Nonlinear analytical approach for preliminary sizing of discrete composite stringer terminations

A recently developed nonlinear approach is adapted and used to predict crack initiation in stringer terminations of discretely assembled composite panels made from skin and stiffeners. A linear elastic fracture mechanics based submodel is used to simulate the crack initiation in the critical regions and the influence of ply drop-off is captured. The von Kármán formulation for moderately large deflections in plates is used to capture the nonlinear structural behavior; three-dimensional assemblies are schematized and the effect of eccentricity is included in the simulation. An optimum design criterion is sought and basic guidelines for good design are provided. Furthermore, a method for preliminary assessment of structural strength is proposed and predictions are validated against detailed nonlinear finite element analysis.