Closed loop recycling of functional carbon fiber epoxy laminates

Abstract

High-performance carbon fiber-reinforced epoxy (CFRE) composites perpetuate a linear economy due to the inherent challenges in recycling their crosslinked matrices. This work presents the development of an advanced, multifunctional CFRE laminate with inherent closed-loop recyclability, enabled by a novel, environmentally benign recycling protocol: the “SaLSO” which utilizes a seawater-derived aqueous medium enriched with naturally occurring citric acid. A dual-functionalization strategy was employed using polyetherimide-modified graphene oxide (GO) as a carbon fiber sizing agent and hydroxyl-functionalized GO uniformly dispersed within the epoxy matrix. Density functional theory (DFT) confirmed strong, multidimensional non-covalent interactions between the GO variants, resulting in significant mechanical enhancement, including a 44% increase in flexural strength and a 41% increase in interlaminar shear strength (ILSS). The laminate also demonstrated inherent self-healing capability with a 61% recovery in ILSS, excellent electromagnetic interference (EMI) shielding effectiveness of 49 dB, and rapid deicing performance in 45 seconds via Joule heating. The recovered materials were successfully used to refabricate the laminate with retained performance, establishing a promising pathway toward a sustainable, circular composite economy. (Figure presented.)