A Study of Environmentally Friendly Titanium Pretreatments for Adhesive Bonding to a Thermoplastic Composite

The increased use of fibre reinforced polymer composites for aircraft structures have highlighted the need for reliable methods of bonding these materials to metallic components such as titanium. There is also a need for a simple test to evaluate adhesive bonds with dissimilar substrates, while under load and in a variety of environments. In this study the Boeing wedge test has been adapted for use with metal to composite adhesive bonds. A flexural rigidity matching approach was used with the addition of a backing beam to the composite coupon. The titanium adherends were surface pre‐treated using novel environmental benign methods, namely argon gas plasma and silicon sputtering. Sodium hydroxide anodisation, which is currently used industrially and alumina grit blasting were used as benchmarks. The composite, glass fire reinforced polyphenylene sulphide was alumina grit blasted. An environmental cycle was used to mimic a typical aircraft service cycle; joints were subjected to 24‐hour cycles of ambient, 60 °C water immersion, 60 °C dry and –55 °C dry for 12 days. Crack propagation and locus of failure were monitored after each cycle.