Small-scale behavior of natural materials
P. Vinci, Richard Chromik, Jon Zeszotarski, Marie Messmer, and
Natural materials (geological or
biological) are often difficult to characterize mechanically, either
because the features are very small or the substance is not compatible
with standardized tests designed for engineering materials.
The behavior of kerogen in shale is one example of a scale-limited
system. Understanding the stresses exerted on kerogen is important for
the evaluation of potentially oil-bearing rock. Chemically extracting
the kerogen from the rock alters its structure and therefore its
mechanical properties. Nanoindentation is one method for exploring the
properties while the kerogen is still embedded in the substrate.
At a much larger scale, the intermandibular tissue of macrophagic
snakes displays remarkable viscoelastic properties. They are also
difficult to test because in-vivo testing of poisonous snakes has
certain hazards associated with it. Nonetheless, it can be done and the
material can be described using classic models from the polymer science
Nanoindentation curves resulting from pockets of kerogen and
the surrounding shale. Large differences in hardness can be seen from
the differences in maximum depth.
Image of in-vivo testing of intermandicular tissue in a
Texas rat snake.
- Work collaboratively with colleagues in chemistry and biology to
perform mechanical tests on challenging natural materials.
- Kerogen in Woodford shale is measurable with nanoindentation.
- Measurements of kerogen in Woodford shale indicate no sign of
anisotropy that might be associated with highly directional forces
- Intermandibular tissue from several macrophagic snakes shows
classic indications of viscoelasticity, including stress relaxation and
- J. Zezotarsky, R.R. Chromik, R.P. Vinci, M.C. Messmer, R.
Michels, and J.W. Larsen, Imaging and mechanical property measurements
of kerogen via nanoindentation, Geochimica et Cosmochimica Acta 68,
2004, p. 4113.
Funding for this work would be welcomed. Support thus far has
- the Donors of the Petroleum Research Foundation, administered by
the American Chemical Society
- Hysitron Inc.
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Last updated: August 2, 2005