Debonding identification of Nomex honeycomb sandwich structures based on the increased vibration amplitude of debonded skin

Accurate debonding identification is essential for subsequent structural repair, however, the research on debonding identification on both sides of the symmetrical honeycomb sandwich structures by means of the vibration-based method faces certain challenges. To address this, a two-step strategy based on the uniform load surface (ULS) curvature method is presented. Specifically, the potential debonding area is first identified through the global debonding detection of the entire sandwich structure. Then, the specific debonding information on both sides is identified by introducing the local constraint to the boundary of the above potential debonding area. The corresponding mechanism is that the local constraint improves the relative vibration amplitude of debonded skin. On this basis, further study on the applicable scope of the ULS curvature method indicates that the debonding of Nomex honeycomb sandwich structures with relatively low-modulus skin and large honeycomb core phenolic resin thickness is relatively easy to be identified. This work is helpful to guide the precise debonding detection of honeycomb sandwich structures.