Additive manufacturing (AM) uses a data computer-aided-design (CAD) model to direct hardware to deposit material, layer upon layer, in precise geometric shapes. As its name implies, additive manufacturing adds material to create an object. By contrast, it is often required to remove material through milling, machining, or other processes in conventional fabrication. AM technology presents exceptional openings to design and build complex structures that are unattainable under conventional manufacturing constraints. AM processes are known mainly by 3D printing also promote the realization of engineered materials with microstructures and properties that are impossible via traditional synthesis procedures. Overall, this thesis scope explores the fabrication of complex structures with exceptional mechanical properties through 3D printing and examines new techniques for printing different materials, including cement, graphite, and copper. The second chapter of this thesis presents several high-performance ultralight polymer-based structures that can only fabricate through AM technology. In addition, this chapter discusses the role of geometry in the mechanical properties of printed structures. Despite their high strength and modulus, ceramic and cementitious materials are limited in many structural applications due to inherent brittleness and low toughness. The third chapter describes a straightforward approach to enhance the fracture toughness of brittle materials, including ceramic and cement.
Chapter fourth describes the development of a nano-clay modified cement-based direct ink that enables high-resolution 3D printing of complex architected structures of tunable geometries, which could alleviate the fracture toughness of cement structures. The fifth chapter reports the development of colloidal graphite ink from commercial graphite powders that allows the fabrication of any complex architectures with tunable geometry and directionality via 3D printing at room temperature. The direct ink printing of complex 3D architectures of graphite without further heat treatments could lead to easy shape engineering and related graphite applications at various length scales, including complex graphite molds or crucibles. The sixth chapter demonstrates the possibilities of printing various metals and dissimilar materials interfaces using direct ink writing (DIW) aided 3D printing via a unique binder, namely clay. Several structures such as copper, copper/graphite, and copper/iron hetero-structures are developed using DIW, with desirable mechanical properties. The printing process and post-sintering have been done in succession to obtain complex architecture from metals and dissimilar metal-metal, metal-nonmetal interfaces. The technique allows enormous flexibility in multi-material printing, leading to various applications involving hetero-interfaces between different materials. The overall significance of the original collective work described here, and future directions are suggested at the end of this thesis.