Mechanical & Materials Engineering, Department of


Date of this Version

Spring 5-2012


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering, Under the Supervision of Professor Carl A. Nelson. Lincoln, Nebraska: May, 2012


Polymers play an essential role in our everyday life due to their employment in a widespread range of applications. Polymers are used in industries such as space, biomedical, electronics, etc. in which their electrical and mechanical properties are major aspects which need to be investigated prior to implementation. When subjected to mechanical stimulations, polymers may exhibit changes in electrical conductivity which can vary locally within the specimens, especially in those of conducting polymers. In mechanical investigations a tensile testing machine is used to understand polymers’ strength, elasticity or other mechanical properties. In electrical analysis, using a four-point probe to examine the electrical resistivity (conductivity) of a material is also frequently applied. However, no studies have been done to explore the relationship between mechanical manipulations and changes in electrical properties in situ. The current study explores this relationship.

An electrical conductivity testing system is designed and developed to couple with a tensile testing machine to measure the electrical conductivity of polymeric specimens while experiencing tensile loading. The system features a commercial four-point probe sensor, which is automatically controlled to approach a specimen and to measure the electrical conductivity of that specimen locally in two directions: longitudinally and transversely to the axis of stress. The method of testing is then implemented to experiment on specimens of high density polyethylene. Other types of specimens such as carbon nanotubes/polyethylene composites and metallic surface layer deposited polyethylene are also tested. Descriptions of the development process of the robotic systems and results of the execution are presented.

Advisor: Carl A. Nelson