Dopamine concentration-dependent surface modification for gaining carbon fiber composites with enhanced interfacial adhesion

Abstract

Self-assembly process of dopamine concentration-dependent polydopamine (PDA) on graphitized carbon fiber is elucidated, as well as its effects on interfacial adhesion of composites. With the increase of dopamine concentration, active PDA nanospheres in Tris-solution first adhere to fiber surface to form a thin film, then accompanies with the creation of ever-increasing PDA aggregates instead of continuing to form a thicker PDA film. The optimal dopamine additive amount is 0.3 g for 52.6% IFSS improvement by analogy to untreated fiber, because of the greatly enhanced epoxy wettability from the contribution of the synergistic actions of more polar groups and rougher surface. Less and higher dopamine additions go against substantial increment in IFSS, especially for higher ones that large-sized PDA nanospheres are apt to induce stress concentration, sacrificing the contribution by more active groups.