How do you analyze postbuckling behavior in composite panels?

Composite postbuckling analysis requires: Geometric nonlinear FEM to capture large displacements after initial buckling; Progressive failure analysis tracking ply failures and delamination growth; Degradation models reducing stiffness of failed plies; Delamination modeling using cohesive zone or VCCT methods; Manufacturing imperfections (ply waviness, thickness variation) as initial perturbations; and Validation through coupon and panel testing. Analysis tracks load path changes as initial buckling mode develops and secondary buckling may occur. Composites show less stable postbuckling than metals due to delamination. Design typically limits postbuckled strain and requires demonstrated ultimate load capability in test.