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Nanoindentation provides a convenient and high-throughput means for mapping mechanical properties and for measuring the strain rate sensitivity of a material. Here, nanoindentation was applied to the study of microcrystalline cellulose. Constant strain rate nanoindentation revealed a depth dependence of nanohardness and modulus, mostly attributed to material densification. Nanomechanical maps of storage modulus and hardness resolved the shape and size of voids present in larger particles. In smaller, denser particles, however, where storage modulus varied little spatially, there was still some spatial dependence of hardness, which can be explained by cellulose’s structural anisotropy. Additionally, hardness changed with the indentation strain rate in strain rate jump tests. The resulting strain rate sensitivity values were found to be in agreement with those obtained by other techniques in the literature. Graphic abstract: [Figure not available: see fulltext.]
Bibliographical noteFunding Information:
The authors thank Fang Zhou at the University of Minnesota Characterization Facility for help with potting and microtoming the samples used in this study. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program. The authors also thank Andres Chavez, Michael Oliver, Adam Pimentel, M. Barry Ritchey, and Mark Rodriguez (SNL) for assistance with microCT, SEM, and XRD analyses, and Dan Bolintineanu, Joel Clemmer, Marcia Cooper, Jeremy Lechman, and Stewart Silling (SNL) for informative conversations regarding the direction and results of this work. Support provided by Sandia National Laboratories Laboratory Directed Research and Development (LDRD). Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE?s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the United States Government.
© 2021, The Author(s), under exclusive licence to The Materials Research Society.
- Elastic properties
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