Date of Award


Document Type


Degree Name



Mechanical Engineering

First Advisor

Maciej Kumosa, Ph.D.


Ab initio modeling, Coating, Hybrid rods, Nanoparticles, Polymer matrix composites, Thermal aging


Increased energy usage in the United States and worldwide is driving the demand for new technologies to transmit electrical power in greater quantities and with reliable, safe, and more efficient methods. One recent innovation is to replace the standard Aluminum Conductor Steel Reinforced electrical transmission conductor with a new conductor design that utilizes a fiber reinforced polymer core rod to support a fully annealed aluminum conductor. This new technology that includes a hybrid carbon fiber/epoxy and glass fiber/epoxy support core allows for better efficiency and for greater current to be transmitted in the same size and weight line. These new conductor lines are part of a new class of conductors called High Temperature Low Sag (HTLS) for their ability to transmit more current while still providing appropriate ground clearance over vegetation. However, long-term exposure to high temperatures can diminish the flexural properties of the hybrid composite core rods.

This dissertation contributes unique and innovative multiscale approaches to understand and reduce the impact of thermal aging on the core rods. The research demonstrates that the source of flexural failure in the rods moves from predominantly physical aging to predominantly chemical aging as a function of time and temperature, a brand new explanation that is validated both experimentally and numerically. Further, for the first time, it is shown that coating the rods with a barrier that may delay thermal oxidation is an effective method of reducing and delaying chemical aging and therefore can be a practical method for increasing their service life. It also finds that while the detrimental impact of physical aging escalates with increasing temperature as expected, the effect of chemical aging is in fact mitigated by moving from aging at 180 °C to 200 °C. In addition, the dissertation evaluates the benefit of increasing radiative cooling on the operating temperature of the conductor in order to find a method of transmitting the same current while reducing the thermal aging. Lastly, the impact of incorporating nanoparticles into the epoxy matrix is assessed to identify an additional method of retarding thermal aging.

Thus, instead of simply identifying and explaining problems, this research goes a step further and offers a comprehensive approach to preventing thermal aging of the conductors and other structures utilizing polymer matrix composites. It offers significant advances in the use of nanotechnology to reduce aging of polymer composites; it identifies a coating to reduce the impact of chemical aging; and it suggests a radiative cooling as an important approach to reduce both physical and chemical aging in the rods. All of these tactics are evaluated both experimentally and numerically in this work. Most importantly, this research advances the understanding and improves the performance of polymer core HTLS conductors along with other polymer composites subjected to high temperatures. With the improvement and adoption of the techniques presented, confidence in the safety and endurance of the novel conductor is increasing its implementation in this country and around the world.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.


Received from ProQuest

Rights holder

Joe D. Hoffman

File size

125 p.

File format





Nanoscience, Materials Science, Mechanical Engineering