A high-sensitivity and fast-response nanocomposites-inspired sensor for acousto-ultrasonics-based structural health monitoring

Promoted by an innovative sensing mechanism, a flexible carbon nanocomposite hybrid sensor made of graphene and polyvinylidene fluoride (PVDF) has been developed. In virtue of the tunneling effect in the conductive network formed in the nanocomposites, the sensor can be used to perceive acoustoultrasonic wave signals with ultralow magnitudes in a broad frequency range. To advance the insight into the sensing mechanism, both the scanning electron microscopy (SEM) and X-Ray diffraction (XRD) are employed to explore the dispersion of nanofillers and the crystal characteristic of the sensor, respectively. The sensing ability of the developed sensor is testified through the acquisition of strain signals from low frequency cyclic tensile loading to high frequency ultrasonic guided waves. Based on excellent mechanical and electrical properties of graphene, the sensor, fabricated with a solution film-forming method, can reach a high gauge factor of 60, responsive to ultrasonic signals up to 300 kHz. Being light weight and chemically stable, the developed sensor can be coated onto or embedded into engineering assets with minute weight penalty and favorable environmental adaptation. The simplified fabrication process can significantly reduce the sensing cost while maintaining high sensing efficiency, benefiting ultrasonic-wave-based structure health monitoring.