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Advisor(s)
Abstract(s)
Many paper mills use ultrasonic techniques to measure the Tensile Stiffness Index, TSI, of the paper sheet. They then
assume that the TSI value is the same as the fibre orientation anisotropy. This is true if the paper is allowed to dry without
any internal tension or elongation, but does not apply to paper manufactured in a paper machine. The paper machine
introduces tension and elongation as soon as the fibre is placed on the forming fabric. These factors increase through the
press section and are accentuated in the drying section. In order to uniquely measure the fibre orientation anisotropy on the
surfaces, the proposed method uses replicas of both paper surfaces to produce a laser diffraction pattern. The obtained
pattern reveals an elliptical shape, which is related to the fibre orientation anisotropy of the paper surface. By measuring the
ellipticity of the diffraction pattern and the deviation with respect to the machine direction, one can quantify the fibre
orientation distribution. Different papers from the bench market have been successfully tested with the developed system.
This article describes the new developed optical system and its innovative capabilities in the field to produce maps of the
fibre orientation of a complete paper sheet surface. A selection of the obtained results to prove its feasibility is also
presented.
Description
Keywords
Optical diffraction Fibre orientation anisotropy Paper surface replicas Paper sheet formation and paper
structure.