03/30/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Doctoral Dissertation defense by Yuvprakash Singh on: "Beyond Prototyping: FFF printing for high-performance and functional materials."

Candidate Name: Yuvprakash Singh
Degree: Doctoral
Defense Date: Thursday, April 2, 2026
Time: Noon - 2 p.m.
Location: ETIC 445

Committee:

  • Advisor: Jay H. Park, Associate Professor, Plastics Engineering, University of Massachusetts Lowell
  • David O. Kazmer, Professor, Plastics Engineering, University of Massachusetts Lowell
  • Amir Ameli, Associate Professor, Plastics Engineering, University of Massachusetts Lowell

Brief Abstract:
FFF 3D printing beyond prototyping: Efforts towards enabling FFF 3D printing to be a viable manufacturing technique for high-performance and functional materials Fused filament fabrication (FFF) is one of the most widely adopted material extrusion additive manufacturing techniques, due to its accessibility, ease of operation, and low setup cost. Despite its widespread use, applications of FFF-printed parts remain largely limited to prototyping, primarily because of poor mechanical strength, lack of functionality and limited compatibility with highly crystalline polymers. As a result, the full potential of additive manufacturing such as freedom of design and low-cost manufacturing remains underutilized for demanding engineering applications.
To address this fundamental challenge, current research efforts are being focused on increasing the strength and improving functionalities of the printed parts. However, challenges such as poor interlayer adhesion, structural instability, and high filler content requirement have prevented FFF from reaching real-world applications. The objective of this PhD dissertation is to advance FFF beyond prototyping by strengthening vertical prints, understanding processability of highly crystalline polymers, and enabling conductive prints with reduced filler content. These attempts are in contribution to making FFF-based additive manufacturing more functional as well as more accessible to highly crystalline polymers, which make up most of the thermoplastics currently produced by volume.

In pursuit of this goal, three aims were executed. Aim 1 focuses on achieving injection-molded strength in vertically printed high-performance plastics via optimized annealing of core-shell polyether imide filaments. Aim 2 investigates the effect of flow-induced crystallization (FIC) on the printability of HDPE, where evidence of FIC was observed through the formation of elongated spherulites and shish-kebab morphology in printed microstructures under processing-induced flow conditions. Aim 3 involves fabrication of low-filler content robust electrically conductive FFF parts using a core-shell filament strategy with a neat PLA core and post processing treatment. Ultimately, this dissertation presents a pathway to making FFF a more functional and industrially relevant manufacturing technique by improving mechanical reliability, understanding microstructural changes and enhancing functionality to expand FFF’s potential for real-world applications.