Date of Award
Daniel Felix Ritchie School of Engineering and Computer Science, Mechanical and Materials Engineering
David Wenzhong Gao
Mechanical properties, Metal-free friction material, Molecular dynamics, Thermal properties, Tribological properties
Metallic friction materials currently used in industry may adversely impact the environment. Substitutions for metals in friction materials, on the other hand, can introduce operational safety issues and other unforeseeable issues such as thermal-mechanical instabilities and insufficient strength. In view of it, this dissertation focuses on developing different kinds of materials from simple structure to complex structure and evaluating the material properties with the assistance of molecular dynamics (MD) tools at the nano scale.
First, the concept of the contacted surfaces in friction at the atomic scale was introduced in order to get accurate understanding of the friction process compared to the macro scale. A MD model of 3C-SiC asperities was constructed for investigating the effect of the asperity-surface on the tribological properties. The surface contact with various number of scenarios were included to show the fundamental characterization of the interface in friction at the nano level. Generic simulation models for analyzing mechanical properties and thermal properties were developed as well to fully study the characteristics of 3C-SiC as a nonmetallic friction material. The predictions on the coefficient of friction (COF), wear rate, Young’s modulus, ultimate tensile strength (UTS), and thermal conductivity under different conditions were made based on the MD simulation.
Second, with the acknowledgement that 3C-SiC has been proven to be an ideal matrix material in friction, a new graphene (Gr) reinforced 3C-SiC nanocomposite model with lamellar structure was designed in MD simulation. The covalent bonding between Gr and 3C-SiC was applied to obtain better performance than the weak bonding. The interfacial energy between Gr and 3C-SiC was studied to examine the stability of the structure. Similarly, the tribological properties, mechanical properties, and thermal properties of the nanocomposite were considered to help understand the effect of Gr as a potential reinforcement for metal-free friction materials.
Finally, a new 3C-SiC spherical nanoparticle reinforced epoxy crosslinked nanocomposite with diglycidyl ether of bisphenol A (DGEBA) as the epoxy monomer and 3,3-diaminodiphenyl sulfone as the curing agent was constructed and studied considering the advantages epoxy have, such as relative low cost, remarkable environmental compatibility, and less powder generation or carbon deposition. Under different degrees of crosslinking, the glass transition temperature, fractional free volume, forces and COF during friction, Young’s modulus, and thermal conductivity of the nanocomposite as well as the pure epoxy with the same configurations were evaluated to provide a reference in designing real 3C-SiC/epoxy friction composite and similar materials with better performances.
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Received from ProQuest
Zhang, Yizhan, "Molecular Dynamics Study of Characterization in Metal-Free Friction Materials" (2023). Electronic Theses and Dissertations. 2358.
Mechanical engineering, Materials science, Nanoscience