Fatigue Damage Evolution in NotchedComposite Plates

Composite materials, increasingly adopted for structural applications, due to their specific stiffness and strength characteristics, are, characterized by complex failure mechanisms interacting each other. These failure mechanisms, under certain loading conditions, can influence the load carrying capability leading to a premature failure of the structure. In order to address this issue, in this paper, a damage propagation numerical model based on customized failure criteria and gradual material degradation rule is proposed. The numerical model has been implemented, by means of FORTRAN user subroutines (UserMat), within the FEM code ANSYS©. The resulting numerical tool is able to simulate the progressive failure in layered structures under arbitrary multi-axial static and fatigue loading conditions. A preliminary validation against literature experimental data on notched composite plates under static and fatigue loading conditions is presented. Comparisons with experimental results have confirmed the effectiveness of the numerical tool in predicting the composite behaviour taking into account static failure mechanisms and fatigue material degradation at ply level.