Durability of nano-reinforced polyimide adhesive bonding of titanium nitride deposited aluminium for aerospace applications

Abstract

This investigation highlights novel surface modification techniques of aluminium by titanium nitride deposition to increase adhesion characteristics of aluminium, when fabricated by polyimide adhesive (PI) and its durability under aerospace environments. The aluminium substrate surface when modified by titanium nitride deposition under physical vapour deposition (PVD), its adhesion strength increases considerably. Incorporation of nano particles in to the polyimide adhesive increases cohesive properties of the adhesive up to a great extent. It is observed that surface modified aluminium shows better adhesion properties in comparison to unmodified aluminium surface because surface modified aluminium results strong interfacial force of attraction with the polyimide adhesive. Addition of silica nano powder increases the adhesive bond strength considerably. However, it is observed that adhesive bond strength increases up to an optimum dispersion of silica nano powder and thereafter it decreases. Thermogravimetric Analysis (TGA) reveals that there is an improvement of thermal stability of the adhesive due to dispersion of silica nano powder. Effects of surface modification of aluminium and reinforced nanoparticles on durability were analysed. It is observed that due to titanium nitride deposition on aluminium and dispersion of silica nano powder in to the polyimide adhesive increases the durability of the adhesive joint up to certain extent. Failure analysis under Scanning Electron Microscopy (SEM) reveals that there is interfacial failure of adhesive bonded joints of unmodified aluminium and in the case of titanium nitride deposited aluminium, the adhesive joint fails cohesively resulting in significant increase in adhesive bond strength.