A physically based fatigue damage model for simulating three-dimensional stress states in composites under very high cycle fatigue loading

Abstract

Over the years, various models have been developed to predict the fatigue behavior in fibre reinforced plastics. Recently, a new fatigue damage model (FDM) was developed. The FDM relates the energy dissipated in the quasi-static case to the energy dissipated under a cyclic loading. The model is based on evolution laws for fatigue based degradation and is more physically oriented than most models as it has an energy based methodology and takes into account Puck’s failure modes for the degradation of strength and stiffness. Since it is based on a macro-mechanical analysis scale and uses a block wise loading approach, the FDM can be applied to arbitrary structures and consideration of a large number of cycles is also possible with this model. Moreover, phenomena such as stress redistribution and sequence effects occurring under fatigue conditions can also be analyzed. Originally, the FDM was based on a two-dimensional (2D) formulation and implemented within layer-based shell elements. In the present work, an extended version of the FDM is presented. The extended version comprises a three-dimensional (3D) formulation and a finite element implementation based on solid elements. The extended FDM is used for numerical simulations of the very high cycle fatigue behavior of laminates for specific reference cases such as four-point bending based cyclic loading. Results obtained from the original FDM (2D FDM) and the present work (3D FDM) are compared and in a final step compared with the results obtained from experiments in a four-point bending test.