Nonlinear FEM 2D failure onset prediction of composite shells based on 6-parameter shell theory

• nonlinear 6 parameter shell theory, drilling rotation, asymmetric strain measures.
• material law for shells with Cosserat type kinematics in FPF analysis.
• Tsai-Wu and Hashin criteria modifications, satisfying the theory requirements.
• FPF loads estimations for theories with symmetric and asymmetric strain measures.
• quantitative and qualitative comparison of results.

Within the framework of the nonlinear 6-parameter shell theory with the drilling rotation and asymmetric stress measures, the modifications of Tsai-Wu and Hashin laminate failure initiation criteria are proposed. These improvements enable to perform first ply failure estimations taking into account the non-symmetric stress measures. In order to check the validity of the proposed criteria, finite element analyses are performed with the use of the Authors’ program and the Abaqus package. It is shown that the classical forms of the well known failure hypotheses can predict different stress capacity of structure, if the stress measures do not preserve the symmetry condition.