A multiscale damage-based strategy to predict the fatigue damage evolution and the stiffness loss in composite laminates

The fatigue life of composite laminates is characterized by several hierarchical damage mechanisms interacting at different length scales and synergically causing the loss of stiffness and strength. In this chapter, a framework developed by the authors to predict the damage evolution and the stiffness loss in multidirectional laminates under cyclic loadings is presented. It integrates models and criteria for predicting crack initiation and propagation under multiaxial fatigue loadings, the stress re-distributions and the stiffness loss in the presence of off-axis cracks, and a procedure to predict the crack density evolution. All the models and criteria were developed based on the damage mechanisms observed at the micro-and macro-scales during uniaxial and multiaxial fatigue tests. The comparison between the crack density and stiffness predictions and the available experimental data from the literature revealed the accuracy and the reliability of the proposed approach.