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The article presents a study which evaluates the interfacial shear strength of carbon fiber (CF) and epoxy microcomposites by the microbond technique and investigates the composition of CF surface by X-ray photoelectron spectroscopy (XPS). The study analyzes the chemisorptions and alignment of adsorbed thiols. Results show that among molecular orientation and chain lengths, the chemical nature of active group was essential for the development of interfacial properties in epoxy or CF composites.

Abstract: An intermittent electrochemical treatment method was developed in this work which was used to modify the surface of carbon fibers in three-dimensional fabrics. The effects of this treatment on the surface chemical components of the fibers in both interior and surface regions of the fabrics were analyzed by X-ray photoelectron spectroscopy. The wettability of the fabrics was evaluated by liquid-drop method. A microdebonding method was employed to determine the uniformity of interfacial shear strength between the fibers and the matrix in different regions of the carbon fabric/phenolic composites. The compressive strength was also tested to evaluate the effects of treatment. The results indicated that the intermittent electrochemical treatment significantly improved the interfacial adhesion by etching and generating oxygenic and nitrogenous functional groups. The processibility of the fabrics was also improved due to improved impregnation of phenolic resin with the fabrics. The compressive strength was significantly increased due to optimized intermittent electrochemical treatment. Moreover, comparing with the traditional continuous electrochemical treatment which the treatment degrees of the fibers in different region of the fabrics were different, the intermittent treatment was a useful method to obtain the relatively uniform properties throughout the fabrics. [Copyright &y& Elsevier]

Abstract: In this paper, a new treatment method based on molecular self-assembly on carbon fiber surface was proposed for obtaining a controlled interface between carbon fiber and epoxy matrix in composite system. To form the controlled interfacial region, the surfaces of carbon fibers were first metallized by electroless Ag plating, then were reacted with a series of thiols (different chain lengths and terminally functional groups) to form self-assembly monolayers (SAMs), which further reacted with epoxy resin to generate a strong adhesion interface. The morphology, structure and composition of untreated and treated carbon fiber surface were investigated by atomic force microscope (AFM), surface-enhanced Raman scattering spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS), respectively. SERS study showed that thiols chemisorbed on Ag/carbon fiber in the form of thiolate species via the strong S–Ag coordinative bond. XPS study further confirmed the chemisorption by an S 2p3/2 component observed at 162.2eV. The binding energy was characteristic of silver thiolate. The interfacial shear strength of the carbon fiber/epoxy microcomposites was evaluated by the microbond technique. The results showed that there was a direct effect of the interfacial parameters changes such as chain lengths and surface functional groups on the fiber/matrix adhesion. [Copyright &y& Elsevier]