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    Simulation of perforation and penetration in metal matrix composite materials using coupled viscoplastic damage model
    (Elsevier Sci Ltd, 2009) Deliktas, Babur; Voyiadjis, George Z.; Palazotto, Anthony N.
    In the first part of the two companion papers, theoretical formulation of the multiscale micromechanical constitutive model that couples the anisotropic damage mechanism with the viscoplastic deformation is presented. In the second part of these companion papers the numerical simulation of the computational aspects of the theory are elaborated. The perforation and penetration problem of metal matrix composites (MMCs) due to high impact loading is simulated. in this sense, the computational aspects of the developed theory are elaborated here. First. the verification of the developed model is performed through its numerical implementation in order to test the model predictions of the material characteristic tests. This encompasses uniaxial monotonic loading and unloading under different strain rates, uniaxial cyclic loading, and uniaxial loading and relaxation. The verified material routine of the developed model is then implemented in the explicit finite element code ABAQUS via the user defined subroutine VUMAT at each integration point in order to analyze the projectile impact and penetration into laminated composite plates. (C) 2009 Elsevier Ltd. All rights reserved.
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    Thermodynamically consistent coupled viscoplastic damage model for perforation and penetration in metal matrix composite materials
    (Elsevier Sci Ltd, 2009) Voyiadjis, George Z.; Deliktas, Babur; Palazotto, Anthony N.
    Accurate modeling and efficient analysis of the metal matrix composite materials failure mechanism during high velocity impact conditions is still the ultimate goal for many researchers. The objective is to develop a micromechanical constitutive model that can effectively simulate the high impact damage problem of the metal matrix composite materials. Therefore in this paper, a multiscale micromechanical constitutive model that couples the anisotropic damage mechanism with the viscoplastic deformation is presented here as a solution to this situation. This coupled viscoplastic damage model is formulated based on thermodynamic laws. Nonlinear continuum mechanics is used for this heterogeneous media that assesses a strong coupling between viscoplasticity and anisotropic damage. It includes the strong directional effect of the fiber on the evolution of the back stress and the development of the viscoplastic strain in the material behavior for high velocity impact damage related problems. (C) 2009 Elsevier Ltd. All rights reserved.