Enhancing CF/PEEK interfacial adhesion by modified PEEK grafted with carbon nanotubes

The weak interfacial adhesion caused by the low wettability of carbon fiber (CF) and inert polyetheretherketone (PEEK) hinders the great application potential of CF/PEEK composites. In this study, the interface between CF and PEEK was modified by coating hydroxylated PEEK grafted onto multi-walled carbon nanotubes (M-HPEEK). Modified CFs by M-HPEEK sizing had rougher surfaces with more polar groups, showing decreased contact angle and increased surface energy. The wettability of these CFs was enhanced, beneficial to PEEK infiltration and physical adhesion improvement. As a result, the interlaminar shear strength, flexural strength, and flexural modulus of modified CF/PEEK composites were increased by 73.0% (84.7 MPa), 163.2% (906.2 MPa), and 84.8% (58.4 GPa), respectively. An improved interface with stress transferring was proved by the interface debonding failure changed to fiber crack and resin yield. M-HPEEK sizing is considered as a promising modification method to optimize the interface performance of composites.