Abstract
Granular chain packings exhibit a striking emergent strain-stiffening behavior despite the individual looseness of the constitutive chains. Using indentation experiments on such assemblies, we measure an exponential increase in the collective resistance force with the indentation depth and with the square root of the number of beads per chain. These two observations are, respectively, reminiscent of the self-amplification of friction in a capstan or in interleaved books, as well as the physics of polymers. The experimental data are well captured by a novel model based on these two ingredients. Specifically, the resistance force is found to vary according to the universal relation , where is the friction coefficient between two elementary beads, is their size, and is the volume fraction of chain beads when semidiluted in a surrounding medium of unconnected beads. Our study suggests that theories normally confined to the realm of polymer physics at a molecular level can be used to explain phenomena at a macroscopic level. This class of systems enables the study of friction in complex assemblies, with practical implications for the design of new materials, the textile industry, and biology.
- Received 27 July 2017
- Revised 16 December 2017
DOI:https://doi.org/10.1103/PhysRevLett.120.088001
© 2018 American Physical Society
Physics Subject Headings (PhySH)
Focus
Bead Chains Impersonate Polymer Molecules
Published 23 February 2018
Chains of metallic beads act a lot like polymer molecules, even though real polymers are in constant motion.
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