The finite element modeling is presented to study the buckling and postbuckling behavior of composite laminates with an embedded delamination. Degenerated shell element and rigid beam element are utilized for the finite element modeling. In the nonlinear finite element formulation, the updated Lagrangian description method based on the second Piola-Kirchhoff stress tensor and the Green strain tensor is used. It is assumed that delamination exists before loading and delamination growth is ignored. Such an assumption for overall compression behavior of composite laminates with a delamination is validated through the experiment.
The buckling and postbuckling behavior of Graphite/Epoxy composite laminates with a delamination are investigated for various delamination sizes, stacking sequences and boundary conditions. Three different possible modes of instability are identified at the critical load. It is shown that bifurcation buckling occurs for composite laminates with a delamination. The buckling load and postbuckling behavior of composite laminates depend on the buckling mode which is determined by the delamination size, stacking sequence and boundary conditions. It is also found that the presence of delamination in composite laminates having stacking sequences to increase buckling load can reduce greatly buckling load.
