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A micro-mechanical model based on the representative volume element (RVE) is presented to study the time-dependent and creep behavior of fibrous composite material. To this aim a finite element model is presented for analysis of creep behavior of material in multi-axial creep are presented. The generalized plane strain condition is employed to model the behavior of the RVE in axial and transverse normal loading. The governing equations of the problem in the RVE are discretized using the presented finite element method and the stiffness and force matrixes are presented. Appropriate boundary conditions are implied to the RVE in order to consider the transverse and axial loading conditions including creep behavior. The Euler explicit method is employed to solve the discretized equations in the time domain. The distribution of micro-stresses and the effect of creep in re-distribution of the stresses are studied. The steady state creep behavior of composite in macro-mechanical scale is investigated by analysis of the micromechanical behavior of the RVE. The macro-mechanical creep behavior of metal matrix composite in axial and transverse loading are predicted from the presented micromechanical model.

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In the present study, the effect of graphite nano platelet (GNP) as a filler on the vibrational properties of the epoxy EP411 DSM matrix was studied. For this purpose, GNP-epoxy composites samples were fabricated with 0-5 wt.% of GNPs using the solution mixing method. Free and forced vibrations tests on the cantilever composite specimens were conducted. Based on the free vibration results, the structural damping loss factor η was obtained as a function of the GNP loading. It was found that η   decreases as the GNP wt.% increases and reaches to the lowest value at 0-3 wt.% of GNP content, and  increases as the GNP loading increases and reaches to the value at 3-5 wt.% of GNP. Also, the frequency response function (FRF) around the second vibration mode was obtained for the neat epoxy. The Rayleigh damping coefficients were calculated employing the free and forced vibration results. The results revealed a nonlinear dependence of damping ratio η on the natural frequency of the neat epoxy. A representative volume element (RVE) incorporating 0-5 wt.% of GNPs was generated and the vibrational properties were numerically simulated. The modeling results were compared with those obtained from the experiment to verify whether the basic assumptions had been chosen properly.