Preliminary investigation on the potential of fractionation for stratified forming: application to maximising bending stiffness

摘要

Fractionation of furnish into fractions having different properties offers vast opportunities for stratified forming. In this preliminary work, we propose a general framework for studying the effect of fractionation conditions for stratified forming. By coupling a fractionation model (based on the concept of fibre passage ratio) with stratification models, we seek the best fractionation efficiency with respect to fractions properties and available flows, for further stratified forming. The objective here was to maximize bending stiffness of the multi-layer sheet. Simulations show that micro-holes screen (0.25 mm aperture) operated at optimum volumetric reject rate (around 0.2 for the tested BCTMP furnish) generates fractions which maximise the bending stiffness of a symmetrical 3-layer sheet (after proper location of the fractions in the sheet structure, i.e. using a mixture of short and long fractions in the outer layers, and long fraction only in the inner layer).