Evaluation of energy release rate for delamination defects at the skin/stringer interface of a stiffened composite panel

This paper deals with numerical investigation on a stiffened composite panel under longitudinal compression load, in presence of artificial delamination defects between skin/stringer interface layers. At first, both the experimental and numerical non-linear equilibrium paths were determined, until the failure load value of the structure was reached. Then local evaluation of the energy release rate parameter was performed at defect front, by means of a hybrid (FEM/analytical) procedure based on a particularized virtual crack closure technique. The same FE shell model was used to perform both global and local calculations by means of a single analysis.