Analytical Prediction of Mode I Stress Intensity Factors for Cracked Panels Containing Bonded Stiffeners Calvin Rans 1 , Riccardo Rodi 2 , René Alderliesten 2 1 Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, K1S 5B6, Ottawa, Canada 2 Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft, the Netherlands ABSTRACT: An analytical model for stress intensity factors in cracked skin panels containing bonded stiffening elements, based on the principles of superposition and displacement compatibility, is presented. The methodology permits assessment of the influence of stiffening elements ahead, behind, and over top of the skin panel crack tip, and allows the influence of stiffener disbond size to be studied. Validation of the model is made using experimental data from various literature sources. The influence of stiffener geometry and disbond size on damage tolerance is discussed using predictions from the presented model. KEYWORDS: Fatigue; damage tolerance; crack growth; bonded stiffener; stress intensity factor. NOMENCLATURE: a half-crack length [mm] A cross-sectional area [mm 2 ] b disbond length [mm] E Young’s modulus [GPa] F bridging load transfer due to bridging stiffener [kN] F broken load transfer due to broken stiffener [kN] F intact load transfer due to intact stiffener [kN] G shear modulus [GPa] K bridging stress intensity factor for skin panel loaded by F bridging [MPa√mm] K broken stress intensity factor for skin panel loaded by F broken [MPa√mm] K intact stress intensity factor for skin panel, with intact stiffening elements ahead of the crack tip, subjected to farfield loading [MPa√mm] K total resultant stress intensity factor in cracked stiffened panel [MPa√mm] P applied total load applied to stiffened panel [kN] P skin far field load in the skin panel [kN] P st,bridging far field load in a bridging stiffener [kN] P st,broken far field load in a broken stiffener [kN] P st,intact far field load in an intact stiffener [kN] R fatigue stress ratio t thickness [mm] v bridging crack opening for skin panel loaded by F bridging [mm] v broken crack opening for skin panel loaded by F broken [mm]