Indentation Behavior of Multilayer Al/SiC Thin Films

Nanoindentation is useful for evaluating the mechanical properties, such as hardness and Youngs modulus, of bulk and thin film materials. Multilayer thin films are an important subset of materials in which alternating layers of two or more materials are deposited on a substrate. Fabrication of multilayer films can result in imperfect layer geometry, particularly the flatness and thickness of each layer. Traditional nanoindentation techniques alone cannot provide insight into the microstructure of each layer. The finite element method is used to investigate the behavior of multilayer aluminum/silicon carbide thin film composites with imperfect internal geometry when subjected to various loadings. Undulating layered geometry is subjected to various loading scenarios, and the response of the structure is measured. The indentation- derived hardness and modulus are shown to be sensitive to the presence of undulating layers and the relative size of the indenter to the undulation. The amount of equivalent plastic strain in the Al layers also increases in the presence of undulating layers. These multilayer films exhibit interesting and complex mechanical behavior under indentation type loading and unloading. The derivation of Young's modulus from nanoindentation testing assumes elastic unloading. It is shown that multilayer thin films may not unload elastically, altering the indentation-derived modulus result. The cyclic behavior of the multilayer thin film is studied in relation to the influence of unloading-induced plasticity. It is found that several cycles are required to minimize unloading-induced plasticity. Lastly, the effect of indentation-induced damage on derived hardness and modulus of multilayer films is investigated.'

Name thesis:degree_name

Mechanical Engineering

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Mechanical Engineering

Year

2015

Author dc:creator

• Jamison, Ryan

Contributors dc:contributor

• Shen, Yu-Lin
• Massad, Jordan
• Tehrani, Mehran
• Tarefder, Rafiqul

• FEA
• Nanoindentation
• Thin Films
• Delamination

Language dc:language

English

Identifier

https://digitalrepository.unm.edu/me_etds/29

OAI identifier oai:identifier

oai:digitalrepository.unm.edu:me_etds-1028