What is Puck's criterion in brief and what failure modes does it consider?

• A. A criterion ignoring ply interactions.
• B. A global laminate buckling criterion under compression.
• C. A ply-level criterion distinguishing fiber-failure along fiber and inter-fiber (matrix-dominated) failures, with interaction between normal and shear stresses.
• D. A criterion focusing only on matrix cracking.

Answer: (C)

Puck's criterion is a ply-level failure rule for composite laminates that distinguishes two main damage modes and includes how normal and shear stresses interact within the ply. The first mode is fiber-failure along the fiber direction, which depends on the stress state parallel to the fibers and how that interacts with transverse normal stress and in-plane shear. The second mode is inter-fiber or matrix-dominated failure, which includes matrix cracking and related issues at the fiber-matrix interfaces, and it is strongly influenced by transverse stresses and shear. By treating these two modes separately and incorporating the coupling between normal and shear components, Puck’s criterion can predict which mode governs failure under a given multi-axial load. This makes it more nuanced than criteria that focus on a single mode or ignore interaction effects. It is not a global laminate buckling criterion, nor is it limited to matrix cracking alone.