Multifunctional Carbon Fiber Sensors: The Effect of Anisotropic Electrical Conductivity

The multifunctional application of carbon fiber reinforced polymer composites (CFRP) can be affected by the anisotropic electrical conductivity of the carbon fiber because it differs in the longitudinal and the transverse direction of the fiber. In our article, we measured the transverse resistivity of the reinforcing carbon fiber bundle in different conditions: when the fibers were dry, when they were impregnated with non-crosslinked resin, and in a crosslinked matrix. We have shown that in the case of dry and impregnated fibers, a compressive force acting on the fiber bundle has a significant effect on the transverse resistance, while when crosslinked, this effect is negligible. We developed a finite element model (FEM) to investigate the area around the electrodes and the current distribution in the fiber bundles. We have shown that due to the pressure dependence of the transverse resistance and the significant difference in length and transverse conductivity, the current density distribution in the cross-section around the current electrode will not be homogeneous, leading to inaccuracies in sensory applications. We have shown by finite element simulation that the current electrode and voltage measurement electrode can be optimized, which was verified experimentally.