With the increased emphasis on reducing the cost of manufacturing composite structures, secondary bonding or co-curing is an attractive option to eliminate the need for mechanically fastening subassemblies. Many composite components in aerospace structures consist of flat or curved panels with co-cured frames and stiffeners. Out-of plane loading such as internal pressure in a composite fuselage or out-of-plane deformations in a compression loaded post-buckled panel may cause the frame or stiffener to debond from the panel [ 1 ].