Strengthening and Modulating Interphases in Carbon Fiber/Epoxy Composites by Grafting Dendritic Polyetheramine With Different Molecular Weights Onto Carbon Fiber

In order to investigate the effects of molecular weights on the interfacial properties of carbon fibers (CFs) reinforced epoxy composites, dendritic polyethyleneimine (PEI) with different molecular weights were grafted onto CF surface by a simple and efficient method. The microstructures, interfacial, and mechanical properties of modified CFs were researched. Raman spectra and X-ray photoelectron spectroscopy (XPS) confirmed the successful growth of PEI dendrimers. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) images showed that grafting PEI could improve surface roughness, and this effect was more pronounced with molecular weight increasing. When the molecular weight of PEI is 600, the interfacial shear strength (IFSS), interlaminar shear strength (ILSS), and flexural strength of CFs/epoxy composites were enhanced by 83.6%, 46.1%, and 22.3% compared with those of unmodified ones, respectively. The fractured surface of composites showed a great enhancement of interfacial adhesion. Moreover, the interfacial enhancement mechanisms and failure modes were also discussed. POLYM. COMPOS., 40:E1525–E1536, 2019. © 2018 Society of Plastics Engineers