چكيده به لاتين
Micromechanics is a technique for the analysis of composites or heterogeneous materials which focuses on the components of the intended structure. Each one of the components can exhibit isotropic behavior, but the microstructure characteristics of the heterogeneous material results in the anisotropic behavior of the structure. In this research, the general mechanical properties of a 3D anisotropic and heterogeneous Representative Volume Element (RVE) have been determined by applying periodic boundary conditions (PBCs), using the Asymptotic Homogenization Theory (AHT) and strain energy. In order to use the homogenization theory and apply the periodic boundary conditions, the ABAQUS scripting interface (ASI) has been used along with the Python programming language. The results have been compared with the results of the Homogeneous Boundary Conditions method, which leads to an overestimation of the effective mechanical properties. In polymer-based composites, the fibers have a linear and brittle behavior, while the resin exhibits a non-linear behavior. Therefore, the effect of resin nonlinearity on the mechanical properties of the composite material is studied using a user-defined subroutine in Fortran (USDFLD). The non-linear shear stress-strain behavior of unidirectional composite laminates has been obtained. The results of this study are in good agreement with the analytical and experimental results available in the literature
In the process of making filament-wound composite pipes, the fiber bundles interweave in each circuit and these intersection areas of the fiber bundles are considered as stress concentration sites due to their wave motion. For this purpose, a three-dimensional RUC is modeled to examine the effect of the fiber bundle width on the mechanical and thermal properties of the composite pipes. In the process of this research, three models of classical lamination theory, mosaic model and fiber undulation model were compared. The RUC is under periodic boundary conditions and asymptotic homogenization theory is used to predict its mechanical and thermal behavior. The results show that the theory of classical lamination theory and mosaic model can lead to a worse estimation of the mechanical and thermal properties of the structure, and they are not sensitive to the various winding patterns. While the fiber undulation model has changed from 3.8 to 13.6 percent in mechanical and thermal properties.
Keywords: Periodic boundary condition, Asymptotic homogenization theory, Three-dimensional representative volume element, Mechanical and thermal properties, Python scripting, USDFLD subroutine, Mosaic model, Fiber undulation model
