01/26/2024
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Doctoral Dissertation Proposal defense by Juhyeong Lee on "The Relationship between ABS Characteristics and Interlayer Bond Formation in MatEX AM."

Candidate Name: Juhyeong Lee
Degree: Doctoral
Defense Date: Friday, Feb. 9, 2024
Time: 10 a.m. to noon
Location: Perry Hall 215

Committee:

  • Advisor Jay Hoon Park, Assistant Professor, Plastics Engineering, University of Massachusetts Lowell
  • David Kazmer, Professor, Plastics Engineering, University of Massachusetts Lowell
  • Amir Ameli, Assistant Professor, Plastics Engineering, University of Massachusetts Lowell
  • Christopher Hansen, Professor (Chair), Mechanical and Industrial Engineering, University of Massachusetts Lowell

Brief Abstract:
Material extrusion additive manufacturing (MatEx AM) has garnered significant attention for its capacity to produce intricate 3D structures cost-effectively and efficiently using a diverse range of materials. Among these materials, Acrylonitrile-Butadiene-Styrene (ABS) is widely utilized due to its favorable rheological and mechanical properties. Nevertheless, the additive layer-by-layer construction with shear gradient and rapid cooling characteristics of ABS result in insufficient interlayer bond formation, leading to reduced interlayer adhesion, the presence of interlayer voids, and anisotropy. Consequently, weaker mechanical properties persist compared to the conventional process.

To address these challenges, current research efforts are concentrated on improving mechanical properties through various strategies, including development of new materials, and implementation of post-processing techniques (e.g., thermal annealing). The objective of this PhD dissertation is to offer new insights into optimizing interlayer bond formation by studying the effects of material characteristics on the behavior of amorphous polymer during printing and thermal annealing, ultimately demonstrating improved mechanical properties.

In pursuit of this goal, three aims are proposed. Aim 1 focuses on the structural and rheological benefits of core-shell dual-materials filaments, consisting of ABS composite as the core and virgin ABS as the shell, on interlayer bond formation. Aim 2 delves into understanding the relationship between ABS polymerization methods, microstructure, and their effects on interlayer bond formation during printing and thermal annealing. Aim 3 involves a thorough evaluation of the effects of rheological behaviors of ABS with different microstructures on interlayer bond formation during printing and thermal annealing. Ultimately, this work aims to present a systematic study of the varied properties of ABS and their impact on interlayer bond formation, providing a new organizing principle for interpreting inconsistent and empirical results obtained with different ABS grades to date.