Damage tolerance evaluation of a stiffened panel with a passenger window cutout of a transport airframe fuselage structure
Ankur Joshi,  Lakshmi Prasad,  Girish K. E.
Aircraft is a complex mechanical structure and must be designed with a very high structural safety also with lightweight. Aircraft will rarely fail due to a static overload during its service life. As the aircraft continues its operation, fatigue cracks initiate and propagate due to fluctuating service loads. Normally fatigue cracks will initiate from stress concentration locations. Window cutout in the fuselage structure is a common functional requirement in the structure. Fatigue cracks will initiate from corners of window cutout since they are the stress concentration regions. To ensure safety of an aircraft during its entire economic service life, fatigue and damage tolerance analysis, testing and service experience correlation play a vital role. Current study includes the crack arrest capability evaluation of the bulkheads in the stiffened panel consisting of a large cutout for passenger window. The passenger window cutout region in the fuselage is a critical region from the fatigue crack initiation point of view. The maximum tensile stress location will be identified in the panel. MSC PATRAN and MSC NASTRAN were used for the static stress analysis. If the crack in a critical location goes unnoticed it could lead to a catastrophic failure of the airframe. Fatigue is a phenomenon by which the load carrying ability of a structure decreases when subjected to fluctuating loads. In a metallic structure fatigue manifests itself in the form of a crack, which propagates. A crack from the highest tensile stress location will be initiated in the analytical model of the stiffened panel. Panel will be analyzed for different crack lengths by growing the crack in the direction perpendicular to the loading direction. Stress intensity factor calculations will be carried out for different crack lengths. Crack arrest capability of the bulkheads on either sides of the window cutout will be evaluated analytically by comparing the stress intensity factor values with fracture toughness of the material at different crack lengths. The residual strength diagram will be plotted for both fuselage skin and bulkheads to demonstrate the crack arrest capability of the bulkheads through analytical approach.
Keywords- Aircraft, Fuselage, Window cutout, stress analysis, FEM, Fatigue, Damage tolerance, Stress intensity factor, Crack arrest capability.
Unique Identification Number - IJEDR1402052Page Number(s) - 1598-1609Pubished in - Volume 2 | Issue 2 | June 2014DOI (Digital Object Identifier) -    Publisher - IJEDR (ISSN - 2321-9939)
Cite this Article
Ankur Joshi,  Lakshmi Prasad,  Girish K. E.,   "Damage tolerance evaluation of a stiffened panel with a passenger window cutout of a transport airframe fuselage structure"
, International Journal of Engineering Development and Research (IJEDR), ISSN:2321-9939, Volume.2, Issue 2, pp.1598-1609, June 2014, Available at :http://www.ijedr.org/papers/IJEDR1402052.pdf