A micromechanical model for viscoelastic-viscoplastic analysis of particle reinforced composite

This study introduces a time-dependent micromechanical model for a viscoelastic-viscoplastic analysis of particle-reinforced composite and hybrid composite. The studied particle-reinforced composite consists of solid spherical particle and polymer matrix as constituents. Polymer constituent exhibits time-dependent or inelastic responses, while particle constituent is linear elastic. Schapery's viscoelastic integral model is additively combined with a viscoplastic constitutive model. Two viscoplastic models are considered: Perzyna's model and Valanis's endochronic model. A unit-cell model with four particle and polymer sub-cells is generated to obtain homogenized responses of the particle-reinforced composites. A time-integration algorithm is formulated for solving the time-dependent and inelastic constitutive model for the isotropic polymers and nested to the unit-cell model of the particle composites. Available micromechanical models and experimental data in the literature are used to verify the proposed micromechanical model in predicting effective viscoelastic-viscoplastic responses of particle-reinforced composites. Filler particles are added to enhance properties of the matrix in the fiber reinforced polymer (FRP) composites. The combined fiber and particle reinforced matrix forms a hybrid composite. The proposed micromechanical model of particle-reinforced composites is used to provide homogenized properties of the matrix systems, having filler particles, in the hybrid composites. Three-dimensional (3D) finite element (FE) models of composite's microstructures are generated for two hybrid systems having unidirectional long fiber and short fiber embedded in cubic matrix. The micromechanical model is implemented at the material (Gaussian) points of the matrix elements in the 3D FE models. The integrated micromechanical-FE framework is used to examine time-dependent and inelastic behaviors of the hybrid composites.