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The application of modeling theories and the choice of failure criteria are difficult in part because they are too varied and must be validated by biaxial tests, which are expensive to be performed. This article is devoted to the nonlinear modeling and failure criteria which are employed in the design and analysis of anisotropic materials. Indeed, in this work, a study of the macroscopic and microscopic behavior of a graphite epoxy under a three-point bending test is conducted, and the successive failures are also predicted. Experimentally, the damage progression and the effect of geometrical parameters are followed and identified in detail. The analytical modeling is based on a recently developed approximation for isotropic materials. This approximation is also valid for the studied quasi-isotropic laminated composite. A software program has been elaborated for the application of the most general failure criteria. The results obtained by this analytical modeling show a good correlation with those of the experimental study.

In order to ensure structural integrity in such applications of composites materials, it is important to understand the material behaviour under mechanical loadings and predict correctly its responses. In this paper, the authors perform several three-point bending tests on a typical stacking sequences used in composite structures. Inspection techniques involving a digital microscope are used to study the successive failures and the effect of the thickness ratio (l h −1 ) on nonlinear behaviour. It was found that successive failures depend on the stacking sequence where the orthogonal sequences have a significant effect on the delamination between the plies. To describe the nonlinear behaviour observed, Von-Karman's large deflection theory and classical plate theory (CPT) are employed in the formulation of analytical modelling used in this work. The Riccati equation obtained leads to predict the experimental nonlinear curves with good accuracy. However, a slight dispersion between the experimental and analytical curves less than 11% was observed at large deflection.

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