FEM analysis of composite materials failure in nonlinear six field shell theory

Bartosz Sobczyk

FEM analysis of composite materials failure in nonlinear six field shell theory

Abstrakt

The monography deals with the problem of failure initiation in thin laminated composites. Known techniques of laminate structures modelling are briefly characterised. Eventually, shell based approach is chosen for the purpose of the description of the composite structures behaviour, as it predicts their deformation and states of stress effectively in a global sense. The nonlinear six parameter shell theory (6p theory) with asymmetric strain and stress measures is mainly used within the work and thus its main properties are described. Selected and commonly known methods of the damage onset description for laminated shells, based on the assumption of stress tensor symmetry, named as standard criteria, are studied and analyzed. These are: Tsai-Hill, Tsai-Wu, Hashin and Puck. Modifications of the aforementioned criteria meeting the requirements of the 6p theory are discussed and proposed, since no precise descriptions of the damage initiation in laminates are found in the literature when asymmetric strain and stress components are utilised. The modified criteria, allowing first ply failure (FPF) analysis of laminates, are implemented into non-commercial finite element method (FEM) code CAM. Finally, six numerical examples are solved using FEM to check if the FPF estimations resulting from the application of the standard and the modified criteria differ.