Enhanced adhesive performance of Ti–6Al–4V/PEEK interface by loading SPEEK on Ti–6Al–4V plates

With the rapid development of the aerospace industry, fiber metal laminates (FMLs) have become crucial composite structures due to their desirable properties. However, FMLs still suffer from poor adhesive performances. In this work, sulfonated poly-ether-ether-ketone (SPEEK) was selected as a modifier to enhance the adhesive performance between Ti–6Al–4V alloy (TC4) plates and PEEK. Anodizing and sandblasting were also utilized as pre-treatments to explore possible synergistic effects with SPEEK modification. The treated TC4 plate surfaces were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), contact angle (CA) measurements, and scanning electron microscopy (SEM). Meanwhile, the adhesive performances were evaluated by single lap shear testing. The successful loading of SPEEK on TC4 plates led to enhancement in interlaminar shear strength by 32.11% to reach 40.77 MPa when compared to the value of the unloaded anodized sample. The surface morphologies revealed bonding mechanisms based on mechanical interlocking, molecular entanglement, hydrogen bonding formed between sulfonic and carbonyl groups, and highly enhanced van der Waals forces generated by sulfonic groups. In sum, these findings look promising for resolving issues related to Ti/PEEK laminate interfacial strengths.