Mechanical Engineering ETDs

Publication Date

Spring 4-28-2022


Despite the design freedom that additive manufacturing (AM) processes provide, there are still challenges in using some AM processes for end-use products. Fused filament fabrication (FFF), also known as material extrusion, is one of the AM technologies that has been used mainly for prototyping due to the low cost of machines, raw material, and ease of operation. Another advantage of FFF is its ease of integration with other additive or subtractive technologies. However, some disadvantages such as relatively poor and anisotropic mechanical properties have hindered FFF for end-use engineering components. The first chapter of this dissertation is a brief review of AM technologies, market trends, motivations for this research, and an overview of all chapters. The second chapter covers design concepts and design for additive manufacturing (DfAM), focusing mainly on polymers and polymer composites. The third chapter examines a core-shell filament for multi-material printing and enhanced interface bonding. Chapter 4 investigates the effects of over-extrusion and build orientations on tensile properties of FFF parts via experiments and modeling. In chapter 5, the impact of build orientation on the fracture toughness of FFF parts is examined experimentally. Chapter 6 provides a demonstration of combining an FFF (additive) process with traditional machining (subtractive) and extrusion-based direct witting of conductive inks for multi-functional structures. Finally, chapter 7 summarizes main findings of this dissertation and proposes topics for future studies.


Fused Filament Fabrication(FFF), Core shell filament, Mechanical anisotropy, Extrusion multiplier

Degree Name

Mechanical Engineering

Level of Degree


Department Name

Mechanical Engineering

First Committee Member (Chair)

Yu-Lin Shen, Ph.D

Second Committee Member

Mehran Tehrani, Ph.D.

Third Committee Member

Pankaj Kumar, Ph.D.

Fourth Committee Member

Maryam Hojati, Ph.D.


Air Force Research Lab (AFRL)

Document Type




Included in

Manufacturing Commons