LAUSR

The relationship between microstructures, surface activities, and mechanical properties of γ-irradiated carbon fibers has been evaluated quantitatively. X-ray photoelectron spectroscopy combined with argon ion sputtering indicated that the outer-surface part (∼10 nm) was functionalized and disordered by the grafting reaction; this led to an increase in the surface activity and loss of mechanical properties of γ-irradiated carbon fibers. The degree of covalent cross-linking between subsurface layers of graphene (∼1.5 μm) showed a more notable increase than that of the core (∼4 μm); this indicated that the sub-surface was mainly responsible for improvement in the tensile strength of γ-irradiated carbon fibers. Increases of 15.5% (argon) and 13.3% (epoxy chloropropane) in tensile strength were achieved. Moreover, interfacial shear strength of a single fiber in matrix increased by 19.15% (argon) and 75.03% (epoxy chloropropane). Therefore, this spatially resolved study paved a meaningful way to understand the relationship among microstructures, surface activities, and mechanical properties of γ-irradiated carbon fibers.