Interface fracture progression of composite T-stiffened skins fabricated by co-bonding and co-curing under tensile loading: an experimental investigation

Composite T-stiffened skins, widely used in aeronautical structures nowadays, are fabricated by co-curing and co-bonding processes in this work. An experimental study was focused on the interface fracture progression of T-stiffened skins under tensile loading, including the macroscopic failure process and the microscopic failure mode at several bonding interfaces. The experimental results showed that a similar damage evolution process is found in co-curing and co-bonding processes. Damage is found to initiate in the triangle filling area or the stiffener/filler bonding interface, and it gradually extends to the web part, and finally rapidly extends to the stiffener/skin bonding interface with a complete separation failure. The final failure position occurs in the skin layers closest to the adhesive layer under the stiffener in the co-bonding process with a failure load of 39% higher than the initial damage load, while the final failure position occurs at the flange/skin bonding interface in the co-curing process. The mixed crack growth of mode I and mode II is the main failure mode at the bonding interfaces of composite T-stiffened skins. Graphical abstract