Kaplamalı takviyeye sahip polimer nanokompozitler için iki seviyeli bir homojenleştirme yöntemi

Polymer nanocomposites are materials which have polymer matrices and nano-scale reinforcement elements. Other than the matrix and the reinforcement element, another phase in nanocomposite systems has been observed and some of the property enhancement or deficiency has been attributed to this phase. The third phase in the composite system is known as the interphase. The local properties of polymer nanocomposites are not easy to distinguish since the length scale is very small and characterization at the nano-scale is not a simple procedure. Macroscopic behavior of nanocomposites can be deducted by homogenization of a representative volume element in many different ways. The aim of the thesis is to propose a new homogenization approach to model the polymer nanocomposites with coated inclusions. Understanding the structure of nanocomposites, formation of the interphase and different characterization techniques for the interphase are important for this aim. Interphase properties affect the overall macroscopic mechanical behavior. So it is important to model the interphase and obtain the effective composite properties accordingly. Different homogenization techniques and applications related to this problem are studied and a new approach is proposed. This method aims to model load transfer between the matrix and the reinforcement element through the interphase in a correct way. Furthermore, a computational gain is aimed with the proposed model in comparison to a full three-phase finite element simulation. Another goal is to extend the proposed method to viscoelasticity. For this purpose two-dimensional and three-dimensional finite element codes are developed for a viscoelastic homogenization framework. The formulations regarding the viscoelastic homogenization are derived and presented.