A mussel-inspired strategy for CNT/carbon fiber reinforced epoxy composite by hierarchical surface modification

The mechanical properties of carbon fiber-reinforced polymer (CFRP) composites are strongly affected by the fiber-matrix interface performance. Here, we report a mussel-inspired nondestructive method to introduce carbon nanotube (CNT) onto carbon fiber (CF) surface using polydopamine (PDA) via 7C-7C interaction and covalent bonding. The analysis of the surface morphologies, chemical properties, and the wettability of CF reveal that the functionalized CF exhibit an increased roughness and better wettability with epoxy matrix. Mechanically, the modification improves the tensile strength of CF by 14.73%, while the interfacial shear strength and interlaminar shear strength of modified CF/epoxy composite are enhanced by 89.72% and 55.44%, respectively. The enhancement mechanism could be attributed to the interpenetrating ultra-adhesive PDA molecules and CNTs network, which provide the synergistic effects of 7C-7C interaction, hydrogen bonding, covalent bonding, and mechanical interlocking at the interface. As a result, the applied load can be effectively transferred from resin to CFs. This study provides a convenient and environment-friendly surface treatment approach to improve the interfacial and mechanical properties of CFRP composites.