(507b) Recycling of Continuous Carbon Fibers from Thermoset Composites Using Joule Heating

In this study, we demonstrate a new methodology for recycling continuous carbon fibers from end-of-life thermoset composite parts using Joule heating. This study addresses the challenge of efficiently recovering carbon fibers from composite scrap, and reusing them to make fresh composites. The conductive carbon fibers heat up when an electric current is passed through them; this allows for volumetric heating of the composite up to the degradation temperature of the matrix. Fibers can be easily separated from the degraded matrix post the direct current (DC) heating process. Fibers reclaimed using this method were characterized to determine their tensile properties and surface chemistry, and compared against as-received fibers. The DC recycled fibers yielded similar elastic modulus values when compared against as-received fibers; however, we observe a ~10-15% drop in the tensile strength of recycled fibers. Surface characterization showed that DC recycled fibers and as-received fibers had similar types of functional groups, which are necessary to form covalent bonds between fibers and matrix in a composite. To demonstrate the reusability of recycled fibers, composites are fabricated by impregnating them with epoxy resin and curing using a heat press. The mechanical properties of these recycled carbon fiber composites (rCFRCs) were compared against composites made using as-received fibers; a drop of ~20% was observed in both elastic modulus and tensile strength values of rCFRCs. This study establishes DC Heating as a promising procedure for recycling carbon fibers, with potential scale-up from lab to industry.