Damage evolution in [±45]s laminates with fiber rotation

The competing effects of increasing stiffness due to fiber rotation and decreasing stiffness due to damage evolution are incorporated into the Ladevèze mesoscale damage model to study the large strain response of [±45]s laminates of IM7-K3B, graphite-fiber/polyimide-matrix composite. It is shown that both of these competing effects are significant and the lack of their consideration can result in significant error when predicting large strain, non-linear response. Predictions of the model with and without fiber rotation are compared with experimental results for the tensile response of [±45]s laminates. It is also shown that variations in cross-sectional area of test specimens plays an important role in the large strain response of this high Poisson-ratio laminate. Improved correlation between theory and experiment is demonstrated when all competing effects are included in the analysis. The study includes predictions of stresses and damage variables in the individual layers of the laminate as a function of the modeling approach.