Effect of Oxidation of Graphene on Agglomeration and the Mechanical Properties of Thermosetting Resins

<p>Thermosetting resins are used extensively worldwide in applications ranging from adhesives to structural components. However, these resins generally fail in a brittle fracture mode which is undesirable in most situations. Graphene (G) and its derivatives have been considered as additives to epoxy for material property enhancement and varied results have been reported in the literature. In this work, the effects of the oxidation of G to graphene oxide (GO) on polymer interactions and plate agglomeration were studied by classical molecular dynamics (MD). Results from those simulations concluded that agglomerates were likely present in all G-based nanocomposites. The effect of these agglomerates on epoxy was investigated by manufacturing G or GO-doped epoxy nanocomposites with no pre-exfoliation method and conducting mechanical property testing in tension, bending, and compression.</p> <p>The response of GO/epoxy was different from that of neat and G-doped resin in all 3 tests, and under compression was dramatically different than under tension and bending. Under compression, the failure mode of the epoxy changed from brittle to slow tearing by adding 0.1 weight percent or greater of GO nanoplates. Computed tomography revealed the presence of previously unreported fissures in the GO samples, which were not seen in the neat or G-doped epoxy samples. These fissures appeared to inhibit crack propagation resulting in the slow, tearing failure mode in compression. Further MD simulations qualitatively supported agglomerations of GO in epoxy could nucleate void formation. Finally, the fracture toughness of these nanocomposites was estimated, showing that doping by agglomerated GO could increase the compressive fracture toughness of epoxy by approximately 1 to 2 orders of magnitude.</p> <p>Although other means of altering the failure mechanism in epoxy exist, doping with GO resulted in a PMPC that showed no reduction in stiffness or coefficient of thermal expansion and should not suffer from thermal degradation as elastomer-doped resins are prone to. The compilation of studies presented in this dissertation lays the foundation for understanding a new energy-absorbing failure mechanism in thermosetting resins.</p>

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Year dc:date.available

2024

Author dc:creator

• Reil, Matthew A.

Contributors dc:contributor

• Maciej Kumosa
• Joseph Hoffman
• Paul Predecki
• Yun Bo Yi
• Sandra Eaton

• Epoxy
• Fracture toughness
• Graphene oxide
• Molecular dynamics
• Nanocomposite
• Polymer composites
• Engineering
• Materials Science and Engineering
• Nanoscience and Nanotechnology
• Other Materials Science and Engineering
• Polymer and Organic Materials

Statement dc:rights

• <p>Copyright is held by the author. User is responsible for all copyright compliance.</p>

Language dc:language

English (eng)

Repository record dc:identifier

https://digitalcommons.du.edu/etd/2431

OAI identifier oai:identifier

oai:digitalcommons.du.edu:etd-3421