محمدحسين كريمي دونا

Elastomeric nanocomposites are a group of polymer-based composite materials in which many physical properties, including the mechanical properties of the elastomer material, are improved by using nanoparticles. This thesis aims to improve classic micromechanical methods to predict the elastic modulus as well as the stress-strain behavior of elastomeric nanocomposites. For this purpose, by using the concept of eigen-strain in nanoparticles and matrix, the Eshelby model, which was initially developed to model the micro-structural defects of solids, is improved. The Mori-Tanaka analytical and self-consistent models for two-phase systems are re-extracted based on the modified Eshelby equivalent inclusion model. Also, a computer code has been developed using MATLAB program to predict the effective elastic properties that use the modified models to compare the results of the new model, the conventional models, and the other related analytical models including the Hashin-Shtrikman model. In this research, in addition to spherical and cylindrical nanoparticles, expanded graphite particles have been investigated by considering new factors including the diameter of primary particles, volume ratio, and real aspect ratio. Also, an improved constitutive-micromechanical model was developed using incremental theory to predict the stress-strain behavior of the elastomeric composite specimen reinforced with expanded graphite particles. Also, the elastic properties of the interphase region were eva‎luated using the molecular dynamics method and the COMPASS potential function. In the experimental program of this research, specimens of pure fluoroelastomer reinforced using carbon black particles (5wt%, 10wt%) and expanded graphite particles (1wt%) were fabricated and subjected to a tensile test under standard conditions. The results have shown that the developed micromechanical models can predict the material's elastic properties and stress-strain behavior with better accuracy than the previous models. Also, compared to carbon black, expanded graphite particles have significantly improved the final strength and elongation at the break of the elastomer, in addition to Young's modulus, even at a small weight fraction.

ميكرومكانيك , نانوكامپوزيت هاي پليمري , الاستومر , ذره بسط يافته گرافيتي

micromechanics , polymer nanocomposites , elastomer , expanded graphite particle

Mohammad Hossein Karimi

Dr. Fathollah Taheri Behrooz