Effects of different rigid-flexible structures of carbon fibers surface on the interfacial microstructure and mechanical properties of carbon fiber/epoxy resin composites

In order to comprehend the influence of different rigid-flexible structures on the interface strength of carbon fiber(CF)/epoxy composites, CNTs was firstly chemically grafted on CFs surface, and then polyamide (PA) was grafted onto CF-CNTs surface through varying anionic polymerization time of caprolactam [CF-CNTs-PAn (n = 6 h, 12 h, 24 h)]. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy indicated the successful establishment of CNTs and PA. TGA demonstrated the different grafting amounts of CF-CNTs-PAn (n = 6 h, 12 h and 24 h). SEM images revealed a compactness and uniform coverage of the CNTs/PA, with increasing polymerization time, the CF and CNTs surface was covered by a thick layer of PA. The surface energy increased and then decreased. The optimal interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the CF/epoxy composites with a polymerization time of 12 h (CF-CNTs-PA12h) was 86.7 and 85.4 MPa, which was 77.6% and 45.7% higher than that of untreated CF/epoxy composite. As the polymerization time grew, the impact toughness and tensile strength of CF/epoxy composites enhanced and conductivity of CF/epoxy composite reduced. In addition, the mechanisms of reinforcement and toughening were also illuminated. This work would provide a certain theoretical basis for the preparation and applications of high-performance CF composites with different structures. (C) 2020 Elsevier Inc. All rights reserved.

Automated summary

Different rigid-flexible structures were studied to understand their influence on the interface strength of carbon fiber/epoxy composites. The optimal interfacial shear strength and interlaminar shear strength were 86.7 MPa and 85.4 MPa, respectively, with a polymerization time of 12 hours. The impact toughness and tensile strength of the composites increased with polymerization time growth, while the conductivity decreased.