Improving resistance-strain effects of conductive polymer composites modified by multiscale fillers: Short carbon fiber and carbon nanotube

Conductive polymer composites (CPCs) have attracted much attention in strain sensing applications due to their excellent conductivities and high sensitivities. However, research on simultaneous modification of CPCs with multiple conductive fillers is lacking. This study aims to systematically investigate the electrical conductivities and strain-sensing properties of two filler-modified epoxy resin (EP) composites with different scale additives-short carbon fibers (SCFs) and carbon nanotubes (CNTs)-obtained by mixing and curing to obtain the samples. Both the SCF/EP and SCF/CNT/EP composite resistivities decreased with increasing filler content, and 1.35 wt% was the percolation threshold for SCF/EP composites; during monotonic tensile loading, the resistance change ratio (Delta R/R0) of the CPCs increased with increasing strain, and the sensitivities decreased with increasing conductive filler content. The CPCs containing SCFs and CNTs exhibited stable and repeatable resistance responses during cyclic tensile loading, among which the SCF/CNT_1.5/0.3 composite was the most suitable for use as a sensing material with a sensitivity of 0.149. According to the conductivity and resistance-strain response mechanism analysis, the CNTs supplementing and refining the CPC conductive network composed of SCFs were considered the main reason for the resistance response linearization and excellent dynamic response repeatability. CPCs can be widely used in strain sensing and damage monitoring.Highlights Provided a strategy for multiscale conductive filler-modified epoxy resins. Realized monotonicity of resistance-strain response by adding multiscale conductive fillers. Explored resistance-strain effect under dynamic cycling loading. Identified optimal materials for damage detection. Analyzed the resistance-strain response mechanism of single and multiscale conductive filler-modified CPCs. Preparation process, resistance-strain responses and schematic illustration of conductive networks of CPCs. image