Failure Prediction of Multidirectional Composite Laminates under Fatigue Loading using an Energy Based Damage Model

The purpose of this study is to estimate the fatigue life of laminated composites using a novel model based on continuum damage mechanics. For this purpose, a closed form criterion based on the energy method has been presented in the context of damage mechanics such that considers the difference of damage in three directions and moreover is not limited to a special layup. The proposed model has been implemented in the ANSYS finite element software using the material coded by the user (Usermat). The method of characterization of the model constants has been presented in this paper and the constants have been determined for AS4/3501-6 Carbon-Epoxy composite and finally, validation of the model for unidirectional and multidirectional layered composites has been evaluated. For multidirectional laminates, results of fatigue life for cross-ply laminates with hole with the layups [04/904]s and [904/04]s compared with experimental results. The results show that the developed model can predict the fatigue life of laminated composites only by using the material constants which is obtained from experiments of unidirectional laminates in two stress levels.