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. Their shape was driven by 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 on honeycomb was used, which allowed better bonding with lower weight.