A parametric study on crack initiation was done by having different sizes of cracks at different locations in a rib section of an aircraft using finite element techniques. A semi-elliptical surface flaw in a typical Boeing-747 rib section having circular cut-out and experiencing an in-plane shear loading was considered for the analysis. A laminated composite square plate around a centrally located cut-out was selected in the wing rib for computation purpose. A delamination has been modeled in between the composite layers in the form of a semi-elliptical surface crack using node duplication technique. As there are no theoretical solutions for mixed mode loading problems, the general purpose finite element package ABAQUS was used to obtain the Stress Intensity Factor (SIF) along the crack edge. These stress intensity factor (KC) values were further compared with the fracture toughness of the material to determine the probability of crack initiation. It was observed that the modes of failure change with the dimensions of the crack and also showed a greater tendency towards the crack initiation. © 2015 ASM International
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Dr. Sivakumar V., Kumar, G. B., and Gautham, A., “Crack Initiation Study on Aircraft Composite Rib with Semi-elliptical Surface Flaw”, Journal of Failure Analysis and Prevention, 2015.