Novel Conductive Polymer Composites for Asphalt Pavement Structure in Situ Strain Monitoring: Influence of CB/CNT and GNP/CNT Nano/Micro Hybrid Fillers on Strain Sensing Behavior

Sensing materials and devices with high sensitivity are necessary for engineering structure monitoring with the rapid development of intelligent infrastructure. This paper provides a novel approach to develop strain sensor with high sensitivity for pavement deformation monitoring by epoxying composites with hybrid nano/micro fillers. The effect of combined carbon black/carbon nanotubes (CB/CNT), graphene nanoplatelet/carbon nanotubes (CNT/GNP) fillers on the self-sensing behavior, morphology, dynamic mechanical performance and thermal properties of epoxy composites was discussed in detail. The incorporation of secondary CB results in significant improved self-sensing ability in micro-strain range. CB-CNT hybrid fillers show positive synergy effect on enhancement of piezoresistive response, while GNP show less positive effect on sensing behavior. The presence of CB forms the conductive core domain surrounded by CNT and constructs the multi scale conductive network of composites. The addition of two secondary fillers improves dynamic mechanical performance of composites. The self-sensing behavior of composites with combined filler was illustrated by SEM morphology and conductive pathway evolution during tensile deformation. Laboratory test showed that relative resistance changes have a linear relationship with the strain for developed sensor embedded in asphalt mixture. The polymer composite sensor shows strong sensing ability for asphalt concrete strain monitoring.