Interface Characterisation for Adhesively Bonded Hybrid Joining
Composites can be employed for bonding with metallic alloys to reduce the mass and improve the performance of modern aerospace structures. Adhesive bonding is a promising technique for joining dissimilar materials, as it maintains the structural integrity of each substrate. The mechanical performance of adhesively bonded structures is affected by the surface properties of the two substrates prior to bonding. Appropriate surface pre-treatment optimizes surface roughness and wettability. It may enhance the interaction between the adhesive and the surfaces so that the final mechanical performance of the joint meets the requirements of the application. In this PhD project, aluminium alloy, titanium alloy, and carbon fibre reinforced polymer composite are used as substrates which have, for example, widely diverse coefficients of thermal expansion. Abrasion and plasma technology are adopted for optimizing the roughness and wettability of the surface of the substrates, respectively. Mechanical tests under different conditions are carried out to evaluate the joint performance. Interface characterisation, including contact angle measuring and diverse microscopic observation, is carried out to further study the surface pre-treatment and adhesive bonding. This research aims to collect data for hybrid joints. It also aims to find the correlation between the final joint strength and the difference of the two adherends (in wettability, roughness, and thermal expansion). This study will provide valuable advice when engineers are selecting materials for an aerospace structure.