Quantification of damage generated during Fortuna splitting of paperboards

Abstract Accurate ply-specific properties are critical for predictive modeling and process optimization in paperboard manufacturing, yet the widely used Fortuna splitting technique may alter mechanical properties. This study addresses the gap by quantifying the damage introduced when three-ply paperboards are separated into individual plies using a Fortuna splitting machine. While grammage remains unaffected, splitting increases surface roughness and slightly inflates measured thickness, requiring correction for accurate laminate modelling. Tensile tests and curve-fitting reveal that splitting reduces the elastic stiffness and yield strength of free-laid plies compared to intact boards. Average reductions were determined as 11 % in tensile stiffness and 7 % in yield strength. Damage distribution is highly non-uniform: the middle ply exhibits the greatest degradation, up to 29 % stiffness loss in CD, while the outer plies are less affected. Splitting quality and direction significantly influence the magnitude of damage; cuts following interfaces minimize damage, whereas cuts propagating through plies increase bond disruption. By introducing damage-compensated properties, the intact board response can be accurately reconstructed from ply data, allowing for reliable finite element modeling. These findings underscore the importance of controlled splitting procedures and correction factors when utilizing free-laid ply properties for design and process optimization.