How do you predict failure in composite laminates under multiaxial loading?

Composite failure analysis uses ply-by-ply stress calculation via Classical Lamination Theory, then applies failure criteria to each ply. Maximum stress/strain criteria are simple but non-interactive. Tsai-Hill and Tsai-Wu criteria capture stress interaction. First-ply-failure is conservative; progressive damage analysis tracks load redistribution after initial failure. Delamination requires fracture mechanics approach. FEA with composite elements and progressive damage models is standard for aerospace structures.