A Proof‐of‐Concept Study on Sustainably Upcycled Chicken Feather Fibers as Interfacial Modifiers and Complementary Fillers in Multiscale Carbon/Epoxy Composites

Chicken feathers (CFs), regarded as agricultural waste, represent a renewable source of protein‐based fibers. This study reports the first successful integration of chicken feather fibers (CFFs) into high‐temperature epoxy composites using a dual strategy: (i) as complementary biofibers within RTM 6 epoxy resin and (ii) as interfacial modifiers between fabric layers to assemble preforms, subsequently fabricated into laminates via the membrane‐aided vacuum infusion process (MAVIP). Among different color variants of CFFs, the brown type, displaying the highest tensile strength (241 ± 21 MPa) and modulus (3.93 ± 0.5 GPa), was selected, mildly pyrolyzed to preserve its morphology, then oxidized and subsequently functionalized with 3‐aminopropyltriethoxysilane (APTS) to improve epoxy interfacial compatibility, as confirmed by rheological, FTIR and XPS analyses. Incorporation of 1 wt.% silanized CFFs yielded an 11% increase in T g and a 49% increase in storage modulus, while reducing the CTE and loss modulus by 59% and 12%, respectively. Untreated CFFs also improved these properties, albeit to a lesser extent. The silanized CFF‐modified composite laminate exhibited mechanical performance gains of 27% in Mode I fracture toughness, 12% in Mode II toughness, 29% in flexural strength, 30% in flexural modulus, 12% in interlaminar shear strength, and 10% in pin‐bearing strength. SEM observations further confirmed strong interfacial bonding between silanized CFFs and the epoxy network, underlining their role in strengthening and toughening the composite laminates.