Publication Date

Spring 2019

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical and Materials Engineering

Advisor

Ozgur Keles

Keywords

3D printing, Additive Manufacturing, Composite, FDM, Mechanical Reliability, Vibrated

Subject Areas

Materials Science

Abstract

Additive manufacturing has seen sustained growth in both consumer and industrial areas. fused deposition manufacturing (FDM), a specific additive manufacturing technology, has seen increased sales in consumer markets. In order to maintain growth, FDM will be increasingly used for load-bearing applications. However, the mechanical reliability of FDM polymers and composites is not well understood. This can be dangerous to property and safety. Presented in this paper are more than 16 distinct populations comprised of at least 23 unique tensile tests, a total of 506 tensile tests. Weibull statistics were used to quantify variance in physical properties of FDMed materials. It is the hope of the author that these data will provide essential information for designers to make parameter selections for safe load-bearing applications of FDM parts. Using the deviations from Weibull, scanning electron microscopy, and micro X-ray CT, the author examined the origins of variations in mechanical properties. A key factor in mechanical reliability comprises variations in the size and shape of inter-bead pores. In the final section, this problem was addressed with a novel vibration assisted FDM (VA-FDM) that reduced the porosity by 3 %, increased the fracture strength by 12 %, and doubled the tensile strength reliability. These findings showed that inter-bead porosity can be significantly reduced by localized extruder vibrations and that reduced inter-bead porosity influences the mechanical properties and variations in those properties.

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