Applied Mechanics Seminar – Feb 18, 2019 – Dr. Jinkyu Yang

The Origin of Softness in Fibre Network 

Dr. Tetsu Uesaka
Professor Emeritus
Mid Sweden University

When: March 18, 2019 | 2 PM
Where: CEME 1203| 6250 Applied Science Lane

Abstract: Fibre network is a ubiquitous structure that is widely seen in plant cells and animal tissues, as well as industrial materials (papers and nonwoven materials). Nature uses this structure as a fundamental building block of plants and animals, probably because it can represent an amazingly rich functionality (mechanical, physical and chemical).

It is, however, not easy to uncover such rich phenomena that nature created, because many fibre networks are disordered, the length scales of such disorders span in decades, and the structures are, often, hierarchical and anisotropic.

In this talk, we first introduce a general framework of our approach, DEM (Discrete Element Method) as a tool to represent disordered fiber networks. Fibre networks in question are those seen in hygiene products, typical low-density networks, such as baby diapers, feminine products, paper towels and bathroom tissues. Main focuses in this talk are on the deformation mechanics and failure of the fibre network, particularly, the origins of “softness”, criticality and scaling laws governing the deformations in both the thickness and in-plane directions.

From the point of industrial practices, low-density fibre networks are known to be extremely sensitive to their structures and fibre properties. This is because the density of those networks is close to, or sometime in the range of, rigidity percolation, jamming transition, and other unique network transition points. Therefore, the fundamental understanding of fibre networks provides a fertile ground for developing new design criteria of hygiene products.

Biography: Tetsu Uesaka was formerly Professor at a Swedish university, called Mid Sweden University. Now he is retired (a free man!). For the last 14 years, his career has been in academics, but previously he worked for paper industry for many years: At a paper company in Japan and also at a research consortium in Canada (PAPRICAN/FPInnovations).

His research interests are in complex systems and complex material, a class of materials of highly interactive multi-body systems, such as fibre networks and fibre suspensions. Those problems reside in the crossroads of traditional disciplines, and are also closely related to many of the outstanding issues of paper industry.

He received his doctoral degree from Kyoto University in 1980. He then worked as postdoc in State University of New York in Syracuse. In 1982, he joined Oji Paper in Tokyo, where he enjoyed fascinating problem-solving in product development and papermachine operation. In 1988 he moved to Montreal to join Pulp and Paper Research Institute of Canada (PAPRICAN), where he worked on the fundamentals of product performance and papermaking issues. He later joined the senior management team of the organisation. In 2003 he took the professorship in Mid Sweden University. His honors include J. A. Van den Akker award (Best paper award in the physics of paper) in 2003, 2007 and 2018, together with his excellent colleagues.