Local fracture mechanics analysis of stringer pull-off and delamination in a post-buckled compression panel

This paper describes some of the current global/local testing and analysis approaches to evaluating the design of composite structure. A case study for the local, fracture mechanics analysis of failure in a 4- stringer compression panel is described in detail. The analysis investigates the variation of strain energy release rate G with debond length using a 2-D plane strain finite element analysis (FEA) of one of the stringers. The boundary conditions on the local model were determined from a global shell element model of the panel. Delamination was also modelled in the cap of the stringer using FEA and a closed form solution. The values of G for these two damage modes were compared with the material's fracture toughness. Using this analysis, the load to initiate the stringer debond and to cause edge delamination of the cap may be determined.