Experimental characterization and modeling of carbon nanotubes modified epoxy mixture: Electrical and mechanical performance

Carbon nanotubes (CNTs) modified epoxy mixture (CEMix) holds the potential to serve as piezoresistive materials for traffic load sensing, thereby contributing to the digitalization of road systems. This study aims to investigate the electrical (conductive and piezoresistive) and mechanical performance of CEMix from both experimental and modeling perspectives. A three-step micromechanics model was developed to describe the conductivity and piezoresistivity of CEMix, which was validated against experimental values obtained from compression tests at 0.7 MPa and 1.0 MPa. The stress compatibility of CEMix with the asphalt surface layer was evaluated using finite element modeling (FEM). Experimental results reveal that the gauge factor (GF) of CEMix exceeds 140 at CNTs volume fractions of 0.16 % and 0.26 %, while the modeled results present a relative error below 20.6 %. At a CNTs volume fraction of 0.21 %, the experimental GF surpasses 430; however, the model error increases to 44 %. The modeled conductivity of CEMix shows a relative error ranging from −0.8 % to 36.4 %. Moreover, CNTs significantly enhance the modulus of the epoxy mixture in the low-frequency (high-temperature) domain. The maximum tensile and shear stresses induced in the asphalt surface layer by embedded sensors made of CEMix are 7 % and 40 % higher compared to pavements without sensors, as determined by FEM. This study is anticipated to provide valuable insights for the design of piezoresistive materials intended for sensitive surface layers in the digital twin of road system. • Characterization and modeling of carbon nanotubes-modified epoxy mixture with high load-sensing capacity. • Establishment of a three-step micromechanics model of conductivity and piezoresistivity. • Evaluation of stress compatibility with asphalt surface layer.