Synergy of interfacial reinforcing and damage monitoring at elevated temperature by constructing fluorescence interphase of perylenediimide nanowires in carbon fiber/bismaleimide composites

Amino-terminated perylenediimide (PDI) was designed and used to construct molecular assembly interphase with high temperature resistance and fluorescence on modified carbon fiber (CF-PDI) surface, and the correlations of the novel interphase with interfacial reinforcement and damage monitoring of carbon fiber/bismaleimide (CF/BMI) composites after treatment at 25 °C, 100 °C, 200 °C and 250 °C were investigated. Reticular nanowire structures from PDI self-assembly were observed on CF-PDI surface, leading to the increase of chemical activity and roughness of fiber surface. The partial detachment and decreased surface activity of the nanowire structures of PDI assembly on CF-PDI surface appeared with increasing the temperature, resulting from the weakening of π-π stacking and sectional breakage of intermolecular hydrogen bonding at high temperature. Compared with CF-desized composites, transverse fiber bundle tensile strength and interfacial shear strength were increased by 76.6 % and 52.2 % after treatment at 250 °C, which was ascribed to the enhanced interfacial bonding between PDI nanowires and BMI matrix. The confocal laser scanning microscope images and grayscale color maps showed the strong green fluorescence on CF-PDI surface and its composites at 25 °C, while the fluorescence intensity was gradually decreased with the increase of temperature. The fluorescence disappearance of damage region after low-velocity impact damage was observed after treatment at 200 °C and 250 °C, which realized damage monitoring at high temperature in CF/BMI composites.