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Author
Title Spherical nanoindentation protocols for extracting microscale mechanical properties in viscoelastic materials
URL
Publication Date
Date Accessioned
Degree PhD
Discipline/Department Mechanical Engineering
Degree Level doctoral
University/Publisher Georgia Tech
Abstract Nanoindentation has a high load resolution, depth sensing capabilities, and can be used to characterize the local mechanical behavior in material systems with heterogeneous microstructures. Recently nanoindentation has been used to extract useful stress-strain curves, primarily in hard materials such as metals and ceramics. To apply these indentation stress-strain methods to polymer composites, we have to first develop analysis techniques for materials that exhibit viscoelasticity. In a lot of current research the viscoelastic material properties are extracted after the material has been deformed enough to initiate plasticity and in some cases the time dependence of the deformation is ignored. This doesn’t give an accurate representation of the material properties of the undeformed sample or the local deformation behavior of the material. This dissertation develops analysis protocols to extract stress-strain curves and viscoelastic properties from the load-displacement data generated from spherical nanoindentation on materials exhibiting time-dependent response at room temperature. Once these protocols are developed they can then be applied, in the future, to study viscoelastic and viscoplastic properties of various mesoscale constituents of composite material systems. These new protocols were developed and tested on polymethyl methacrylate, polycarbonate, low-density polyethylene, and the bio-polymer chitosan. The properties extracted were consistent under different conditions and we were able to produce stress-strain curves for different loading rates and different indenter tip sizes. This dissertation demonstrates that a set of protocols can be used to reliably investigate the mechanical properties and deformation behavior of time-dependent materials using nanoindentation.
Subjects/Keywords Nanoindentation; Viscoelastic; Polymers; Stress-strain; Mechanical properties
Contributors Kalidindi, Surya R. (advisor); Zhou, Min (committee member); Gall, Ken (committee member); Wegst, Ulrike G. K. (committee member); Jacob, Karl I. (committee member)
Language en
Country of Publication us
Record ID handle:1853/54359
Repository gatech
Date Indexed 2018-01-11
Issued Date 2015-08-25 00:00:00
Note [degree] Ph.D.;

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