Date of Award

Fall 12-2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical and Aerospace Engineering

Committee Director

Oleksandr Kravchenko

Committee Member

Krishnand Kaipa

Committee Member

Mileta Tomovic

Committee Member

Drew Landman

Abstract

Among many thermoplastics that are used in engineering, polyamide 6 (nylon 6) is an extremely versatile engineering thermoplastic. Nylon filled with glass fibers has higher mechanical strength and high wear resistance than general purpose nylon. 3D printed composites, based on fused filament modeling, typically suffer from poor bead-to-bead bonding and relatively high void content, limiting their mechanical properties

This thesis explores the effect of compaction pressure and temperature on improving the mechanical properties of 3D printed composites. Engineering moduli in the printing and transverse to printing direction, as well as ultimate strength were measured using the tensile testing with Digital Image Correlation (DIC). Tensile testing is performed on the samples that are compacted at different temperatures with pressure. In addition, microscopic studies were carried out to evaluate the void content for different compaction pressures and temperatures. Fiber orientation state was measured for different sets of samples. Differential scanning calorimetry (DSC) was carried out to calculate the degree of crystallinity and possible changes in crystalline morphology as a result of annealing temperature profile.

The results indicate that by selecting appropriate heat treatment profiles both strength and modulus of 3D printed composites can be significantly improved. Strength was improved by over 50% and 100% in printing and transverse directions respectively, and twofold increase of the modulus in printing direction was found. In this respect, the observed mechanical behavior will be explained in terms of various parameters such as degree of compaction, crystalline structure, orientation state and void content.

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DOI

10.25777/fghz-m472

ISBN

9798557054294

ORCID

0000-0002-6008-0116

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