Micro-mechanics based Progressive Fatigue Damage models of laminated composite
The increased demand for new advanced composites in the aerospace, automotive, civil and military applications necessitates predictive fatigue failure models of composite materials and structures at different loadings. While the mechanical behavior under fatigue loading of metallic materials is well established, this is not the case for composites. Fatigue in composite materials is associated with several interacting damage mode systems, often leading to sudden brittle failure.
Predictive fatigue damage models in composite materials are also challenging due to the complex failure mechanisms under static and fatigue loading and because of the anisotropic elastic and strength properties.
However, a good model has the potential to reduce the sizeable experimental effort needed to test for different composite material systems and their constituents, such as fibers, matrices, lamination stacking sequences, etc. In addition, fatigue experiments are expensive as a single coupon may need to be tested for up to several weeks. In this study, two micromechanical methods are proposed for the fatigue failure prediction of unidirectional, cross-ply and multidirectional laminated composites under general loading with minimal dependence on empirical parameters. Both of the methods are based on using the generalized method of cells (GMC) micromechanical model. The first approach is based on fatigue micro-failure criteria, which are applied separately to the fiber and matrix regions and examines stresses and energy-based criteria. The second approach is implementing a damage law evolution for isotropic materials that applied only to the matrix zones.
T
he proposed model is aimed to supply predictive data for fatigue life, residual strength and stiffness degradation. To this end, a new multi-scale fatigue module is implemented in the Abaqus FE code for the fatigue analysis of plates with an open hole. The use of micromechanics allows the study of damage at both the micro and macro scales that explicitly recognize the fiber and matrix constituents. The proposed GMC-Fatigue constitutive equations enable a multi-scale fatigue analysis of laminated composite structures.