Modeling of the piezoresistive behavior of carbon nanotube/polymer composites during stress relaxation

Abstract

The resistance change of carbon nanotube (CNT)/polymer composites during stress relaxation depended strongly on the CNT concentration and aspect ratio. At low concentration, the resistance of the composites increased regardless of aspect ratio of CNTs as relaxation progressed, while the relaxation modulus accordingly decreased. This trend changed with CNT concentration. To investigate the mechanism, a new resistor model was developed based on the number of contacts between CNTs within tunneling distance of each other. Simulations revealed that when the number of contacts between CNTs is insufficient to form multiple conducting pathways, the increased tunneling resistance has more influence on the overall resistance, leading to the increased resistance. Finally, the proposed resistor model was used to qualitatively explain the resistance change of the composites at different CNT concentration and aspect ratios during tensile test, demonstrating its validity.