Interfibre joint strength under peeling, shearing and tearing types of loading

• The mechanical properties of interfibre joints are essential for the load carrying capacity of fibre network materials such as paper and board. Mechanical measurements of fibre–fibre crosses can been used to characterize the strength of these interfibre joints in order to obtain knowledge on how these hierarchical network materials behave at the micrometer scale. The general method for these interfibre joint strength experiments has been to pull one of the fibres of a fibre–fibre cross and attribute the force at rupture to the shear strength of the interfibre joint. However, without taking the geometry of the fibres and the resulting mixed mode of loading at the interfibre joints into account, limited information on the strength properties can be obtained using this technique. In this study, isolated fibre–fibre crosses have been tested mechanically using four distinctly different load cases; peeling, shearing, tearing and a biaxial type of loading, in order to gain more information on how interfibre joints behave in different modes of loading. The centerline geometry of the fibres, microfibril angles, initial twists as well as the wall thickness of each individual test piece was used to model each experiment using the finite element method, and from the simulation results, the local state of loading in the interfibre joints at failure was obtained for each specific experiment. The force–displacement curve for the experiments as well as the estimated local state of loading was also used to compare the different load cases and to evaluate the information that can be obtained on the strength properties of interfibre joints using these load cases.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Teknisk mekanik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Applied Mechanics (hsv//eng)

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