Design a Rigid‐Flexible Interfacial Structure for Improving the Interfacial and Mechanical Properties of CF / PAEK Composites

ABSTRACT The weak interfacial adhesion between carbon fiber (CF) and polyaryletherketone (PAEK) matrix has become a core bottleneck restricting CF/PAEK composites from fully exerting their intrinsic mechanical properties. Herein, a rigid‐flexible sizing agent is designed to enhance the interfacial adhesion between CF and PAEK matrix, which contains the PEKC‐NaPSS and multi‐dimensional hybrid carbon nanoparticles consisting of 1D carboxylated carbon nanotubes (CNT‐COOH) and 2D aminated graphene nanoplatelets (GnP‐NH 2 ). The surface reactivity, roughness, and resin wettability of CF are effectively optimized by this (CNT/GnP)/PEKC hybrid sizing agent. When the mass fraction of hybrid carbon nanoparticles in the sizing agent is optimized to 1%, the flexural strength, flexural modulus, and ILSS of the modified CF/PAEK composites reach 615.46 MPa, 51.23 GPa, and 61.44 MPa, up 65.28%, 65.01%, and 43.22% compared with desized CF reinforced composites, respectively. The enhanced performance is mainly ascribed to the structural complementarity and combined contribution effect of 1D CNT‐COOH and 2D GnP‐NH 2 , which builds a multi‐scale and multi‐level interfacial network between CF and PAEK matrix, realizing efficient interfacial stress transfer and blocking crack growth and propagation. This work provides a facile and efficient interfacial modification strategy with potential for further development.