Flexural stiffness of multi-ply paperboard

Abstract An equation for calculating the flexural stiffness of multi-ply paperboard has been derived from classical lamination theory. Calculations using the equation are simpler to perform than those following the methods previously proposed in the literature as no reference to a neutral surface is necessary. The application of the equation was tested on both homogeneous boards and three-ply boards. Good agreement was obtained between calculated and measured values of the flexural stiffness if the specific elastic modulus and density of the plies were correctly measured. The practical significance of the equation is demonstrated in an example where the optimal flexural stiffness was investigated for a multi-ply board of different combinations of a groundwood pulp and a chemical pulp.