Progressive Fatigue Damage Modeling of Composite Materials, Part II: Material Characterization and Model Verification

To validate the fatigue progressive damage model, developed in the first part of this paper, an experimental program was conducted using graphite/epoxy AS4/3501-6 material. As the input for the model, the material properties (residual stiffness, residual strength and fatigue life) of unidirectional AS4/3501-6 graphite/epoxy material are fully characterized under tension and compression, for fiber and matrix directions, and under in-plane and out-of-plane shear in static and fatigue loading conditions. An extensive experimental program, by using standard experimental techniques, is performed for this purpose. Some of the existing standard testing methods are necessarily modified and improved. To evaluate the progressive fatigue damage model, fatigue behaviour of pin/bolt-loaded composite laminates is simulated as a complicated example. The model is validated by conducting an experimental program on pin/bolt-loaded composite laminates and by comparison with experimental results from other authors. Different capabilities of the model are examined by conducting different types of experiments. The comparison between the analytical results and the experiments shows the successful simulation capability of the model.