Experimental Evaluation of a Composite Sandwich Panel for Aircraft Landing Gear Doors

Aircraft landing gear doors serve as lightweight auxiliary structures and are exposed to bending loads, localized compressive stresses, and occasional accidental impacts during their service life. Sandwich composite structures consisting of carbon-fiber reinforced polymer (CFRP) face sheets and a honeycomb core have become a preferred solution for such applications due to their high weight efficiency, corrosion resistance, and adaptable design characteristics. However, these structures may still develop internal damage mechanisms—such as delamination, honeycomb cell collapse, and skin–core debonding—that often remain undetected and create challenges for certification and durability evaluation.

In this study, a CFRP–honeycomb sandwich panel designed for landing gear door applications was fabricated and experimentally investigated. Mechanical characterization involved low-velocity drop-weight impact testing, three-point bending, and flatwise compression to represent realistic operational loading conditions. Microstructural examination using Scanning Electron Microscopy (SEM) was carried out to analyze damage progression, including matrix cracking, fiber fracture, adhesive degradation, and honeycomb cell wall deformation.

The results show that impact loading mainly produces subsurface delamination and surface indentation, flexural loading promotes core shear failure and face-sheet instability, and compressive loading leads to progressive collapse and densification of the honeycomb core. Overall, the experimental findings provide insight into failure evolution and mechanical response, supporting improved design considerations, inspection strategies, and damage-tolerance assessment for aerospace-grade sandwich composite structures.