An advanced model for initiation and propagation of damage under fatigue loading – part I: Model formulation

This paper presents a method for modelling initiation and propagation of damage in composites under fatigue loading in a single, coherent analysis using cohesive interface elements. Damage initiation laws based on SN-curves for initiation are applied to all interface elements within a zone of characteristic length, the so-called initiation zone. The formulation allows for a fully automated identification of the location of the initiation zone as well as automatic extraction of the local severity from the identified interface elements. Once a macroscopic crack has been initiated, it is propagated using damage accumulation laws based on the Paris-law. The formulation has been applied to the Short Beam Shear test and the Double Notched Shear test under fatigue loading. For both tests, good agreement was achieved with experimental data from the literature using an initiation zone length of 3.0 mm.