Comparative analysis of carbon fiber reinforced composites: evaluating recycled carbon fibers as substitutes for commercial grades

The objective of this study was to evaluate the applicability of recycled carbon fibers (rCFs) as substitutes for commercial carbon fibers (cCFs). To this end, recycled carbon fiber reinforced thermoplastic (rCFRTP) composites were fabricated using chopped (6 mm) rCFs recovered through three different recycling methods: mechanical shredding, pyrolysis, and chemical dissolution. The surface characteristics of the recycled and commercial fibers were analyzed using field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). Mechanical properties were evaluated through tensile and flexural strength tests, and thermal conductivity was measured using a transient plane source method. As a result, the rCF/PA66 composites exhibited over 80 % of the physical properties of the cCF/PA66 composites. Among them, the C-rCF/PA66 composite showed the most comparable performance to the cCF-based composite, which is attributed to the high interfacial compatibility between the PA6-based sizing on the recycled fibers and the PA66 matrix. These results show that rCFs can effectively replace cCFs in non-structural parts requiring lightweight, impact resistance, and recyclability, and that matrix-specific tailored sizing is expected to further enhance the performance and applicability of rCFs.