Date of Award:

12-2008

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Mechanical and Aerospace Engineering

Advisor/Chair:

Brent E. Stucker

Abstract

This research is a systematic study exploring a new fabrication methodology for long-fiber-reinforced metal matrix composites (MMCs) using a novel additive manufacturing technology. The research is devoted to the manufacture of long-fiber-reinforced MMC structures using the Ultrasonic Consolidation (UC) process. The main objectives of this research are to investigate the bond formation mechanisms and fiber embedment mechanisms during UC, and further to study the effects of processing parameters on bond formation and fiber embedment, and the resultant macroscopic mechanical properties of UC-made MMC structures. From a fundamental research point of view, bond formation mechanisms and fiber embedment mechanisms have been clarified by the current research based on various experimental observations. It has been found that atomic bonding across nascent metal is the dominant bond formation mechanism during the UC process, whereas the embedded fiber are mechanically entrapped within matrix materials due to significant plastic deformation of the matrix material during embedment. From a manufacturing process point of view, the effects of processing parameters on bond formation and fiber embedment during the UC process have been studied and optimum levels of parameters have been identified for manufacture of MMC structures. An energy-based model has been developed as a first step toward analytically understanding the effects of processing parameters on the quality of ultrasonically consolidated structures. From a material applications point of view, the mechanical properties of ultrasonically consolidated structures with and without the presence of fibers have been characterized. The effects on mechanical properties of UC-made structures due to the presence of embedded fibers have been discussed.

Comments

This work was revised and made publicly available electronically on August 3, 2011.

Share

COinS