Pulp Fiber Bending Stiffness in Wet and Dry State Measured from Moment of Inertia and Modulus of Elasticity

Christian Lorbach, Wolfgang J. Fischer, Adriana Gregorova, Ulrich Hirn, Wolfgang Bauer


The bending stiffness of pulp fibers in both dry and wet states is of great importance with respect to many optical and physical paper properties. We introduce a method that evaluates fiber bending stiffness from the fibers’ Young’s modulus (E) and the area moment of inertia (I) from the fiber cross section. The values for E and I in the dry state are obtained from single fiber tensile testing and image analysis of the fiber cross section. The values for the wet state are estimated from literature results for decreasing elastic modulus due to wetting and by the measurement of swollen, freeze-dried fiber cross sections by serial sectioning. We show a comparison between the results from our method and the bending stiffness of individual fibers measured with other methods.


Microtomy; Serial sectioning; Single fiber testing; Mechanical properties; Cross sectional properties; E-modulus; Bending stiffness; Fiber flexibility

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