What failure criteria are used for composite materials and when is each appropriate?

Common composite failure criteria include: Maximum stress/strain criteria - simple but don't account for interaction; Tsai-Hill and Tsai-Wu - account for stress interaction, widely used for design; Hashin criteria - separate fiber and matrix failure modes; Puck criteria - distinguishes inter-fiber failure modes (IFF); and LaRC criteria - advanced physics-based, used for certification. Selection depends on application: Tsai-Wu for initial design screening, Hashin or Puck for detailed analysis distinguishing failure modes, LaRC for damage progression. First-ply failure is conservative; progressive failure analysis captures post-failure redistribution. Allowables include environmental knockdowns (hot-wet conditions).