The nanomechanics during the indentation test on low-density nanoporous silica aerogels remains one of the least understood and explored areas of mechanics. In the present work, we performed nanoindentation using a spherical indenter on silica aerogels to investigate the mechanical properties, such as elastic modulus and hardness, and also, the deformation behaviour. Using all-atom simulations on large samples, the elastic modulus is computed from the elastic part of force–depth curves that can be fitted to the Hertz law, which shows that it increases with density. We proposed a novel approach to calculate the projected true contact area in nanoindentation and to estimate an accurate hardness of silica aerogel, which has a highly complex and randomly arranged network of atoms structure. The experimental studies of nanoindentation are performed on silica aerogel, which reveals that the measured elastic modulus is in good agreement with the simulations. However, the measured hardness values are nearly close to the projected contact area method. It suggests that in all-atom simulations the computed high hardness values using the proposed true area method are the actual local contact pressure. This new understanding may help to expand the use of computer simulations to explore the nanoindentation processes at the molecular level and to advance the macroscopic hardness calculation.
Bibliographical noteFunding Information:
The authors gratefully acknowledge the computing time granted on the supercomputer JURECA (project ID: jhpc35) at the Jülich Supercomputing Centre (JSC). This work was supported by Korea-Africa Joint Research Programme grant funded by the Korea government ( Ministry of Science, Technology & ICT ), Republic of Korea in 2017K1A3A1A09085891 .
© 2018 Elsevier B.V.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering