Shear modulus of single wood pulp fibers from torsion tests

Michael Dauer, Angela Wolfbauer, Tristan Seidlhofer, Ulrich Hirn

Research output: Contribution to journalArticlepeer-review


The shear modulus of pulp fibers is difficult to measure and only very little literature is available on this topic. In this work we are introducing a method to measure this fiber property utilizing a custom built instrument. From the geometry of the fiber cross section, the fiber twisting angle and the applied torque, the shear modulus is derived by de Saint Venant’s theory of torsion. The deformation of the fiber is applied by a moving coil mechanism. The support of the rotating part consists of taut bands, making it nearly frictionless, which allows easy control of the torque to twist the fiber. A permanent magnet moving coil meter was fitted with a sample holder for fibers and torque references. Measurements on fine metal bands were performed to validate the instrument. The irregular shape of the fibers was reconstructed from several microtome cuts and an apparent torsion constant was computed by applying de Saint Venant’s torsion theory. Fibers from two types of industrial pulp were measured: thermomechanical pulp (TMP) and Kraft pulp. The average shear modulus was determined as (2.13 ± 0.36) GPa for TMP and (2.51 ± 0.50) GPa for Kraft fibers, respectively. The TMP fibers showed a smaller shear modulus but, due to their less collapsed state, a higher torsional rigidity than the kraft fibers.

Original languageEnglish
Pages (from-to)8043-8054
Number of pages12
Issue number12
Publication statusPublished - Aug 2021


  • Permanent magnet moving coil instrument
  • Pulp fiber
  • Shear modulus
  • Taut band
  • Torsion theory

ASJC Scopus subject areas

  • Polymers and Plastics

Fields of Expertise

  • Advanced Materials Science


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