Delamination buckling and growth for delaminations at different depths in a slender composite panel

A numerical and experimental investigation for delamination buckling and growth for slender composite panels loaded in compression is presented. The investigated panels consisted of 35 plies in a cross-ply layup with artificially embedded delaminations inserted after three, five or seven plies from the upper surface. The tests clearly and consistently showed that for all delamination depths, delaminated panels failed by delamination growth slightly below the global buckling load of the undamaged panel, whereas the undelaminated panels failed in compression at global buckling. The analysis was done with a finite element based computational model that accounts for contact between delaminated members and fracture mode separation and where crack propagation was simulated with a moving mesh scheme. For all delamination depths, the analysis showed a dramatic increase in the energy release rate when global buckling takes place. Features seen in the tests were captured in the computational analysis. Excellent agreement with tests was found for loads at which delaminated members buckle, the load for onset of delamination growth and the evolution of delamination, e.g., delamination shape and out-of-plane displacements.