Numerical micromechanics-based evaluation of mechanical and thermal properties of polypropylene/MMT clay nanocomposites

This study numerically investigates mechanical and thermal properties of polypropylene/montmorillonite (MMT) clay nanocomposites, focusing on Young's modulus, thermal expansion coefficient (TEC), and thermal conductivity. A three-phase representative volume element (RVE) with periodic boundary conditions (PBCs), incorporating polypropylene matrix, MMT clay nanoplatelets and an interphase, is employed to conduct micromechanics-based finite element simulations. The interphase, modeled with variable characteristics, represents the interaction zone between the matrix and nanofillers. The MMT clay nanoplatelets are dispersed randomly, aligned and agglomerated within the polypropylene matrix, with their aspect ratio and volume fraction systematically changed to investigate the microstructural influences on the nanocomposite's properties. Uniform dispersing MMT clay nanoplatelets into the polypropylene matrix is found to improve the elastic modulus, TEC and thermal conductivity of resulting nanocomposites. However, the nanofiller agglomeration leads to localized stress concentrations, potentially reducing mechanical properties, and introduces thermal barriers that can lower overall thermal conductivities. Results show that alignment of MMT clay nanoplatelets within the polypropylene matrix can be useful from the structural point of view because the nanocomposite gives higher material performances in the longitudinal direction as compared to other states. Higher aspect ratios, where nanoplatelets are aligned, lead to more improvements in the nanocomposite longitudinal properties. Comparisons reveal a good agreement between present numerical results and existing data in the literature.