Finite element analysis of the folding process of creased white-coated paperboard using a combined fluffing resistance and shear yield glue model

摘要

This study aims to develop a numerical simulation model of the folding process of a creased paperboard and to reveal the deformation characteristics of the creased paperboard. A cantilever type bending moment measurement apparatus was experimentally examined with a 0.43-mm thickness paperboard. To verify the folding mechanics of the creased part, the initial crease was varied within a certain range, and the lamination numbers were considered with 8 layers. A fluffing resistance model based on the z-directional (out-of-plane) tensile test was developed and simulated using isotropic elasto-plastic solid properties. However, because the fluffing resistance is restricted in the normal direction of the detached interface, in-plane shear resistance is not considered. When investigating the folding process of a creased part, the in-plane shear resistance and its breaking limit seem to be the primary characteristics. Therefore, in this work, in order to characterize the delamination and bulging deformation, an internal breaking criteria was numerically analyzed using a new combination model. A general purpose finite element method (FEM) code was applied to develop a combination model comprising the out-of-plane fluffing subroutine and the in-plane shear glue strength. Through the FEM simulation of the folding process of creased paperboards, the following results were revealed: (1) The simulated bulging profile of the creased part and its bending moment resistance well matched with the corresponding experimental result at the stationary folding state with a folding angle >20°. (2) The in-plane shear glue strength characterizes the pattern of the interlayer delamination in the folding process of the scored zone. (3) The initial delaminated span of the scored zone is estimated as >150% of the creasing width. (4) The initial gradient of the bending moment resistance is characterized by the scored depth.