Presenter Information

Ashley Bucsek, University of Wyoming

Department

Mechanical Engineering

First Advisor

Dr. Chung - Souk Han

Description

Small - scale polymers are increasingly being applied to a variety of fields, making it important to understand the behavior of polymers at small length scales. Indentation size effects (ISE) is the apparent increase in ma terial - specific properties at very low indentation depths. These effects are observed for a wide range of materials, including polymers and metals. Unlike in metals, ISE in polymers is neither well understood nor well documented. The ISE in properties suc h as universal hardness and elastic modulus were investigated using nanoindentation. For this study, polydimethylsiloxane (PDMS) was chosen as a common polymer. Surface detection criteria were experimentally determined, and a consistent Berkovich indenter tip was used for all tests. The results for a cross - link density of 5% indicate two characteristics: first, there is a clear increase in universal hardness and elastic modulus with decreasing indentation depths, and second, the hardness and elastic modulu s reach transient values as indentation depth increase. This illustrates the drastic ISE in PDMS at low indentation depths. The research group members and I will be combining the results for different cross - link densities to examine the effect of cross - l ink density on ISE. These findings will be incorporated into a manuscript to be submitted for publication.

Comments

Oral Presentation, Wyoming NSF EPSCoR

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Nanoindentation of Polymers

Small - scale polymers are increasingly being applied to a variety of fields, making it important to understand the behavior of polymers at small length scales. Indentation size effects (ISE) is the apparent increase in ma terial - specific properties at very low indentation depths. These effects are observed for a wide range of materials, including polymers and metals. Unlike in metals, ISE in polymers is neither well understood nor well documented. The ISE in properties suc h as universal hardness and elastic modulus were investigated using nanoindentation. For this study, polydimethylsiloxane (PDMS) was chosen as a common polymer. Surface detection criteria were experimentally determined, and a consistent Berkovich indenter tip was used for all tests. The results for a cross - link density of 5% indicate two characteristics: first, there is a clear increase in universal hardness and elastic modulus with decreasing indentation depths, and second, the hardness and elastic modulu s reach transient values as indentation depth increase. This illustrates the drastic ISE in PDMS at low indentation depths. The research group members and I will be combining the results for different cross - link densities to examine the effect of cross - l ink density on ISE. These findings will be incorporated into a manuscript to be submitted for publication.