Doctoral Dissertations

Keywords and Phrases

Additive Manufacturing; Lattice Structure; Lightweight Composites; Lightweight Structural Material; Metal Matrix Composite; Metallurgy

Abstract

”In this work, two lightweight structures – lattice structures and metal matrix syntactic foams (MMSF) – were studied. Honeycomb lattices were manufactured by powder bed selective laser melting (SLM) from 304L stainless steel. The wall thicknesses of these structures ranged from 0.2 to 0.5 mm. Surface roughness was the primary cause of dimensional mismatch between the expected and as-built structures with an average wall thickness increase of 0.12 mm. The strength of the honeycombs increased with increasing wall thickness. A feature of the SLM microstructure, the melt pool boundary, was also studied as a part of this work. 3D models of the melt pool boundary network were developed. The goal of this study was to determine if the melt pool boundary significantly affects elastic or plastic properties in SLM materials. The study found a negative correlation between the concentration of the melt pool boundary network and the yield strength. The melt pool boundaries also seem to contribute to anisotropic plastic deformation. The copper matrix syntactic foams studied in this work were manufactured using low-pressure binder injection molding. The binder was a water-agar-glycerin gel optimized to achieve the highest sintered density for metal matrix syntactic foams. Syntactic foams use hollow or porous particles as their filler material. The two fillers used here were porous silica and bubble alumina, selected for their extreme differences in size, material, and porosity distribution. Three samples for each filler with increasing filler volume fraction were manufactured. The specific strength of the copper-porous silica samples increased with increasing volume fraction. The copper-alumina bubble sample greatly improved the impact resistance of the foam at low filler volume fraction”--Abstract, page iv.

Advisor(s)

Newkirk, Joseph William

Committee Member(s)

Chandrashekhara, K.
Watts, Jeremy Lee, 1980-
Gu, Yijia
O'Malley, Ronald J

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2020

Journal article titles appearing in thesis/dissertation

  • Build accuracy and compression properties of additively manufactured 304L honeycomb
  • Effect of the melt pool boundary network on the anisotropic mechanical properties of selective laser melted 304L
  • Optimization and characterization of novel injection molding process for metal matrix syntactic foams
  • Influence of filler material and volume fraction on copper matrix syntactic foams

Pagination

xiii, 138 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2020 Myranda Shea Spratt, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11799

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