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

A numerical and experimental investigation for delamination buckling and gr owth for slender composite panels loaded in compression is presented. The i nvestigated panels consisted of 35 plies in a cross-ply layup with artifici ally embedded delaminations inserted after three, five or seven plies from the upper surface. The tests clearly and consistently showed that for all d elamination depths, delaminated panels failed by delamination growth slight ly below the global buckling load of the undamaged panel, whereas the undel aminated panels failed in compression at global buckling. The analysis was done with a finite element based computational model that accounts for cont act between delaminated members and fracture mode separation and where crac k 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 fo r loads at which delaminated members buckle, the load for onset of delamina tion growth and the evolution of delamination, e.g., delamination shape and out-of-plane displacements. (C) 2001 Elsevier Science Ltd. All rights rese rved.