Protocols for studying the time-dependent mechanical response of viscoelastic materials using spherical indentation stre
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Protocols for studying the time-dependent mechanical response of viscoelastic materials using spherical indentation stress-strain curves M.T. Abba1 · S.R. Kalidindi1
Received: 2 June 2019 / Accepted: 1 October 2020 © Springer Nature B.V. 2020
Abstract Spherical nanoindentation has been used successfully to extract meaningful indentation stress-strain curves in hard materials such as metals and ceramics. These methods have not yet been applied on viscoelastic-viscoplastic polymer samples. This study explores the potential of the current spherical nanoindentation analysis protocols in extracting indentation stress-strain curves and viscoelastic properties on samples exhibiting time-dependent material response at room temperature. These new protocols were tested on polymethyl methacrylate, polycarbonate, and low-density polyethylene. The properties extracted under different loading rates and indenter tip sizes conditions were observed to be consistent. It is further demonstrated that it is possible to recover the compression stress-strain curves for polymethyl methacrylate and low-density polyethylene from the measured indentation stress-strain curves. This study establishes some of the foundations needed for the development of protocols needed to reliably investigate the local time-dependent mechanical response of materials using spherical nanoindentation. Keywords Nanoindentation · Viscoelasticity · Stress-strain · Microscale · Finite element analysis
1 Introduction Optimizing the overall mechanical properties of most advanced materials requires a good understanding of the mechanical properties of its microscale constituents. This task requires the development and validation of novel multi-resolution mechanical characterization assays (Hemker and Sharpe 2007; Jaya and Alam 2013; Srikar and Spearing 2003). In addition to being able to measure the mechanical properties in very small volumes typical of the sizes of the microscale constituents in advanced materials, it is desirable to develop methods capable of high-throughput testing. This is essential to obtain critical information on the very
B S.R. Kalidindi
[email protected]
1
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA
Mech Time-Depend Mater
large variety of potential microscale constituents that could be found in advanced material systems (Kalidindi et al. 2017). Nanoindentation offers tremendous promise in addressing this critical need, and has been successfully employed to study the microscale properties of metal and ceramic constituents in advanced material systems (Khosravani et al. 2020; Weaver and Kalidindi 2016; Fischer-Cripps 2002). There is a critical need to extend these protocols to measuring the time-dependent mechanical responses of the viscoelastic constituents in complex material systems. More specifically, modern nanoindenters possess high load resolution and depth sensing capabilities, and can be used to characterize the local mechanical behavior in materi
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