Cyclic loading behaviour and crack monitoring potential of graphene nanoplatelet (GNP) based strain sensors in simple structures

Graphene Nanoplatelet (GNP)/poly methylmethacrylate (PMMA) based strain sensors were prepared via solution casting process at different initial resistances. The real time strain monitoring capability under various loading conditions (ramp, step and cyclic) and stability of the sensor was explored. The effectiveness of the sensor for crack monitoring in a simple structure was also studied and compared with a standard strain gauge. Experimental results showed a linear change in resistance with the strain in all loading conditions. In cyclic loading at a frequency of 5 Hz, high sensitivity sensors exhibited a considerable amount of time lag for steady response with the strain which was observed to be absent at 0.1 Hz. A significant amount of unrecoverable change in the resistance was observed in the sensors even after unloading, because of which the effective gauge factor of the sensor was reduced. The magnitude of this unrecoverable change in resistance was found to decrease with decrease in the gauge factor and frequency of cyclic loading. However, the GNP/PMMA sensor had shown a greater sensitivity in monitoring a crack in a cantilever beam over a conventional strain gauge.