Mechanical recycling of CFRP Composites—Part I: Characterizing carbon fiber and cured epoxy as dispersed phases

This study investigates carbon-fiber fabric and cured epoxy as separate fractions to establish a baseline for the mechanical valorization of carbon fiber-reinforced polymers (CFRP). Unrecycled components were used to isolate the effects of identity, geometry, processing, and reinforcement content without the variability of CFRP recyclates. Millimeter-scale fabric fragments and cured-epoxy chips from face and peripheral milling were added to an epoxy matrix at 1–5 wt%. High-energy ball milling (HEBM) was also used to produce CF–HEBM, EL–HEBM, and ES–HEBM, added at 3–10 wt%. Morphology and mechanical response were evaluated using optical microscopy, SEM–EDS, tensile, flexural, and Izod impact tests. No single fraction improved all properties. Short carbon fragments at 1–3 wt% yielded the highest mean Izod impact strength (∼33–34% above neat epoxy), though this difference was not significant after Holm–Bonferroni correction, and tensile strength was lowered. Epoxy-derived chips acted mainly as fillers, maintaining baseline tensile strength at 5 wt% without flexural or impact gains. HEBM had the strongest impact on carbon fibers: CF–HEBM-3 reached 42.22 MPa tensile strength (neat: 30.31 MPa), and CF–HEBM-10 reached 96.60 MPa flexural strength (neat: 64.58 MPa). Microstructural analysis showed that ball milling reduced fibers into particulate matter, whereas epoxy retained angular, plate-like fragments, with minor Fe and Cr contamination detected by SEM–EDS.