Abstract
The paper presents development of a repair procedure for a severely damaged primary laminate structure of a light aircraft, certified in accordance with CS22. The procedure was developed with the assumption that it would be a field repair carried out by people of average manual skills, who have not been trained in repairs of composite structures. To develop the procedure, a typical FG/epoxy laminate glider fuselage was used. The primary objective of the repair was to restore the original fuselage stiffness, while maintaining possibly low stress concentrations resulting from the repairs. To facilitate development of the repair, an FE model was developed. It was parametrized to be useful for design of similar repairs of similar structures. The experimental work done with the use of a real structure allowed the authors to verify numerical simulations, which were found to be correct.
Highlights
The presented repair technology was designed for structural reinstatement of a severely damaged fuselage, including complete break, Fig. 1
Repair of such damage is not allowed by CS23 [1], but CS22 does not impose any limitation concerning this issue and the presented repair technology can be applied to small aircrafts, motor-gliders and gliders certified under CS22
The described repair procedure could be applied to a solid laminate monocoque structure for which critical buckling load was significantly lower than that needed to overrun materials strength
Summary
The presented repair technology was designed for structural reinstatement of a severely damaged fuselage, including complete break, Fig. 1 (such damage is often caused by a ground loop). Repair of such damage is not allowed by CS23 [1], but CS22 does not impose any limitation concerning this issue and the presented repair technology can be applied to small aircrafts, motor-gliders and gliders certified under CS22. The relevant requirements were defined as follows: the repair technology should be such that the repair could be done out-of-factory (field repair), but under expert supervision, by people of average manual skills, who have not been trained in repairs of composite structures, the repair should restore the original stiffness of the structure not producing excessive stress concentrations in the parent structure, it should be possible to complete the repair with one-side access, the repair could be done either with the help of a vacuum bag or without it, the patch should maintain its mechanical properties up to 54°C
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