Crossover from mean-field compression to collective phenomena in low-density foam-formed fiber material

Tero Mäkinen*, Juha Koivisto, Elina Pääkkönen, Jukka A. Ketoja, Mikko J. Alava

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

10 Citations (Scopus)

Abstract

We study the compression of low-weight foam-formed materials made out of wood fibers. Initially the stress-strain behavior follows mean-field like response, related to the buckling of fiber segments as dictated by the random three-dimensional geometry. Our Acoustic Emission (AE) measurements correlate with the predicted number of segment bucklings for increasing strain. However, the experiments reveal a transition to collective phenomena as the strain increases sufficiently. This is also seen in the gradual failure of the theory to account for the stress-strain curves. The collective avalanches exhibit scale-free features both as regards the AE energy distribution and the AE waiting time distributions with both exponents having values close to 2. In cyclic compression tests, significant increases in the accumulated acoustic energy are found only when the compression exceeds the displacement of the previous cycle, which further confirms other sources of acoustic events than fiber bending.
Original languageEnglish
Pages (from-to)6819-6825
JournalSoft Matter
Volume16
Issue number29
DOIs
Publication statusPublished - 7 Aug 2020
MoE publication typeA1 Journal article-refereed

Funding

We acknowledge the financial support from the Academy of Finland through the Centers of Excellence program (Project No. 251748), and the postdoctoral grant 308235 (J. K). M. A. acknowledges support from the European Union Horizon 2020 research and innovation programme under grant agreement No. 857470 and from European Regional Development Fund via Foundation for Polish Science International Research Agenda PLUS programme grant No. MAB PLUS/2018/8. The work has been partly supported by the European Regional Development Fund (grant number A73089, A73092). We are also grateful for the support by the FinnCERES Materials Bioeconomy Ecosystem. We acknowledge the computational resources provided by the Aalto University School of Science ‘‘Science-IT’’ project.

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