Debond resisting composite stringers

The following extends existing work done by Cosentino and Weaver on predicting crack initiation in discretely assembled skin/stringer composite panels. This allows for the anal- ysis of fully coupled systems ie. non-zero B matrix. The nonlinear structural behaviour is obtained by means of the von Karman formulation for moderately large deections in plates; three-dimensional assemblies are schematized and the effect of eccentricity is in- cluded in the simulation. Solutions are calculated by means of a Rayleigh-Ritz approach based on Galerkin's method, and a linear elastic fracture mechanics-based model is used to simulate the crack initiation in the critical regions. Using this method a bi-level opti- misation using lamination parameters was performed subject to closed form buckling and debonding constraints. The optimisation was performed with respect to improving the strength and overall load carrying capacity for a fixed geometry. The results show through the use of layup optimisation incorporating exure-membrane coupling effects debonding can be reduced.