Prediction of the adhesive fillet size for skin to honeycomb core bonding in ultra-light sandwich structures

The formation of resin fillet between honeycomb core cell walls and skin in light sandwich structures was studied to gain a better understanding of the bonding process. A method was developed for tailoring the amount of adhesive between 8 and 80 g/m2. The size of the adhesive menisci and the contact angles between the adhesive and the skin and the core materials were measured. A model was developed to predict the size of the menisci, based on the surface energy of skin and honeycomb materials. When adhesive films were used for bonding, up to 50% of the adhesive did not form the menisci whereas 100 % did when the newly-developed adhesive deposition method was used, which allowed better bonding with lower weight.