Experimental Investigation of Disbond Growth in Sandwich Panels Under Pressurization and Compression

Honeycomb-core sandwich structures are increasingly used in aircraft, making disbond propagation driven by ground–air–ground (GAG) pressurization cycles a significant safety concern. Because this mechanism involves coupled structural, thermodynamic, and fracture processes, its behavior remains insufficiently understood. This study experimentally characterizes disbond propagation at the facesheet–core interface of honeycomb panels under static and fatigue loading. Two experimental configurations were developed to replicate GAG-induced cavity pressurization with and without uniaxial in-plane compression: one setup directly pressurized the disbond cavity, while the other applied equivalent pressure changes using a vacuum chamber. Disbond bulging and crack growth were monitored using three-dimensional digital image correlation. The results show that the direction of disbond propagation is governed by the applied in-plane load. Under fatigue, the disbond growth rate depends on the magnitude of the compressive load and, more critically, on the gauge pressure and initial disbond size. In addition, the disbond propagation path was visually inspected after the tests. The observations indicate that, under the conditions studied, disbond propagation driven by GAG and in-plane compression occurs along the interface beneath the meniscus layer, predominantly in mode I.