The repair node analysis of the semi-monocoque aircraft structure

The purpose of the study was to perform a repair that would restore the original strength and fatigue life of the Mi-8 helicopter tail beam structure. Diagnostics were carried out at the point where the skin is subjected to buckling during loading of the structure. Changes in deformation in the tested structure were recorded using strain gauges. After removing the skin sheet, the measured values of deformation on the skin increase in the area of the made hole in the airframe and frame elements. On the other hand, after removing a section of the stringer, the strain values increase locally in the area where the modification was made. Making a repair of a fragment of the skin by making a hybrid joint - the use of a patch of AW 2024-T3 sheet metal with one-sided fasteners of the PLT210-5 type, as well as Raychem S1125 adhesive plastic and stringer, the measured values of deformation in the study area significantly decreased, especially in the place of repair. It was found that the repair patch certainly strengthened and stiffened the joint of the structure locally. No damage to the beam structure, mechanical fasteners or the adhesive layer was identified during the fatigue tests. The recorded strain values testify to the full efficiency and functionality of all elements of the installed hybrid connection.