Investigation of Fuselage Structure Subject to Widespread Fatigue Damage

Abstract

Abstract : Tbis report documents the results of the 'Investigation Of Fuselage Structure Subject To Widespread Fatigue Damage' contract. The primary program objective was to obtain data on airplane fuselage structures subject to multiple site damage (NlSD) in an environment that reflects typical commercial jetliner manufacturing and operating conditions. The program involves three technical tasks which include flat panel material characterization testing (Task I), Full-scale fuselage pressure panel testing (Task II) and predictions of pressure panel behavior through finite element modeling (Task III). In Task I. six specimens were tested to characterize the lot of 2024-T3 clad material used to fabricate the skins for die Task II pressure test panels. Material static, crack growth and toughness (Kapp and R-curves) data were generated. Task II. two generic wide-body curved fuselage panels were fabricated and pressure tested. Frame centered cracks in the die lap joint outer skin upper fastener row were grown by pressure cycling to two frame bays A panel residual strength test was taken conducted with die skin crack centered on a broken frame. Panel lap joints were fabricated with and without NISD sawcuts in the fasteners ahead of die lead crack to develop the head-to-head comparison. In Task III, a detailed finite element model was constructed to analyze the pressure test panels. Predictions were made of the pressure test panel strain gage stresses, crack growth life and residual strength. General conclusions from the testing and analysis were drawn.