The self-healing of micro and macro cracks is vital for eliminating defects such as damage progression and loss of strength in structures. In this study, a polyurethane (PU) based geometrically self-healing sandwich structure was developed. The geometric healing agent, PU resin, and activator, were filled into macro capsules, and these capsules were filled into the Aluminum (Al) honeycomb cells. Self-healing of structural strength, large holes and cracks in developed sandwich structures were investigated by performing quasi-static compression and impact penetration tests. The sandwich structure with a self-healing capsules-filled core was damaged by subjecting it to quasi-static and penetration impact loads, and the healing agents in the broken capsules were mixed. The damage in the specimen was removed by geometric self-healing. Liquid and air permeability tests were applied to the PU foam used as a healing agent. No liquid permeability was
observed in the structure. In addition, significant reductions in air permeability were obtained. Scanning electron microscope images were used to explore the characterization of the PU foam structure cells.