A Study on the Effect of Crack Stopper for Enhanced Damage Tolerance Behavior of a Fuselage Stiffened Panel

Abstract

During the design and development phase of a large transport aircraft, a considerable amount of parametric analysis and testing is carried out to bring out an optimum structure. Two-bay longitudinal crack arrest feature is the main aspect of design for damage tolerance of the pressurized fuselage cabin. Under fuselage pressurization load cycles, fatigue cracks develop at location of maximum tensile stress. There are locations on the airframe which are favorable for the initiation of longitudinal cracks. This investigation identifies one such location in a fuselage panel from where a longitudinal crack can initiate and studies the fast fracture and crack arrest features under the action of uniaxial hoop stress. The main crack arresting features are the bulkheads and crack stopper straps. A finite element modeling and analysis approach will be used for simulating stiffened panel with and without the presence of tear strap and their role in the two-bay crack arrest capability of the aircraft fuselage is assessed. Stress intensity factor for progressive crack lengths and the fatigue crack growth rate of the cracked stiffened panel was estimated. A tear strap crack stopper was introduced for evaluating the damage tolerance capability of the stiffened panel again fatigue crack growth rate was estimated for a realistic representation of two-bay cracking scenario, it will be examined under what condition a two-bay crack can be arrested. By this new design, the stiffened panel was found to be more damage tolerant compared to the earlier one.