Establishing a phthalocyanine-based crosslinking interphase enhances the interfacial performances of carbon fiber/epoxy composites at elevated temperatures

Abstract

A novel phthalocyanine-based interphase with a higher crosslinking density and glass transition temperature (Tg) was designed to enhance the interfacial properties of the carbon fiber/epoxy composite at elevated temperatures. The crosslinking density and the Tg of the interphase were tailored by tetraaminophthalocyanine (TAPc) with abundant amine groups and rigid heteroaromatic structures coated on the surface of the carbon fibers. Characterizations of the fiber surface properties were performed before and after coating, including topography, surface chemistry and surface energy. A sharp improvement in the interfacial shear strength for TAPc-coated carbon fibers (CF-TAPc) of 127.3% was obtained compared to that of the commercial carbon fibers (CF-commercial) at 150 °C. The modulus of the carbon fiber composite at the interface was investigated by force-mode atomic force microscopy (AFM), which indicated that the interphase of the CF-TAPc was stiffer than that of CF-commercial at 180 °C. Following the experimental observations, the dynamic mechanical thermal properties were investigated to confirm the better thermomechanical stability of the CF-TAPc interphase. This strategy is based on multireactive sites and the stiff structures of TAPc that generate higher Tg and act as a buffer between the fiber and matrix to counteract the generation of stress in the interphase, resulting in increased interfacial shear strength at elevated temperatures.