Honeycomb sandwich structures continue to find new applications in a variety of engineeredstructures. One issue that continues to be problematic, and is often a main contributing factor infailure of these structures is the bond between the outer skins and the honeycomb core. Thestrength of this bond comes primarily from the formation of fillets on the honeycomb cell walls,made from the resin in the prepreg or from an additional adhesive layer placed between the outerskins and the core. In an attempt to better understand the skin to core bond in honeycombsandwich panels, this research investigated the correlation between the size and quality of thefillets and the fracture toughness of the bond. Sandwich panels constructed using self-adhesiveprepregs were investigated, but the results obtained are believed to be applicable to otherbonding methods and materials. Sandwich panels were fabricated with different fillet sizes.Fillets were measured using a digital microscope, and several fillet dimensions were investigatedto establish their correlation with bond quality. The bond quality was assessed using a Mode Ifracture toughness test in which the critical Mode I energy release rate, Gic was measured.Results suggest that a critical fillet area exists, and fillets must be of this critical size to achieveoptimal bond performance.
展开▼
