A two-step strategy to graft CNTs onto titanium/CFRP interface for interfacial enhancement

The primary challenge of fiber metal laminates (FMLs) is the insufficient interfacial adhesion between metal and resin, which impedes the realization of the full potential. To address this issue, a two-step strategy has been proposed: firstly, via the cerium coordination-based approach, followed by grafting carbon nanotubes onto the titanium surface. This modification enhances the interfacial behavior between titanium sheets and polyetheretherketone (PEEK), resulting in increased roughness and wettability on the titanium surface, facilitating tight contact between PEEK and titanium sheets while reducing defects at the interface. Compared to CF/PEEK-sandblasted Ti, the modified CF/PEEK-Ti composites exhibit significantly enhanced interfacial shear strength, equivalent flexural strength, and interlaminate shear strength with an increase of 205.4 % (39.4 MPa), 133.3 % (1434.3 MPa) and 95.2 % (93.7 MPa), respectively. Additionally, the failure mode has shifted from interfacial failure to cohesive failure. The interface enhancement mechanism can be attributed to the synergistic effects of coordination bonding, mechanical interlocking, and multiple interactions. This facile two-step modification method demonstrates the potential to enhance the interfacial properties of CF/PEEK-Ti composites.