Type of Document Thesis Author Oliver, Anita Author's Email Address firstname.lastname@example.org URN etd-12132007-115917 Title Mechanical and Electrical Properties of Carbon Nanotube Reinforced Polycarbonate at Liquid Nitrogen Temperature Degree Master of Science Department Mechanical Engineering, Department of Advisory Committee
Advisor Name Title Anter El-Azab Committee Member Justin Schwartz Committee Member Richard Liang Committee Member Keywords
- Nonfunctionalized Multiwall Carbon Nanotube
- Mechanical Properties
- Electrical Properties
- Cryogenic Temperature
Date of Defense 2007-11-30 Availability unrestricted AbstractMechanical and electrical properties of non-functionalized, multiwall carbon nanotube reinforced polycarbonate composites are studied at 77 K. There are five sample groups tested in this study which included 0 wt%, 0.1 wt%, 1.0 wt%, 5.0 wt%, and 10.0 wt% carbon nanotube reinforced polycarbonate samples. Some data at room temperature is also reported, but has not been investigated extensively because it was used for comparison to the 77 K data only. As anticipated, the distribution, interfacial bonding, and concentration of nanotubes within the individual samples play a major role with respect to electrical and mechanical properties.
During mechanical testing, stress, strain and temperature measurements have been performed in order to characterize the mechanical and thermal behavior of the composite. The temperature measurements have revealed little to no heat dissipation during tensile testing. Mechanical testing has shown an increased strength of the composite samples with increasing amount of nanotubes as well as an increase in brittleness and Young’s modulus. The 5.0 wt% carbon nanotube reinforcement has emerged as the concentration which resulted with best mechanical properties compared to the other samples tested, with highest strength of 192 MPa and relatively high strain-to-failure of about 4%. The distribution of yield stress data for each sample group has been analyzed using Weibull distributions.
By comparison of 77 K to room temperature data, it was evident that the cryogenic testing temperature was the cause for greater interfacial debonding effects and that higher concentration samples were affected the most. Higher concentration samples showed an increase in bundling as well while the low concentration samples did not demonstrate much improvement in mechanical properties in general. SEM imaging was used to look at fracture surfaces and an agreement with collected data has been established.
Preliminary electrical measurements have been used to determine the onset voltage for the samples in order to set the stage up for possible electromechanical testing. Electrical testing data has revealed that the percolation point is around 1.0 wt% for electrical conductivity of the composite with the 1.0 wt% samples representing the transitional phase from insulating to conducting material.
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