A novel synergistic approach to improve the interfacial and mechanical properties of CF/PEEK-Ti laminates through GNPs

The insufficient bond strength at the fiber/metal interface of fiber metal laminates (FMLs) is a primary obstacle to their widespread application. To address this issue, a strategy is proposed to introduce graphene nanoplatelets (GNPs) to enhance the bond strength at the carbon fiber/polyether ether ketone (CF/PEEK)-titanium interface. This approach comprises two main components. First, GNPs were deposited onto the surface of the titanium layer to form a micro-nanolayer using electrophoretic deposition (EPD). The effects of varying voltages, deposition times, and GNPs concentrations on the EPD results were investigated. Second, the PEEK matrix was modified with GNPs to further enhance the interfacial bond strength of CF/PEEK-titanium. The results indicated that optimal EPD parameters-30 V, 90 s, and a GNP concentration of 0.75 mg/mL-yielded the best outcomes. Under these conditions, the flexural strength, interfacial shear strength, and shear adhesion strength of FMLs improved by 201.9 %, 133.9 %, and 91.4 %, respectively, compared to unmodified FMLs. When combining GNPs-modified PEEK with EPD, these properties increased further, with flexural strength, interfacial shear strength, and shear adhesion strength enhanced by 281.7 %, 238.7 %, and 112.4 %, respectively, compared to unmodified FMLs. Molecular dynamics simulations were performed to further investigate the role and mechanism of GNPs in the GNPs/PEEK/titanium ternary system. The simulations revealed that combining a GNPs-modified matrix with EPD significantly enhances the system's interfacial energy. Moreover, GNPs substantially influence the torsional behaviour of the PEEK main chain. These combined experimental and simulation results offer new insights into applying GNPs in composite materials.