Tetsu Uesaka's KTH Solid Mechanics KENOTE Seminar "Non-affine Deformation of Fibre Network: The Origin of Stiffening and Softening"

Tetsu Uesaka_Feb_22_2024.pdf (pdf 191 kB)

Abtract. A fibre network is a ubiquitous structure, which is seen in the cytoskeleton in plant and animal cells, paper, nonwoven, and their composites. These structures are generally highly disordered, and thus their deformations are not “affine”, that is, local strains are not equal to macroscopic strains (non-affine). In this talk, we take an example of a paper fibre network and investigate non-affine deformation fields in the fibre scale by using a Discrete Element Method (DEM). With the DEM, fibres are represented by a series of connected spherical particles (“beads”). The bead-bead interactions, within a fibre and between fibres, are represented by forces and moments in stretching, shear, bending and twisting. Non-affine deformation is a result of the system’s attempt to minimise its total strainenergy. Therefore, the system tends to settle in the lower-energy modes of deformation, such as bending and twisting over stretching. An astonishing feature is that only a few fibres carry the most strain energy or forces, whereas the majority of fibres almost “rest”. Therefore, the peak of the distribution of strain energy of individual fibres resided very close to zero. The implications of these results is discussed in relation to the stiffening and softening phenomena of the fibre network