Effects of Electrospun GNP@PEI Nanofibrous Mats on the Interlaminar Fracture Toughness and Viscoelasticity of CFRP Composites Laminates

Preventing interlaminar crack propagation is essential to improve the properties of CFRP laminates. In this study, electrospun GNP@PEI nanofibrous mats were embedded into CFRP laminates. Flexible PEI nanofibers could form ductile interlayers to alleviate interfacial stress, and uniformly dispersed GNPs provide multi-scale synergistic toughening. The influence of GNP content was systematically investigated via double cantilever beam (DCB) tests, end-notched flexure (ENF) tests, and dynamic mechanical analysis (DMA). The research results indicated that the toughening effect exhibits a significant concentration-dependent behavior. Specimens with 1.5 wt% GNPs exhibited optimal performance, whose Mode I ( G IC ) and Mode II ( G IIC ) fracture toughness values improved by 111% and 100%, respectively. However, the content of 2.0 wt% GNP caused local agglomeration, inducing stress concentration and weakening the toughening effect. Furthermore, DMA results showed that appropriate GNP introduction enhanced the interfacial restriction, successfully restoring the storage modulus and thermal stability. Finally, fracture morphology characterization confirmed the multi-scale synergistic tuning mechanisms. Highlights Interleaving GNP@PEI nanofibrous mats enhances CFRP interlaminar properties. Adding 1.5 wt% GNPs improved Mode I and II toughness by 111% and 100%. The effects of GNP@PEI on composite viscoelastic properties are elucidated. Excessive GNPs lead to agglomeration and degradation of mechanical properties.