Dynamic Crease Stiffness Reduction Ratios under Ultra High Speed Packaging Line Strain Rates
Dynamic crease stiffness reduction ratios must be evaluated under operational strain rates of 1000°/s to 5000°/s to prevent high-speed cartoning line jams.
Static Bending Moment
Resistance Torque
Paperboard flexural testing measures the mechanical resistance offered by a clamped specimen when deflected through a specified angular arc under static loading conditions. In structural board evaluation, static bending moment quantifies the internal torque generated by the paperboard structure to resist applied bending forces.
Stiffness Calculation
Standardized test procedures clamp a fifty-millimetre wide paperboard strip and apply a bending force at a fixed distance from the clamp until the specimen reaches a fifteen degree deflection angle. The resulting force required to hold the deflection multiplied by the bending distance yields the bending moment value expressed in millinewton metres. Bending resistance correlates directly with carton opening force and top-load stack strength on automated packaging lines.
Multi-ply paperboard structures achieve high bending moments by placing high-elastic-modulus bleached chemical pulps on the outer layers and bulky mechanical pulps in the core. Maximizing outer ply distance from the neutral bending axis maximizes structural stiffness while minimizing total sheet weight.
Fibre Orientation
Machine-direction alignment of cellulose fibres during web formation produces significantly higher bending resistance along the machine direction than across the cross direction. Anisotropy ratios between machine and cross direction typically range from one point five to two point five depending on headbox flow hydraulics. Balancing fibre orientation profiles ensures uniform carton folding behavior during conversion.