Silane‐Functionalized Recycled Chopped Carbon Fibers for Interlaminar Toughening of Hybrid GFRP Laminates

Abstract

Laminates made from carbon‐ and glass‐fiber‐reinforced polymers (FRP) possess excellent specific strength and stiffness, making them suitable for structural applications. However, the high cost of virgin carbon fibers has increased interest in using recycled or chopped carbon fibers (CCFs) recovered from waste CFRP. In the present study, both untreated and silane‐functionalized CCFs were incorporated into an epoxy matrix at loadings of 0.5, 1.0, and 1.5 wt%, and used to fabricate hybrid glass fiber‐reinforced polymer (GFRP) laminates. Silane‐treated CCFs improved laminate performance by enhancing compatibility between the CCF and the epoxy, promoting stress transfer at the interface, bridging and deflecting microcracks, and suppressing interlaminar delamination. At 0.5 wt% S‐CCF, reinforcement was effective due to relatively uniform dispersion, whereas higher CCF loadings could form CCF‐rich regions and local stress concentrations, reducing strength and toughness. The 0.5 wt% S‐CCF laminates showed the best performance. Compared with control GFRP, tensile strength, tensile modulus, and toughness increased by about 27%, 4%, and 39%, respectively, while flexural strength and short‐beam shear strength improved by 38% and 13%. These results demonstrate that surface‐modified recycled CCFs can enhance mechanical performance and delamination resistance in a sustainable and potentially cost‐effective manner.