PVDF) nanofibres was applied directly onto the surface of carbon fibres (CF) via electrospinning, creating fully embedded, flexible, and lightweight piezoelectric sensors. Careful optimisation of the crystalline structure of PVDF leads to high piezoelectric performance for sensing with a β-phase content of 84.1 ± 0.5% and a piezoelectric coefficient d₃₃ of 5.42 ± 2.3 pC/N, representing the highest piezoelectric performance for sensing displaying 90 times more sensitivity than the previous state-of-the-art of voltage response for organic sensors. Single-step production via the electrospinning process ensures strong adhesion and conformal coverage of the CF without the need for post-processing allowing direct integration into CF for ease of optimisation of sensor fabrication. While a reliable and repeatable data acquisition system was established to characterise the sensor performance under mechanical loading. The piezoelectric coating studied reacts to dynamic mechanical stimuli, producing pulsed signals. Although this limits direct measurement of static forces, the impulsive responses reliably indicate dynamic mechanical events and relative force magnitudes. Finally, the PVDF-based sensors were successfully embedded within CFRP laminates and subjected to mechanical testing for up to three months. This work introduces an optimised integration strategy for real-time structural health monitoring (SHM) applications. These advances represent a new benchmark for real-time, non-destructive SHM of advanced composites.