Microstructure variations in carbon fiber reinforced plastics under ultraviolet-ray irradiation

Abstract

Carbon fiber reinforced plastics (CFRPs) were irradiated with ultraviolet rays (UVR), and its structural variations were observed by high-resolution transmission electron microscopy. The lattice images of the resin, fibers, and fiber/resin interface regions in CFRPs and their spatial frequencies were investigated before and after UVR irradiation. In the fiber regions, the layer spacing of graphite structures increased after UVR irradiation. In the fiber/resin interface regions, the resin and the fiber adhered tightly at the atomic level before UVR irradiation. The anisotropic interface phases, in which atom-pairs having wide spacings were aligned along the direction perpendicular to the interface planes, were formed. After UVR irradiation, the tight interface adhesion was maintained, whereas the roughness of the interface shape increased. The effects of UVR irradiation on the mechanical properties of CFRPs were revealed from the atomistic structural variations in the resin, the fibers, and the fiber/resin interfaces.