Enhancement of interfacial properties of HMCF composites by constructing of rigid‐flexible interphase through naphthalenediimide with different flexible chain lengths

Abstract

AbstractNaphthalenediimide copolymers with long, middle and short flexible chain lengths (LN, MN and SN) were designed and used to construct rigid‐flexible interphase on high‐modulus carbon fiber (HMCF) surface, and the interfacial performance and interphase reinforcing mechanism of composites were explored. Compared with desized HMCF (HMCF‐desized), the surface activity and roughness of HMCF‐LN, HMCF‐MN and HMCF‐SN were gradually increased. In contrast to HMCF‐LN and HMCF‐MN composites, wider transit‐modulus platform and increased interphase thickness were detected in HMCF‐SN composites, the improved deformation and decreased thermal residual stress from rigid‐flexible interphase were obtained. The highest improvement of transverse fiber bundle test strength (TFBT) and interfacial shear strength (IFSS) of HMCF‐SN composites were achieved, which was ascribed to the effective relaxation of interfacial stress and stronger chemical interaction of HMCF‐SN with matrix by the reduced flexible chain lengths and the increased functionality of SN copolymers.Highlights Rigid‐flexible interphase was constructed by naphthalenediimide copolymers. Wider transit‐modulus platform was detected in HMCF‐SN composites. Improved deformation and decreased residual stress of interphase were obtained. The interfacial performance of HMCF‐SN composites were greatly improved.