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The present work concerns the state-of-the-art of the surface modification of polyacrylonitrile (PAN) based carbon fibers using different methods, so as to control the increase in surface roughness in order to improve the fiber/matrix interface of fiber reinforced polymer composites. The surfaces of the PAN-based carbon fibers were chemically and physically treated using nitric and hydrochloric acids, as well as cold plasma in argon and oxygen atmospheres, and the changes on their surfaces evaluated. The physicochemical properties and morphological changes of the surfaces were investigated by tensile strength tests, scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The nitric acid treatment was found to cause the most significant chemical changes on the carbon fiber surface, introducing the largest number of chemical groups and augmenting the roughness. The oxygen plasma treatments caused ablation of the carbon fiber surface, removing carbon atoms such as CO and CO2 molecules. In addition, the argon plasma treatment eliminated defects on the fiber surface, reducing the size of critical flaws and thus increasing the fiber’s tensile strength. |