Health monitoring for composite materials with high linear and sensitivity GnPs/epoxy flexible strain sensors

The graphene platelets (GnPs)/epoxy flexible sensor with high sensitivity and linear can be used to monitor the deformation and damage in structural composites. The dispersion of GnPs in an epoxy matrix was better improved by optimizing ultrasonic time and using the ball mill mixing process. The GnPs/epoxy mixture exhibited relatively low percolation threshold of 0.76 vol.% and its analysis model was analyzed. In this paper, GnPs/epoxy mixture with GnPs loading of 1.00 vol.% was selected as damage detecting and strain sensor, and the characteristics of sensor was demonstrated via various mechanical tests. The monotonic tensile results suggested that there are two different linear change sensing stages, (0–5000^με) and (5000–16700^με), and it exhibits relatively high gauge factor (GF) of 6.5 and 11.6 in different sensing stages. The linear relationship and sensitivity were recoverable and stable upon loading and unloading tensile test. And the gauge factors upon loading and unloading test agree with the GF in monotonic tensile test. The GnPs/epoxy flexible sensor show promising applications for the damage monitoring of structural composite in the field of aerospace.