Design and durability of titanium adhesive joints for marine applications

Comparative measurements of strength and Griffith's critical strain energy release rate GIc were carried out on adhesively bonded joints with different surface treatments of titanium, before and along 13 weeks of accelerated aging in salted or deionized water at 50 °C. Thermo-mechanical measurements were carried out on the bulk epoxy adhesive, with the same aging conditions. A combined surface treatment of sanding, degreasing and chemical etching showed the best durability, whereas a treatment using an additional sulphuric anodic oxidation showed the best adhesion before aging. Aging decreased the strength and the critical strain energy release rate of bonded joints by 30–70%. Joint design with a finite element calculation using a cohesive failure law at the interface, accounting for surface treatment, aging effects and safety factors, can thus be performed, from a limited set of experimental values.