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Title: Broadband nanoindentation of glassy polymers: Part II. Viscoplasticity

Source: J. Mater. Res.

Author(s)Jakes, Joseph E.; Lakes, Rod S.; Stone, Don S.

Publication Year: 2012  View PDF »

Category: Journal Articles
Associated Research Project(s):   FPL-4707-3A

Abstract: The relationship between hardness and flow stress in glassy polymers is examined. Materials studied include poly(methylmethacrylate), polystyrene, and polycarbonate. Properties are strongly rate dependent, so broadband nanoindentation creep (BNC) is used to measure hardness across a broad range of indentation strain rates (10-4 to 10 s-1). Molybdenum (Mo) is also studied to serve as a “control” whose rate-dependent hardness properties have been measured previously and whose flow stress, unlike the polymers, is pressure insensitive. The BNC hardness data are converted to uniaxial flow stress using two methods based on the usual Tabor–Marsh–Johnson correlation. With both methods the resulting BNC-derived uniaxial flow stress data agree closely with literature compression uniaxial flow stress data for all materials. For the polymers, the BNC hardness data depend on initial rate of loading, indicating that the measured properties are path dependent. Path dependence is not detected in Mo.

Keywords: broadband nanoindentation; viscoplasticity; flow stress; hardness; polymer

Publication Review Process: Formally Refereed

File size: 302 kb(s)

Date posted: 03/26/2012

This publication is also viewable on Treesearch:  view
RITS Product ID: 41761
Current FPL Scientist associated with this product
Jakes, Joseph
Research Materials Engineer
  

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