Monotonic strain sensing behavior of self-assembled carbon nanotubes/graphene silicone rubber composites under cyclic loading

Conductive polymer composites can detect strain and pressure when subjected to large deformations. However, the complex strain sensing behaviors of the composites, such as the non-monotonic resistance response during cyclic loading, limit their further application. In this paper, the strain sensing behaviors have been optimally regulated through the synergistic effect and self-assembly of carbon nanotubes (CNTs) and graphene (GR) in silicone rubber (VMQ) composites. We found that the self-assembled CNTs-GR/VMQ composites have an incredibly low percolation threshold of 0.92 wt%, which is 53% lower than that of the CNTs/VMQ composites. Additionally, the resistance response of CNTs/VMQ and CNTs-GR/VMQ composites showed a significant downward drift and shoulder peak phenomenon, whereas the self-assembled CNTs-GR/VMQ composites exhibited a monotonic and more stable resistance response. Based on the morphology results of transmission electron microscopy and theoretical analysis, the uniform distribution of nanoparticles and the bridging structure formed by CNTs and GR are considered as the main reasons for the lower percolation threshold and the better resistance response.