The stiffened panel consists of three components: the skin, the stringer web, and the stringer flange. The construction of stiffeners (stringer web and flange) repeats at a fixed interval, as shown in the figure below. All three components are made of layered composite materials. An in-plane compressive load is gradually applied, causing the panel to buckle and the bond between the skin and the flange to be damaged. The debonding is initialized at an artificial imperfection and allowed to propagate as the load increases.