Nano-engineered Functional Composites with Self-sensing Capability for Ultrasonics-based Structural Health Monitoring

Abstract

The emerging nanotechnology has ushered a new avenue to tailor conventional composite materials. In this study, a new kind of nano-engineered composite material has been developed with a self-sensing capability for guided ultrasonic waves (GUWs)- based structural health monitoring (SHM). In the composites, a graphene-based selfsensing network is designed, developed and “dispersed” in the epoxy matrix of conventional glass fibre-reinforced composites. The nano-structure of the graphene conductive network is optimized, via which the quantum tunnelling effect formed in the network is linked to material elastic deformation when GUWs traverse the composites, via measuring the changes in the conductivity of the dispersed network. Measurement can be implemented at any position of the composites, owing to the “dispersed” sensing capability of the composites, and this renders a possibility to monitor GUW propagation throughout the entire composite structures at any desired position of the structures, while without a need to use any additional sensor externally attached to or internally embedded in the composites. Experimental validation is conducted, in which GUWs that are self-sensed by the composites are compared with the counterpart signals obtained by conventional sensors (piezoelectric wafers), to observe that the developed composites can be responsive to GUWs with frequencies in an ultrasonic regime up to several hundreds of kilohertz, with no prominent discrepancy compared with conventional piezoelectric wafers. This study has spotlighted a new breed of composites with a capacity of self-sensing and self-diagnosis towards online health monitoring of composite materials and structures