In the present paper 3D rate sensitive constitutive model for modeling of laminate composites is presented. The model is formulated within the framework of continuum mechanics based on the principles of irreversible thermodynamics. The matrix (polyester resin) is modeled by employing a 3D rate sensitive microplane model. For modeling of fibers (glass) a uni-axial constitutive law is used. The fibers are assumed to be uniformly smeared-out over the matrix. The formulation is based on the assumption of strain compatibility between matrix and fibers. Total stress tensor is additively decomposed into the contribution of matrix and fibers, respectively. To model de-lamination of fibers, the matrix is represented by periodically distributed initial imperfection over the pre-defined bands, which are parallel to fibers. Physically, this assumption accounts for the matrix-fiber interface in a smeared way. The input parameters of the model are defined by the mechanical properties of matrix and fibers (elastic properties, strength and fracture energy), the volume fraction of fibers and by their spatial orientation. The model is implemented into a 3D finite element code. To assure mesh objective results crack band method is employed. The model is first calibrated using a few basic test results. Subsequently, the model is validated with several numerical examples for specimens loaded in uni-axial tension, uni-axial compression and shear. Comparison between numerical and test results shows that the proposed model is able to predict the resistance and failure mode of complex fiber-reinforced composite for different orientation of fibers and different loading conditions with sufficient accuracy. Finally, based on the qualitative type of the finite element analysis, it is demonstrated that the strain rate dependency becomes more important when the angle between the fiber and load direction increases.
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