Post-Failure Behavior of Laminates I — No Stress Concentration

Experimental and analytical results are presented for the post-failure behavior of unnotched quasi-isotropic glass-epoxy laminates. The analysis is based on a simplified tangent modulus method and a maximum stress ply failure criterion. Several ply failure models are considered, involving vari ous combinations of stiffness reduction. The most significant finding is that matrix failure in the 90° layers must be supplemented by reduction of E 11 as a result of a fiber instability mode.