Joule Heating of Carbon Fibers and Their Composites in Radio-Frequency Fields

Carbon fibers (CFs) show the ability to generate heat when exposed to radio-frequency (RF) fields, but little is known about the relationship between material properties and heating behavior. The group has previously shown that this heating response can be used for the manufacturing of CF-reinforced composites. Herein, the effect of electrical conductivity on the RF-induced Joule heating patterns of CFs is analyzed. Unidirectional CF tows and their composites show different heating rates when their orientations relative to the RF field are changed due to their anisotropic conductivities. It is observed that the CFs and their composites show higher heating responses when they are placed perpendicular to the RF field lines. Herein, an increase in the heating response with increasing conductivity is observed; however, beyond a certain conductivity value, the heating response decreases because the samples with very high conductivities reflect the RF field. Also, the RF-induced heating of unidirectional CF tows in different orientations is simulated, with qualitative agreement between experimental results and simulations. Herein, the effect of electrical conductivity on field-induced Joule heating of CFs is explained by the findings of this work; these results pave the way for energy-efficient, out-of-oven processing of thermoset composites at an industrial scale.