Meso-scale progressive damage modeling and life prediction of 3D braided composites under fatigue tension loading

3D braided composites have broad potential applications in the high-tech industries because of their superior mechanical properties. Fatigue is an essential design factor for their use in those engineering applications. The fatigue damage accumulation during cyclic loading should be involved in the numerical models in order to predict the fatigue life accurately. In this paper, a unit-cell based finite element model in conjunction with continuum damage mechanics (CDM) is developed for simulating the fatigue damage evolution process and predicting the fatigue life of 3D braided composites under fatigue tension loading. This meso-scale fatigue modeling, including stress analysis, failure criteria and material property degradation scheme, is implemented via a user-material subroutine UMAT based on ABAQUS/Standard platform with FORTRAN code. The fatigue damage initiation and propagation processes of 3D braided composites with typical braiding angles on the unit-cell model as a function of number of cycles are presented in detail. The fatigue life of 3D braided composites is predicted from the computed S-N curve and the stiffness degradation process is also investigated. The obtained numerical results indicate that the present model can provide a suitable reference to the numerical study of the fatigue issues in other textile composites.