Fabrication and analysis of graphene nanoplatelet-doped strain sensors in two distinct matrix systems

This study investigates piezoresistive strain sensors based on graphene nanoplatelets (GNP) incorporated into SX10 EVO epoxy and Elium® matrices at loadings contained in range 1–35 wt%. Electrical characterization revealed a lower percolation threshold and up to three folds higher conductivity in the Elium® system, compared with GNP/epoxy composites. The highest strain sensitivity was observed near the percolation threshold, where tunneling-dominated conduction governs the electromechanical response. In particular, the 2 wt% GNP/Elium® composite exhibited the best sensing performance, with gauge factors of 40 (up to 0.6% strain) and 54 (up to 1.0% strain). Increasing GNP content improved conductivity however, the sensitivity was reduced due to the transition toward overlap-dominated conduction. Cyclic loading tests (1000 cycles at 0.5% strain) confirmed stable and repeatable electromechanical behavior, and temperature and humidity cross-sensitivity were also evaluated. Overall, GNP/Elium® nanocomposites demonstrated superior sensitivity, conductivity, and durability, highlighting their strong potential for structural health monitoring applications.