Synergistic Interface Modification Strategy to Enhance Interfacial Bonding of High-Modulus Carbon Fiber/PEEK Composites

High-modulus carbon fiber reinforced polyetheretherketone (HMCF/PEEK) composites theoretically exhibit extremely excellent properties. However, limited by the high incompatibility between HMCF and PEEK, the bonding effect at the interface between HMCF and PEEK is extremely poor, which seriously affects the performance of HMCF/PEEK composites. Therefore, it is necessary to carry out reasonable surface modification on HMCF to improve the bonding effect at HMCF/PEEK interface. In this paper, PEI/MXene (PMX) and sulfonated PEEK (SPEEK) were prepared. The surface of HMCF was treated by cathodic electrophoretic deposition and sizing method, respectively. The results show that PMX is uniformly and closely arranged on the surface of HMCF. The interlaminar shear strength (ILSS) of PMX-HMCF/PEEK composites can reach up to 57.98 MPa. Notably, SPEEK demonstrates a more potent reinforcing effect on the composite interface than PMX. The ILSS of the S-HMCF/PEEK composite reaches 63.48 MPa. S-PMX-HMCF/PEEK modified by the joint treatment of PMX and SPEEK exhibits the optimal interfacial bonding effect (ILSS reached 75.34 MPa, representing a 133.52% increase over D-HMCF/PEEK), with the expected bridging effect of SPEEK at the interface fully realized. PMX and SPEEK jointly provide higher surface energy for HMCF, form a modulus gradient change at the interface, significantly improve the interfacial bonding effect.