Damage evolution in [+/- 45](s) laminates with fiber rotation

The competing effects of increasing stiffness due to fiber rotation and dec reasing stiffness due to damage evolution are incorporated into the Ladevez e mesoscale damage model to study the large strain response of [+45](s) lam inates of IM7-K3B, graphite-fiber/polyimide-matrix composite. It is shown t hat both of these competing effects are significant and the lack of their c onsideration can result in significant error when predicting large strain, non-linear response. Predictions of the model with and without fiber rotati on are compared with experimental results for the tensile response of [+/-4 5](s) laminates. It is also shown that variations in cross-sectional area o f test specimens plays an important role in the large strain response of th is high Poisson-ratio laminate. Improved correlation between theory and exp eriment is demonstrated when all competing effects are included in the anal ysis. The study includes predictions of stresses and damage variables in th e individual layers of the laminate as a function of the modeling approach. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.