Modeling and additive manufacturing of multi-material structures

Official URL: http://risc01.sabanciuniv.edu/record=b1662492 (Table of Contents)

Multi-material objects are composed of two or more materials put together to produce specific properties or functionality which cannot be achieved using a single material. Traditional manufacturing processes may not be used for manufacturing multi-material products. Recently, Additive Manufacturing processes have been developed for manufacturing of complex geometries. However, most of the parts made by Additive Manufacturing processes consist of single materials and thus they have limited or single functionality. Progress in Additive Manufacturing demands substantial improvements in deposition techniques and multi-material developments while addressing current challenges in controlling structural features in macro as well as micro scales. This thesis is dedicated to research in different domains of multi-material development. This work is divided into two main sections. The computational part of this work is on the application of Finite Element Method (FEM) to study the mechanical properties of different multi-material systems, including the elastic analysis of bulk composites of polymer/carbon nanostructures and continuous fiber reinforced composites. Representative Volume Element (RVE) based FEM analysis was applied to study the isotropic and anisotropic mechanical properties of such structures to determine process parameters based on the requirements of each material system. It was found out that the most important parameters in the reinforcement are the geometry of fillers in nanocomposites while in case of coaxial printing the process parameters like layer thickness and pattern geometries are very critical. The second section is related to the Additive Manufacturing of multi-material structures. To manufacture multifunctional structures, a custom-made additive manufacturing platform (SU3D) have been designed and developed. The developed hardware includes reconfigurable multi-nozzle deposition units; each can be operated independently based on the physical properties of the targeted materials. The functions of different hardware elements in conventional platforms were innovatively redefined in SU3D resulted in significant flexibility of the system in adoption with the properties of the processed materials. A fully automated process plans were also developed to completely integrate with the hardware functionalities. Two novel multi-material additive manufacturing methods have also been developed for printing of heterogeneous hydrogel and hybrid structures.