Modeling the influence of drying conditions on the stress buildup during drying of paperboard

This paper concerns the drying process in the manufacturing of paperboard. Of particular interest are the effects of through-thickness property variation in paperboard during drying. In addition, resulting average properties from different drying hi stories are discussed. A mathematical model of the drying process is presented. It allows the moisture and temperature histories, the stress and strain histories, and the buildup of mechanical properties to be simulated. The temperature of the heating medium, the humidity and pressure of the ambient air, and either applied loads or prescribed strains are required input data. For symmetric convective drying, the ambient temperature, the humidity, and the thickness of the board were varied. For drying on a heated plate, the temperature of the plate and the thickness of the board were varied. Results regarding the moisture history, the stiffness development, and the buildup of residual stresses are presented and compared to literature experimental data. Also, sheets with a varying fiber base through the thickness, which affects both the moisture history and the influence of moisture on shrinkage, were studied. The model was shown to yield predictions qualitatively inline with empirical knowledge.