UC San Diego

The relationship between synthesis, structure, and mechanical properties of additively fabricated materials are studied in this thesis. The goal is to determine how mechanical treatments during or post synthesis of the material can affect its microstructure and overall performance when compared to traditionally manufactured materials. Chapter 1 details how mechanical manipulation during fabrication can affect the graphitic and mechanical properties of electrospun carbon fibers. The fibers are characterized through tensile tests, Raman spectroscopy, and transmission electron microscopy. The carbon nanofibers have been found to have improved strength and stiffness when subjected to compressive stresses during the fabrication process when compared to untreated and tensile-treated samples.

In chapter 2, we describe how shot-peening additively manufactured 316L stainless steel samples affects its mechanical properties. The post-processed samples are characterized through tensile and fatigue tests to study the effect of surface compression on their mechanical behavior. Static and dynamic mechanical behaviors have been found to significantly benefit from the surface cold working, increasing tensile strength by 20% and fatigue life up to tenfold. Scanning electron microscopy allowed us to analyze the microstructure of the different samples in both 316L and the carbon nanofibers. The data collected is used to corroborate how the mechanical treatments of the samples have affected material behavior and structure. Developing insight into how these materials react to their respective mechanical treatments can help influence the methods in which they are produced, giving way to stronger and more efficient materials for load-bearing and structural applications.